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Amelia Earhart Search Forum => Aircraft & Powerplant, Performance and Operations => Topic started by: Gary LaPook on October 14, 2011, 11:53:21 PM

Title: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 14, 2011, 11:53:21 PM
See:

http://www.hawaiinewsnow.com/story/15646096/hawaii-rescue-crews-ready-for-emergency-landing

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 15, 2011, 09:12:44 AM
Thanks Gary.  Very interesting.  The pilot did a beautiful job. 
So a low wing, twin engined airplane with empty long-range ferry tanks in the cabin (safe assumption) remained afloat for 15 minutes after a well-executed ditching.

A Lockheed 10E with standard in-the-wings tanks ditched off Cape Cod in 1967 and remained afloat for 8 minutes.  In each case we're probably looking at the amount of time it took for the tanks to loose their buoyancy.

The Cessna 310, although smaller than an Electra, should be roughly proportional in terms of weight versus buoyancy.  I think 15 minutes is a pretty good estimate for how long NR16020 would float.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 18, 2011, 01:03:41 AM
Thanks Gary.  Very interesting.  The pilot did a beautiful job. 
So a low wing, twin engined airplane with empty long-range ferry tanks in the cabin (safe assumption) remained afloat for 15 minutes after a well-executed ditching.

A Lockheed 10E with standard in-the-wings tanks ditched off Cape Cod in 1967 and remained afloat for 8 minutes.  In each case we're probably looking at the amount of time it took for the tanks to loose their buoyancy.

The Cessna 310, although smaller than an Electra, should be roughly proportional in terms of weight versus buoyancy. I think 15 minutes is a pretty good estimate for how long NR16020 would float.
----------------------------------------

Well actually, no.

Let's do the computation. It is 2015 NM from Monterey to Hilo. A Cessna 310 gets 8.6 NAM (Nautical Air Miles) per gallon at best range speed and power so it would take 234 gallons to make the flight. Add to this a 25% reserve and you end up with 293 gallons, let's call it 300 gallons. Sea water weighs 8.5 pounds per gallon so empty 300 gallon tanks provide 2550 pounds of buoyancy. The standard empty weight of a Cessna 310 is 3170 pounds though almost all weigh quite a bit more. Since aluminum weighs 169 pounds per cubic foot, the airplane consisted of 18.8 cubic feet of aluminum so displaced 18.8 cubic feet of seawater which weighs 64 pounds per cubic foot so the empty airplane also experienced a buoyancy of 1203 pounds. Putting all of this together, we have buoyancy of 2550 + 1203 = 3753 pounds of buoyancy. Subtract the empty weight of 3170 pounds makes the plane have 583 pounds of buoyancy which would have kept the plane afloat. Since it sank after the cabin flooded we know the total weight in the plane must have exceeded 3753 pounds. This is explained by the empty weight being more than standard, which is the usual case, plus the pilot's equipment and the weight of the ferry tanks made the weight exceed the buoyancy. And, if they only tanked the plane for a 20% reserve then the tankage would have only been 280 gallons so 170 pounds less buoyancy than the above computation assumed with 300 gallons of tankage.

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We can do the same computation for the Electra. The empty weight was (in round numbers) 7,000 pounds meaning it consisted of 41.33 cubic feet of aluminum which displaced 41.33 cubic feet of sea water providing 2645 pounds of buoyancy. Add to this the buoyancy provided by 1151 gallon empty fuel tanks, 9783 pounds, makes the total buoyancy of 12,428 pounds. Subtract the empty weight of 7,000 pounds leaves 5,428 pounds of positive buoyancy. Based on this, assuming no damage to the fuel tanks during a ditching or landing, the plane should have floated almost indefinitely. The fuel caps are airtight as are the fuel lines so the only way for water to enter the fuel tanks was through the vent lines which are very small, say 3/8th of an inch, so water could not enter at any great rate through them. In addition, depending on the attitude of the plane and the routing of the vent lines, it is also likely that no water could enter the tanks at all through the vent lines. So if the plane was washed off the reef at Niku, there is no reason to think that it sank anywhere near that island, so your ROV search, just offshore of the reef, is probably a waste of money.

--------------------------------------------------

Addition:

I did not allow for the buoyancy of the oil tanks that had a volume of 75 gallons. Assuming that two-thirds of the oil had been burned, 50 gallons, then the empty space in the oil tanks would provide an additional 425 pounds of buoyancy, bringing the total up to 5853 pounds of buoyancy.


gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 18, 2011, 01:35:12 AM
Thanks Gary.  Very interesting.  The pilot did a beautiful job. 
So a low wing, twin engined airplane with empty long-range ferry tanks in the cabin (safe assumption) remained afloat for 15 minutes after a well-executed ditching.

A Lockheed 10E with standard in-the-wings tanks ditched off Cape Cod in 1967 and remained afloat for 8 minutes.  In each case we're probably looking at the amount of time it took for the tanks to loose their buoyancy.

The Cessna 310, although smaller than an Electra, should be roughly proportional in terms of weight versus buoyancy.  I think 15 minutes is a pretty good estimate for how long NR16020 would float.
----------------------------------------------

BTW, I worked on a case in which a Navajo ditched just off shore of Hilo, it sank in about one minute taking one passenger to the bottom of the ocean. One engine had failed and the plane wouldn't maintain altitude on the remaining engine although it should have been able to, since the single engine service ceiling was about 8,000 feet at the weight of 7,000 pounds, so this did not make any sense. We found out the reason when we took the deposition of the mechanic. It turned out he had not used the proper procedure in adjusting the wastegate controller which then prevented the good engine from actually producing full power.

See:
http://dms.ntsb.gov/aviation/AccidentReports/gsoirwf4xfbwxlflxz02foj21/O10182011120000.pdf

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 18, 2011, 04:44:39 AM
BTW, I worked on a case in which a Navajo ditched just off shore of Hilo, it sank in about one minute taking one passenger to the bottom of the ocean.

Any explanation for why it sank so quickly?
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 18, 2011, 05:58:56 PM
BTW, I worked on a case in which a Navajo ditched just off shore of Hilo, it sank in about one minute taking one passenger to the bottom of the ocean.

Any explanation for why it sank so quickly?

------------------------------------
Contrary to the Cessna 310 and the Electra, it didn't have any extra fuel tanks to provide positive buoyancy and the standard fuel tanks that were there had fuel in them (duh) so didn't provide much buoyancy,  and the exit was open to allow the passengers to get out so the cabin flooded quickly.
gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 20, 2011, 08:42:35 PM
Please forgive a newbee, but wouldn't rectangular tanks collapse pretty easily from seawater pressure?  They're designed to withstand pressure from the inside, not from the outside.  Are there drawings of the internal tank structures?

JohnO
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 20, 2011, 09:06:40 PM
Please forgive a newbee, but wouldn't rectangular tanks collapse pretty easily from seawater pressure?  They're designed to withstand pressure from the inside, not from the outside.

Interesting thought. The tanks were lightly built.  Would water pressure cause them to collapse, forcing the air out through the vents?

  Are there drawings of the internal tank structures?

Unfortunately, no.

JohnO
[/quote]
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 21, 2011, 12:44:37 AM
Please forgive a newbee, but wouldn't rectangular tanks collapse pretty easily from seawater pressure?  They're designed to withstand pressure from the inside, not from the outside.

Interesting thought. The tanks were lightly built.  Would water pressure cause them to collapse, forcing the air out through the vents?

  Are there drawings of the internal tank structures?

Unfortunately, no.

JohnO
[/quote]
------------------------------------

Assuming that the vent lines led out the bottom of the wings (a certainty for the wing tanks) and out the bottom of the fuselage for the extra tanks (which seems most probable so that any expansion of the fuel would result in the fuel being ported overboard out the bottom rather than running over the skin of the fuselage) then pressure on the tanks could not squeeze the air out of the tanks nor could water enter the tanks through the vent lines. And this is true even if the tanks were made out of rubber.

Federal Aviation Regulation, FAR 23.975 states in part:

"(6) No vent may terminate at a point where the discharge of fuel from the vent outlet will constitute a fire hazard or from which fumes may enter personnel compartments;"

(FAR part 23 controls the design of aircraft. In the '30 this was controlled by CAR part 3 but the two sets of regulations are almost identical.)

You can prove to yourself that the air won't be squeezed out of the tank through a vent line that comes out the bottom of the fuselage  by making a simple model of the system. Fill the kitchen sink with water, turn a glass upside down and immerse it in the water. The bottom edge of the glass represents the end of the vent line coming out the bottom of the plane. Notice that the air can't get out.

Looking at the size and placement of the fuselage tanks, as long as they and their plumbing were not damaged, it is impossible that the plane would sink so far as to allow the water in the flooded cabin to reach the tops of the tanks. At this position the roof of the plane would not be immersed so the buoyancy that would have been produced by the immersion of the roof would not be available but this is probably not more than 400 pounds of buoyancy. Since the fuselage tanks appear to be less than three feet tall, even if they were made out of rubber and squeezed by the water pressure of that depth, then only about 4.5% of the tanks' buoyancy would be lost so causing a loss of about 450 pounds, still leaving  more than 5000 pounds of buoyancy.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 21, 2011, 08:06:47 AM
Good point about the vents.  The tanks would therefore provide very significant buoyancy until something happened to let the trapped air out.  There's a photo of AE kneeling on top of the tanks that clearly shows the vent lines and fill ports.  The filler tubes are very large diameter and lead to the port side exterior.  I have no knowledge of the sort of caps used, but I'll assume they would hold air in the tanks against modest pressure.  The location of the vent lines in the photo is interesting - they are routed to a pair of "header tanks" (my term) on either side of AE.  The vent lines appear to be about 1/2 inch diameter, making a significant restriction for escaping air if the tanks were submerged, and if the exit end(s) of the vent lines were above the tanks.  It would take a while for the tanks to collapse if the only outlet for trapped air were through those small diameter lines - long enough that the plane would sink slowly at first, so it could drift a long ways before heading to the bottom. If the vent lines terminated at the bottom of the aircraft, then the tanks would provide long-term buoyancy as long as there was no other outlet for trapped air.
What is known about surface and deep currents around Niku?  A sinking aircraft would probably descend in a spiral, rather than a long, straight, flat glide, especially if there is any significant damage.  If it started sinking as soon as it slipped off of the edge of the reef, it would tend to return to the cliff face as it spiralled down.  If it drifted away first, it could be somewhere in a broad wedge-shaped region "down-stream".
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Bob Brandenburg on October 22, 2011, 11:03:27 AM
Gary,

Some observations on your analysis of the Electra's buoyancy:

Your airframe displacement buoyancy calculation uses the total empty weight of the  aircraft to find the volume of seawater displaced, assuming everything in the plane was aluminum.   

Since the aircraft was not watertight, it is correct to assume that it would flood.  However, in order for the combined volume of all the material in the aircraft to contribute to displacement buoyancy, it would be necessary for the aircraft to be fully submerged, in which case it would have sunk.

As for the assumption that everything was aluminum (169 lbs per cubic foot), it's worth noting that there was steel (491 lbs per cubic foot)in the aircraft -- notably in the landing gear and the pinion gears driven by various motors, etc.  There was copper (550 lbs per cubic foot)in power distribution wiring, generator and dynamotor armatures and field coils, etc.  And then there were two storage batteries at 78 pounds each, mostly lead (709 lbs per cubic foot), the radio equipment, navigator's table and equipment, etc. 

Correctly calculating the displacement requires accounting for the densities and amounts of the various materials in the aircraft.  But if the aircraft is floating, any parts not submerged do not contribute to displacement buoyancy. If the plane is afloat, and all fuel has been expended, it will float in a nose down attitude, with much of the airframe aft of the wing out of the water.  The weight of that section would be supported by the buoyant section, but would not contribute to total buoyancy.

You assume that all fuel tanks are intact and dry when the plane is floating.  That's possible but not a sure thing.  There was a spring tide on July 9, 1937, and swells  running on the reef flat from the northeast could have pushed the plane southwestward to and over the reef edge.  During that process, a landing gear assembly -- possibly both -- could have collapsed.  Nessie seems to suggest one got stuck in a crevice, but we know from the Luke Field crash that when one gear collapsed under lateral loading, the other also can fail.  Such an event could deform the gear support structure, directly above which on each side was a 102 gallon fuel tank which could be punctured. 

And swells on the reef impacting the aircraft could deliver considerable jolts, loosening or breaking tank connections.  For example, a 2-foot swell has 32 foot-pounds of energy per square foot of the swell face.  Such a swell impacting a 20-foot section of the aircraft would deliver 1280 foot-pounds.  For a swell period of ten seconds, such a jolt would be delivered 6 times per minute.  A 3-foot swell would deliver a 4320 foot-pound impact.  So it's possible that at least some of the tank connections permitted flooding, reducing buoyancy.

Another consideration is that with the plane floating nose down, a considerable weight is suspended from the cabin tanks, which are held in place by thin metal tie-down straps.  This could result in deforming or tearing of the thin tank walls, reducing buoyancy due to decreased volume, or even allowing flooding through the tears.  If tie-down straps fail, the tanks would be free to float in the cabin, allowing the plane to sink lower in the water.  If the freed tanks are ruptured by objects in the cabin, they could flood.  And, depending on the waterline location, the tank vents on the top of the fuselage could be submerged, allowing flooding.

So, it's by no means clear that the plane would simply flaot away from the island, never to be seen again.  While that's a possibility, it's also possible that whatever buoyancy the plane had was compromised during the chain of events leading to its departure from the reef, and the plane sank in the vicinity of the island.

Bob     

   

   
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 22, 2011, 01:11:18 PM
Gary,

Some observations on your analysis of the Electra's buoyancy:

Your airframe displacement buoyancy calculation uses the total empty weight of the  aircraft to find the volume of seawater displaced, assuming everything in the plane was aluminum.   

...So, it's by no means clear that the plane would simply flaot away from the island, never to be seen again.  While that's a possibility, it's also possible that whatever buoyancy the plane had was compromised during the chain of events leading to its departure from the reef, and the plane sank in the vicinity of the island.

Bob

----------------------------------------

All good points, Bob.

Responding in the same order.

1. I assumed that the cabin and the wings were flooded and provided no buoyancy, the only buoyancy being provided by the empty 1151 gallon fuel tanks plus 2/3rds empty 75 gallon oil tanks (50 gallons of air in the oil tanks) plus the buoyancy of the aircraft structure itself. The empty tanks total 1201 gallons so produce a buoyancy, in seawater, of 10,208 pounds equal to the weight of 1201 gallons of seawater. So, without even considering the contribution of the structure, there would be excess buoyancy of 3,208 pounds and approximately one-half of the plane, whatever its attitude, would be floating above the waterline.

2. I used the simplifying assumption that the structure was all aluminum but, obviously, some parts were made of steel and other denser materials. Steel is more than twice as dense as aluminum but there was a lot more aluminum in the structure than steel so the average density would have been closer to aluminum than to steel. Had the plane been entirely of aluminum, then 7,000 pounds of aluminum immersed in seawater would have produced an additional 2,676 pounds of buoyancy added to that of the empty tanks for a total 5,884 pounds, almost the entire weight of the plane, so the plane would have floated with most of it above the waterline. But, as you point out, the portion out of the water would not contribute to the total buoyancy (I did subtract 400 pounds for this factor in my prior post) so the plane would actually float lower in the water but no lower than approximately half way since that much buoyancy was provided by the empty tanks alone. Even if the entire plane had been made of steel, then the structure would still have provided 918 pounds of buoyancy for a total of 4,126 pounds so the plane would have ridden lower in the water but most of it would still be above the waterline. To take this to extremes, even if the plane had been made entirely out of lead, 7,000 pounds of lead immersed in seawater still provides 636 pounds of buoyancy so the total buoyancy would have been 3,844 pounds causing the plane to float quite nicely.

3. I do assume that the tanks were intact but this seems quite reasonable since the landing on the reef was gentle enough to end up with the plane still standing on its landing gear so that the engine could be operated. According to FAR 23.303 and FAR 23.337 and the parallel 1937 regulations, aircraft structures were required to be much stronger than needed and the Electra's structure, and its components, had to be strong enough to support 3.8 times its weight plus a 50% margin or 5.7 times its designed gross weight of about 10,000 pounds so the structure could support 57,000 pounds before suffering permanent deformation. The tanks structures had to be designed to deal with the loads imposed with them full of fuel and with them empty the forces developed by the tanks in a sudden deceleration would be trivial and easily contained by the structure. And this applies to jolts from swells too.

4. Still using the simplification that the structure was entirely aluminum providing 2,676 pounds of buoyancy, to keep the 7,000 pound plane afloat would only require an additional 4,324 pounds of buoyancy provided by empty fuel tanks meaning that it would take only 509 gallons total of intact fuel tanks to keep it afloat. This means that it would take damaging many of the tanks to make the plane sink. There were 10 fuel tanks total so if even only the smallest 6 held air the plane would float and this does not take into consideration the oil tanks. If the oil tanks were intact then it would take only the 5 smallest fuel tanks to keep the plane afloat. If only the four largest fuselage tanks held air then the plane would float, again without taking into consideration the oil tanks. Taking into consideration the oil tanks, then even the 4 smallest fuselage tanks would keep the plane afloat.

