drgondog
Major
Doesn't sound difficult drgndog, simply source the NACA report for Jan24 1939 pilot H Lloyd Child a/c P-36A, the flight was just before noon at Buffalo.
I couldn't source the report in the NASA/NACA records - do you have a copy?
The book is quite well presented, with plenty of primary source references and a glowing foreword praising it is by NACA test pilot Richard Collins.
Glowing Forwards are Nice
And the flight test itself is clearly explained and witnessed and published in the media as the dive that was "faster than a bullet," at the time it made Curtiss and the pilot Child quite famous. Hallion himself writes "one can have little doubt the Hawk exceeded 500mph during the dive but 600mph?"
Bold claims are Nice". A .45ACP at 830 fps is about as slow a bullet as existed in Gov't service - that would be .74M (830/1161) at SL. You think a P-36A could do .74M at SL (or any altitude) ? Did any of the reports specify what they meant by a 'speeding bullet"?
He also notes there was some controversy about the French recording instrumentation placed aboard the a/c as a result. In any case it is the pilot's testomony he exceeded 500mph by a count of seventeen seconds in a vertical dive. Child wrote "It was a good opportunity to see what the Hawk could do, if let out a little, and I gave the plane its head."
Child is one of the most respected test pilots who ever lived.
The world is full of great and respected pilots that looked at their instrumentation while diving. The world has seen infinite testimonials about Mustangs and Spitfires 'exceeding 600-650 mph' in dives in combat Encounter Reports. Would you consider those claims credible?
The facts to support the claims via calibrated instruments, compensated for stagnation pressure/temperatures induced under compressibility effects are Zero in the 1930-1945 timeframe.
He was also quite explicit that the F3F biplane routinely attained 400mph in dives. The reference to the XF4U-1 routinely achieving 550mph in dive tests is also quite explicit.
I would come closer to believeing 400mph for the F3F than 500 for P-36A. Ditto on the instrumentation questions but 400mph, at altitudes near 10,000 feet, is closer to .55M where the instrument readings (IAS) were corrected for altitude w/o much error. .55M is where compressibility becomes a factor in pitot tube reliability w/o Temp sensor corrections.
but I would more believe the F4U results as 'close' to 550mph TAS than a P-36A at 500 mph -
Since this book is mostly based on the commentaries of the test pilots themselves and their official reports, I can really see little manner in which to challenge its voracity.
I didn't question veracity - they believed what they saw. I question whether what they saw (instrument readings) was corrected for compressibiliy effects - and QED whether the claims matched reality.
It even goes so far as to directly challenge manufacturer listed technical specifications of aircraft, though again it uses test pilot reporting and service documentation (for example Lindbergh's contractual flights for the DoD in the P-47 and F4U) to do it.
I appreciate your personal disbelief, I find the challenging and controversial statements made by test pilots amusing and fascinating.
It is not only credible the P-36 achieved 500mph, it is really incontrovertible. Else you call the pilot, the French contingent, the airfield personnel, the testors, all liars, or a very detailed description of the test itself, referencing test pilot Child's own statements, obviously available official reports, media publication of the time, and with the support of Richard Collins on the general voracity of the author...complete fiction. Perhaps it could be, though I assure you I am more than satisfied.
Good for you.
I assume you are not only a fact driven rational person but also a technically competent individual.
To embrace the narratives in complete confidence that the engineering level compressibility calculations were made prior to and after the statements were published would suggest that you a.) understood the instrumentation, b.) understand the REQUIREMENT to both sense and record the stagnation temperatures when the free stream pressures are brought to a rest, along with the stagnation pressures, and c.) can point out that such instruments existed in 1940-1945 - much less in 1939?
Sources, Please!
I reiterate that I am willing to supend belief and examine the reports but I have a far better Engineering education in Aero than any of the aero engineers of the 30's and 40's (simply because far more Aerodynamics knowledge was available and taught in the 60's and 70's).
I am NOT saying smarter - just more knowledgable about compressibility and the effects to instruments, flow characteristics and stability and control of aircraft in that regime than the guys who were seeing it for the first time and scratching their heads... and sure as hell more than the test pilots of the 30's
I need to see the actual reports to better understand how they arrived at their conclusions regarding the speeds attained in the dive tests before I believe the conclusions.
Even a time/altitude and IAS series of data points would help but IAS would be significantly overstated at speed near .6 to .7M simply because of the significant temperature rise of the air brought to a rest, causing an error in the stagnation pressure reading.
If there was a camera mounted with time stamps to monitor altimeter readings versus time, they could could get an accurate true 'vertical' (perpendicular vector to ground) velocity. If they had that plus an accurate method to measure dive Angle - then they could finally plot the TAS along the angle of the dive .. but not with instruments of the day
Summary - Absent the camera/altimeter/dive angle verification, They REQUIRE temperature sensors within the pitot tube, to compare against the actual Temp at that altitude, to arrive at the Temp corrected density and therefore the corrected TAS.
If you have your hands on the Report see what it says about the instrument correction methodology.