Wonder why they didn't go ahead and produce the xp-40Q
420mph isn't bad at all and considerablly faster than other variants not to mention fast enough for contemporary fighters of the time
Karnak provided a good general reason for the XP-40Q not getting a contract.
There were other reasons as well.
By late 1943, the USAAF had come to the conclusion that range was now a very high priority. This was not only observed in the ETO and MTO, but it was even more important in the SWPA theater. There, when worn out P-38F and G models were retired, they were replaced by razorback versions of the P-47D. At once, the number of kills dwindled down to next to nothing. It wasn't that the Jug wasn't superior to the Japanese, it was because the P-47 lacked the range to reach many areas of Japanese air ops. The 49th FG experienced this more than any other, as some squadrons were still flying P-40s too. Before the Mustang showed up late in the war, the P-38 was THE fighter to have in the SWPA. Eventually, enough P-38s were delivered, but some were hand-me-downs.
Curtiss had been in a muddle for years, even prior to WWII. The P-40 was their last fighter accepted by the USAAF. By 1941, it was marginal. By 1943 it was clearly obsolete. Updates were pedestrian, and it was obvious that the airframe was not capable of much more speed, regardless of what engine was employed. It was very draggy, and had limited capacity for fuel. Curtiss had thrown a ton of money down the hole designated as the proposed replacements for the P-40. Early on, the XP-46 proved to be no faster than the P-40. The USAAF saw no reason to order it.
Next, Curtiss wasted more time, talent and money on the XP-53 proposal. It was designed with a long span laminar flow wing, but was to be powered by the failed Continental XIV-1430-3 engine. The USAAF didn't want to waste any time with the Continental and ordered Curtiss to re-design for the Packard built Merlin (that ended up in the P-40F). This new design was designated as the XP-60. Curtiss then went through no less than six major iterations of the XP-60. Donovan Berlin's design team could not think outside of their small box, and program management was horrendous. Finally, the XP-60E was delivered for evaluation and performed sub-standard, and still had too many unresolved problems. Moreover, now fitted with the gas guzzling P&W R-2800, its range was reduced to half that of the P-40N. The final version, the good looking YP-60E, was highly maneuverable, and had an outstanding rate of climb. It would have been a very good interceptor and air superiority fighter, but it's range was a mere 300 miles on internal fuel. Curtiss, yet again, had completely misunderstood what the AAF wanted and needed. The program was cancelled. Curtiss, it seems, was utterly incapable of adapting to the changing needs of their customers and fast evolving aviation technology.
Combine this with the failed XP-62 program, and the God-awful XF14C design for the Navy. Things were looking dismal for Curtiss Wright. Curtiss, which apparently could not design or develop a competitive fighter was offered a contract to build P-47s. Once again, management failed badly. There were continuous production issues with the P-47. Quality control was terrible and delivery was never close to being on time. Curtiss was beginning to look like Brewster, but on a grander scale. The P-47 contract was cancelled and all of the P-47Gs built were individually sorted and repaired as required. All were retained in the States and issued to training squadrons. Curtiss was pretty much done as a builder of fighters for the military.
When the XP-40Q was more or less ready for evaluation by the AAF at Eglin, Germany was just four months from surrendering. Performance was generally competitive with existing fighters already in the field. However, newer fighters being built or in testing offered a far higher benchmark. This and the fact that the XP-40Q offered no improvement in range over the P-40, the fighter was superfluous and unwanted. The USAAF also had grave doubts that Curtiss could meet any reasonable timetable for production and delivery. One AAF test pilot stated his thoughts simply... "It's a nice little fighter, but it's two years too late for our current needs".
Curtiss was a company managed by people who no longer had any strategic vision. Their inability to manage their many fighter programs compounded their inability to anticipate the future needs of the USAAF. Even though the Curtiss Helldiver did replace the SBD in Navy service, no Navy aircraft was more hated for it's poor handling. Its development was typical of Curtiss, years of teething issues and bad management. Beyond the P-40 series and the miserable SB2C, the only other truly successful military aircraft program was the excellent C-46 transport.
With the cancelling of the XF-87 contract in 1948 (Curtiss Wright's last try to be a builder of fighters), Curtiss Wright was officially out of the airplane business, managed into the ground by poor leadership and no genuine understanding of how military aviation had evolved.