5. Once the tanks were submerged there would be an upward strain on the tiedowns equal to the buoyancy being created by the air in the tanks, they act like inflatable life vests. The very minimum load that must be designed for is in an upward direction and is 1.52 times the weight of the tank itself plus the fuel contained in the fuel tank. To this must be added the 50% safety factor making the tank tiedowns capable of holding 2.28 times the weight of the full fuel tanks. Aviation gas has a density of 6 pounds per gallon and seawater has a density of 8.5 pounds per gallon, only 1.41 times that of gas. Thus the buoyancy exerted by empty fuel tanks immersed in seawater can never exceed the 1.52 minimum structural design limit without even taking into consideration the required 50% safety margin. An example will make this clear. The 148 gallon fuselage tanks hold 888 pounds of gas so the tiedowns must be designed to restrain 1.52 times this weight (plus the weight of the tanks themselves) so must be strong enough to hold down at least 1,350 pounds. Add the 50% safety factor and the minimum strength must have been 2,025 pounds. Since seawater has a density of 8.5 pounds per gallon, the maximum amount of buoyancy that could be produced if this empty tank was entirely submerged is 1,258 pounds, equal to the weight of 888 gallons of seawater, well within the design requirements of the structure.

6. So if the plane were swept off the reef it is unlikely that it sank rapidly so a search limited to the sea bottom in close proximity to the edge of the reef is likely to prove fruitless.

gl

Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 23, 2011, 02:10:33 PM
Since the photos of the tanks appear to show all of the vent lines manifolded together, an air leak in any one tank would allow air to escape from all of the tanks, through the vent lines to the damaged tank.  This also assumes the external vent is line is routed to the bottom of the aircraft.  If it's out the top, then nothing will prevent the tanks from filling or crushing.

Gary wrote"...This means that it would take damaging many of the tanks to make the plane sink.", to which I would add "...to sink quickly", but even a single damaged tank would eventually result in sinking, if the tank vents are indeed all manifolded together.

Assuming any initial submersion does not generate any significant pressure in the the tanks, and assuming one vent line is open to the atmosphere, and assuming 1/2 inch ID vent line, how long would the tanks provide net positive buoyancy?  At a modest 125 ft/sec velocity of escaping air (a bit faster than the maximum recommended velocity in compressed-air systems), through a single 1/2 inch diameter tube, it would take about 17 minutes for 1251 gallons/167 cu.ft of air to escape.  To just reach zero net buoyancy only needs the loss of 393 gallons/53cu.ft, which would take just 5 minutes.

It seems unlikely that a tank could be ruptured by any successful landing, so there would be no obvious way for the tanks to lose their buoyancy unless the vent(s) were open to atmosphere somehow.  If the vents were in the top of the aircraft, and if the tanks could flood or crush, then the a/c might be expected to lose buoyancy and sink within a very short time/distance.  If the vents were in the bottom, or otherwise not open to the atmosphere, then the tanks might provide buoyancy indefinitely.

Knowing where the vent was located might narrow the search area significantly.

Where are the best photos to study that might show vent locations?
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 23, 2011, 05:01:31 PM
Since the photos of the tanks appear to show all of the vent lines manifolded together, an air leak in any one tank would allow air to escape...If it's out the top, then nothing will prevent the tanks from filling or crushing.

Gary wrote"...This means ...how long would the tanks provide net positive buoyancy?  At a modest 125 ft/sec velocity of escaping air (a bit faster than the maximum recommended velocity in compressed-air systems), through a single 1/2 inch diameter tube, it would take about 17 minutes for 1251 gallons/167 cu.ft of air to escape.  To just reach zero net buoyancy only needs the loss of 393 gallons/53cu.ft, which would take just 5 minutes.

It seems unlikely that a tank could be ruptured by any successful landing, ...Knowing where the vent was located might narrow the search area significantly.

Where are the best photos to study that might show vent locations?
------------------------------
All interesting points.
1. To get the tanks to fill with water there needs to be two openings, one to let the water in and another to let the air out. So even if the vent line led upward so that the air could get out you still need an opening into each tank to allow water to enter each tank. Suppose one tank was holed then water would enter that tank and fill it up but after  that one tank was full the water would not travel back through the vent line to flood the other tanks so you would only lose the buoyancy of that one tank. So it would take damaging many tanks individually to lose all of their buoyancy.

2. If a tank was pierced near the top so that the opening acted like a vent then the other tanks still will not fill unless each of them have their own opening to allow the water to enter. Depending upon which of the tanks had the vent like opening it would only allow the other tanks to vent until the holed tank sank below the water line of the other tanks (even if they were holed also) at which point no more air could come out through that hole. For example, if the forward 118 gallon tank sustained damage then it would provide a vent for the other tanks only until the nose tipped down, submerging the hole below the level of the other cabin tanks.

3. The rate of air loss through the 1/2 line would not be nearly as fast as the rate you mentioned for compressed air. The air pressure in a holed tank would only be about 1 & 1/2 or 2 psi, not the normal 100 psi found in your compressed air tank so the air would flow out much more slowly.

4. I don't understand how you computed that it would take losing only 393 gallons of buoyancy to allow the plane to sink. This number means that you figured that the plane had only 3340 pounds of positive buoyancy which is about the amount of buoyancy provided by the tanks alone, I figured 3208 pounds from that source. Did you forget to allow for the buoyancy of the aircraft structure itself? If the plane had been made entirely out of aluminum then the structure would have provided an additional 2676 pounds of buoyancy making the total buoyancy 5,884 pounds. To lose this much buoyancy would take losing 692 gallons of air trapped in the tanks, not the 393 gallons that you stated. Since the plane was not entirely aluminum it would take slightly less than this. Even if the plane was entirely steel it would still have 4,126 pounds of buoyancy so would have to lose 485 gallons of air from the tanks. Since there was a lot more aluminum in the structure than steel we can expect the correct value to be much nearer the 692 gallons than to the 485 gallons figure.

5. You are correct in noting that if the tanks crushed then there would be no need for a hole in each tank to admit water. However, assuming the plane was floating near level, the water pressure on the outside of the tanks would only be about 2 psi so it seems very unlikely that this would be sufficient to crush the tanks. The tanks have to be strong enough to contain the fuel  even in a crash with partial tanks allowing the fuel to exert a great deal of impact force due to its sloshing in a crash. Although they are designed to withstand this force from within, not from without, it seems highly likely that the use of materials strong enough for this purpose would also be strong enough to withstand the unexpected pressure of only 2 psi from the outside.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 23, 2011, 09:25:33 PM
Gary,

This is all reminding me of your learned recitation of all the reasons that Noonan could not possibly have missed Howland Island.   And yet he did.
You have also maintained that it was not possible for AE and FN to dead reckon a few hundred miles down the LOP to Gardner.
Now you have offered computations and cited regulations to explain why the Electra would float indefinitely. If the airplane could truly float indefinitely it should still be bobbing around out there somewhere.  Perhaps we should be looking for it on Google Earth. I hasten to say that I'm kidding. I don't think you really mean that the Lockheed has remained afloat for 74 years, but if it did, in fact, eventually sink - what happened?  Once what you describe as a reliably buoyant aircraft was away from the island and removed from the possibility of collision with hard objects, what would make it sink?  When a hurricane is coming, the Navy puts its ships to sea for that very reason - so they don't bump into things. What part or parts of the incredibly robust flotation system you describe failed?  Why did those components fail then and not earlier?  Did some crucial part deteriorate over time?  What part?  How long did it take to deteriorate?  Hours?  Days?  Weeks?  Months?  If the airplane ditched anywhere near Howland and floated indefinitely, why didn't Itasca spot it?  If Itasca somehow missed it, why didn't the planes from the Lexington find it? 

If the intact and indestructible plane you describe floated far away from Gardner (or was never there) why was there such a strong and consistent tradition among the islanders that there was airplane wreckage on the reef when the first settlers arrived in 1938?  As we've often said, anecdotal recollections (old stories) are not evidence unless corroborated by archival records, photographs and/or artifacts.  In this case, we have found no archival records to corroborate the old stories.  Apparently the British authorities were never aware of the wreckage.   We do, however, have 1953 aerial mapping photos that appear to show a debris field of light-colored metal on the reef and an October 1937 photo that shows unexplained debris on the reef in the same spot where a former-resident described seeing wreckage from an aircraft.  Stories of airplane parts being found on the reef or shoreline are corroborated by aircraft artifacts found in the abandoned village that are consistent with a Lockheed 10.

Theoretical calculations suggesting that the intact airplane could have floated far away from the island and sunk in very deep water are trumped by the abundant evidence that it sank in the near-shore environment in water shallow enough for it to be, to some degree, broken up in later storms with some lighter components being cast up onto the reef and shoreline.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 24, 2011, 12:40:39 AM
Gary,

This is all reminding me ...Did some crucial part deteriorate over time?  What part?  How long did it take to deteriorate?  Hours?  Days?  Weeks?  Months?  If the airplane ditched anywhere near Howland and floated indefinitely, why didn't Itasca spot it?  If Itasca somehow missed it, why didn't the planes from the Lexington find it? 

If the intact and indestructible plane you describe floated far away from Gardner (or was never there) why was there such a strong and consistent tradition among the islanders that there was airplane wreckage on the reef when the first settlers arrived in 1938?  ...debris on the reef in the same spot where a former-resident described seeing wreckage from an aircraft.  Stories of airplane parts being found on the reef or shoreline are corroborated by aircraft artifacts found in the abandoned village that are consistent with a Lockheed 10.

Theoretical calculations suggesting that the intact airplane could have floated far away from the island and sunk in very deep water are trumped by the abundant evidence that it sank in the near-shore environment in water shallow enough for it to be, to some degree, broken up in later storms with some lighter components being cast up onto the reef and shoreline.
-------------------------
If they ditched near Howland then there would have been a much higher likelihood of damage to the fuel system components so a greater likelihood that it would sink more quickly than in your scenario of a controlled landing on a smooth reef surface, soft enough to leave the plane standing on its landing gear.

The pieces you have found are also "consistent with" other aircraft. The only way the aluminum would not be "consistent with" Earhart's Electra is if the pieces were stamped "MANUFACTURED IN 1938" or later. I have cross-examined many adverse expert witnesses who have tried to use that "consistent with" terminology to cover up the weaknesses in their theories, its SOP for many plaintiff's experts.

As for being "trumped" I don't think you are there yet. When you find any piece that can be positively connected to NR16020 (and you haven't yet) then you will have the trump card. Until then, I calls 'em as I sees 'em.

As for a "tradition" of islanders  seeing aircraft parts on the reef, I have been a lawyer for a long time and almost all of my cases involved airplane crashes. Based
on my experience I have come to be distrustful of “eyewitness testimony.” Even if a witness is
trying to be truthful it doesn’t mean that they actually saw what they think they saw. I’ll give you
an example. A number of my cases involved airplane crashes involving fires with the wreckage
badly burned up. We would take the testimony of 3 or 4 and in one case 6 eyewitness who
testified under oath “I looked up and I saw the airplane on fire, fire was coming out of the front
of the plane!” If islanders' "tradition" was sufficient then this testimony from so many eye witnesses would
establish the fact that the plane was on fire while it was still up in the sky, case closed.

Well, not so fast. When a plane catches fire after it impacts the ground, the fire and smoke goes
upward, just like the fire in your fireplace. When a plane is on fire while in flight the smoke trails
back and deposits soot on the tail of the plane, no soot on the tail, no in-flight fire. All these
witnesses that testified under oath (not just a "tradition") that they saw a plane on fire up in the air were wrong. They
weren’t lying, they were just wrong. This is just a sample but when you take sworn testimony
many times you start to realize that eyewitness testimony is not all that reliable. And these
witnesses were testifying shortly after the accidents, not many years later. It is also quite common for witnesses to give you the answer you are looking for unless you are careful to ask the questions in such a way that the witnesses can't guess what you are looking for.

"Did you see aircraft wreckage on the reef?"

"Oh, yes."

I have a suggestion for you for an experiment to test your theory on your next trip to Niku.  Bring a bunch of pieces of aircraft aluminum, say four feet by four feet. Inscribe each piece "NOT FROM EARHART PLANE." On the first day go to many places along the edge of the reef and chuck them over the edge. Record the locations from your GPS.  Then on the last day see where those pieces ended up. Did they slide all the way down to the abyssal plain? Did they get caught in shallower water by protuberances on the side of the reef? Did they end up on the various shelves on the side of the reef that you showed in your recent movie? Were they cast back up on top of the reef?

Then on the following trip look for them again, see if they have moved from their original resting places.

It's a good experiment. If they get tossed back on top of the reef then it supports your explanation for the bits found on the island. If they disappear down all the way to very deep water then it also supports your theory since it explains why you haven't been able to find pieces in the shallow water on the side of the reef. I'll predict that they don 't slide very far down the side of the reef before getting caught in pretty shallow water where they will stay forever, but I could be wrong. It shouldn't cost very much for the pieces of aluminum so an inexpensive experiment that might help with your theory.

Ric, do you have diagram or drawing showing where the vent line for the cabin tanks led?

Another question for you. After Earhart landed on the flat reef is there some reason that she couldn't taxi up onto the beach to get away from the tide?

gl

Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 24, 2011, 07:10:05 AM
Gary - thankyou for catching my errors.  I respondeded too quickly and didn't take the time to read your analysis carefully, or to check my own figures - my bad.  You're right that the tanks would need an entry, as well as an exit to fill with water.  I'm not convinced they would withstand crushing, but only because I'm ignorant of the design of their internal bracing.  I've seen many examples of slab-sided tanks that begin to crush at trivial pressures - a foot of water depth is suffiicient in some cases, yet only develops about 1/2 psi.  There are a lot of square inches being pushed upon, and the skin and bracing were not designed with external pressure in mind. Internal baffles for example are simply flat metal sheets spanning the tank width in several places.  Holes in the baffles allow slow liquid flow and reduce weight.  Forces from the action of fuel (sloshing, sudden deceleration, turbulence, etc) are resisted by shear and tension in the baffles.  There are no significant compression loads on the baffles in normal operation.  A flat sheet with holes in it is not capable of withstanding significant compression loads without buckling.  If the baffles have stiffening features, then they can resist buckling and can carry compression loads.  I'm anxious to learn more about the tank design, since it might be important to define the search area. 

I'm inclined to assume the internal bracing of the extra tanks used simple flat sheets with lightning holes, welded or riveted to the skins.  Such a design provides almost no resistance to crushing by submersion in water, but the displaced air would still need to escape for the a/c to sink.

As Ric points out, there was a tradition of an airplane wreck on the reef at one time.  What is known about the ways aircraft breakup on reefs over time?  Surely it wouldn't take much wave and wind action to move an aircraft around on the reef - one modest storm would be enough.  What would be damaged first  - the landing gear getting caught in a crack, anchoring it to one spot?  If so, then the aircraft would "weather-vane" about the stuck wheel, damaging the attach points and nearby structure.  At what point are the empty fuel tanks compromised to an extent they can't float the wreckage?  They would seem to be well protected inside the main fuselage. Would it take a year or two of constant saltwater exposure and pounding by waves to break the stuck parts free of the main body, which then floats away?  I'm guessing something like that could happen, implying there might only be a few pieces deposited near the reef - the larger pieces containing the buoyant tanks might have drifted miles away. 
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 24, 2011, 06:23:01 PM
Thanks Gary.  Very interesting.  The pilot did a beautiful job. 
So a low wing, twin engined airplane with empty long-range ferry tanks in the cabin (safe assumption) remained afloat for 15 minutes after a well-executed ditching.

A Lockheed 10E with standard in-the-wings tanks ditched off Cape Cod in 1967 and remained afloat for 8 minutes.  In each case we're probably looking at the amount of time it took for the tanks to loose their buoyancy.

The Cessna 310, although smaller than an Electra, should be roughly proportional in terms of weight versus buoyancy.  I think 15 minutes is a pretty good estimate for how long NR16020 would float.
----------------------------------------------

BTW, I worked on a case in which a Navajo ditched just off shore of Hilo, it sank in about one minute taking one passenger to the bottom of the ocean. One engine had failed and the plane wouldn't maintain altitude on the remaining engine although it should have been able to, since the single engine service ceiling was about 8,000 feet at the weight of 7,000 pounds, so this did not make any sense. We found out the reason when we took the deposition of the mechanic. It turned out he had not used the proper procedure in adjusting the wastegate controller which then prevented the good engine from actually producing full power.

See:
http://dms.ntsb.gov/aviation/AccidentReports/gsoirwf4xfbwxlflxz02foj21/O10182011120000.pdf

gl

...or at least what you got out of the mechanic was not 'inconsistent with' what happened... but it's hardly 'proof'.

Sounds like your 'proof' is still on the ocean floor, but that you were able to make your case via preponderance. 

Some days that's the best one can do.

