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Author Topic: Underwater airplane parts  (Read 34875 times)

Ric Gillespie

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Underwater airplane parts
« on: January 05, 2013, 09:11:32 AM »

If we're looking for airplane parts in underwater photographs we need to know what airplanes parts look like when they have been underwater for a protracted period of time in a similar underwater environment.  Such models are hard to find but the recent discovery of an F2A Brewster Buffalo that landed short of the runway at Midway atoll in 1941 or '42 may qualify.  What do you see?  What questions does the photo raise?
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Chris Johnson

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Re: Underwater airplane parts
« Reply #1 on: January 05, 2013, 10:19:39 AM »

Yes, slightly dfferent environment but it does beg the question on the Rope/Wire video - If the rope/wire is part of the wreck and there are other items that have been identified, why is the rope/wire more visble than some of the other 'larger' peices?
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Tim Mellon

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Re: Underwater airplane parts
« Reply #2 on: January 05, 2013, 11:02:36 AM »

Yes, slightly dfferent environment but it does beg the question on the Rope/Wire video - If the rope/wire is part of the wreck and there are other items that have been identified, why is the rope/wire more visble than some of the other 'larger' peices?

That is a great question, Chris. I think that the cable is under some tension, as it seems to have eaten channels into the coral below it from place to place. If it moves, even infrequently, it could sluff off whatever plankton has settled on it in the meantime, wheras other more stable parts might tend to stay at rest. Just a guess, of course.

I might add that this plankton/snow stuff might make a major difference in the appearance of objects after a period of 75 years. You won't find in in as great abundance at the depths where the divers are examining the three-bladed propeller, I don't think.
Tim
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« Last Edit: January 05, 2013, 11:06:44 AM by Tim Mellon »
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Ric Gillespie

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Re: Underwater airplane parts
« Reply #3 on: January 05, 2013, 11:11:50 AM »

It is odd to me how many times I've seen propellers separated from engines like this, but with the shaft / splines appearing intact.  How?

I'd be interested to see other examples of props separating from shafts but leaving the splines/shaft intact.  I've seen lots of crashes on land but I don't recall ever seeing a prop come off the shaft.

An abandoned latter-day salvage attempt or by natural forces during the accident?  Always a bit strange.  Same for missing jugs when impact damage isn't so clear.

This is reported as a new discovery so an abandoned salvage attempt seems unlikely.  The accident was apparently just an inadvertent ditching and the pilot swam to shore so the forces generated during the accident couldn't have been enough to account for the damage we see in the photo.  The depth is only ten feet.  I suspect that we're seeing the effects of many years of the wreck being tumbled about by the surf.

ADDED: It is probably fair to note that what we are seeing here lies in a somewhat less complex environment than is the case at Niku so far: shallow, sandy and less-than precipitous, whereas Niku has a more severe and somewhat shifting 'landscape' due to the reef slope, etc.  By this I can realize by graphic contrast what we've long realized - that we could well have buried / semi-covered items lying about in those waters that are difficult to see.  None-the-less, form is form, and we can see here the sort body that might be found yet.

The prop appears to be partially buried but other pieces of debris are not.  Note the lack of coral growth on the metal except for the two large clumps - one on the prop hub and one on the engine case.  We see the same phenomena on the shallow (50 ft) TBD in Jaluit lagoon.   

I'd love to know more about the balance of the airframes remains, but there is not yet much being released.  I looked this find up and found that the Marine Corps has closed the area around Midway while more archeology is being done.  Fascinating.

This is a NOAA Marine Heritage survey.  We know those guys well.  We should be able to get more details and possibly photos.
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Jim Thwaites

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Re: Underwater airplane parts
« Reply #4 on: January 07, 2013, 11:27:39 AM »

If the engine was running during the ditiching, would it be possible that the damage to the cylinders be due to the intake of water and the resultant hydrostatic lock? Considerable rotating mass would be involved, with the propeller acting as a flywheel. This could possibly also result in shearing the crankshaft and the resulting liberation of the propeller.
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Ric Gillespie

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Re: Underwater airplane parts
« Reply #5 on: January 07, 2013, 11:41:40 AM »

If the engine was running during the ditiching, would it be possible that the damage to the cylinders be due to the intake of water and the resultant hydrostatic lock? Considerable rotating mass would be involved, with the propeller acting as a flywheel. This could possibly also result in shearing the crankshaft and the resulting liberation of the propeller.

Sounds like that might be theoretically possible but I've never known it to happen.
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Bob Lanz

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Re: Underwater airplane parts
« Reply #6 on: January 07, 2013, 12:47:57 PM »

My guess so far is that what I took to be a 'clean' departure of the prop from the splines is really at least partly an illusion, and that some direct force is responsible for a failure in some manner that we cannot discern from the picture.

Not likely a "hydrolock" in this scenario but more likely as you say Jeff, a direct force as in the prop impacting the water at high speed shearing it off from the shaft, imo, which could possibly explain it's close proximity to the rest of the engine.  What say our former aircraft accident investigator?
Doc
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richie conroy

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Re: Underwater airplane parts
« Reply #7 on: January 07, 2013, 02:14:42 PM »

Hi All

Just a quick question, If the Electra was in deepish water on reef and Amelia an Fred wanted to run engines would they have been able to remove the propellers tools permitting ?
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Bob Lanz

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Re: Underwater airplane parts
« Reply #8 on: January 07, 2013, 02:56:39 PM »

Hi All

Just a quick question, If the Electra was in deepish water on reef and Amelia an Fred wanted to run engines would they have been able to remove the propellers tools permitting ?

