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Gaston Marty
Canada
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The Data on these 3 cards has been updated:

http://forums.ubi.com/eve/forums/a/tpc/f/4811054957/m/503108...

The P-47D now has a prolonged sustained turn rate, below 250 MPH (speed value of 4 maximum), superior to just about anything else except the FW-190A, if the P-47D is turning to the left, but it's turn rate at higher speeds is only about even with the Me-109G, and progressively inferior to the P-51D as speed increases past 300-350, However above 250 MPH it is better than the FW-190A at these higher speeds if turning to the right at high Gs (Slip/double turn).

The turn performance of the P-47D is extremely hard to pin down, between US side-by-side tests that have its sustained turn much inferior to both the P-51 and P-38 (it loses out in around 3 X 360°), and combat pilot hype who make claims that it out-turned everything in the sky above 22 000 ft, (not really that true), it is hard to form even a marginally plausible conclusion...

An indication of just how hype-prone P-47D combat pilots are, is the claim, which I have heard from several interviews of them now, that field-boosting of its power to 72" or 80" would yield TAS speeds of 470 MPH, for the D, to 500 MPH for the M at 30 000 ft... In other words + 40-60 MPH above 25 000 ft.... The reality, from detailed test charts done with the very same levels of power, is rather disheartening to anyone who wants to take pilot claims at face value: Increasing power from 57" to 72" yields ZERO increases in speed above 24 000 ft. for the D model, but substantial 30-40 MPH increases BELOW that height...

The best thing to do is to study actual combat reports, which are away from test pilot theory, and yet force the occasionally fanciful combat pilot to go through a step-by-step narration of what happened...

The picture that then emerges of the P-47D in actual combat, especially for the Razorback, is completely different from anything one would expect from tests, and from the lore vehiculated by some of its pilots...

What emerges is a rather startling similarity to the equally startling, and little-known, FW-190A reality: A fighter happy to out-turn much lighter opponents at low speeds, if not quite as good at low speeds as the FW-190A, and slightly better than it above 250 MPH, especially in harsh right turns.

The Spitfire can initiate harder short-term unsustained turns than either of them, but if my reading of thousands of combat accounts is correct, when the turning got prolonged over several 360°, these two heavy, burly short-nosed radial fighters were actually better than the Spitfire in sustaining quicker consecutive turns. (This was for sure the case for the FW-190A, and to left the P-47D Razorback was a close match to it until the FW-190A-8 got a broader prop and the P-47D became a seemingly less low-speed friendly Bubbletop)

The other two Data Cards received the changes already described earlier.

Of note is my P-38L Data Card, which I will keep here, but I no longer consider it accurate: There are few combat accounts of the P-38L vs Western fighters, and lightweight Japanese fighters are not very indicative of its performance relative to the heavier Western types...

Therefore much of that Data Card was based on a very detailed confrontation between a P-38G and a Spitfire Mk XIV, after the gauntlet was thrown by the British pilot in a rather loud and implausible way... That story had a somewhat authentic and detailed feel to it, but strangely enough, no unit numbers or other corroborating evidence ever surfaced about it (the lack of unit numbers is a big give-away)... It may well have been told by an actual WWII pilot, but some details now seem contrived for dramatic purposes, and the comparative performance of the two aircrafts is not accurate to my eyes from what I have read elsewhere: I am now nearly sure the story is a fraud, and this effectively destroys much of the credit I gave to my P-38 Data Card... The roll rate, climb rate, speed and dive performance are all accurate, but that is about all I would vouch for... Fighting mostly with Japanese aircrafts, the P-38 simply does not give me a clear enough picture of its turn performance... In the Pacific, only the F6F was said, by the Japanese themselves, to regularly try and turn-fight with them...

I have a theory as to why heavier short-nosed fighters are superior at low speeds and low G sustained turns. It has to do with the prop moving forward more slowly on the inside part of the turn, an effect that has the increasing angle of attack (to make the turn) forcing the prop backwards (versus the trajectory) against its own thrust (unlike with the thrust as on jets), and slanting said thrust at a slight nose-down downward angle, which creates a new "induced" wing angle of attack, thus increasing the wing's ability to bear extra loads.

The lenght of the nose then becomes a negative leverage on the wings, whose Center of Lift becomes the principal bearer of the prop's leveraged "tilt-back" load. This is likely because somehow the total downforces are now behind the total lift forces...

In the accepted theory, the tailplanes does not provide lift, but normally always provides a slight downforce instead, which is why their action is seen as a torque on a single point of lift/downforce.

I think the elevator action, in nose traction aircrafts, does not act like a torque on a single point of rotation, as is now assumed, but instead acts as an additional downforce, moving total downforces behind the center of lift, which is itself boosted by gaining lift from the deflected thrust angle, this boost in lift augmenting the elevator effort, like a pulley effect, to help beat backwards the top of the prop compared to the trajectory...

This explains why "pulling back on the prop" is not experienced as a huge stick effort by the pilot.

My theory would explain why many pilots have reported faster sustained turn rates at reduced power, which current propulsion-based (as opposed to traction-based) theories do not explain. The reduced power claims by pilots are very credible, and confirm there is something going on here aero engineers have not yet figured out...

Regardless if my theory is true or not, the Data Cards now reflect combat reports and many side-by-side tests better, and that's what matters...

Gaston

P.S. If you have any questions, please contact me at: Gaston1_01@hotmail.com

G.
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