I rest.
---------------------------

The proof was when we had our mechanic expert adjust the wastegate controller on an exemplar engine using the procedure described by the A&P who had worked on the accident plane and then test running the exemplar and determining that it put out significantly less power than it should have. Lycoming's engineers also testified the same way.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 25, 2011, 12:46:44 PM
Thanks Gary.  Very interesting.  The pilot did a beautiful job. 
So a low wing, twin engined airplane with empty long-range ferry tanks in the cabin (safe assumption) remained afloat for 15 minutes after a well-executed ditching.

A Lockheed 10E with standard in-the-wings tanks ditched off Cape Cod in 1967 and remained afloat for 8 minutes.  In each case we're probably looking at the amount of time it took for the tanks to loose their buoyancy.

The Cessna 310, although smaller than an Electra, should be roughly proportional in terms of weight versus buoyancy.  I think 15 minutes is a pretty good estimate for how long NR16020 would float.
----------------------------------------------

BTW, I worked on a case in which a Navajo ditched just off shore of Hilo, it sank in about one minute taking one passenger to the bottom of the ocean. One engine had failed and the plane wouldn't maintain altitude on the remaining engine although it should have been able to, since the single engine service ceiling was about 8,000 feet at the weight of 7,000 pounds, so this did not make any sense. We found out the reason when we took the deposition of the mechanic. It turned out he had not used the proper procedure in adjusting the wastegate controller which then prevented the good engine from actually producing full power.

See:
http://dms.ntsb.gov/aviation/AccidentReports/gsoirwf4xfbwxlflxz02foj21/O10182011120000.pdf

gl

...or at least what you got out of the mechanic was not 'inconsistent with' what happened... but it's hardly 'proof'.

Sounds like your 'proof' is still on the ocean floor, but that you were able to make your case via preponderance. 

Some days that's the best one can do.

I rest.
---------------------------

The proof was when we had our mechanic expert adjust the wastegate controller on an exemplar engine using the procedure described by the A&P who had worked on the accident plane and then test running the exemplar and determining that it put out significantly less power than it should have. Lycoming's engineers also testified the same way.

gl

You certainly proved that was ONE WAY to get that particular result - and kudos, perhaps it was the most LIKELY way -

Just as TIGHAR has made a most credible case regarding the AE disappearance... except TIGHAR seems to hold more probable physical evidence today than you managed to regain from the Navajo, and has done so before what is likely a far more technically-critical and qualified 'jury' than the typical civil case would face ;D

Now maybe you can understand how TIGHAR has won the positive opinion of so many of us.

LTM -
----------------------
Since a Navajo flies fine on one engine  (especially at sea level, I have quite a few hours in them) the other possibility was that the pilot did not use the proper procedure in dealing with the loss of the engine, which was our first thought. But the wreckage was recovered and the prop was feathered and the pilot described using the correct procedure. It wasn't until we took the deposition of the A&P that we got the clue to the actual cause which was confirmed by testing.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 25, 2011, 03:21:09 PM
Since the photos of the tanks appear to show all of the vent lines manifolded together, an air leak in any one tank would allow air to escape from all of the tanks, through the vent lines to the damaged tank.  This also assumes the external vent is line is routed to the bottom of the aircraft.  If it's out the top, then nothing will prevent the tanks from filling or crushing.

Gary wrote"...This means that it would take damaging many of the tanks to make the plane sink.", to which I would add "...to sink quickly", but even a single damaged tank would eventually result in sinking, if the tank vents are indeed all manifolded together.

Assuming any initial submersion does not generate any significant pressure in the the tanks, and assuming one vent line is open to the atmosphere, and assuming 1/2 inch ID vent line, how long would the tanks provide net positive buoyancy?  At a modest 125 ft/sec velocity of escaping air (a bit faster than the maximum recommended velocity in compressed-air systems), through a single 1/2 inch diameter tube, it would take about 17 minutes for 1251 gallons/167 cu.ft of air to escape.  To just reach zero net buoyancy only needs the loss of 393 gallons/53cu.ft, which would take just 5 minutes.

It seems unlikely that a tank could be ruptured by any successful landing, so there would be no obvious way for the tanks to lose their buoyancy unless the vent(s) were open to atmosphere somehow.  If the vents were in the top of the aircraft, and if the tanks could flood or crush, then the a/c might be expected to lose buoyancy and sink within a very short time/distance.  If the vents were in the bottom, or otherwise not open to the atmosphere, then the tanks might provide buoyancy indefinitely.

Knowing where the vent was located might narrow the search area significantly.

Where are the best photos to study that might show vent locations?
---------------------------
It looks like possible vent lines along the bottom of the cabin in the attached photo.

gl


Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 25, 2011, 07:48:50 PM
It looks like possible vent lines along the bottom of the cabin in the attached photo.

Gary,

If you're talking about the two lines in the photo that run along the starboard wall below the pelorus, I think you'll find that they're electrical cables--typically shown as connecting to the auxiliary battery.

See the attached photo for how the cabin tank venting was arranged--at least early on. There are port and starboard vent manifolds, the aft ends of which bend downwards 90 degrees. Each of the four transverse tanks has a pair of vent lines; one connecting to the port manifold, the other to the starboard manifold. The port and starboard tanks forward of the transverse tanks each have a single connection to a manifold.

Chuck 
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 25, 2011, 09:16:10 PM
It looks like possible vent lines along the bottom of the cabin in the attached photo.

Gary,

If you're talking about the two lines in the photo that run along the starboard wall below the pelorus, I think you'll find that they're electrical cables--typically shown as connecting to the auxiliary battery.

See the attached photo for how the cabin tank venting was arranged--at least early on. There are port and starboard vent manifolds, the aft ends of which bend downwards 90 degrees. Each of the four transverse tanks has a pair of vent lines; one connecting to the port manifold, the other to the starboard manifold. The port and starboard tanks forward of the transverse tanks each have a single connection to a manifold.

Chuck
------------------------

There is also this diagram that appears to show the same arrangement with the vent lines going down to the floor aft of the last fuel tank. This photo also shows the vent lines. I have attached a second photo showing Manning doing some plotting. Is that a vent line running under the platform along the left side of the cabin?

gl

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 25, 2011, 10:50:02 PM
It looks like possible vent lines along the bottom of the cabin in the attached photo.

Gary,

If you're talking about the two lines in the photo that run along the starboard wall below the pelorus, I think you'll find that they're electrical cables--typically shown as connecting to the auxiliary battery.

See the attached photo for how the cabin tank venting was arranged--at least early on. There are port and starboard vent manifolds, the aft ends of which bend downwards 90 degrees. Each of the four transverse tanks has a pair of vent lines; one connecting to the port manifold, the other to the starboard manifold. The port and starboard tanks forward of the transverse tanks each have a single connection to a manifold.

Chuck
------------------------

There is also this diagram that appears to show the same arrangement with the vent lines going down to the floor aft of the last fuel tank. This photo also shows the vent lines.

gl

gl
-------------------
I have attached a frame from a movie showing the plane taking off. You can see three objects projecting from the belly aft of the trailing edge of the wing.  Two are rear antenna masts for the two belly antennas but the third may be the vent line or possibly the mast for the longwire antenna. Any idea which is correct?
gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 26, 2011, 06:58:38 AM
The Aircraft-diagram clearly depicts the manifolded vents connecting the extra fuel tanks along their tops.  The one shown turns down and disappears from view behind the aft-end of the tanks.  This would be consistant with the idea that they eventually route to the bottom of the a/c, approximately in the vicinity of the mystery projections apparent in the PDVD_009 video still.
Also, The amelia-earhart-equipment_tn photo shows what appear to be the port and starboard vent lines routing to the tops of the two tanks on either side of her, but not visibly connecting to any external vent(s) at those ends.  It is not shown whether the filler connections(?) for those two tanks are external through the upper skin, nor whether such fillers had vented caps.  In an earlier post I refered to those tanks as "header tanks".  They are also shown in the Aircraft-diagram, the port one even showing the vent line connection, as well as what appears to be an access cover over the filller neck.  I've seen no protruberances in photos in those areas, so I assume the access covers are flush, and the filler neck ends are in boxed assemblies, similar to the sider filler arrangements on the aux. tanks. Such "boxes" are barely visible in the Aircraft-diagram drawing, but not in the photo.  The inside surface of the fuselage above AE appears to be covered in fabric, which may hide any box structure.  Would it be likely that the covered filler ends or the "boxes" were connected to the vent lines, providing a vent to the atmosphere in the top of the a/c?  Then what does the aft line connect to?
I'd conclude from these photos and drawings that the most likely vent location for the extra tanks was through the bottom of the fuselage.
While studying the photos (btw, thanks for posting them gary and chuck), the visible surface of the aft-most tank can be clearly seen to be dented and bulged, giving the impression of very light-gage sheet metal construction.  Rivets connecting the skin to their internal structure are clearly visible.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 07:19:56 AM
These are valuable discussions.  I'm going to post a number of photos that should help us answer some important questions.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Friend Weller on October 26, 2011, 07:48:36 AM
All,

I hope I haven't overlooked this already being mentioned and if so, apologies in advance.  That said, it was mentioned by John that the interior of the aircraft appears to be covered by some sort of fabric as seen in the amelia-earhart-equipment_tn photo.  Compare that to the vent_lines photo posted by Chuck where the "fabric" does not appear to be installed as the bulkheads/formers are clearly visible.  I wonder which of these photos was taken earlier and/or if the fabric was removed as a lightening measure after the Luke Field accident.  Vent lines aside, perhaps this might provide insight into modifications made before the 2nd World flight attempt.

LTM,
Friend
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 07:56:07 AM
There is also this diagram that appears to show the same arrangement with the vent lines going down to the floor aft of the last fuel tank. This photo also shows the vent lines.

Gary,

Yes. (There’s a color illustration in Women Aloft on pp130-131 identical to your drawing.)

I’ve attached a larger version of your Amelia-in-cabin photo (yours, BTW, is a .png file mislabeled as a .jpg).

Quote
I have attached a second photo showing Manning doing some plotting. Is that a vent line running under the platform along the left side of the cabin?

I can’t say for certain, but I doubt it, as the vertical runs from the aft ends of the manifolds lie between the cabin liner and skin. (I’ve attached a copy of your compressed Manning photo, stretched to approximately the right proportion.)

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 08:02:11 AM
I have attached a frame from a movie showing the plane taking off. You can see three objects projecting from the belly aft of the trailing edge of the wing.  Two are rear antenna masts for the two belly antennas but the third may be the vent line or possibly the mast for the longwire antenna. Any idea which is correct?

Gary,

The third item is the trailing wire antenna "fish" (antenna weight) stowed in the fairlead (an insulated tube through which the antenna wire passes).

I've attached a stretched version of your photo.

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 08:06:47 AM

I hope I haven't overlooked this already being mentioned and if so, apologies in advance.  That said, it was mentioned by John that the interior of the aircraft appears to be covered by some sort of fabric as seen in the amelia-earhart-equipment_tn photo.  Compare that to the vent_lines photo posted by Chuck where the "fabric" does not appear to be installed as the bulkheads/formers are clearly visible.  I wonder which of these photos was taken earlier and/or if the fabric was removed as a lightening measure after the Luke Field accident.

Friend,

In the photos that have been posted so far, the without-liner photos are earlier than the with-liner photos.

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 08:22:43 AM
I wonder which of these photos was taken earlier and/or if the fabric was removed as a lightening measure after the Luke Field accident.  Vent lines aside, perhaps this might provide insight into modifications made before the 2nd World flight attempt.

It's the other way around.  The photo without the fabric is quite early - probably August or September 1936.  Initially they tried to use a manifold system for filling the fuselage tanks.  Note that there is no filler neck over the starboard 118 gallon tank forward and only two fueling ports on the port side of the cabin.  Later they gave each tank its own fueling port.

Dating the various photos of the cabin interior is important - and tricky.  The aircraft went though many changes in the year between its delivery in July '36 and its disappearance in July '37.  The fuel system was jiggered around, radios and antennas came and went, interior furnishing were added and removed.  Many photos were taken of preparations for the first world flight attempt because Earhart was courting publicity.  Unfortunately, there are no known photos of the cockpit or cabin interior after the April/May repairs.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 08:30:52 AM
The amelia-earhart-equipment_tn photo shows what appear to be the port and starboard vent lines routing to the tops of the two tanks on either side of her, but not visibly connecting to any external vent(s) at those ends.  It is not shown whether the filler connections(?) for those two tanks are external through the upper skin, nor whether such fillers had vented caps.

John,

I think you'll be able to see in the larger version of the subject photo that I posted with Reply #30 that the vent lines from the tops of your "header tanks" connect to the forward ends of their respective vent manifolds, and that both tanks have filler necks accessed externally from above.

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 08:49:34 AM
I think you'll be able to see in the larger version of the subject photo that I posted with Reply #30 that the vent lines from the tops of your "header tanks" connect to the forward ends of their respective vent manifolds, and that both tanks have filler necks accessed externally from above.

Chuck,

I agree.

Next question.  If the manifolds along the cabin walls are vents for the tanks (and I can't imagine what else they would be), why both sides?  Why two vents on each tank?
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Friend Weller on October 26, 2011, 08:56:25 AM
Chuck, Ric:

"Without fabric" preceding "with fabric" makes perfect sense as I initially thought about the need/desire for "under construction" photos during the pre-flight publicity timeframe yet also knowing that various changes and lightening measures took place during the rebuild is what raised the question in my mind.  I was unaware (or had inadvertently overlooked the fact) that no interior photos were taken after the Luke Field accident.  Thanks to both of you for the clarification....and your patience!

LTM,
Friend
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 10:45:50 AM
Next question.  If the manifolds along the cabin walls are vents for the tanks (and I can't imagine what else they would be), why both sides?  Why two vents on each tank?

Ric,

I don't know what drove the designers, but the scheme interconnects all six tanks without running any vent plumbing across the fuselage width, and it (presumably) provides two dump ports to the outside that are separated by about a fuselage width. In the event that one of those ports were obstructed, all six tanks still have a vent path to the outside.

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 11:49:41 AM
I don't know what drove the designers, but the scheme interconnects all six tanks without running any vent plumbing across the fuselage width, and it (presumably) provides two dump ports to the outside that are separated by about a fuselage width. In the event that one of those ports were obstructed, all six tanks still have a vent path to the outside.

By "dump ports" I assume you mean unobstructed outlets to the outside so that air can flow in to replace the fuel as it is fed to the engines.  If that is the case, it would appear that the dump ports were co-located with the filler ports for the two tall 118 gallon tanks at the forward end of the cabin. 
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Chuck Varney on October 26, 2011, 12:41:02 PM
By "dump ports" I assume you mean unobstructed outlets to the outside so that air can flow in to replace the fuel as it is fed to the engines.

Ric,

Yes--or to allow venting air from the tanks while filling them, or venting fumes from filled tanks, which is the mind set I had when I wrote that. I should have simply called them "ports".

Chuck
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 05:19:24 PM
Nice system redundancy for venting the tanks but if the airplane goes in the drink it's a quick trip to Davey Jones Locker.  The airplane is going to float nose down and the dual vents provide an open hole for water to go in and another open hole for air to get out.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 05:52:01 PM
Nice system redundancy for venting the tanks but if the airplane goes in the drink it's a quick trip to Davey Jones Locker.  The airplane is going to float nose down and the dual vents provide an open hole for water to go in and another open hole for air to get out.
--------------------------------------------
Two problems with that. First, if they came out even with each other then no water would flow through the vent lines. But the biggest problem with that is that the vent lines go up over the tanks, well above the waterline of the nose down illustration in your book so no water is going to flow uphill to get above the fuel tanks.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 06:13:32 PM
It looks like possible vent lines along the bottom of the cabin in the attached photo.

Gary,

If you're talking about the two lines in the photo that run along the starboard wall below the pelorus, I think you'll find that they're electrical cables--typically shown as connecting to the auxiliary battery.

See the attached photo for how the cabin tank venting was arranged--at least early on. There are port and starboard vent manifolds, the aft ends of which bend downwards 90 degrees. Each of the four transverse tanks has a pair of vent lines; one connecting to the port manifold, the other to the starboard manifold. The port and starboard tanks forward of the transverse tanks each have a single connection to a manifold.

Chuck
--------------------------
This is obviously an early picture and the filler neck has not yet been installed for the starboard 118 gallon forward tank. This filler neck is visible in the other pictures.
I suspect that the caps for the filler necks are the type of airplane gas caps that when you turn the center knob the gasket expands radially to seal the filler neck. Ric, do you have any information on the gas caps?

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 06:16:40 PM
By "dump ports" I assume you mean unobstructed outlets to the outside so that air can flow in to replace the fuel as it is fed to the engines.

Ric,

Yes--or to allow venting air from the tanks while filling them, or venting fumes from filled tanks, which is the mind set I had when I wrote that. I should have simply called them "ports".