Not in their wildest dreams Richie could they have removed the props much less having the tools and the hydraulic lift to take one off.
Doc
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JNev

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Re: Underwater airplane parts
« Reply #9 on: January 07, 2013, 04:14:50 PM »

Hi All

Just a quick question, If the Electra was in deepish water on reef and Amelia an Fred wanted to run engines would they have been able to remove the propellers tools permitting ?

Ah, THAT'S why...

No - you can't run the engine without the prop, Richie.  The 'flywheel' effect (mass) is needed to damp out the power pulses, etc. in a recip.

If they got to that point of need, they would have been in deep... ah, well, worse than water.
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« Last Edit: January 07, 2013, 04:16:48 PM by J. Nevill »
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Ric Gillespie

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Re: Underwater airplane parts
« Reply #10 on: January 07, 2013, 04:21:21 PM »

Not likely a "hydrolock" in this scenario but more likely as you say Jeff, a direct force as in the prop impacting the water at high speed shearing it off from the shaft, imo, which could possibly explain it's close proximity to the rest of the engine.  What say our former aircraft accident investigator?

When turning props impact water or land they bend. At idle or low power the blades been back.  Under high power the blades bend forward.  At least one of the Buffalo's props is bent back, which is consistent with the supposed ditching.  I've never heard of an impact with the water, or ground for that matter, causing the prop to separate from the shaft.
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Bob Lanz

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Re: Underwater airplane parts
« Reply #11 on: January 07, 2013, 06:38:47 PM »

Not likely a "hydrolock" in this scenario but more likely as you say Jeff, a direct force as in the prop impacting the water at high speed shearing it off from the shaft, imo, which could possibly explain it's close proximity to the rest of the engine.  What say our former aircraft accident investigator?

When turning props impact water or land they bend. At idle or low power the blades been back.  Under high power the blades bend forward.  At least one of the Buffalo's props is bent back, which is consistent with the supposed ditching.  I've never heard of an impact with the water, or ground for that matter, causing the prop to separate from the shaft.

Ric, of course you are right.  I should have thought further than I did before making that comment. 

Bad Bob, who never was spanked with a fly swatter.  ;)
Doc
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John Joseph Barrett

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Re: Underwater airplane parts
« Reply #12 on: January 08, 2013, 04:02:07 AM »

Not being an airplane mechanic and confining my skills to engines that remain on terra firma, or sometimes water, I am not overly familiar with how the propellor is mounted to the shaft. It appears that it fits onto a splined shaft. I would presume that it is then held in place with a nut of some type, similar to a crankshaft pulley on a car engine. If that is the case, would there possibly be a dissimilarity in the metals used which would allow the nut to corrode away? I dive alot and I know that in shallow waters the wave action can really move stuff about. My thought is that the nut holding the prop to the shaft may have corroded away, allowing the prop to come off when the entire assembly was rolled about by the surf. After separating, there isn't alot of surface area for the surf to act on with the prop, allowing it to drop to the ocean floor. The engine itself now has a lot less surface area compared to mass and would require heavier surf action in order to move it. I think this would help explain the current condition of the parts. Prop attached, the whole assembly is rocked back and forth and rolled about, dislodging cylinders, etc. Prop detached, the prop lays flat and the engine moves much less, if at all, allowing the two parts to remain close to each other. Separation took place a fair time ago judging by the coral build-up on the prop hub. I'm curious as to how far the engine assembly made it from the airframe. My $.02 for the day. LTM- John
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Bob Lanz

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Re: Underwater airplane parts
« Reply #13 on: January 08, 2013, 07:58:09 AM »

Not being an airplane mechanic and confining my skills to engines that remain on terra firma, or sometimes water, I am not overly familiar with how the propellor is mounted to the shaft. It appears that it fits onto a splined shaft. I would presume that it is then held in place with a nut of some type, similar to a crankshaft pulley on a car engine. If that is the case, would there possibly be a dissimilarity in the metals used which would allow the nut to corrode away? I dive alot and I know that in shallow waters the wave action can really move stuff about. My thought is that the nut holding the prop to the shaft may have corroded away, allowing the prop to come off when the entire assembly was rolled about by the surf. After separating, there isn't alot of surface area for the surf to act on with the prop, allowing it to drop to the ocean floor. The engine itself now has a lot less surface area compared to mass and would require heavier surf action in order to move it. I think this would help explain the current condition of the parts. Prop attached, the whole assembly is rocked back and forth and rolled about, dislodging cylinders, etc. Prop detached, the prop lays flat and the engine moves much less, if at all, allowing the two parts to remain close to each other. Separation took place a fair time ago judging by the coral build-up on the prop hub. I'm curious as to how far the engine assembly made it from the airframe. My $.02 for the day. LTM- John

John, here is a picture of an R985 Wasp Radial engine.  The prop shaft is steel and the nut that holds the prop hub on is also steel.  There are no dissimilar metals I am aware of in the assembly of a prop hub to the shaft.  That would be a recipe for disaster even on dry land.  Aircraft components are inspected for corrosion during every annual inspection of an aircraft. 

Edit:  This is very similar to the Pratt and Whitney R1340's were on Amelia's Electra L-10E.

Doc
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« Last Edit: January 08, 2013, 09:03:04 AM by Bob Lanz »
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Ric Gillespie

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Re: Underwater airplane parts
« Reply #14 on: January 08, 2013, 09:11:25 AM »

However it happened, if Earhart's prop came off the shaft that entire hub assembly had to slide off - and for that to happen the nut on the end had to somehow go away.
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