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[Greg Daspit]

Regarding possible oil canning:
Two of the original stringers were cut to make the big square opening for the added Lav window. Per the hypothesis, the new stringers did not line up with the original ones and the structure was not brought back to its original design.  It seems to me that because the added stiffeners were not aligned with the original stringers, this big square area is still a weakness in the fuselage. Now imagine this big square being deformed into a diamond shape everytime the plane lands and flexes. What happens to this skin when the shape it covers goes from square to diamond shaped?

Also the vertical stiffener at 307 not being riveted and possibly being more segmented, or having more nothces for the added stiffeners, is an area of concern too.

(I keep hearing Seinfeld in my head saying "Who would do such a thing? It doesn't make sense")

[Bill Lucas]

Hi,

Being a tool design engineer up in Philadelphia for a number of years and watching aircraft being assembled and coming down the line all day long,
I have countless times looked at the contours of brand new aircraft and have sworn that they had concave pockets in the skin or high spots which
looked pretty crummy until going over to the aircraft and running my hands over the area proved that what I was seeing was the light creating illusions.
These were composite skins though and not aluminum sheet.

Bill

[Ric Gillespie]

It seems to me that because the added stiffeners were not aligned with the original stringers, this big square area is still a weakness in the fuselage. Now imagine this big square being deformed into a diamond shape everytime the plane lands and flexes. What happens to this skin when the shape it covers goes from square to diamond shaped?

Exactly.
When I was at MIT we were looking at the way the skin tore along the double staggered row of #5 rivets along the bottom of the artifact.  I asked Prof. Eagar, "It must have taken a lot of force to cause that kind of tearing."  He said, "Not at all.  I see evidence of fatigue cracking around those rivet holes."

Seems to me that the flexing you describe would put a lot of stress on that bottom row of rivets.

Also, in the area where deformation of the artifact appears to match oil-canning of the patch, five of the small #3 rivet holes show pronounced dimpling.  It seems possible that flexing from another hard landing somewhere between Java and Darwin caused these five rivets to fail, allowing the skin to pull free from the underlying stiffener and bulge as we see in the Darwin photos. 

Also the vertical stiffener at 307 not being riveted and possibly being more segmented, or having more nothces for the added stiffeners, is an area of concern too.

Jeff Glickman sent this false color image showing that the mark left by the vertical stiffener seems to be present in the Darwin Fueling photo. 

[Ron Lyons]

If we suspect that it's just a play of light creating an illusion on the patch, then why isn't it playing a similar illusion on the other skin of the plane?

... it's because the other skin of the plane was properly supported, and original to the design of the plane. 

We do see some light play doing weird things on the other skins, on say the Darwin photo, but you see a clear and different... 'deformity' on the patch. 

[JNev]

That's a bit of a jump in my amateur opinion, Ron.

This looks dramatic, but it might be useful to understand what all the colors really mean.  I just don't buy that we're seeing serious deformations or that the patch somehow found itself suddenly unstable - especially with all the surrounding skins seemingly intact.

Why not also use Glickman's skills to check the cover dimensions and juxtaposition to STA 320 rivets?  That seems like a more direct investigatory effort to answer this riddle.

AS might the photo review this coming week in Miami.  A really good picture can remove all doubt, either way.  I hope one is found.

[Ric Gillespie]

If we suspect that it's just a play of light creating an illusion on the patch, then why isn't it playing a similar illusion on the other skin of the plane?

There's really no doubt about it.  In the opinion of a professional who makes his living as an expert witness in court cases involving photogrammetric interpretation, both Darwin photos (hangar and fueling) taken under entirely different lighting conditions show unmistakable deformation of the patch consistent with oil-canning.  In the opinion of a forensic metallurgist professor at MIT, the row of large rivet holes along the bottom edge of the artifact show evidence of fatigue cracking and the smaller rivet holes in the oil-canning area show dimpling that indicates pressure that is trying to force the skin outward.

In the Darwin Fueling photo deformation in the patch matches deformation in the artifact.  In the same photo, other deformation suggesting the presence of a vertical stiffener at Station 307 matches the presence of deformation on the artifact suggesting the presence of a vertical stiffener at Station 307. 