Chuck
-------------------------
And it is not allowable by today's regulations, and presumably not by the 1937 regulations either, to allow any venting inside the cabin.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 06:24:32 PM
Gary - thankyou for catching my errors.  I respondeded too quickly and didn't take the time to read your analysis carefully, or to check my own figures - my bad.  You're right that the tanks would need an entry, as well as an exit to fill with water.  I'm not convinced they would withstand crushing, but only because I'm ignorant of the design of their internal bracing.  I've seen many examples of slab-sided tanks that begin to crush at trivial pressures - a foot of water depth is suffiicient in some cases, yet only develops about 1/2 psi.  There are a lot of square inches being pushed upon, and the skin and bracing were not designed with external pressure in mind. Internal baffles for example are simply flat metal sheets spanning the tank width in several places.  Holes in the baffles allow slow liquid flow and reduce weight.  Forces from the action of fuel (sloshing, sudden deceleration, turbulence, etc) are resisted by shear and tension in the baffles.  There are no significant compression loads on the baffles in normal operation.  A flat sheet with holes in it is not capable of withstanding significant compression loads without buckling.  If the baffles have stiffening features, then they can resist buckling and can carry compression loads.  I'm anxious to learn more about the tank design, since it might be important to define the search area. 

I'm inclined to assume the internal bracing of the extra tanks used simple flat sheets with lightning holes, welded or riveted to the skins. Such a design provides almost no resistance to crushing by submersion in water, but the displaced air would still need to escape for the a/c to sink.

As Ric points out, there was a tradition of an airplane wreck on the reef at one time.  What is known about the ways aircraft breakup on reefs over time?  Surely it wouldn't take much wave and wind action to move an aircraft around on the reef - one modest storm would be enough.  What would be damaged first  - the landing gear getting caught in a crack, anchoring it to one spot?  If so, then the aircraft would "weather-vane" about the stuck wheel, damaging the attach points and nearby structure.  At what point are the empty fuel tanks compromised to an extent they can't float the wreckage?  They would seem to be well protected inside the main fuselage. Would it take a year or two of constant saltwater exposure and pounding by waves to break the stuck parts free of the main body, which then floats away?  I'm guessing something like that could happen, implying there might only be a few pieces deposited near the reef - the larger pieces containing the buoyant tanks might have drifted miles away.

-----------------------

Looking at the rivet pattern  in the rearmost fuel tank visible in the posted photos it appears that there was quite a bit of stuff inside the tanks including baffles that kept the fuel from sloshing side to side. Such baffles would probably resist crushing of the fuel tanks.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 06:57:18 PM
Two problems with that. First, if they came out even with each other then no water would flow through the vent lines. But the biggest problem with that is that the vent lines go up over the tanks, well above the waterline of the nose down illustration in your book so no water is going to flow uphill to get above the fuel tanks.

We're not talking about an airplane in a swimming pool.  We're talking about an airplane being bashed about in the surf at the reef edge, caught between conflicting forces - the waves refracting around the NW tip of the island and driving southwestward (that's what knocked it off its gear and pushed it over the edge) and the swells rolling in from the west, pushing it eastward against the reef edge.  It's an extremely violent environment.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 06:58:36 PM
Ric, do you have any information on the gas caps?

No.  Wish I did.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 07:00:11 PM
By "dump ports" I assume you mean unobstructed outlets to the outside so that air can flow in to replace the fuel as it is fed to the engines.

Ric,

Yes--or to allow venting air from the tanks while filling them, or venting fumes from filled tanks, which is the mind set I had when I wrote that. I should have simply called them "ports".

Chuck
-------------------------
And it is not allowable by today's regulations, and presumably not by the 1937 regulations either, to allow any venting inside the cabin.

gl

I don't think Chuck was implying that the tanks vented into the cabin.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 08:47:16 PM
Two problems with that. First, if they came out even with each other then no water would flow through the vent lines. But the biggest problem with that is that the vent lines go up over the tanks, well above the waterline of the nose down illustration in your book so no water is going to flow uphill to get above the fuel tanks.

We're not talking about an airplane in a swimming pool.  We're talking about an airplane being bashed about in the surf at the reef edge, caught between conflicting forces - the waves refracting around the NW tip of the island and driving southwestward (that's what knocked it off its gear and pushed it over the edge) and the swells rolling in from the west, pushing it eastward against the reef edge.  It's an extremely violent environment.
----------------
So, water still ain't going to flow uphill.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 09:01:19 PM
I wonder which of these photos was taken earlier and/or if the fabric was removed as a lightening measure after the Luke Field accident.  Vent lines aside, perhaps this might provide insight into modifications made before the 2nd World flight attempt.

It's the other way around.  The photo without the fabric is quite early - probably August or September 1936.  Initially they tried to use a manifold system for filling the fuselage tanks.  Note that there is no filler neck over the starboard 118 gallon tank forward and only two fueling ports on the port side of the cabin. Later they gave each tank its own fueling port.

Dating the various photos of the cabin interior is important - and tricky.  The aircraft went though many changes in the year between its delivery in July '36 and its disappearance in July '37.  The fuel system was jiggered around, radios and antennas came and went, interior furnishing were added and removed.  Many photos were taken of preparations for the first world flight attempt because Earhart was courting publicity.  Unfortunately, there are no known photos of the cockpit or cabin interior after the April/May repairs.
---------------------
The tanks were just being installed and the filler neck for the starboard 118 gallon tank had not yet been installed, it is visible in  the other photos.
I am attaching two diagrams of the tanks filling setup.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 09:13:56 PM
The tanks were just being installed and the filler neck for the starboard 118 gallon tank had not yet been installed, it is visible in  the other photos.
I am attaching two diagrams of the tanks filling setup.

As I said, initially they tried to use a manifold system for filling the fuselage tanks.  The airplane was delivered with only one fueling port on the top of the fuselage and two on the left-hand side of the cabin.  Apparently if didn't work well and they gave each tank its own port.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 26, 2011, 09:15:44 PM
So, water still ain't going to flow uphill.

It doesn't need to if waves are breaking over the airplane.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 26, 2011, 09:31:09 PM
Most vehicle fuel tanks with sealed filler caps and flat-top construction have two vent locations in my limited experience, connecting to opposite sides or ends, and commonly opposite corners. Alternatives are to have a vapor dome, or curve the top of the tank with the vent at the highest point, or route a single vent line to a small header tank with it's own vent arrangement.  Here's why flat top tanks benefit from two vents:
Imagine a tank almost completely filled with cool gasoline.  If the port wing is a little bit low, the tank will also have a bit of a tilt.  The port vent connection on the tank will be submerged in gas, while the starboard one is above the liquid level. Now warm the fuel slightly, so it expands a bit.  If there were only one vent on the port side, then the warming and expanding liquid gasoline would be pushed out the vent, even though there is some room left in the tank.  With two vents, there is always some room to expand at one of the vent locations, unless the tank is 100% full. In that case, with luck, the manifold will route any displaced gasoline into another tank, rather than on the ground.

Wasn't "gas on the ground" one of the 3 useless things, along with altitude above you, and runway behind you?
The pictures are a big help.  I've got to get the CD's as soon as my membership arrives.

Regarding the tank internal bracing - lots of rivets do indicate lots of internal structure.  If the apparant thinness of the outer surface is an indication, the internal bracing may also be equally thin.  That works fine for holding fuel in, but not resisting external pressure.  Any internal structure is certain to be heavier than foil, but not much more.  I hope to find some contemporary tank construction for simple analysis.  Until we know for sure how the tanks were made, it's only conjecture how they would respond to submersion.  With vent lines out the bottom, trapping the air inside them, intact tanks would offer a LOT of excess buoyancy, even if they partially crushed until pressure was equalized.  In that case they would be metal balloons.  However, if the plane tried to float nose-down, as Ric suggested, then the vent lines exiting from the belly behind them would be "above" the tanks.  If the tanks crushed, then they would "deflate" and quickly lose all buoyancy as the air escaped through the vent line.  If they stayed "inflated" due to strong internal bracing as Gary suggests, then they would continued to provide a lot of excess buoyancy even if vented to the open air.
If the plane was banged around on the reef, then anything might have happened, but damage would be certain.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 09:36:49 PM
So, water still ain't going to flow uphill.

It doesn't need to if waves are breaking over the airplane.
-----------------------------
Get one of those straws that bend in the middle, bend it into an "L" shape, hold it with the bend uppermost, immerse the whole straw to simulate waves splashing higher than the vent lines, observe if any water flows up through the straw and over the bend in the middle. You can also slosh the water in the sink at the same time.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 26, 2011, 09:50:40 PM
Most vehicle fuel tanks with sealed filler caps and flat-top construction have two vent locations in my limited experience, connecting to opposite sides or ends, and commonly opposite corners. Alternatives are to have a vapor dome, or curve the top of the tank with the vent at the highest point, or route a single vent line to a small header tank with it's own vent arrangement.  Here's why flat top tanks benefit from two vents:
Imagine a tank almost completely filled with cool gasoline.  If the port wing is a little bit low, the tank will also have a bit of a tilt.  The port vent connection on the tank will be submerged in gas, while the starboard one is above the liquid level. Now warm the fuel slightly, so it expands a bit.  If there were only one vent on the port side, then the warming and expanding liquid gasoline would be pushed out the vent, even though there is some room left in the tank.  With two vents, there is always some room to expand at one of the vent locations, unless the tank is 100% full. In that case, with luck, the manifold will route any displaced gasoline into another tank, rather than on the ground.

Wasn't "gas on the ground" one of the 3 useless things, along with altitude above you, and runway behind you?
The pictures are a big help.  I've got to get the CD's as soon as my membership arrives.

Regarding the tank internal bracing - lots of rivets do indicate lots of internal structure.  If the apparant thinness of the outer surface is an indication, the internal bracing may also be equally thin.  That works fine for holding fuel in, but not resisting external pressure.  Any internal structure is certain to be heavier than foil, but not much more.  I hope to find some contemporary tank construction for simple analysis.  Until we know for sure how the tanks were made, it's only conjecture how they would respond to submersion.  With vent lines out the bottom, trapping the air inside them, intact tanks would offer a LOT of excess buoyancy, even if they partially crushed until pressure was equalized.  In that case they would be metal balloons.  However, if the plane tried to float nose-down, as Ric suggested, then the vent lines exiting from the belly behind them would be "above" the tanks.  If the tanks crushed, then they would "deflate" and quickly lose all buoyancy as the air escaped through the vent line.  If they stayed "inflated" due to strong internal bracing as Gary suggests, then they would continued to provide a lot of excess buoyancy even if vented to the open air.
If the plane was banged around on the reef, then anything might have happened, but damage would be certain.
----------------------------------------
I don't know what it looks like inside those tanks but I am going with the theory that the vertical rows of rivets indicates a baffle to stop right to left sloshing that would resist some level of compressive load from the front and back of the tank.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 27, 2011, 06:58:12 AM
Gary sez: "... the vertical rows of rivets indicates a baffle to stop right to left sloshing..."

I agree.  Also the pictures clearly show the several round plugs where access was had to the tank interiors.  Those round holes were necessary to contruct the tanks, especially when bucking rivets - you need access to both ends of a rivet (except with modern Cherry "pop" rivets or explosive rivets).  The holes were then sealed with a circular plug that fit from the inside of the tank.  Those plugs had a "lip" that was a bit bigger than the hole, so internal pressure helped hold them in place.  The ones I've seen were soldered or welded in place, and not removable.  They also would not pop into the tank from external pressure, although they weren't quite as strong as a tank wall that had no hole in it. 
I'm curious what the tanks material was - aluminum, or tern, or stainless steel?  I haven't stumbled across any references.  A SS tank would survive in salt water just fine. Tern might last nearly as long.  The vent lines might be SS, in which case they would remain after the aluminum fuselage dissolved.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 27, 2011, 01:27:29 PM
Tern might last nearly as long. 

What is tern?

The vent lines might be SS, in which case they would remain after the aluminum fuselage dissolved.

Aluminum aircraft immersed in salt water don't "dissolve."  They corrode (quickly and badly) when recovered if not properly conserved but aircraft underwater hold up quite well.  The deeper the better.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 27, 2011, 02:31:53 PM
Stainless is a posssibility - but I believe NR16020's tanks would have not been a strong candidate for that in the 1930's.  Welded / spot-welded construction would be more the norm for stainless, not the riveted / welded construction type we see in NR16020. 
I am not so familiar with the use of terne metal except that I think it commonly refers to terne-cladded copper and stainless sheet.

Wouldn't any those materials be a LOT heavier than 1100 aluminum?

Vents do not themselves allow a dramatic exchange of liquid - it takes time since they are relatively small and meant to allow for the evacuation of fuel at normal burn rates plus some margin by permitting the flow of fluid (air) into the space as liguid leaves.  But, they DO allow fluid to move readily once there is any substantial breach by allowing the relatively rapid expulsion of air - another possibility to consider; if a tank (or tanks) shifted during a hard landing, crash or during abuse in the surf, enough breach(es) could occur to allow a great deal of water into the tanks fairly quickly.

Here's another thought.  There were multiple fuselage tanks, rather than one big one, because they had to fit through the cabin door.  The tanks were anchored to the floor - or rather to the structure under the plywood floor - by means of what appear to be thin metal rods with dark felt?, leather?, or rubber? padding between the tanks and the rods.  The system for securing the tanks in the cabin was, logically, designed to keep the tanks from shifting in flight.  Just as logically, the system was not designed for the tanks to be flotation devices with the weight of the aircraft suspended from the rods.

If the aircraft floated nose down with the tanks providing the buoyancy, it seems like there would be tremendous tension upward and rearward on the rods. If the tanks buckled under the rods or the rods cut through the padding into the tank it would be Katie-Bar-The-Door.  If the rod anchors failed, the tanks would probably tear loose from the vents and filler necks and pile up in the rear of the cabin with equally entertaining results.
 [/quote]

It would be good to have a breakthrough in finding the technical details on NR16020's tanks somehow - it could tell us a great deal about how the ship might have behaved with a low-fuel state in water, heavy surf, etc.

The only paperwork on the Earhart Electra that has surfaced is what the FAA has - and it's not much.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 27, 2011, 03:44:03 PM
Terne plate was a common gas tank material at one time, I'd guess roughly before 1960.  In my experience, it refers to light gage sheet steel with a lead or lead/tin coating, although I've also seen it used in reference to a copper tubing coating.  The coating made it non-sparking, and easy to fabricate by soldering or welding.  The steel used underneath was dead-soft/low-alloy, making it very easy to form, especially deep-drawing.  My experience is with old farm equipment with Terne-plate tanks.  As long as the coating held up, they didn’t rust or corrode.  Unlike galvanizing though, scratches weren’t self-healing, and the coating wasn’t very abrasion resistant – they’d rust through in a year once the steel was exposed.  My strongest suspicion is that the fuselage tanks are soft aluminum, and pretty thin at that, to save weight.  Besides, Northrop is good at fabricating things out of aluminum.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 27, 2011, 06:37:49 PM
Most vehicle fuel tanks with sealed filler caps and flat-top construction have two vent locations in my limited experience, connecting to opposite sides or ends, and commonly opposite corners. Alternatives are to have a vapor dome, or curve the top of the tank with the vent at the highest point, or route a single vent line to a small header tank with it's own vent arrangement.  Here's why flat top tanks benefit from two vents:
Imagine a tank almost completely filled with cool gasoline.  If the port wing is a little bit low, the tank will also have a bit of a tilt.  The port vent connection on the tank will be submerged in gas, while the starboard one is above the liquid level. Now warm the fuel slightly, so it expands a bit.  If there were only one vent on the port side, then the warming and expanding liquid gasoline would be pushed out the vent, even though there is some room left in the tank.  With two vents, there is always some room to expand at one of the vent locations, unless the tank is 100% full. In that case, with luck, the manifold will route any displaced gasoline into another tank, rather than on the ground.

Wasn't "gas on the ground" one of the 3 useless things, along with altitude above you, and runway behind you?
The pictures are a big help.  I've got to get the CD's as soon as my membership arrives.

Regarding the tank internal bracing - lots of rivets do indicate lots of internal structure.  If the apparant thinness of the outer surface is an indication, the internal bracing may also be equally thin.  That works fine for holding fuel in, but not resisting external pressure.  Any internal structure is certain to be heavier than foil, but not much more.  I hope to find some contemporary tank construction for simple analysis.  Until we know for sure how the tanks were made, it's only conjecture how they would respond to submersion.  With vent lines out the bottom, trapping the air inside them, intact tanks would offer a LOT of excess buoyancy, even if they partially crushed until pressure was equalized.  In that case they would be metal balloons.  However, if the plane tried to float nose-down, as Ric suggested, then the vent lines exiting from the belly behind them would be "above" the tanks.  If the tanks crushed, then they would "deflate" and quickly lose all buoyancy as the air escaped through the vent line.  If they stayed "inflated" due to strong internal bracing as Gary suggests, then they would continued to provide a lot of excess buoyancy even if vented to the open air.
If the plane was banged around on the reef, then anything might have happened, but damage would be certain.
-------------------
The regulations in 1937 required that the tank withstand an internal pressure of 3.5 pounds per square inch. Although this is from the inside pushing out it is also possible that material that can deal with this much internal pressure might be strong enough to withstand pressure from the outside too that is only about half as much, and not collapse like a balloon.
gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 27, 2011, 06:46:24 PM
Gary sez: "... the vertical rows of rivets indicates a baffle to stop right to left sloshing..."

