Stealth and Supersonic Aircraft - Buckling????
Stealth and Supersonic Aircraft - Buckling????
(OP)
I was wondering if anyone could tell me for sure if skin buckling is permitted to on stealth or supersonic aircraft?
I assume it is not allowed on a stealth plane because the skin buckling would cause a change in the skin shape which is important to the stealth characteristics of the plane.
For a supersonic aircraft I think it could go either way. Depending on the speed it may or may not be desirable to change the loft of the wings.
I assume it is not allowed on a stealth plane because the skin buckling would cause a change in the skin shape which is important to the stealth characteristics of the plane.
For a supersonic aircraft I think it could go either way. Depending on the speed it may or may not be desirable to change the loft of the wings.





RE: Stealth and Supersonic Aircraft - Buckling????
RE: Stealth and Supersonic Aircraft - Buckling????
I was just looking for a general answer. I am trying to justify if the panels are designed to account for load carrying capabilities beyond initial bucking (ie post-buckling) under a standard, non-event, operational flight profile. Say during a long-range cruise.
RE: Stealth and Supersonic Aircraft - Buckling????
If you saw a car that had buckled skin, would you not assume that it had been in a crash, and therefore is possible compromised?
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RE: Stealth and Supersonic Aircraft - Buckling????
IRstuff, the commerical aircraft industry often takes advantage of elastic buckling of the skin below ultimate load (see Bruhn). Buckling may even occur for benign load cases, provided it is elastic and does pose a fatigue problem. Clearly, the redistribution of load must be accounted for.
Brian
www.espcomposites.com
RE: Stealth and Supersonic Aircraft - Buckling????
Wing panels can carry additional load beyond the initial buckling load. It is common practice to utilize this additional load bearing capability, even for below limit load cases. I included one quick ref from an online search.
"In a typical wing structure the skin panels are subjected to in-plane stresses under various load conditions. Under compressive and shear loads, the buckling behaviour of the panels becomes a driving factor for design. Often the panels have high reserve strength beyond buckling, which can be exploited to achieve efficient structures. Hence, buckling and postbuckling studies of composite panels have received much attention over the years." - Varughese, B. "Buckling and Post-buckling Studies on Stiffened Composite Panels with Circular Cutouts"
To your point, designers typically take into account the perception of the passengers in the design, avoiding any possible concern from passenger visible buckling.
RE: Stealth and Supersonic Aircraft - Buckling????
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RE: Stealth and Supersonic Aircraft - Buckling????
permanent buckling would be limited to ultimate.
personally i find the initial post too vague ... we start talking about stealth or supersonic a/c. then its "I was just looking for a general answer. I am trying to justify if the panels are designed to account for load carrying capabilities beyond initial bucking (ie post-buckling) under a standard, non-event, operational flight profile. Say during a long-range cruise."
is that rodent i smell ?
RE: Stealth and Supersonic Aircraft - Buckling????
Agree with rb, initial post is vague. With a stealth fighter one would expect that analyses of radar XC for various loadings and deflections of surfaces would need to be analyzed.
FWIW, several years ago I had an opportunity to get up close and personal with F16 fighters on the factory floor, and a year or so later to a veteran Mig 21, both times in the company of some very bright engineers and pilots. For all the benefits of smooth skins for supersonic fighters, the Mig got by just fine with fairly rough construction details downstream of say 10% of chord. Flush, filled rivets and smooth construction on leading edges, but very rough (quite evidently hand-beaten to shape) surfaces, unfilled and domed rivets elsewhere. Contrast to a typical Western fighter with very smooth surfaces and attention to contour on every surface. Of course, the Mig's had very powerful engines for their time, and endurance was not as critical to their mission as for Western fighters.
RE: Stealth and Supersonic Aircraft - Buckling????
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RE: Stealth and Supersonic Aircraft - Buckling????
Even for stealth aircraft it could vary based on if they are optimized to stealth from ground based or also airborne radar.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Stealth and Supersonic Aircraft - Buckling????
The 21 was one of the first supersonic fighters, and was designed for area defense/interception, not air superiority/loiter. My point was that if clean, smooth surfaces were so critical to M>1 performance, one would expect time and attention to be paid to it. The 21's wing surfaces give proof that with enough horsepower and a fairly easy endurance requirement, you don't need to pay much attention to the surface details, just get the shape pretty close and smooth out the leading edges.
RE: Stealth and Supersonic Aircraft - Buckling????
This is in contrast to US planes that need to be stored in hangars, have flat runways, and an army of guys sweeping FOD off the runway.
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RE: Stealth and Supersonic Aircraft - Buckling????
RE: Stealth and Supersonic Aircraft - Buckling????
RE: Stealth and Supersonic Aircraft - Buckling????
When designing a commercial aircraft, do companies ever decide that it is acceptable to allow for buckling below limit? Ans: YES, effect on aero performance can be minimal.
When designing a stealth aircraft, do companies ever decide that it is acceptable to allow for buckling below limit?
When designing a supersonic aircraft, do companies ever decide that it is acceptable to allow for buckling below limit?
RE: Stealth and Supersonic Aircraft - Buckling????
Dunno, suggest you ask them. Prepare for silence, as that is probably very highly classified information.
"When designing a supersonic aircraft, do companies ever decide that it is acceptable to allow for buckling below limit?"
Likely yes, but that's just an opinion. Inlets and leading edges need to be clean, and any buckling in those locations is likely designed out. But on wing surfaces past the 10% chord location or further, it likely is less of a concern, and the weight savings in structure that can be gained by thinning the skin and allowing elastic buckling will likely be important for the performance to the same or greater degree than the hit on aero drag.
I know that the P-38 maintenance crews were given an allowable amount of dimpling on the upper wing surface, i.e. some amount of permanent set due to buckling between ribs was deemed acceptable for a front-line fighter. Ok, it's not supersonic, but did operate in the transonic regime and suffered from compressibility issues. This is, however, hearsay from an old pilot I spoke with many years ago.
RE: Stealth and Supersonic Aircraft - Buckling????
If you are suggesting I hijacked the thread, I apologize. Will stay out of yer sandbox.
RE: Stealth and Supersonic Aircraft - Buckling????
it sounds to me like you're trying to check up on something you've been told.
your areas of interest (SS/stealth) are way to restricted for you to get a sensible answer on an open forum. for all we know you could be a north korean trying to find out secret information !? at the same time, for all you know we could be a bunch of lunes.
RE: Stealth and Supersonic Aircraft - Buckling????
BTW this is my second thread, first one was over the summer is a different forum. You are somewhat correct about my reasons for looking although the person I am trying to check is myself. I believe that this is true, just curious if anyone could validate this for me. As btrueblood points out it is hard to get a valid answer. You are probably correct though even if I got an answer here how much credit could I actually give it???
Thanks everyone for the help!
RE: Stealth and Supersonic Aircraft - Buckling????
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?