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[Ric Gillespie]

would the "in flight" loading of the airframe be sufficiently different to the "on ground" loading to highlight any weaknesses
in that particular location on the plane ?

Good question.  I don't know, but .032 sheet does not bend easily.  I would think that once it's bent it stays bent.

[Bill Mangus]

would the "in flight" loading of the airframe be sufficiently different to the "on ground" loading to highlight any weaknesses
in that particular location on the plane ?

Good question.  I don't know, but .032 sheet does not bend easily.  I would think that once it's bent it stays bent.

It may be just semantics, but when someone says 'bend' I think of a resulting crease that's permanent.  Perhaps what we appear to see is more of a 'flexing' of the sheet aluminum, popping in-and-out as the load changes.  This could certainly put a varying load on one section of the rivet line.  To me, that's what I visualize when someone says 'oil-canning'.  If that is truly what's happening, Patrick may be right, it may just be different on the ground than in-flight, especially if there is some kind of weakness near the bottom of the a/c.

[Patrick Dickson]

...it could be that by this point in the Around-the-World flight, the rough landings and take-offs from less-than-ideal runways have taken their toll on the heavily loaded Electra's airframe, and we're actually looking closely enough to see that. Maybe AE and FN saw it too, IF it was indeed the case.

[Ric Gillespie]

...it could be that by this point in the Around-the-World flight, the rough landings and take-offs from less-than-ideal runways have taken their toll on the heavily loaded Electra's airframe, and we're actually looking closely enough to see that. Maybe AE and FN saw it too, IF it was indeed the case.

Good point about the heavy loads and rough fields.  Tough duty, and any weakness is likely to show up.

[Ron Lyons]

Ric I can't see the deformity in the picture you posted above, but I'm not sure if it's because it's not there or because it's just not lit up in the right angle to show it. 

I went back and tried to find all the pictures we've talked about in this thread, and I agree with you, I can only see it on the two in Darwin. 

Also when I used the word 'bent' I'm just saying in the photo it's not the shape it should be, it may or may not be permanently that way.  I suppose "deformity" is the best word I've seen used for it so far.  Oil-canning sounds proper as well...

They of course installed this patch while the plane was on the ground... so we cannot have a situation where it looks fine in the air, but not on the ground, because they wouldn't have been able to install it that way!

So since a couple pictures pretty conclusively show it oil-canned, I think there are only two possiblities.  Either

A. It was installed with a deformity and that was the best they could get it... it at all times had a deformity and the pictures that appear to NOT show the oil-canning are just shot at an angle or a resolution that it's not apparent.... or

B. It was installed relatively properly formed, but got more deformed as the plane landed and took off on the journey. 

I use the phrase "properly formed" because it's not flat, it's curved slightly to fit the curvature of the fuselage. 

Ric's hypothesis that the rivets tore lose and that's what caused the sag sounds plausible to me. 

[Jay Burkett]

You can get "oil canning" without a permanent deformation being set in the material.  The B-52 forward fuselage is a classic example.  See the attached photo.  The "oil canning" disappears in flight.  If I remember correctly the plating in that area is also .032 (I was astounded when I learned how thin a lot of the skin was on that bird!).

I believe the "oil canning" or "puckering" seen on the patch is the result of fitting stock .032 material to a section of the fuselage that has a compouond curvature (i.e. the skin surface is changing in more than one dimension at the same time) and doing it in the field without the proper tools.

The only way to get a rectangular piece of material to lay flat against a compound curavature surface to stretch-form it over a form block that matches the surface you wish to match, or roll it with an "English Wheel", and then trim it to fit.  Otherwise, only three of the four sides can be made to naturally contact the fuselage at the desired loaction.  The fourth edege will have to be forced into position.  The result is the oil canning we see.  Now, once the patch is firmly attached with the "pucker" in place, if you then had a hard landing you could probably "set", or crease, the pucker premantly in to the material.

One other thought:  It is possible to have "oil canning" on the ground that go away in flight and visa-versa.  The loads on that area of the fuselage will differ a good bit between what it sees on the ground and what it sees in the air.  That may explain the absence of the "pucker" on the airborn photo.

[Ron Lyons]

Jay, how did they install it puckered on the ground in such a way that it would disappear in the air?

[Jay Burkett]

I don't think that it was originally present on the ground.  You would never design that way.  I assume that the air loads must offload some of the drooping (and as a result the oil-canning) inflight becasue I have never seen a photo with the oil-canning present in flight --- only on the ground.