I agree.  Also the pictures clearly show the several round plugs where access was had to the tank interiors.  Those round holes were necessary to contruct the tanks, especially when bucking rivets - you need access to both ends of a rivet (except with modern Cherry "pop" rivets or explosive rivets).  The holes were then sealed with a circular plug that fit from the inside of the tank.  Those plugs had a "lip" that was a bit bigger than the hole, so internal pressure helped hold them in place.  The ones I've seen were soldered or welded in place, and not removable.  They also would not pop into the tank from external pressure, although they weren't quite as strong as a tank wall that had no hole in it. 
I'm curious what the tanks material was - aluminum, or tern, or stainless steel?  I haven't stumbled across any references.  A SS tank would survive in salt water just fine. Tern might last nearly as long.  The vent lines might be SS, in which case they would remain after the aluminum fuselage dissolved.

It would be very useful to know what the tanks on NR16020 were made of and how they were constructed. 

In mulling over these posts, I'd like to share a bit of thought from experience -

It is not unheard of to find older airplane tanks made of 1100 aluminum alloy in "0" (annealed) state.  Large "A" (1100 - "soft") rivets were also commonly used in such tanks - they are more compatible with the soft base material in terms of being worked (bucked) and relative strength.  The large size of the rivets also is compatible in terms of the needed bearing area in soft material.  The 1100 "0" state aluminum also allows easy welding of apertures for fittings, etc. during the build process very readily.  1100 can also be very corrosion resistent since it has little alloy inclusion in it. 

These tanks have the appearance of such construction in the photos but we can't know for certain without more information. 

Stainless is a posssibility - but I believe NR16020's tanks would have not been a strong candidate for that in the 1930's.  Welded / spot-welded construction would be more the norm for stainless, not the riveted / welded construction type we see in NR16020. 

I am not so familiar with the use of terne metal except that I think it commonly refers to terne-cladded copper and stainless sheet.  My understanding also is that terne metal has to be painted to effectively weather the elements, but that it lasts well with an organic coating.  I am familiar with 'metalizing', i.e. the application of a soft 1100-type aluminum to steel parts such as naval aircraft cylinders to protect them from the elements, but do not know of terne metal being used in aviation per se.

It cannot be said for certain what the tanks were made of without real records, but I know from experience you cannot easily buck large, hard rivets (like big brazier head 2117s or similar of the day) that I see in these pictures without severly deforming and tearing the base material.  It is also possible that soft-state tanks could be heat-treated after construction (if other alloy than 1100 which doesn't heat treat so well), but the size of these tanks could have made that problematic.  Heat treatment proably would not be necessary for the use such tanks would see anyway.

It is entirely possible that the tanks were of soft material and considered adequate for their specialized, limited use.  If they were, they could have been quite crushable under pressure - even with baffling within.  The large surface area means you could generate substantial crushing forces at relatively meager pressures per square inch. 

My experience includes outfitting a certain large-cabin business jet with large, temporary in-cabin tanks for an around-the-world record flight - the construction method was quite similar to what I have described and one good reason was ease of manufacture and installation.  Malleable material is easier to work with.  The tanks did not need a long-life - just enough to get them reliably through the intended mission.  Such may well have been the case for NR16020.

Of course we can't know how these things might apply to NR16020 without direct evidence of how they were constructed - that would be good to know, for sure.  It may well have been a factor in how long the ship could have floated after going into the water.

As to the venting, everything I can discern from the pictures and from what I know of tank venting suggests that the vent outlets would have been placed as high as possible on the airframe, not low.  Venting would have also been by the most direct route.  We see vents for wing tanks on top and on the bottom of wings - often both as a redundant means of venting.  Again, it would help to know even gas-cap details - many are vented, and it would not be a surprise to find that NR16020 had vented caps of some sort. 

Vents do not themselves allow a dramatic exchange of liquid - it takes time since they are relatively small and meant to allow for the evacuation of fuel at normal burn rates plus some margin by permitting the flow of fluid (air) into the space as liguid leaves.  But, they DO allow fluid to move readily once there is any substantial breach by allowing the relatively rapid expulsion of air - another possibility to consider; if a tank (or tanks) shifted during a hard landing, crash or during abuse in the surf, enough breach(es) could occur to allow a great deal of water into the tanks fairly quickly.

It would be good to have a breakthrough in finding the technical details on NR16020's tanks somehow - it could tell us a great deal about how the ship might have behaved with a low-fuel state in water, heavy surf, etc.

LTM -

-------------------------
But the hypothesis is that the plane made a normal soft landing on the smooth reef surface, soft enough that the landing gear was not damaged, allowing the engines to be run. At the time of the landing the tanks held very little fuel (and most likely all the cabin tanks were completely empty with the remaining fuel being in the wing tanks) so there should have only been light, normal stresses on the cabin tanks so the tanks should not have suffered any damage during the landing. As for damage by the surf, the cabin tanks were inside the cabin so the cabin itself protected the tanks from dynamic pressure from the waves so, again, unlikely to have suffered any damage.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 27, 2011, 07:35:35 PM
But the hypothesis is that the plane made a normal soft landing on the smooth reef surface, soft enough that the landing gear was not damaged, allowing the engines to be run. At the time of the landing the tanks held very little fuel (and most likely all the cabin tanks were completely empty with the remaining fuel being in the wing tanks) so there should have only been light, normal stresses on the cabin tanks so the tanks should not have suffered any damage during the landing. As for damage by the surf, the cabin tanks were inside the cabin so the cabin itself protected the tanks from dynamic pressure from the waves so, again, unlikely to have suffered any damage.

If tank connections could be dislodged in a hard landing, they could certainly be dislodged by the shock of the aircraft being repeatedly hammered by waves with enough force sufficient to knock it off its gear and drive it over the edge of the reef.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 27, 2011, 11:01:22 PM
But the hypothesis is that the plane made a normal soft landing on the smooth reef surface, soft enough that the landing gear was not damaged, allowing the engines to be run. At the time of the landing the tanks held very little fuel (and most likely all the cabin tanks were completely empty with the remaining fuel being in the wing tanks) so there should have only been light, normal stresses on the cabin tanks so the tanks should not have suffered any damage during the landing. As for damage by the surf, the cabin tanks were inside the cabin so the cabin itself protected the tanks from dynamic pressure from the waves so, again, unlikely to have suffered any damage.

If tank connections could be dislodged in a hard landing, they could certainly be dislodged by the shock of the aircraft being repeatedly hammered by waves with enough force sufficient to knock it off its gear and drive it over the edge of the reef.
----------------------------
I didn't say they could be damaged by a "hard landing," maybe by a crash or a bad ditching. Since they were empty, the fuselage being batted around by waves shouldn't damage the tanks because they would not resist the movement since they were very light so no great inertial forces so again, no damage.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 01:38:10 AM
The only paperwork on the Earhart Electra that has surfaced is what the FAA has - and it's not much.

------------------------------------------------------


Let's do the math. The airplane was produced under Air Bulletin 7a and 26 effective 1934. Using the method provided in those bulletins to calculate the allowable design load factors is more complicated than in the subsequent CAR 3 and in the current FAR part 23 but you end up with the same result plus 3.8 and minus 1.52 Gs. These bulletins also require the same 50% safety margin.
Assume the 149 gallon tanks weighed 100 pounds and were made out of aluminum. Fill them with 149 gallons of aviation gas weighing 894 pounds so the total is 994 pounds. The hold downs will have to be strong enough to keep this tank from displacing upward either due to maneuvering loads or from buoyancy from the immersed empty tank. This must be 1.52 times that total weight or 1511 pounds. Add to this the 50% safety factor and the strength must be, at a minimum, 2266 pounds. And at this load the straps could suffer permanent deformation but would not fail completely even at that load.

 Now let's calculate the maximum buoyancy force that could be created by this empty tank. The buoyancy of the air in the tank is equal to the weight of the water that would have filled the tank. Seawater weighs 8.5 pounds per gallon so the buoyancy of the air in the tank is 1266.5 pounds. To this we must add the buoyancy of the aluminum in the tank itself. The specific gravity of aluminum is 2.7 meaning that it has a density of 2.7 times that of fresh water. So just divide the 100 pounds of aluminum by the specific gravity and you find the buoyancy of the aluminum tank itself. One hundred pounds divided by 2.7 equals 37 pounds of buoyancy in fresh water. Seawater is denser than fresh water by 3% so buoyancy in seawater is 3% greater so the tank makes an upward buoyancy of 38.1 pounds. Add this to the buoyancy of the 149 gallons of air and the total upward force on the tie downs is 1304.6 pounds which is well below the 1511 pounds designed strength of the hold downs and 961 pounds below the strength of the tie downs required by the 50% safety factor. This is a safety margin actually 74% greater than the buoyancy of the fuel tank.

So, the tank tie downs will not fail due to the maximum buoyancy force that could be created by the empty fuel tank. You can work your own examples using different assumptions about the material and the weight of the tank and you will see that no combination comes anywhere close to exceeding the strength of the tie down straps. For instance if the tanks were made out of steel then there would be even less buoyancy and, since the tank would be heavier, then the strength of the tie downs would have to be even stronger so an even greater safety margin would exist.

This computation also shows why the tanks would not have been displaced in a normal or hard landing. The strength of the the tie down in the upward direction 2266 pounds and the assumed weight of the tank is only 100 pounds so it would take more than 22 Gs for an empty tank to displace upward in a crash or hard landing and the strength requirements in other directions are even greater. If the plane had been subjected to 22 Gs when landing on the reef it would not have ended up standing on its own legs so no running engines and no radio messages. It would also take more than 22 Gs from wave impacts to tear the tanks loose so that is not too likely either.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Don Dollinger on October 28, 2011, 09:59:45 AM
Quote
If the plane had been subjected to 22 Gs when landing on the reef it would not have ended up standing on its own legs so no running engines and no radio messages. It would also take more than 22 Gs from wave impacts to tear the tanks loose so that is not too likely either.

But if the wave action ripped at least one of the landing gear struts and wheel assemblies off the electra (the theory has one stuck in a reef groove, later believed to be nessie) would'nt the suspected damage to the underbelly and substructure have to be figured (or at least considered) into this equation as to whether that type of damage would have weakened the area of the attaching points?
 
I think Ric with his aircraft accident investigator experience could provide a fair estimation of whether the stresses caused by that action would or would not weaken that area enough so as to lessen the amounts of force you propose OR is there not enough informatiion as to how they were attached to completely nullify this as part of the equation?

LTM,

Don
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 10:29:28 AM
Quote
If the plane had been subjected to 22 Gs when landing on the reef it would not have ended up standing on its own legs so no running engines and no radio messages. It would also take more than 22 Gs from wave impacts to tear the tanks loose so that is not too likely either.

But if the wave action ripped at least one of the landing gear struts and wheel assemblies off the electra (the theory has one stuck in a reef groove, later believed to be nessie) would'nt the suspected damage to the underbelly and substructure have to be figured (or at least considered) into this equation as to whether that type of damage would have weakened the area of the attaching points?
 
I think Ric with his aircraft accident investigator experience could provide a fair estimation of whether the stresses caused by that action would or would not weaken that area enough so as to lessen the amounts of force you propose OR is there not enough informatiion as to how they were attached to completely nullify this as part of the equation?

LTM,

Don
------------------------------------

I've spent 22 years investigating and litigating airplane crash cases, attended very many wreckage inspections accompanied by my metallurgist, my accident reconstructionist, my aircraft mechanic, engineers, and other appropriate experts and I've looked though many electron microscopes at fracture surfaces. My first college major was Aeronautical Engineering and I also took a course in aircraft accident investigation given jointly by the University of Illinois and the Air Force at Chanute AFB (I got an "A", BTW.) I've cross-examined many adverse expert witnesses on all of these issues and taken the depositions of many NTSB investigators. I'll match my credentials and experience on this against Ric's anytime.
---------------------------------------------

As a humorous side story, I had an experience that only comes along once in a lawyer's lifetime. Many years after taking his course, my accident investigation professor was hired by a plaintiff's attorney as an accident reconstructionist expert (my prof was also an A&P and an IA) so I had to take his deposition in San Francisco. After I got his "creative" sworn testimony recorded by the court reporter, I reached into my briefcase and took out a blue covered book, I still have it
.
"Do you recognize this book professor?"
"Yes I do."
"Its title is 'Aircraft Accident Investigation, Aviation 355,' isn't it?"
"Yes."
"Who wrote this book?"
"I did."
"Look at the last paragraph on page 314."
"O.K."
"Did you write that paragraph?"
"Yes."
"Please review that paragraph."
"O.K."
"That paragraph contradicts the testimony you just gave here today, doesn't it professor?"
"Uh, yes."
"Thank you, no further questions."

The case went away.

I ran into him at Oshkosh the next year.
"Remember me professor?"
"Oh yes, you took my deposition last year."
"I guess that you didn't recognize me then because the last time you had seen me I was wearing shorts and sandals when I took your course several years ago."
"Oh, now I remember you, I wondered how you had gotten my book."
----------------------------------------------
It would take a whole lot less than 22 Gs to tear off the landing gear, so such damage (if it happened) doesn't indicate any likely damage to the fuel tanks.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Don Dollinger on October 28, 2011, 12:04:15 PM
Quote
I've spent 22 years litigating airplane crash cases, attended very many wreckage inspections accompanied by my metallurgist, my accident reconstructionist, my aircraft mechanic, engineers, and other appropriate experts and I've looked though many electron microscopes at fracture surfaces. My first college major was Aeronautical Engineering and I also took a course in aircraft accident investigation given jointly by the University of Illinois and the Air Force at Chanute AFB. I've cross-examined many adverse expert witnesses on all of these issues and taken the depositions of many NTSB investigators. I'll match my credentials and experience on this against Ric's anytime.

Please accept my apologies if you took offense to that, I was not trying to insinuate you were not qualified to answer my question, its just the facts that I knew:
#1.  That Ric had worked in the Aircraft Accident Investigation Field
#2.  I was not aware of your qualifications for my question
#3.  You are a Lawyer
I do not know the answer which is why I posed the questions.  So I gather from your answer that any resulting damage from the landing gear being ripped from the fuselage/superstructure would not affect the attaching points of the fuel tanks and weaken them which would result in less force being needed to dislodge the fuel tanks?

LTM,

Don
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 12:12:42 PM
Quote
I've spent 22 years litigating airplane crash cases, attended very many wreckage inspections accompanied by my metallurgist, my accident reconstructionist, my aircraft mechanic, engineers, and other appropriate experts and I've looked though many electron microscopes at fracture surfaces. My first college major was Aeronautical Engineering and I also took a course in aircraft accident investigation given jointly by the University of Illinois and the Air Force at Chanute AFB. I've cross-examined many adverse expert witnesses on all of these issues and taken the depositions of many NTSB investigators. I'll match my credentials and experience on this against Ric's anytime.

Please accept my apologies if you took offense to that, I was not trying to insinuate you were not qualified to answer my question, its just the facts that I knew:
#1.  That Ric had worked in the Aircraft Accident Investigation Field
#2.  I was not aware of your qualifications for my question
#3.  You are a Lawyer
I do not know the answer which is why I posed the questions.  So I gather from your answer that any resulting damage from the landing gear being ripped from the fuselage/superstructure would not affect the attaching points of the fuel tanks and weaken them which would result in less force being needed to dislodge the fuel tanks?

LTM,

Don
----------------------
Although very unlikely, it is possible that tearing off a landing gear could cause it to puncture a wing tank which is located near the gear but the plane would float with just some of the cabin tanks intact so the plane would float even if the gear had punctured a wing tank.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 28, 2011, 01:18:04 PM
Let's do the math. The airplane was produced under Air Bulletin 7a and 26 effective 1934. Using the method provided in those bulletins to calculate the allowable design load factors is more complicated than in the subsequent CAR 3 and in the current FAR part 23 but you end up with the same result plus 3.8 and minus 1.52 Gs. These bulletins also require the same 50% safety margin.

If it please the court, the following excerpt is from Air Bulletin 7a (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgccab.nsf/0/96a3f126d9326ea886256e23006e73f0/$FILE/ab_7a.pdf) is submitted:

(B)   These requirements are based on the present development in the science of airplane design. Experience indicates that, when applied to conventional types of construction, they will result in an airworthy and well- proportioned aircraft. New types of aircraft and new types of construction may, however, incorporate features to which these requirements cannot be logically applied. In such cases, special consideration will have to be given the particular new problems involved. In cases where the deviation from conventional practice is small, approval may be granted if sufficient evidence is submitted to show that the proposed deviation will not be detrimental to the airworthiness of the design. When the deviation from conventional practice is considerable, a special aircraft license may be granted pending a thorough study of the principles involved. Such aircraft will, by their very nature, be experimental and cannot be licensed for general commercial use until their airworthiness has been established.

