F4U G Limits

[Toad]

What I'm saying is that the wingman would have come back and said: "geez! we went in to a dive with a rolling pullout and lead's wing snapped off. I was late following, so I wasn't going as fast and eased on out"

Or some such...if wings were snapping off, someone would have seen it and the warstories would exist.

It might indeed take telemetry or other types of investigations to determine why it was happening but you can be pretty sure if it had happened a very much it would be in the F4U's "public" history, like the Typhoon's problem.

[This message has been edited by Toad (edited 02-02-2000).]

[Sharky]

Hello all,

I think the problem here is, correct me if I'm wrong, is not one of excess "G" forces in a dive that is causing the stress failures in the wings.  Seems to me I read somewhere that as speed increases the center of lift moves forward on the wing and this can cause a twisting and shearing force on the wing.  Increase the speed high enough (as in a high speed dive) and the wings can sorta peel themselves right off the airplane.  Seems in this case that the wing is seeing more "G"s than the pilot so you don't gray or black out but the wings come off.

Sharky

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You can run, but you just die tired.

[funked]

Yeah you're right Toad.  Fits in more with the fatigue type damage I mentioned above.  It wouldn't happen frequently enough to become infamous.

[wells]

Going back to the stress calculations.  I made some more 'accurate' measurements using my 1/48 scale model...hehe

I figure the ailerons span about 50 sq ft of wing surface.  From the center of the aileron to the wing folding joint is about 8 feet.  With the outer wing panels being some 95 sq ft, I figure a torque load of about 170000 lbs.ft at 7.5 G is the limit.

I ran the airfoil (NACA23009) through the analysis program with aileron deflections of 19 down and 14 up.  Here's what it spit out!

The ailerons change the lift coefficient by about 0.5.  Doing the math for various G loads, I came up with the following speed limits:

1G - 540 mph
2G - 490 mph
3G - 450 mph
4G - 390 mph
5G - 330 mph
6G - 260 mph (Note:  This is only barely achievable before stalling)

I would say that full deflection could be used at higher speeds, depending on G load, but that in keeping with the 300 knts force limit, you were pretty safe, regardless of any G load within the allowable limit.  there was still a 50% margin of safety on top of that.

[Toad]

Thx, wells.

I think I'm losing wings in rolls well below those limits. Going to have to start filming, I guess

[wells]

It doesn't seem too bad to me.  I really had to pull to a full blackout at 400 mph to break the wing off by rolling.