The fuselage is built in sections in jigs.  The jigs support the fuselage section all around.  The seperate sections are mated together.  The forward section is basically cantelivered from a ring frame on the aft end.  The struture forward of the ring-frame "droops", hence, the oil-canning.  The loading is differs when the aircraft is on its wheels from when it is in flight.  The last Buff was delivered in 1963.  I'm not sure what vintage this aircraft is.  The all had a LOT of electronics upgrades while in service.  A notable one is readily visible in this photo:  The twin FLIR turrets.  Origianlly the oil-canning was probably not present on the ground.  It may have shown up after a lot of heavy modifications were done forward of the wing/MLG. 

It has occured to me that this is the case on AE's Electra and the patch.  If, say, the patch was installed with the fuselage tanks empty, and the the deformation may not be present when the aircraft is basically empty.  Once the fuselage tanks are full there might be enough flex in that area to load up the "patch" and cause the "puckering".  That patch was installed for a reason.  I go with the assumption that the section properties of the fuselage in the area of that window turned out to be a lot less capable that would normally be desired, hence, too much flexing under various load conditions (full fuel? hard landing?, etc.).  I would wager enough flexing to cause the Plexiglas to crack and the "patch" to be installed becasue, maybe, the material and tooling (an maybe expertise to form the Plexiglas) was not available at an outstation like Miami.

The "patch" did not provide any stiffness to the fuselage at that location.  It did not overlap the structure nor did it have enough fasteners to do so.  Any loading that perhaps would have casued enough flexing to crack the Plexiglas would show up as a deformation the the "patch".

[Diego Vásquez]

The question of whether the artifact fits within the dimensions of the patch was addressed and answered by physical comparison with a Lockheed 10 aircraft.

Ric - Were you ever able to determine the dimensions of the Miami patch?  If so, what were those dimensions and how did you determine them?  Thank you for whatever information you can provide.


Diego

[Jay Burkett]

Ron,

I guess they have always been there. They were on the YB-52 prototype ...

[Ric Gillespie]

Ric - Were you ever able to determine the dimensions of the Miami patch?  If so, what were those dimensions and how did you determine them?  Thank you for whatever information you can provide.

We know the dimensions of the artifact and we know the dimensions of the aircraft.  By physical comparison we know the artifact fits with room to spare between Station 293 5/8 and Station 320.
So far we have not found a photo of the airplane/patch with sufficient resolution to tell the exact dimensions of the patch.

[Diego Vásquez]

The question of whether the artifact fits within the dimensions of the patch was addressed and answered by physical comparison with a Lockheed 10 aircraft.

Ric - Were you ever able to determine the dimensions of the Miami patch?  If so, what were those dimensions and how did you determine them?  Thank you for whatever information you can provide.

We know the dimensions of the artifact and we know the dimensions of the aircraft.  By physical comparison we know the artifact fits with room to spare between Station 293 5/8 and Station 320.
So far we have not found a photo of the airplane/patch with sufficient resolution to tell the exact dimensions of the patch.

Ric –

Physically fitting 2-2-V-1 between the two stations may put it in the ballpark as far as the horizontal dimension is concerned, but mere entry into the ballpark is a far cry from saying the question of fit is resolved.  There are plenty of posts and photos, along with your own structural analysis and reports, that clearly indicate that neither the window coaming nor the subsequent Miami patch ran the full length between the two stations you mentioned.  The Miami patch was obviously somewhat shorter in length than the distance between those two stations.  The fact that 2-2-V-1 fits between those two stations does not answer the question of whether it fits within the horizontal dimensions (length) of the Miami patch. 

Do you have any evidence that would show that 2-2-V-1 fits within the horizontal dimensions of the Miami patch (as opposed to just noting that it fits between the two stations)?

I know you are already very busy with other things, including reviewing more photos from Miami and elsewhere that might provide more valuable information on this very topic, so as always I thank you very much for taking the time to provide whatever information you can. 

Diego

[JNev]

The question of whether the artifact fits within the dimensions of the patch was addressed and answered by physical comparison with a Lockheed 10 aircraft.

Ric - Were you ever able to determine the dimensions of the Miami patch?  If so, what were those dimensions and how did you determine them?  Thank you for whatever information you can provide.

We know the dimensions of the artifact and we know the dimensions of the aircraft.  By physical comparison we know the artifact fits with room to spare between Station 293 5/8 and Station 320.
So far we have not found a photo of the airplane/patch with sufficient resolution to tell the exact dimensions of the patch.

