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Author Topic: FAQ: Electra bouyancy, Ditching at sea  (Read 110146 times)

Don Dollinger

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #60 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
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #61 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
« Last Edit: October 28, 2011, 12:06:36 PM by Gary LaPook »
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Don Dollinger

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #62 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
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #63 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
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Ric Gillespie

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #64 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 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.
 
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Ric Gillespie

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #65 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.
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #66 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 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
« Last Edit: October 28, 2011, 02:39:11 PM by Gary LaPook »
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #67 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
« Last Edit: October 28, 2011, 02:36:00 PM by Gary LaPook »
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #68 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 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
« Last Edit: October 28, 2011, 02:42:04 PM by Gary LaPook »
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #69 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.)
« Last Edit: October 28, 2011, 03:23:21 PM by Gary LaPook »
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #70 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
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John Ousterhout

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #71 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.
Cheers,
JohnO
 
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Gary LaPook

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #72 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
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John Ousterhout

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #73 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.
Cheers,
JohnO
 
« Last Edit: October 29, 2011, 09:03:36 AM by John Ousterhout »
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John Ousterhout

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Re: FAQ: Electra bouyancy, Ditching at sea
« Reply #74 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.
Cheers,
JohnO
 
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