Paul,

I did the same calculation as you did and got a different result.
Assuming a density altitude of 7,000 feet and a true airspeed of 500 mph,
the indicated airspeed is 450. The corresponding q is 520 lb/sq ft.
The wing area is 170, not 235, because 10 feet had been clipped off, so the
available force at CL=1.0 would be 170 * 520 or 88,400 pounds.
Assuming the airplane weighed 8,840 pounds (as good a guess as any; probably
a bit more than that, actually), CL or rather normal force in 1G level
flight would be 0.1. CL required for 11 G would be 11 times that, or 1.1.
For a wing of aspect ratio 4.3, lift curve slope is probably around 0.08 per
degree, so an angle of attack increase of 12.5 degrees would be required.

 From this I conclude that the 11 G reported from the telemetry was a
transient, and the stable G with a floating elevator would have been quite a
bit lower. But the initial shock may have slammed him down against the stick
or panel (the acceleration would have been down and forward, because of
deceleration from G and also from temporary loss of fuel flow) and knocked
him out, or at least made him blind and woozy.
Speed over the top of the loop was around 360, I think; power came back in,
speed was 505 at impact with 105 in. Hg.

Peter Garrison

It all depends on what you start with:) I did not know about the 10 foot
wing clip. The stock P51 empty weight was:

Model.........     XP-51..    P-51A...P-51B/C-1...P-51B/C...P-51D/K...P-51H
Empty Weight...    6280 ...6433....6840........6985.......    7635 ....7040

I assumed there was a weight reduction as when you are pulling a bunch of
G's in the corner weight has a large affect on induced drag.
C sub L squared over pi times the  Aspect Ratio. Short wings sometimes hurt
:) As I recall there is now a weight minimum for unlimited's.

Dave Leonard was pulling 2.5 G's with his lowly turbo rotary powered
230 MPH RV6. Confirmed by the G meter tell tail. I don't know what the
unlimited's are pulling in the corners.


BTW I just finished a great book on the the development of the P51 called
"Mustang Designer Edgar Schmued and the P-51" By Ray Wagner. The Brits
criticized the P-51 as being too heavy. North American initially used higher
design G limits load factors than the Brits. When the Mustang P51-G was
redesigned for the lighter weight using the Brit G limits it came out about
600 pounds lighter. The redesign used thiner (.042 instead of 065) 2025-T6
skins in some areas. 7075T6 was invented about that time but it was in short
supply so North American decided to make their own 2025-T6. Note the wrinkle
in the GG fuse!

Thanks for redoing the calcs Peter.



Paul Lamar

Paul,

This guy is talking about a broken aileron trim tab, but all of the previous
discussion was about a broken elevator trim tab. There have also been photos
clearly showing the latter. This discrepancy makes me doubt this
explanation.

Csaba

Yes, Good observation Csaba.

Paul Lamar