Ric –

Physically fitting 2-2-V-1 between the two stations may put it in the ballpark as far as the horizontal dimension is concerned, but mere entry into the ballpark is a far cry from saying the question of fit is resolved.  There are plenty of posts and photos, along with your own structural analysis and reports, that clearly indicate that neither the window coaming nor the subsequent Miami patch ran the full length between the two stations you mentioned.  The Miami patch was obviously somewhat shorter in length than the distance between those two stations.  The fact that 2-2-V-1 fits between those two stations does not answer the question of whether it fits within the horizontal dimensions (length) of the Miami patch. 

Do you have any evidence that would show that 2-2-V-1 fits within the horizontal dimensions of the Miami patch (as opposed to just noting that it fits between the two stations)?

I know you are already very busy with other things, including reviewing more photos from Miami and elsewhere that might provide more valuable information on this very topic, so as always I thank you very much for taking the time to provide whatever information you can. 

Diego

Further to Diego's concern, I've come to notice what may be a conflict in one of the Wichita shots, which uses measure tapes to help us understand fitment / scale to some degree.  Ric has captioned the picture to emphasize alignment of the vertical stiffener line found on 2-2-V-1 (and a possibly related 'tear' near that line) with the STA 307 rivet line on the Wichita Electra.  That was an amazing find and the alignment on the bird was exciting to see, but -

In that same picture, I note that the forward edge of 2-2-V-1 is also pushed forward up hard against the aft skin edge at STA 293 5/8.  This 'forward edge' area is captioned as to the presence of the fatigue failure, where the part failed by bending against the edge of a fixed component. 

That appears problematic in that it would seem for STA 307 to align as shown, it is required that the 'patch' be over-extended forward.  This conflicts with what we know about the coaming fitment, which was clearly displaced aft in the Nilla-Amelia shot.  It also conflicts with what appears to be the case about the forward end of the patch in the Darwin ramp photo and the Miami photo, both seemingly showing an aft placement away from the skin edge at STA 293 5/8.

Was this accounted for?  It seems important if that vertical stiffener line truly relates to STA 307.

Thanks for consideration of this.

[Ric Gillespie]

Attached are jpegs (full frame and detail) of the original Albasi photo loaned by Jonell Gill.  The resolution is better but still not great.  There is some improvement in the resolution of skin edges and vertical rivet lines.  Jeff Glickman is working with the image to see if he can pull out more detail.

I understand Diego's and Jeff's concerns. I agree that the forward edge of certainly the window coaming and apparently the subsequent patch were set back from Station 293 5/8.  Based on the known 1.5 inch rivet pitch on the skin forward of the window/patch, the window coaming looks to have been riveted about an inch and a half aft of the edge of the skin. There's normally nothing there to rivet to so we must assume a structure was added. We can't see the forward edge of the patch nearly as well as we can see the window coaming but we've been assuming that the patch was riveted to the same underlying structure added for the window. If that is true, we can place the forward edge of the patch at 295 1/8. The aft edge of the patch appears to have been right on Station 320. That makes sense.  There would be no need to add structure there.  So the horizontal dimension of the patch would be 24 7/8 (320 minus 295 1/8). The horizontal length of the artifact is 24 3/8 so the artifact fits within the horizontal dimension of the patch with half an inch to spare - assuming all of our assumptions are correct.
If the assumptions are correct, the line up of the tear and "ghost" vertical stiffener with Station 307 is problematic.  307 minus 295 1/8 = 11 7/8 but the distance on the artifact from the edge that presumably failed against an underlying structure at 295 1/8 is 13 inches from the line of the "ghost" vertical and tear - an inch and an eighth too much to line up with Station 307.  Maybe the tear and "ghost" stiffener are not associated with Station 307, or maybe our assumptions are off - but it certainly doesn't disqualify the artifact as the patch.

[JNev]

Ric,

Thanks for sharing these photos and for acknowledging the concerns about fitment.  You have offered a lot for thought which is helpful.

I'm not sure how the 'ghost' brace question resolves if it cannot be validated to STA 307, but it is something to ponder.  The bigger concern may be that which I think Diego touched on: can we be sure that the patch's overall length was sufficient to have contained enough of 2-2-V-1 such that the forward and aft edge rivet holes could have been lost as the yield we see in the surviving artifact emerged.

Thanks for this thoughtful reply.