The defense will stipulate that the Lockheed Model 10 was certificated for commercial use under the provisions of this bulletin.  The prosecution, however, has based its calculations on the supposed strength of the tanks and associated hardware aboard NR16020 upon the assumption that those features met the requirements of Air Bulletin 7a.  Such is not necessarily the case.  Lockheed 10E Special c/n 1055 was not licensed for commercial use.  It was licensed "Experimental" (X16020) on July 17, 1936 while still owned by Lockheed. It was officially sold to Earhart on July 24, 1936 and was licensed in the "Restricted" category (R16020) on August 7, 1936.  The special license issued August 18, 1936 specifies that the aircraft is "Restricted for long distance flights and research.  No persons may be carried except bona-fide members of the crew."  On September 21, 1936 Earhart received permission to "display international prefix license symbol N on your Lockheed Electra 10-E serial 1055 license R16020 subject to provision that you will not engage in international flight without having obtained prior permission in accordance with Section 36B of Air Commerce Regulations."

The necessity to license the airplane Experimental and then Restricted suggests that there was, as Air Bulletin 7a puts it, significant deviation from conventional practice.  The prosecution's calculation of the strength of the fuel tanks and associated connections, and the conclusions derived from them, are based upon speculation that appears to be contradicted by the available documentation.
 
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 28, 2011, 01:34:35 PM
I'll match my credentials and experience on this against Ric's anytime.

My credentials are somewhat different from Gary's.  We're both experienced pilots but my degree is in history, not aeronautical engineering.  I too have specialized training and practical experience in aircraft accident investigation but I'm not a lawyer.  I worked for an insurance company and the investigative work I did was in the context of claims adjusting and risk management, not litigation.  My focus was, and still is, to discover the truth - not win the case.

I would never ask anyone to accept my opinions about what happened to NR16020 based on my credentials or anyone else's.  "Arguments from authority" are inherently invalid.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 01:43:00 PM
Let's do the math. The airplane was produced under Air Bulletin 7a and 26 effective 1934. Using the method provided in those bulletins to calculate the allowable design load factors is more complicated than in the subsequent CAR 3 and in the current FAR part 23 but you end up with the same result plus 3.8 and minus 1.52 Gs. These bulletins also require the same 50% safety margin.

If it please the court, the following excerpt is from Air Bulletin 7a (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgccab.nsf/0/96a3f126d9326ea886256e23006e73f0/$FILE/ab_7a.pdf) is submitted:

(B)   These requirements are based on the present development in the science of airplane design. Experience indicates that, when applied to conventional types of construction, they will result in an airworthy and well- proportioned aircraft. New types of aircraft and new types of construction may, however, incorporate features to which these requirements cannot be logically applied. In such cases, special consideration will have to be given the particular new problems involved. In cases where the deviation from conventional practice is small, approval may be granted if sufficient evidence is submitted to show that the proposed deviation will not be detrimental to the airworthiness of the design. When the deviation from conventional practice is considerable, a special aircraft license may be granted pending a thorough study of the principles involved. Such aircraft will, by their very nature, be experimental and cannot be licensed for general commercial use until their airworthiness has been established.

The defense will stipulate that the Lockheed Model 10 was certificated for commercial use under the provisions of this bulletin.  The prosecution, however, has based its calculations on the supposed strength of the tanks and associated hardware aboard NR16020 upon the assumption that those features met the requirements of Air Bulletin 7a.  Such is not necessarily the case.  Lockheed 10E Special c/n 1055 was not licensed for commercial use.  It was licensed "Experimental" (X16020) on July 17, 1936 while still owned by Lockheed. It was officially sold to Earhart on July 24, 1936 and was licensed in the "Restricted" category (R16020) on August 7, 1936.  The special license issued August 18, 1936 specifies that the aircraft is "Restricted for long distance flights and research. No persons may be carried except bona-fide members of the crew." On September 21, 1936 Earhart received permission to "display international prefix license symbol N on your Lockheed Electra 10-E serial 1055 license R16020 subject to provision that you will not engage in international flight without having obtained prior permission in accordance with Section 36B of Air Commerce Regulations."

The necessity to license the airplane Experimental and then Restricted suggests that there was, as Air Bulletin 7a puts it, significant deviation from conventional practice.  The prosecution's calculation of the strength of the fuel tanks and associated connections, and the conclusions derived from them, are based upon speculation that appears to be contradicted by the available documentation.
-----------------------------
But you are now speculating that the deviations from 7a requiring the Experimental and Restricted category licensing related to the strength of the extra fuel tanks and their tie down method. It is as more likely that it was the mere presence of the extra fuel tanks that led to these licenses even though the strength of this construction met standards. These types of modifications are commonly licensed as Experimental by manufacturers (I've represented many manufacturers too) to prove the safety of a design in testing prior to applying for a Standard certificate. Since Lockheed never planned to request  a Standard certificate for this configuration (there being no market for a plane that didn't have any room for passengers or cargo) there  was no reason to go through the cost and trouble to get the government to license it as Standard even though the tanks probably met the standards of 7a, so retained the Experimental and then the Restricted certificates, it costs less that way. (BTW, these types of certificates always have that restriction,  "No persons may be carried except bona-fide members of the crew." )
Just speculating Ric, same as you.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 01:46:01 PM
I'll match my credentials and experience on this against Ric's anytime.

My credentials are somewhat different from Gary's.  We're both experienced pilots but my degree is in history, not aeronautical engineering.  I too have specialized training and practical experience in aircraft accident investigation but I'm not a lawyer.  I worked for an insurance company and the investigative work I did was in the context of claims adjusting and risk management, not litigation.  My focus was, and still is, to discover the truth - not win the case.

I would never ask anyone to accept my opinions about what happened to NR16020 based on my credentials or anyone else's.  "Arguments from authority" are inherently invalid.
------------------------
BTW, what company was that Ric, we probably have some acquaintances in common? We should have a beer together sometime.

g
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 02:33:20 PM
Let's do the math. The airplane was produced under Air Bulletin 7a and 26 effective 1934. Using the method provided in those bulletins to calculate the allowable design load factors is more complicated than in the subsequent CAR 3 and in the current FAR part 23 but you end up with the same result plus 3.8 and minus 1.52 Gs. These bulletins also require the same 50% safety margin.

If it please the court, the following excerpt is from Air Bulletin 7a (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgccab.nsf/0/96a3f126d9326ea886256e23006e73f0/$FILE/ab_7a.pdf) is submitted:

(B)   These requirements are based on the present development in the science of airplane design. Experience indicates that, when applied to conventional types of construction, they will result in an airworthy and well- proportioned aircraft. New types of aircraft and new types of construction may, however, incorporate features to which these requirements cannot be logically applied. In such cases, special consideration will have to be given the particular new problems involved. In cases where the deviation from conventional practice is small, approval may be granted if sufficient evidence is submitted to show that the proposed deviation will not be detrimental to the airworthiness of the design. When the deviation from conventional practice is considerable, a special aircraft license may be granted pending a thorough study of the principles involved. Such aircraft will, by their very nature, be experimental and cannot be licensed for general commercial use until their airworthiness has been established.

The defense will stipulate that the Lockheed Model 10 was certificated for commercial use under the provisions of this bulletin.  The prosecution, however, has based its calculations on the supposed strength of the tanks and associated hardware aboard NR16020 upon the assumption that those features met the requirements of Air Bulletin 7a.  Such is not necessarily the case.  Lockheed 10E Special c/n 1055 was not licensed for commercial use.  It was licensed "Experimental" (X16020) on July 17, 1936 while still owned by Lockheed. It was officially sold to Earhart on July 24, 1936 and was licensed in the "Restricted" category (R16020) on August 7, 1936.  The special license issued August 18, 1936 specifies that the aircraft is "Restricted for long distance flights and research. No persons may be carried except bona-fide members of the crew." On September 21, 1936 Earhart received permission to "display international prefix license symbol N on your Lockheed Electra 10-E serial 1055 license R16020 subject to provision that you will not engage in international flight without having obtained prior permission in accordance with Section 36B of Air Commerce Regulations."

The necessity to license the airplane Experimental and then Restricted suggests that there was, as Air Bulletin 7a puts it, significant deviation from conventional practice.  The prosecution's calculation of the strength of the fuel tanks and associated connections, and the conclusions derived from them, are based upon speculation that appears to be contradicted by the available documentation.
-----------------------------
But you are now speculating that the deviations from 7a requiring the Experimental and Restricted category licensing related to the strength of the extra fuel tanks and their tie down method. It is as equally likely (just speculating) that it was the mere presence of the extra fuel tanks that led to these licenses even though the strength of this construction met standards. These types of modifications are commonly licensed as Experimental by manufacturers (I've represented many manufacturers too) to prove the safety of a design in testing prior to applying for a Standard certificate. Since Lockheed never planned to request  a Standard certificate for this configuration there  was no reason to go through the cost and trouble to get the government to license it as Standard even though the tanks probably met the standards of 7a so retained the Experimental and then the Restricted certificates, it costs less that way. (BTW, these types of certificates always have that restriction,  "No persons may be carried except bona-fide members of the crew." )
Just speculating Ric, same as you.

gl
---------------------
Giving it more thought, I believe my explanation for the licensing holds more water than yours for two reasons. Lockheed had a very strong motivation to make sure the tanks were secure, meeting or even exceeding the 7a requirements, because it would not have helped Lockheed's marketing department if the tanks had torn loose in flight due to maneuvering or turbulence causing the loss of the plane or even just the termination of this high profile flight.
The second reason is that since the hold down structure is so small, constituting a very small percentage of the total airplane, the weight and cost penalty for making them extra strong was negligible so no reason not to do it.

Giving it even more thought, we can get away from any speculation on the strength of the tank tie downs since a full scale test of the tie downs was conducted with the tanks full of fuel, thereby putting much more stress on them than any landing with empty tanks or any buoyancy loads. This full scale test was performed by Earhart herself when she crashed the plane at Luke field. Did the tanks tear loose during that experiment?

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 02:57:18 PM
Most vehicle fuel tanks with sealed filler caps and flat-top construction have two vent locations in my limited experience, connecting to opposite sides or ends, and commonly opposite corners. Alternatives are to have a vapor dome, or curve the top of the tank with the vent at the highest point, or route a single vent line to a small header tank with it's own vent arrangement.  Here's why flat top tanks benefit from two vents:
Imagine a tank almost completely filled with cool gasoline.  If the port wing is a little bit low, the tank will also have a bit of a tilt.  The port vent connection on the tank will be submerged in gas, while the starboard one is above the liquid level. Now warm the fuel slightly, so it expands a bit.  If there were only one vent on the port side, then the warming and expanding liquid gasoline would be pushed out the vent, even though there is some room left in the tank.  With two vents, there is always some room to expand at one of the vent locations, unless the tank is 100% full. In that case, with luck, the manifold will route any displaced gasoline into another tank, rather than on the ground.

Wasn't "gas on the ground" one of the 3 useless things, along with altitude above you, and runway behind you?
The pictures are a big help.  I've got to get the CD's as soon as my membership arrives.

Regarding the tank internal bracing - lots of rivets do indicate lots of internal structure.  If the apparant thinness of the outer surface is an indication, the internal bracing may also be equally thin.  That works fine for holding fuel in, but not resisting external pressure.  Any internal structure is certain to be heavier than foil, but not much more.  I hope to find some contemporary tank construction for simple analysis.  Until we know for sure how the tanks were made, it's only conjecture how they would respond to submersion.  With vent lines out the bottom, trapping the air inside them, intact tanks would offer a LOT of excess buoyancy, even if they partially crushed until pressure was equalized.  In that case they would be metal balloons.  However, if the plane tried to float nose-down, as Ric suggested, then the vent lines exiting from the belly behind them would be "above" the tanks.  If the tanks crushed, then they would "deflate" and quickly lose all buoyancy as the air escaped through the vent line.  If they stayed "inflated" due to strong internal bracing as Gary suggests, then they would continued to provide a lot of excess buoyancy even if vented to the open air.
If the plane was banged around on the reef, then anything might have happened, but damage would be certain.
-----------------------
I agree with you since this is what is required by regulations since CAR 3 and most likely the 1937 regulations (I don't want to read them again.)
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 03:22:09 PM
Gary sez: "... the vertical rows of rivets indicates a baffle to stop right to left sloshing..."

I agree.  Also the pictures clearly show the several round plugs where access was had to the tank interiors.  Those round holes were necessary to contruct the tanks, especially when bucking rivets - you need access to both ends of a rivet (except with modern Cherry "pop" rivets or explosive rivets).  The holes were then sealed with a circular plug that fit from the inside of the tank.  Those plugs had a "lip" that was a bit bigger than the hole, so internal pressure helped hold them in place.  The ones I've seen were soldered or welded in place, and not removable.  They also would not pop into the tank from external pressure, although they weren't quite as strong as a tank wall that had no hole in it. 
I'm curious what the tanks material was - aluminum, or tern, or stainless steel?  I haven't stumbled across any references.  A SS tank would survive in salt water just fine. Tern might last nearly as long.  The vent lines might be SS, in which case they would remain after the aluminum fuselage dissolved.

It would be very useful to know what the tanks on NR16020 were made of and how they were constructed. 

In mulling over these posts, I'd like to share a bit of thought from experience -

It is not unheard of to find older airplane tanks made of 1100 aluminum alloy in "0" (annealed) state.  Large "A" (1100 - "soft") rivets were also commonly used in such tanks - they are more compatible with the soft base material in terms of being worked (bucked) and relative strength.  The large size of the rivets also is compatible in terms of the needed bearing area in soft material.  The 1100 "0" state aluminum also allows easy welding of apertures for fittings, etc. during the build process very readily.  1100 can also be very corrosion resistent since it has little alloy inclusion in it. 

These tanks have the appearance of such construction in the photos but we can't know for certain without more information. 

Stainless is a posssibility - but I believe NR16020's tanks would have not been a strong candidate for that in the 1930's.  Welded / spot-welded construction would be more the norm for stainless, not the riveted / welded construction type we see in NR16020. 

I am not so familiar with the use of terne metal except that I think it commonly refers to terne-cladded copper and stainless sheet.  My understanding also is that terne metal has to be painted to effectively weather the elements, but that it lasts well with an organic coating.  I am familiar with 'metalizing', i.e. the application of a soft 1100-type aluminum to steel parts such as naval aircraft cylinders to protect them from the elements, but do not know of terne metal being used in aviation per se.

It cannot be said for certain what the tanks were made of without real records, but I know from experience you cannot easily buck large, hard rivets (like big brazier head 2117s or similar of the day) that I see in these pictures without severly deforming and tearing the base material.  It is also possible that soft-state tanks could be heat-treated after construction (if other alloy than 1100 which doesn't heat treat so well), but the size of these tanks could have made that problematic.  Heat treatment proably would not be necessary for the use such tanks would see anyway.

It is entirely possible that the tanks were of soft material and considered adequate for their specialized, limited use.  If they were, they could have been quite crushable under pressure - even with baffling within.  The large surface area means you could generate substantial crushing forces at relatively meager pressures per square inch. 

My experience includes outfitting a certain large-cabin business jet with large, temporary in-cabin tanks for an around-the-world record flight - the construction method was quite similar to what I have described and one good reason was ease of manufacture and installation.  Malleable material is easier to work with.  The tanks did not need a long-life - just enough to get them reliably through the intended mission.  Such may well have been the case for NR16020.

Of course we can't know how these things might apply to NR16020 without direct evidence of how they were constructed - that would be good to know, for sure.  It may well have been a factor in how long the ship could have floated after going into the water.

As to the venting, everything I can discern from the pictures and from what I know of tank venting suggests that the vent outlets would have been placed as high as possible on the airframe, not low.  Venting would have also been by the most direct route.  We see vents for wing tanks on top and on the bottom of wings - often both as a redundant means of venting.  Again, it would help to know even gas-cap details - many are vented, and it would not be a surprise to find that NR16020 had vented caps of some sort. 

Vents do not themselves allow a dramatic exchange of liquid - it takes time since they are relatively small and meant to allow for the evacuation of fuel at normal burn rates plus some margin by permitting the flow of fluid (air) into the space as liguid leaves.  But, they DO allow fluid to move readily once there is any substantial breach by allowing the relatively rapid expulsion of air - another possibility to consider; if a tank (or tanks) shifted during a hard landing, crash or during abuse in the surf, enough breach(es) could occur to allow a great deal of water into the tanks fairly quickly.

It would be good to have a breakthrough in finding the technical details on NR16020's tanks somehow - it could tell us a great deal about how the ship might have behaved with a low-fuel state in water, heavy surf, etc.

LTM -
-----------------------------
1. How did you make your temporary cabin tanks (and vent them) so that they didn't collapse due to the cabin differential pressure, a pressure much greater than submerged tanks in the Lockheed?

2. I have flown 67 different types of planes and all of them had tank vent lines coming out of the bottom of the plane, none on top, so I am curious, can you give us some examples of planes with the the vents on top of the cabin?

