Originally Posted by
Pilot DAR
I agree that WWII propeller powered fighters might have differing handling, which perhaps would not be compliant to today's certification standards, and probably the experience base for the WWII types is small.
That is a very interesting comment, as I usually hear the exact opposite... I would also suspect the "experience base" is not only small, but quite
old, using old measuring protocols and instrumentation...
One of those questionable test data results would be this: The 1940s flight manual of the P-51 claims the minimum speed for a P-51D to briefly "touch" 6 Gs is 255 mph ias (240 with flaps), but when the SETP in 1989 did a test with 4 old warbirds at METO power, the minimum speed needed for the P-51D was nearer 300 mph ias at 10k, and they could not touch 6G under 276 mph even when spiralling down... (The manual, as I said, claims 255 mph ias, presumably including level flight...): The SETP tests were during actual 6G
level turns, and I think this made the difference...
My theory for this is that the manual's data was extrapolated from doing dive pull-outs at 6 Gs (an easier maneuver to execute consistently while "upright"), and that this was assumed to be the same limiting speed for horizontal turns (in theory, there is nothing about the horizontal that would change the data, except -in my view- that the prop blades are unloaded in a dive)...
You also mention power in the 210 hp range: I suspect data at this power level might not linearly translate ("scale up") to low wing single engine types in the 1500-2000 hp range.
I would like to ask you this question concerning my theory, given your experience: I'll quickly recap it here:
"The effect on the prop I would see is that, in a low wing position, the prop's exit spiral is, by necessity, "split" into above wing or below wing airflows. Increasing the angle of attack by turning, while curving the incoming air upward to the fuselage, might cause that "split" to change in its above-below wing distribution, some of the "below wing" air "shifting" to above the wing. If that proportion of change is significant, this air would then be forced into a kind of "dogleg" path, which would lenghten its path, and so accelerate this portion of the air, depressurizing the corresponding area of thrust within the prop disc (in this case the below wing area)."
Although you might think weakening the outer turn (lower) prop half would yield a nose down trim while banked, I believe in low-speed turns (thus at high prop load) the effect is actually to cause a turn to "self-tighten" on high power low wing monoplanes, this due to the CL shifting forward in response to the turn-aversion of the prop... (This would explain the horizontal turn "self tightening" at low speeds -presumably causing mild stick pushing-, but not high speeds, an odd phenomenon that is described on some WWII fighter types)
My question would be this:Are thereknown differences of handling in horizontal turns between low wing and high wing single engine aircrafts? I note nearly all WWII fighters are of low wing design, while most post-WWII civilian/utility single engine prop aircraft are of high wing design. These differences are probably mostly related to stability in flight and the lenght of take-off, but I wonder what is said about the difference in steep turn handling, since a high wing obviously "splits" the prop spiral differently?
I'll note that this is not an insignificant issue, since one of the the rare WWII mid-wing fighters (converted from a floatplane), the N1K1, had a mysterious tendency to go in "auto-rotation" during turning combat (flipping on a vertical or vertical axis, sometimes alternating both unpredictably), this being severe to such an extent that the entire aircraft was redesigned with a conventional low wing...
Wing height on a prop-bearing fuselage seems to be a truly major handling issue...
Gaston