I think it's pretty clear if you read my sentence about corner speed that I know it's not sustained; I said continuous over SECONDS, to distinguish it from a micro-second "bump" in Gs for which the airframes are stressed at; 13 Gs for the P-51, 15 Gs for the 109...
There IS something sustained about it, because otherwise, if that was the ABSOLUTE G limit for ANY lenght of time, there would be no need for 15 Gs airframes now would there?
I added that corner speed is usually equivalent to the smallest unsustained turning radius, but you still have to sustain the Gs for at least 180° to make a radius... Diving in the turn to maintain the "perfect" corner speed and the smallest possible turning radius could be implied, but I said "should" because I wasn't talking about absolute theoretical perfection...
These airframes had to be overstrenght, just like an alpinist rope has to have a breaking strain many times a body's weight, because even a slip or shake can cause 10 Gs for miliseconds, just like wind buffeting or a small pitch-up can cause 10 Gs for periods of time far too short to black-out the pilot, but long enough to cause a crack!
WW II fighters, incidently, were not normally structurally overstressed in turns, but in dive pull-outs above 400 MPH TAS, because the parallel pull of gravity added a lot to the pitch-up instability and the pull-out strain...
This reminds me of a gruesome anecdote I heard of a North American engineer visiting front-line units. A pilot told him; "the wings are breaking off in the dive pull-out", to which the engineer, knowing about the Mustang's 13 Gs rating, confidently replied; "Impossible, you cannot exert that much force on the airframe at the required speed; we tested it." The pilot describes what happened next; "He had not finished speaking his words that we heard the familiar clap-boom of a p-51B's breaking its wings, the clap being the wings breaking, the boom being the fuselage burying itself 10 ft. into the ground. We turned in time to see two fluttering Mustang wings, the fuselage and pilot having long since dived into the ground. "What was that?" he said. "It just happened again" I said..."
So trained engineers who had designed, tested and calculated the stresses on the P-51 for YEARS did not know everything about their creation... So much for "calculated" figures...
On the delayed response issue, there is the time for the pilot to pull the required force (as pointed out); this is what I call the pilot-stick delay, then there is the time for the control suface to overcome the pitch stability; elevator-pitch delay (usually very quick as fighters are designed with low stability), finally there is the pitch-trajectory delay, a critical one because not all aircraft do the same at the same speeds, the Spitfire/FW-190A being great at low speeds, but tending to mush at higher speeds (the Spitfire above 300 MPH did not allow the pilot to pull the top of the stick more than 3/4 inch before mushing. The good thing was that the mush still allowed full 3 axis control.), while the P-47 mushed at lower speeds, and maybe also at higher speeds, without the help of gravity in the "oblique turn trick", to the point Robert Johnson described performing a full roll OPPOSITE to the 190's turn, just to "take out" the mushing that for some reason "disapeared" after a full 360° opposite roll but not before...
This alone shows mushing was a considerable issue, and is mentionned by pilots at all kinds of speeds, except that I think that at 350-400 MPH TAS and above the differences in mushing tendend to "narrow down" among many aircrafts, especially in horizontal turns, but less so in dive pull-outs if the FW-190A is taken as an example...
I don't think "mushing" can be described as being anything other than a delay in turning...
As for the "corner speed very close to the max. level speed", I think since they did stall these aircrafts in turns, and if they found it best to do turns with flaps at, say 310 MPH IAS-370 TAS at 10 000ft., then it could mean we don't know the Mustang as well as we think we do... These were, after all, a bunch of seasoned test pilots with modern instruments... It does corroborate the anecdotal increasing turn disparity with German fighters above 300 MPH TAS. That they didn't go to 8G does raise questions, assuming that the 8 G/270 MPH IAS corner speed was not a "calculated" figure, such things being often unmentionned in 1940's data... (Remember the Noth American engineer's absolute trust in his math?)
The main problem I have with what they are saying is their perhaps jet bias that makes them underestimate the low speed sustained turn rate acceleration below a speed they may have avoided. Also, we don't know what they meant by "very close". Finally, learning the Mustang stall is a fine art, though I wouldn't assume that they didn't know that.
They do however mention using 67" MAP in the test.
Gaston.