3. Although regulations allow for vented gas caps, only two examples come immediately to mind, and neither were part of the original design of the plane. The Cessna 150 has only one vent that is under the left wing and leads only to the left wing fuel tank. The right tank is vented by a cross-over pipe from the left tank. This caused a problem that made the left tank  feed fuel more rapidly than from the right tank. An Airworthiness Directive required the installation of a vented cap on the right tank to deal with this problem. (It is not uncommon to find this vented cap on the left tank by mistake, installed by some idiot that didn't understand the reason for the A.D.) The other one is that some Bonanzas have vented caps, also required by A.D., due to clogged vent lines causing the collapse of the rubber fuel bladder installed in the wing tanks. I suppose there must be other similar examples. Do you know of any planes that had vented caps as part of the original design?

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 28, 2011, 08:24:09 PM
Does anyone have ANY information on any fuel tank construction or fuel caps used by Lockheed, in any model aircraft, in the late 1930's?  It would be a big help reducing the assumptions.  Knowing what was done by some other manufacturer may not be much help.
The '46 Aeronca 7AC I learned to fly in had a vented cap with a tube that pointed into the airstream, with a wire and cork-float arrangement in a clear plastic tube tied to the right hand down tube in the cockpit to tell me how much fuel remained.  They're not applicable to this discussion, being built a decade later than AE's craft, but I have fond memories of those days.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 28, 2011, 08:50:24 PM
Does anyone have ANY information on any fuel tank construction or fuel caps used by Lockheed, in any model aircraft, in the late 1930's?  It would be a big help reducing the assumptions.  Knowing what was done by some other manufacturer may not be much help.
The '46 Aeronca 7AC I learned to fly in had a vented cap with a tube that pointed into the airstream, with a wire and cork-float arrangement in a clear plastic tube tied to the right hand down tube in the cockpit to tell me how much fuel remained.  They're not applicable to this discussion, being built a decade later than AE's craft, but I have fond memories of those days.
-----------------------
J-3s had the same fuel gauge.

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 29, 2011, 08:54:47 AM
http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/51_HeatShields/51_DetectiveStory.html
The above link is to a 2007 report on a visit to the crashed Electra in Alaska.  It includes a photo showing the added "small auxiliary fuel tank" installed in the cabin. It also includes a very clear photo of AE's Electra aux. tanks during installation, clearly showing rivets, ports and lumps.  The vent lines are also clearly visible, but are missing the aft portion that turns down.  The glare obscures the tops of the tanks, which do not have the platforms installed.  I can't tell if the fuel line connections might be visible in the original photo, can someone with access to the original or a high-resolution copy check?
The bracing of the tanks is also clearly visible.  They are well restrained for vertical stresses, and are presumably well braced against the wing spar structure against deceleration forces, but there is no obvious bracing against horizontal forces towards the tail, as might occur if the aircraft were floating nose-down, with buoyant forces trying to push the tanks towards the tail.  If the structure on top of the tanks tied into the aircraft structure at the forward end, then the tanks would be pretty well restrained against rearward forces.
The article also mentions another 10E:  "Wall Street brokers Ben “Sell ’em short” Smith and Jack Bergen bought Vanderbilt’s 10E and had Lockheed modify it similarly to Amelia Earhart’s long-range Electra, although in this case the fuel capacity would total a whopping 1270 gallons. The ship, registered as NR16059, was christened “Daily Express” after a British newspaper owned by Smith’s friend Lord Beaverbrook."  It made a round-trip flight over the Atlantic, and was eventually sold to the Soviet Union. Might there be Lockheed records of this aircraft's aux. tank construction?  It's a shame the whereabouts are unknown.  It might be sittting in a Russian museum, or in the back of a hanger in Siberia.  What a wealth of information that would be.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 30, 2011, 09:46:51 AM
I initially hesitated to post this, but in the spirit of looking at all evidence from every angle, ‘here ‘goes:

OK, I’d like to take a step back and look at the two stories we’re building here:

1) an island tradition that an aircraft was deteriorating on the reef in 1938 or so, leaving scattered parts for locals to remember and use over the years.

2) a compelling argument that the aircraft floated away after landing on the reef, buoyed by  the aux. fuel tanks, not long after AE landed there.

Did it break up locally, or did it float away and sink a long ways away?  The time lines for each scenario seem quite different – the “float away” idea happens pretty quickly (days or weeks), but the “break-up on the reef” idea happens slowly (years).  Can these be reconciled?
If we assume NR16020 landed on the reef, then it must have landed gently enough that we can also assume the aux. tanks were intact after landing. Therefore it would readily float if the water level was relatively deep enough. To break up on the reef, the tanks must not provide enough flotation to lift it clear of the reef.  I can imagine it being lifted and banged onto the reef, but cannot imagine it remaining in one place while that happened.  Stormy/extreme tide conditions that could float it away may have occurred within days of landing, and almost certainly within months.  If it floated away after landing, then the islanders’ tradition must have been of some other aircraft on the reef (unless it floated back?).

I’ll add 3): At the risk of heresy (“opinion…contrary to a… generally accepted belief”, Webster’s), I’ll posit some other options that come to mind: that NR16020 ditched at sea, and eventually drifted onto the reef.  This would not explain the radio traffic, and the chance of actually floating to the reef from any particular ditching point seems vanishingly small in most cases. However, the presence of AE/FN present or alive on the aircraft is not necessary for this scenario.  It only offers one explanation of how an aircraft mysteriously appears on the reef for the island tradition to grow around.  If there was also a tradition of corpses or skeletons associated with the aircraft, then they might have perished at sea before arriving on the reef.  If the tanks provided flotation for a long period of time, then the Electra could have eventually ended up on a beach or reef somewhere, so why not Gardner?  Perhaps the Electra ditched immediately upwind of the island and drifted to the reef. Perhaps the Electra ran off the end of the reef, losing a landing gear in the process, and the survivors swam/boated to the island, followed by the wreck of the aircraft?  That would rule out running the engines ever again, and ruin the belly antenna, but might preserve the radio and batteries.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Tom Gallagher on October 30, 2011, 10:45:09 AM
Does anyone have ANY information on any fuel tank construction or fuel caps used by Lockheed, in any model aircraft, in the late 1930's?  It would be a big help reducing the assumptions.  Knowing what was done by some other manufacturer may not be much help.
The '46 Aeronca 7AC I learned to fly in had a vented cap with a tube that pointed into the airstream, with a wire and cork-float arrangement in a clear plastic tube tied to the right hand down tube in the cockpit to tell me how much fuel remained.  They're not applicable to this discussion, being built a decade later than AE's craft, but I have fond memories of those days.
-----------------------
J-3s had the same fuel gauge.

gl

Indeed they did.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 30, 2011, 11:42:40 AM
OK, I’d like to take a step back and look at the two stories we’re building here:

1) an island tradition that an aircraft was deteriorating on the reef in 1938 or so, leaving scattered parts for locals to remember and use over the years.

Let's be clear about the evidence which suggests that the aircraft did not float away undamaged. Let's go through it chronologically.

- a photograph which shows debris (aka "Nessie (http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/58_NessieHypothesis/58_NessieHypothesis.html)") which may be aircraft wreckage on the reef in October 1937
- the anecdotal recollection of Emily Sikuli who saw debris on the reef (http://tighar.org/Publications/TTracks/1999Vol_15/carpenters.pdf) in the same location in 1940 or '41.  Her father told her it was from an airplane.
- the anecdotal recollection of Dr. John Mims who saw aircraft debris (http://tighar.org/Publications/TTracks/1995Vol_11/catch.pdf) in use by the locals on Gardner in 1944 and was told it was from an airplane that was there when the first settler arrived in 1938.
- the anecdotal recollection of former island resident Taniana who, as a boy in the late 1940s or early '50s, played with a curved metal door found on the lagoon shore near the southern passage. (No link yet.  New anecdote from the recent Solomons expedition.)
- aerial mapping photos taken in 1953 that show what appears to be a debris field (http://tighar.org/Publications/TTracks/1997Vol_13/corroboration.pdf) of light-colored metal on the reef near the entrance to the main passage.
- the anecdotal recollection of Pulekai Songivalu who saw aircraft debris (http://tighar.org/Publications/TTracks/1997Vol_13/pieces.pdf) washed up on the lagoon shore opposite the main passage some time in the late 1950s
- the anecdotal recollection of Tapania Taiki who saw "part of a wing (http://tighar.org/Publications/TTracks/1997Vol_13/pieces.pdf)" on the reef flat and airplane parts on the shore near the main passage some time in the late 1950s
- aircraft structures that may be heat shields (http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/51_HeatShields/51_DetectiveStory.html) from the Electra cabin found in the abandoned village by TIGHAR in 1989 and 2003.
- a sheet of 24ST ALCLAD (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html) that may be from the Electra found washed up near the abandoned village by TIGHAR in 1991.
- a shard of plexiglas (http://tighar.org/Publications/TTracks/1996Vol_12/40552.pdf) that matches Lockheed Part #40552 found in the abandoned village by TIGHAR in 1996.
- the anecdotal recollection of Dr. Greg Stone who saw an airplane wheel (http://tighar.org/Publications/TTracks/2003Vol_19/WOF.pdf) in the main lagoon passage in 2002.

A word about anecdotal recollections or "eyewitness testimony."  Gary is preaching to the choir when he says that it's the least reliable form of evidence.  The entire Japanese Capture canon consists of unsubstantiated and often contradictory anecdotal recollections.  To be meaningful, old stories must be corroborated by hard evidence, i.e. archival records, photographs or artifacts - and even then they must be taken with the proverbial grain of salt. Memory is unreliable, but when recollections from a variety of witnesses seem to tell a consistent story that is corroborated with photos and artifacts it's time to pay attention.

2) a compelling argument that the aircraft floated away after landing on the reef, buoyed by  the aux. fuel tanks, not long after AE landed there.

I've seen no compelling argument that the airplane floated away.  I've seen argument based upon admitted speculation that the airplane should have floated if it went into the water undamaged.  A compelling argument that the airplane floated away would have to include some kind of real evidence suggesting that it did  - for example, an anecdotal sighting of a floating aircraft or an absence of stories, photos or artifacts suggesting debris washing up on the island.  We have quite the opposite.

I’ll add 3): At the risk of heresy (“opinion…contrary to a… generally accepted belief”, Webster’s), I’ll posit some other options that come to mind: that NR16020 ditched at sea, and eventually drifted onto the reef.  This would not explain the radio traffic, and the chance of actually floating to the reef from any particular ditching point seems vanishingly small in most cases. However, the presence of AE/FN present or alive on the aircraft is not necessary for this scenario.  It only offers one explanation of how an aircraft mysteriously appears on the reef for the island tradition to grow around.  If there was also a tradition of corpses or skeletons associated with the aircraft, then they might have perished at sea before arriving on the reef.  If the tanks provided flotation for a long period of time, then the Electra could have eventually ended up on a beach or reef somewhere, so why not Gardner?  Perhaps the Electra ditched immediately upwind of the island and drifted to the reef. Perhaps the Electra ran off the end of the reef, losing a landing gear in the process, and the survivors swam/boated to the island, followed by the wreck of the aircraft?  That would rule out running the engines ever again, and ruin the belly antenna, but might preserve the radio and batteries.

We can posit almost any scenario if we choose to disregard selected bodies of evidence.  Your #2 ignores the abundant evidence that the plane broke up near the reef. Your #3 ignores the post-loss radio signals.  We can put the airplane in the water near Howland if we ignore everything TIGHAR has found that says the flight ended at Gardner.  A good hypothesis needs to take all the evidence into account.  You can't complete a jigsaw puzzle and have pieces left over unless you can convincingly explain why it's not part of the puzzle.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: John Ousterhout on October 30, 2011, 03:38:07 PM
Ric sez: "...I've seen no compelling argument that the airplane floated away."
Thanks for catching my poor wording.  The idea I was attempting to convey was that there is a compelling argument that the aircraft would be quite likely to float (re: the current discussion about the buoyancy and survivability of the tanks), given what is assumed about the landing and subsequent evidence (the islander's tradition, radio logs, aerial photos showing debris, "nessie", etc).
To restate my question; how could an Electra retain significant buoyancy, yet stay in the vicinity long enough for the tradition to develop?
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 30, 2011, 08:27:03 PM
To restate my question; how could an Electra retain significant buoyancy, yet stay in the vicinity long enough for the tradition to develop?

Well, one way would be for it to lose bits and pieces - landing gear, outer wing panels, tail surfaces - that would eventually turn up on the reef or on shore, but the center section and fuselage might remain afloat to sail off into the sunset.  The problem with that scenario is that we have artifacts - the putative heat shields - that were attached to the cabin flooring. In order for pieces of the flooring with heat shields attached to wash up on the beach where they could be salvaged by the locals, the fuselage structure has to be breached.  We also have the anecdote about the boys playing with a curved metal door which also suggests severe damage to the fuselage.

Neither of these pieces of evidence is proof that the cabin of the plane was smashed to pieces against the reef by the surf.  The heat shields and the door could be from some other source we haven't thought of.  They are not smoking guns.  They are clues - pieces of real evidence that may or may not be pieces of our puzzle.  Calculations of the plane's buoyancy and resistance to damage are just that - calculations, nothing more, nothing less.  They may or may not be accurate depending upon the many estimates and assumptions made, but they are not clues to what happened.   No one knows what happened when the plane went over the reef edge - if it went over the reef edge -  but the available evidence, the available clues, suggest that whatever happened was violent enough to exceed the aircraft's structural limits.  Is the blue Pacific capable of beating a Lockheed Electra to death against a reef?  No contest.

In short, it is possible that the aircraft broke up near the reef edge.  It is also possible that it floated away. We have clues that suggest that it broke up near the reef edge.  We have no clues that suggest it floated away.
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Gary LaPook on October 30, 2011, 09:04:01 PM
OK, I’d like to take a step back and look at the two stories we’re building here:

1) an island tradition that an aircraft was deteriorating on the reef in 1938 or so, leaving scattered parts for locals to remember and use over the years.

Let's be clear about the evidence which suggests that the aircraft did not float away undamaged. Let's go through it chronologically.

- a photograph which shows debris (aka "Nessie (http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/58_NessieHypothesis/58_NessieHypothesis.html)") which may be aircraft wreckage on the reef in October 1937
- the anecdotal recollection of Emily Sikuli who saw debris on the reef (http://tighar.org/Publications/TTracks/1999Vol_15/carpenters.pdf) in the same location in 1940 or '41.  Her father told her it was from an airplane.
- the anecdotal recollection of Dr. John Mims who saw aircraft debris (http://tighar.org/Publications/TTracks/1995Vol_11/catch.pdf) in use by the locals on Gardner in 1944 and was told it was from an airplane that was there when the first settler arrived in 1938.
- the anecdotal recollection of former island resident Taniana who, as a boy in the late 1940s or early '50s, played with a curved metal door found on the lagoon shore near the southern passage. (No link yet.  New anecdote from the recent Solomons expedition.)
- aerial mapping photos taken in 1953 that show what appears to be a debris field (http://tighar.org/Publications/TTracks/1997Vol_13/corroboration.pdf) of light-colored metal on the reef near the entrance to the main passage.
- the anecdotal recollection of Pulekai Songivalu who saw aircraft debris (http://tighar.org/Publications/TTracks/1997Vol_13/pieces.pdf) washed up on the lagoon shore opposite the main passage some time in the late 1950s
- the anecdotal recollection of Tapania Taiki who saw "part of a wing (http://tighar.org/Publications/TTracks/1997Vol_13/pieces.pdf)" on the reef flat and airplane parts on the shore near the main passage some time in the late 1950s
- aircraft structures that may be heat shields (http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/51_HeatShields/51_DetectiveStory.html) from the Electra cabin found in the abandoned village by TIGHAR in 1989 and 2003.
- a sheet of 24ST ALCLAD (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html) that may be from the Electra found washed up near the abandoned village by TIGHAR in 1991.
- a shard of plexiglas (http://tighar.org/Publications/TTracks/1996Vol_12/40552.pdf) that matches Lockheed Part #40552 found in the abandoned village by TIGHAR in 1996.
- the anecdotal recollection of Dr. Greg Stone who saw an airplane wheel (http://tighar.org/Publications/TTracks/2003Vol_19/WOF.pdf) in the main lagoon passage in 2002.

A word about anecdotal recollections or "eyewitness testimony."  Gary is preaching to the choir when he says that it's the least reliable form of evidence.  The entire Japanese Capture canon consists of unsubstantiated and often contradictory anecdotal recollections.  To be meaningful, old stories must be corroborated by hard evidence, i.e. archival records, photographs or artifacts - and even then they must be taken with the proverbial grain of salt. Memory is unreliable, but when recollections from a variety of witnesses seem to tell a consistent story that is corroborated with photos and artifacts it's time to pay attention.

2) a compelling argument that the aircraft floated away after landing on the reef, buoyed by  the aux. fuel tanks, not long after AE landed there.

I've seen no compelling argument that the airplane floated away.  I've seen argument based upon admitted speculation that the airplane should have floated if it went into the water undamaged.  A compelling argument that the airplane floated away would have to include some kind of real evidence suggesting that it did  - for example, an anecdotal sighting of a floating aircraft or an absence of stories, photos or artifacts suggesting debris washing up on the island.  We have quite the opposite.