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.

Amateur opinions will invariably vary. 

 

[JNev]

Amateur opinions will invariably vary.

As will some by other professionals.  But Godspeed to Miami - hopefully more can be found.

[Ron Lyons]

I say this with all respect, it's just a supposition... I wonder if some observers just aren't good at seeing ripples and deformities in sheet metal?  I remember these tests in school when I was a kid where they would show you geometric shapes, and rotate them all these different ways, and you were supposed to pick the proper one, rotated a different way.  Some people did well on them, others just didn't see it.

Sort of like how certain people are really good at body work (car repair) because they can see and feel deformities, other people aren't good at it and can't tell if something's tweaked slightly.

To my eyes, the thing is clearly bent, yet several people in several comments don't seem to see anything.  Every picture of the patch I've seen shows the metal is clearly bent.  Whether it was distorted when installed, or distorted after some hard landings may be arguable, but it's hard for me to ignore my eyes and suppose that it's a trick of light... in every photo... on only that 1 panel...

[JNev]

With all due respect to all myself, why not wait and see if better photos surface in Miami this week?  That might just take  the guesswork out of this.

Nobody but possibly Ric would like to see 2-2-V-1 pan out here more than me, I assure you.

[Tim Collins]

So now it actually IS oil caning? I thought it was

It's either just the way the light is reflecting off the patch or it's a map of the 18th Congressional District in Kansas.

Some how I sense vindication.

On the first pic that Ric post above (the BW one) does anybody else see what looks like an "O" or similar letter just below his first (left) two arrows? About twice the size of the "alclad" D. What is that dark green stuff on the patch anyway?

[Bill Lucas]

Ron is right on some people struggling with being able to see in 3 dimensions.
I've been doing 3D cad images for more years than I want to admit and we have had people who struggle with 3D
as opposed to just 2D. They just can't seem to wrap their brain around it. Not being derogatory that's just the way it is.
My post above was just saying there can be optics illusions when viewing at certain angles in certain light.
I'm not saying that I believe it is a dent but it APPEARS that there is a wedge-shaped concave depression.....
the length of which (station measurement) spans almost the entire width of the patch and the shorter side of the "wedge" faces forward
and is about half the "length" (in waterline dimension that is) of the rearward side of the "wedge". The angled part of the wedge faces down
while the top part of the "wedge" is pretty much parallel to the top of the fuselage.

The fueling photo SEEMS (faintly) to back that up but the white patch of light seen in the fueling photo in my view doesn't correlate
to anything in the hangar photo. We might have an illusion there in just that 1 spot.

Bill

[Ric Gillespie]

On the first pic that Ric post above (the BW one) does anybody else see what looks like an "O" or similar letter just below his first (left) two arrows? About twice the size of the "alclad" D. What is that dark green stuff on the patch anyway?

There is no "O" on the artifact.  There is a letter "D" preceded by a letter "A".
On another part of the artifact there is an identical letter "D" followed by "24".
The dark green stuff is organic material (we had it tested).  Some kind of marine growth.

[Ric Gillespie]

Every picture of the patch I've seen shows the metal is clearly bent.  Whether it was distorted when installed, or distorted after some hard landings may be arguable, but it's hard for me to ignore my eyes and suppose that it's a trick of light... in every photo... on only that 1 panel...

So far, I only see oil-canning in the two Darwin photos.  I do not see oil-canning in photos that show the patch at earlier times (Miami, Karachi, and Java).  The resolution of the photo taken in Lae is not sufficient to tell one way or the other.
The air-to-air shot in Java is particularly good and I don't see any indication of deformation to the patch.  Do you?
I think the oil-canning is a problem that developed sometime between Java and Darwin when some of the rivets in the stiffeners let go (as evidenced in the dimpling of the revet holes) after too much flexing and too many landings.

[Bill Lucas]

Looks clean to me.......now that's a photo where the light is obvious.

Bill

[Patrick Dickson]

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 ?