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,

That wrinkle in the fuselage is probably related to the removal of the
belly scoop and a lot of shearing material with it. Also, from the
direction of the wrinkle it looks like an up load on the tail is causing
it (not engine torque; that would be reacted by the ailerons). I don't
know, but I doubt that North American would have allowed that much
diagonal tension wrinkling in a fighter fuselage. The picture is from a
different race and anyway I don't see what it has to do with the accident.

Peter Garrison

Did I say it was from torque? :)
I did not know that picture was from a different race. I saw it on somebody's
else's computer at Reno in the hangar within an hour or so of when the crash
happened. What race was it? At the same Reno?

I agree with your North American contention. IMHO it was not until the B52
when that was allowed.  From your use of terms I gather you have Bruhn :)
Back in the late 60's Bernie Pershing, late of the AIAA, would kid me
when I walked into his house carrying a copy in Manhattan beach and said
I was loaded for bear :)


Paul Lamar