I’ll add 3): At the risk of heresy (“opinion…contrary to a… generally accepted belief”, Webster’s), I’ll posit some other options that come to mind: that NR16020 ditched at sea, and eventually drifted onto the reef.  This would not explain the radio traffic, and the chance of actually floating to the reef from any particular ditching point seems vanishingly small in most cases. However, the presence of AE/FN present or alive on the aircraft is not necessary for this scenario.  It only offers one explanation of how an aircraft mysteriously appears on the reef for the island tradition to grow around.  If there was also a tradition of corpses or skeletons associated with the aircraft, then they might have perished at sea before arriving on the reef.  If the tanks provided flotation for a long period of time, then the Electra could have eventually ended up on a beach or reef somewhere, so why not Gardner?  Perhaps the Electra ditched immediately upwind of the island and drifted to the reef. Perhaps the Electra ran off the end of the reef, losing a landing gear in the process, and the survivors swam/boated to the island, followed by the wreck of the aircraft?  That would rule out running the engines ever again, and ruin the belly antenna, but might preserve the radio and batteries.

We can posit almost any scenario if we choose to disregard selected bodies of evidence.  Your #2 ignores the abundant evidence that the plane broke up near the reef. Your #3 ignores the post-loss radio signals.  We can put the airplane in the water near Howland if we ignore everything TIGHAR has found that says the flight ended at Gardner.  A good hypothesis needs to take all the evidence into account.  You can't complete a jigsaw puzzle and have pieces left over unless you can convincingly explain why it's not part of the puzzle.
------------------------------------------


You like to set up a "strawman" so that you can easily knock it down. You demand that the "crash and sankers," and now the "floated away from Gardners," to provide physical proof to back up their theories knowing full well that inherent in those theories is that the plane sank somewhere on the 70% of the earth's surface that is ocean so that it is highly unlikely that the plane will ever be found. So as long as the plane is not found you can claim that those theories are weaker than yours, this is a pretty clever tactic on your part.

But lets turn this around and as Lucy said in one episode:

"Oh Ricky, you've got some 'splaining to do."


1. What became of all the debris in the 1937 photo?
2. What became of the metal door?
3. How did the debris field move over to the main entrance, and what happened to all that debris?
4. How did the debris move to inside the lagoon opposite the main entrance and what happened to all that debris?
5, What happened to the wheel?
6. Why didn't Lambrecht notice any of these shiny debris fields since they were obvious enough to show up in a photo?

"A debris field here, a debris field there, here a debris field there a debris field everywhere a debris field, old McDonald had a farm, ee eye ee eye oh."

You have the same problem that the various Japanese capture theories have, conflicting locations that can't all be right and if three out of four are wrong then there is a good chance that all four out of four are wrong. Same with all of your "debris fields."

Up to this point you have recovered about five pounds of materials that you speculate could have come from the Electra. You have not been able to prove that any piece that you recovered came from the Electra and from nowhere else. Stuff was "consistent with" the Electra but also "consistent with" other sources. The plane weighed 7,000 pounds, where are the other 6,995 pounds of the wreckage that you claim was seen at various times? Since the pieces of metal would have been valuable materials, they should have been recovered by the natives and put to use in their village and you should have found a whole lot more than five pounds of questionable materials. These island people are very adept at harvesting things from the sea and they had plenty of time to do it. They would not have just passed a "legend" down that there was such valuable stuff out on the reef, they would have gone and gotten it. So Ric, what did you do with all that other stuff?

gl
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Mona Kendrick on October 31, 2011, 12:10:16 AM
Since the pieces of metal would have been valuable materials, they should have been recovered by the natives and put to use in their village and you should have found a whole lot more than five pounds of questionable materials. These island people are very adept at harvesting things from the sea and they had plenty of time to do it. They would not have just passed a "legend" down that there was such valuable stuff out on the reef, they would have gone and gotten it. So Ric, what did you do with all that other stuff?


     As you point out, aluminum scrap was valuable to the islanders.  I would guess that they packed up all the pieces they had on hand along with their other possessions when they abandoned Niku in the early 1960's.


     
Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: Ric Gillespie on October 31, 2011, 08:01:41 PM
You like to set up a "strawman" so that you can easily knock it down. You demand that the "crash and sankers," and now the "floated away from Gardners," to provide physical proof to back up their theories knowing full well that inherent in those theories is that the plane sank somewhere on the 70% of the earth's surface that is ocean so that it is highly unlikely that the plane will ever be found. So as long as the plane is not found you can claim that those theories are weaker than yours, this is a pretty clever tactic on your part.

It is not a strawman and it is not a tactic.  I merely ask that proponents of other theories do what TIGHAR has done - present evidence.  The champions of Japanese Capture have failed to produce evidence other than contradictory anecdotal recollections and a few fancifully misinterpreted archival documents such as the Love To Mother  (http://tighar.org/Projects/Earhart/Archives/Forum/FAQs/ltm.htm)telegram and the Morgenthau transcript (http://tighar.org/Projects/Earhart/Archives/Forum/FAQs/morgenthau.htm).
The advocates of Crashed & Sank don't even have that much, but it's not for want of effort.  The Howland Group, Nauticos, and most recently Waitt have spent orders of magnitude more money than TIGHAR searching the ocean bottom in the area where they calculated the plane should be (somewhat less than 70% of the earth's surface).  They have found exactly nothing.  That, of course, does not prove that the plane isn't there - only that they didn't find it.  What says that it isn't there are the post-loss radio signals.  If only one of the signals is genuine, then the airplane can't have crashed and sank.  Our catalog and analysis (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/signalcatalog.html) of all the known reported signals leaves us with two possibilities:
-Either the Earhart aircraft was on land and on its gear in the Phoenix Islands area for several nights following its disappearance
or
- There was a hoaxer in the Phoenix Islands area who had the capability to transmit on Earhart's frequencies, could mimic her voice, had information about her that few people were aware of (such as her incompetence at Morse code), and just happened to be in the Phoenix Group on July 2 or had positioned himself there because he knew ahead of time that she would not reach Howland.
 
Which possibility do you feel is the most likely? 

The Floated Away hypothesis has the same problem as Crashed & Sank.  You can do calculations all day long but the available evidence argues against it.

But lets turn this around and as Lucy said in one episode:

"Oh Ricky, you've got some 'splaining to do."

Fire away Lucy.

1. What became of all the debris in the 1937 photo?

I don't know.  It was there then and it's gone now.  That's a given.  It was apparently still there in 1940 or '41 when Emily Sikuli saw what her father said was debris from an airplane in the same spot.  The reef edge is an extremely dynamic environment.  Norwich City looks a tad different today than it did in 1937.  I'm frankly surprised the debris Bevington photographed in '37 was still there three or four years later.

2. What became of the metal door?

Beats me.  Maybe it's still somewhere back in the bush where the kids left it.  We'll take a look when we're there next summer but that area where the door was reportedly found - just south of Bauareke Passage, known as Nurabu - gets overwashed periodically.  One thing we've learned is that the sea giveth and the the sea taketh away.

3. How did the debris field move over to the main entrance, and what happened to all that debris?

I wasn't there so I can't say for sure, but Norwich City provides us with an excellent model for what happens to man-made structures that get hung up on the reef.  The ship went aground in November 1929 and remained largely intact until January 1939 when the aft half - the part that was not aground on the reef - broke off and sank. There is some, but surprisingly little, wreckage on the reef slope down to about 150 meters.  The bulk of the stern must be deeper than we've looked so far.
The massive triple-expansion steam engine was amidships and remains on the reef edge to this day. Over the years, the half of the ship from the engine forward gradually weakened due to rust, broke up in storms, and was scattered across the reef flat.  Only the lower structure of the hull and keel now remain where they were in 1929.  Most of the ship is just gone. A debris field of heavy components - oil tanks, boiler, winches, etc. - runs in an east and southeasterly direction across the flat.  There's a large section of hull plating up against the shoreline about halfway to the entrance of the main lagoon passage.  There is some shipwreck debris on the shore of the lagoon peninsula (Taraia) opposite the main passage and there is a large tank from the ship on the lagoon shore just north of Bauareke (the southern) Passage. 

So .... at least in the case of Norwich City, some parts of the wreck went into the water and sank to a depth greater than we have yet explored, and parts that were on the reef were scattered in an east and southeasterly direction, then along the shore toward the main passage.  The passage is basically a venturi and there is a strong flow in or out of the lagoon depending on the state of the tide. Floating debris moved through the passage and either across or down the lagoon, probably depending on the direction of wind and surge through the main passage.  Most of the wreckage from the forward half of the ship - tons and tons - is just gone, apparently rusted away.

4. How did the debris move to inside the lagoon opposite the main entrance and what happened to all that debris?

My guess would be that it got there the same way floating debris from Norwich City got there.  Based on what we have found in the abandoned village, the aluminum used by the locals - from whatever source - was primarily sheet (skin).  They made combs, decorative inlays for carved wooden crafts they traded or sold to servicemen, but mostly they just cut it up into small rectangles they used as fishing lures.  In other words, most of their use of aluminum was consumptive.  They used it up.

5, What happened to the wheel?

I don't know.  What I do know is that in the year between the time Greg Stone says he saw it (2002) and we were able to get a team out there to look for it, the west end of the island was hit with weather that did significant damage to the shoreline where he said he saw the wheel.  Over the years we've been going to the island we've seen a regrettable increase in the severity of storms.  Buildings that have stood since the place was abandoned in 1963 have only recently been flattened by waves coming ashore in storms and parts of the old village that were still rich with artifacts in 1989 have since been swept clean by overwash. 

6. Why didn't Lambrecht notice any of these shiny debris fields since they were obvious enough to show up in a photo?

I don't think the debris fields were there yet. At the time Lambrecht flew over I think the wreckage of the airplane was hung up in relatively shallow water just past the reef edge and obscured from view by the surf.  Had there been aircraft debris washed up all over the place, Bevington and Maude should have seen it in October 1937; the new Zealand Survey party should have seen it in late 1939/early 1939; the Grumman Duck from USS Pelican should have seen it in April 1939; the USS Bushnell survey party should have seen it in November 1939.  The earliest report we have of airplane debris being seen is Emily in 1940 or '41 and she doesn't see a debris field.  She sees one piece of wreckage, apparently jammed in the reef, that can only be seen at low tide on a calm day and doesn't look like an airplane.  How did her father know it was part of an airplane?  Somebody must have seen more than that, either her father himself or villagers who fished on the reef edge.  By 1944 the locals were decorating carved wooden boxes with bits of aluminum they told U.S. servicemen were from "the downed plane" so they apparently had some access to pieces of wreckage - but the Coasties were certainly not aware of any great mysterious debris fields of airplane wreckage.  The first debris field we know of turns up in the 1953 aerial mapping photos and it's only four pieces of light colored metal, but they're along the shore just at the ocean side entrance to the main passage - just where they should be if the plane has started to seriously break up and the wreckage is following the same distribution pattern as the Norwich City wreckage.  Later in the 1950s we have reports of part of a wing on the reef in that same area, another piece of wreckage on the Taraia lagoon shore and the door down by Bauareke Passage - all consistent with the known distribution pattern of Norwich City wreckage.

"A debris field here, a debris field there, here a debris field there a debris field everywhere a debris field, old McDonald had a farm, ee eye ee eye oh."

You have the same problem that the various Japanese capture theories have, conflicting locations that can't all be right and if three out of four are wrong then there is a good chance that all four out of four are wrong. Same with all of your "debris fields."

Not so but far otherwise. The anecdotes and photos do not conflict.  They fit a known model of wreckage distribution determined by the natural forces acting upon the island.

Up to this point you have recovered about five pounds of materials that you speculate could have come from the Electra.

I wasn't aware you had weighed it.  I haven't.

You have not been able to prove that any piece that you recovered came from the Electra and from nowhere else. Stuff was "consistent with" the Electra but also "consistent with" other sources.

Which pieces are you referring to that are consistent with the Electra but also consistent with other sources?  If an artifact is so amorphous that it's consistent with the Electra but also consistent other sources we don't pay much attention to it.  It's the ones that we can't connect with other sources that get our attention.
We've tried our level best to match our piece of aluminum skin (2-2-V-1) to something, anything, other than an Electra.  I could bore you for hours with the aircraft we've crawled over and measured. The closest match is still to the Lockheed 10.  Everything fits except the rivet pattern - and that comes darn close. We know the metal is from a repair.  We don't know how the repairs to NR16020 were actually carried out. Find me an airplane that it fits better than an Electra and I'll thank you sincerely.  That thing has been driving me nuts for 20 years.
Our piece of plexi matches the engineering drawing for the cabin windows of the Model 10. The material, thickness, color, and compound curvature are right.  I can't find a match anywhere on WWII airplane but i haven't checked them all.  Maybe you can find one.
The things we think are heat shields are puzzling.  We can imagine how they might have been used on Earhart's aircraft but we haven't been able to find any other aircraft that has any part anything like them.  Maybe you'll have better luck.



The plane weighed 7,000 pounds, where are the other 6,995 pounds of the wreckage that you claim was seen at various times? Since the pieces of metal would have been valuable materials, they should have been recovered by the natives and put to use in their village and you should have found a whole lot more than five pounds of questionable materials.

As I hope I've 'splained above, I think most of those 6,995 pounds are underwater and the bits that did wash ashore were, for the most part, salvaged and used up.  What we have found in the village are the scraps left over from that activity.

These island people are very adept at harvesting things from the sea and they had plenty of time to do it. They would not have just passed a "legend" down that there was such valuable stuff out on the reef, they would have gone and gotten it. So Ric, what did you do with all that other stuff?

Would have?  Did the people who lived on Nikumaroro harvest things from the sea by diving or didn't they?  I've often wondered whether a fisherman who looked down from the reef edge on a rare, flat calm day and saw a wrecked airplane five or ten feet below might dive down and try to salvage something.  I sure wouldn't.  Torn aluminum is sharp and there are always plenty of sharks around - but I'm not Gilbertese.  In numerous interviews with former residents and reading thousands of pages of archival documents I've never heard or seen a reference to the people who lived on Nikumaroro diving in the ocean, or in the lagoon for that matter. They did a lot of fishing but you don't need to dive to get fish there.  At Niku you don't even need bait. Just put a line in the water with something shiny on it (like a little piece of airplane skin) and in no time you'll have a fish.  They mostly fished from sailing canoes in the lagoon.  Getting out over the reef through the breakers to the ocean was dangerous and usually only done in the whaleboat that was used to ferry supplies ashore from ships. There was apparently also some ocean fishing done by standing out at the reef edge at low tide on calm days (the ONLY time you'd want to be anywhere near that reef edge).

Sorry for the length of this posting but your questions and tone made it apparent that some 'splainin' was indeed in order.  If you could have so many misconceptions, so might others.   That's our fault, not yours, or theirs.  It's our job to make what we've learned easily and clearly accessible so that interested people like yourself can form their opinions based on accurate information. We try, but we clearly need to do better. I hope this overly-long posting helps.

Title: Re: FAQ: Electra bouyancy, Ditching at sea
Post by: JNev on November 01, 2011, 01:06:54 PM

I have flown 67 different types of planes and all of them had tank vent lines coming out of the bottom of the plane, none on top, so I am curious, can you give us some examples of planes with the the vents on top of the cabin?

I didn't say 'on top' - I suggested they might be 'as high as practical' (or words to that effect). 

Quote
Although regulations allow for vented gas caps, only two examples come immediately to mind, and neither were part of the original design of the plane. The Cessna 150 has only one vent that is under the left wing and leads only to the left wing fuel tank. The right tank is vented by a cross-over pipe from the left tank. This caused a problem that made the left tank  feed fuel more rapidly than from the right tank. An Airworthiness Directive required the installation of a vented cap on the right tank to deal with this problem. (It is not uncommon to find this vented cap on the left tank by mistake, installed by some idiot that didn't understand the reason for the A.D.) The other one is that some Bonanzas have vented caps, also required by A.D., due to clogged vent lines causing the collapse of the rubber fuel bladder installed in the wing tanks. I suppose there must be other similar examples. Do you know of any planes that had vented caps as part of the original design?

Examples -

- Cessna 120 / 140 - 2 vented caps
- Maule M-4 series - 2 vented caps
- Luscombe 8 series - vented cap atop fuselage
- Cessna Cardinal RG (C177RG) - two vented and raised caps (new style caps by A.D. - the old ones were flush and vented) and two cross-vents - one to each opposite wing-tip trailing edge
- Piper Cherokee (PA-28) series - commonly had raised, vented caps in addition to tank vents under wing 
- Piper J-3 and others of similar type commonly depended on simple, vented caps

Others such as Aeronca, Ercoupe, and others of this genre more often than not were dependent on vented caps.

These are a few that I've flown and know of, I'm sure there are many others.  Make a point to look more closely at the local airport sometime, don't take my word for it.

In any case - should the plumbing become compromised while the tanks are in water, it matters not where the vent outlets are located - water will eventually fill the tanks, matter of time.