That's bogus Shortround. What you said may be technically correct, but the speed difference is zero for all practical purposes and so it doesn't wash at all.
Why is it bogus? because you don't like it?
The D-9 may not have a lot less drag but was somewhat lower or it wouldn't have gone about 1% faster on 6% less power, not counting the drop tank-rack which was good for 4-6mph speed loss or another 1% in speed. The D-9s wing was also bit old by 1944, dating from 1938/39. Newer than the P-36 wing but perhaps not quite up to recent developments?
As I stated, the XP-40Q had a superior rate of climb to the Fw 190D-9, the roll was the best or near the best of Allied fighters, and it is upposed to have been as maneuverable as a regular P-40 in turn. I just don't see at all why it should be judged as uncompetitive.
We have several things going on here with the "Q". The Prototype may have climbed faster than the D-9 (D-9 climb rates are all over the place as the engine was up-rated several times
without any real change in designation) production version vs D-9 depends on
which Allison the "Q" was using
when vs
which D-9 and
When.
The bit about "to have been as maneuverable as a regular P-40 in turn" needs a bit of explaining as the "Q" weighed about 600-900lbs more than older P-40s. depending on model and had a slightly smaller wing. Perhaps they were close but " as maneuverable as"?
We also have the question of armament. Four .50 cal guns with 235rpg. Not exactly first class in 1944. P-51s with Four .50s at least carried 250rpg for inboard guns and 350rpg for the outers and"D"s could carry 500rpg for 4 guns.
Production P-40Qs were
supposed to have six .50s or four 20mm guns. No mention is ever made of what effects this would have on performance.
BTW the D-9 had two 13mm guns with 475rpg and two 20mm cannon with 250rpg. A much great weight of installed armament.
Granted a few seconds is all you need for ONE kill but the "Q" seems a bit lacking in combat duration, of course this is not a big problem because it is also lacking in fuel capacity and range so it is not likely to get too deep into enemy territory. One fuel tank under the fuselage is not going to be enough even if the internal fuel (160 gallons?) was enough for the missions required. A bit of problem in the Pacific in 1944/45, doesn't really matter if you can outfight the Japanese fighters if you can't reach them from the majority of you land bases. Granted you could probably plum the wing racks for fuel tanks if it wasn't done on the last of the P-40Ns already.
SO lets see where we are as far as
fast introduction goes, bearing mind that the first P-51D rolled out the factory door in Jan 1944 and sizable numbers only showed up in England in June ( 4 month minimum from Jan 31s to June 1st).
Need a
production Allison with two stage supercharger. 1325hp for take-off or 1425hp for take-off? the 1325hp versions offered over 1800hp at sea level with water injection but performance at altitude sucked Relatively speaking, they were down to 1500hp by 6,000ft and 1150hp at 22,400ft.
Need to do a bit of work on the wing? Q used the inner gun bays for radiators and/or oil coolers (accounts differ) so going to six guns means moving the cooling equipment or adding gun bays outboard of the existing ones, I wouldn't say impossible but adds to work needed. Changing to 20mm guns may also be quite possible but again needs new drawings and fixtures. The hit to performance could be substantial, both weight and drag of the gun barrels.
Needs more fuel. Mustang not only carries more fuel inside it can carry 1000lbs under each wing which usually meant 75 or 110 gallon drop tanks for combat operations (corrections welcome) Perhaps a P-40 with plumbed wings could carry a 75 gallon under each wing? Late P-40s did carry a 500lb bomb under each wing and earlier versions were often field modified to carry much more than the "book" 100lb bomb under each wing. I tend to doubt you could fit more than the 52 gallon tank under the fuselage due to ground clearance problems. 202 max external fuel?
Please remember that P-47Ds with the bigger fuselage tank begin to roll out the doors in April of 1944 so work to extend the range of the P-47 was being done in the fall/winter of 1943/44. The bigger fuselage tank extended the "book" radius by 100 miles without drop tanks and by 175 miles when carrying a pair of 150 gallon drop tanks.
The USAAF was not looking for short range fighters in the winter of 1943/44.
Not a lot of engineering work but some, so production examples are NOT going to be rolling out the door in April or May of 1944 even
IF you can get the engines.
Looks to me as if were very competitive. Just wasn't selected for production. I suppose we can look at the same data and see diffferent things, which is OK
.
The "Q" might have been competitive for certain limited roles. However the US wasn't really interested in limited use fighters unless there was something
really extraordinary about their performance (P-47M ?)
The US didn't even want the P-63, which using the same engine/s (or close) was faster and carried a heavier armament. Had shorter range than even the P-40Q though which explains a lot about why the US didn't want it.