When comparing the Hellcat with Mustang, quirk is that those two machines were excellent in each of their own domains, and would be hard pressed to undertake jobs of the another machine. Hellcat was a fighter that offered docile handling characteristics (crucial for run-on-the-mill aviators, let alone for the carrier duties), ability to shrug off plenty of enemy hits that landed home, perfect weapon layout for it's job and war theaters, an engine that offered plenty of power at all altitudes for the heavy brute. On the other hand, Hellcat was offering less performance and range than Merlin Mustang (even without fuselage tank), or even P-51A (V-1710). Sending droves of Hellcats at 25-30000 ft against Luftwaffe would've meant plenty of dead Allied airmen, due to lack of performance.
Mustang was a fine-land based fighter even with V-1710, let alone with 2-stage Merlin aboard. It went into a contested airspace some 15 months before Hellcat, and was not considered as a pushover by anyone. Despite having no advantage worth speaking of vs. Luftwaffe. Mustang got better with different V-1710 and drop tanks capability (P-51A/Mustang II). On the other hand, the tested P-51D was not that well regarded as the Hellcat as a carrier bird, though we might wonder how good would've been the lighter P-51/51A in that role.
The Mustang required an engine transplant and an extra fuel tank which adversely affected its stability when full, to be truly effective in the role of long-range fighter escort.
Again, P-51A was already longer ranged and better performer than Hellcat. The capability to have a new engine and fuel tank installed is simply that - a capability, not a shortcoming.
We might recall that even the A-36, with a true low-level V-1710 installed, was used as an escort fighter in MTO. That is several moths before the Hellcat 1st fights.
And I find it a little insulting people are trivializing the opposition and difficulties faced by Allied forces in the PTO or the achievements of pilots like McCampbell - who achieved ace in a day twice as well as being the commanding officer of the Essex's air group, which achieved outstanding performance under his leadership. Harris, Vraciu, Voris, and other standout Hellcat aces were I'd wager just as capable as anyone in any other branch.
Don't think that anyone wants to make insults to any of the pilots or crewmen. The fact is that Japanese opposition was flying, in 90% during the 1st Hellcat's war year, the fighters that were making between 330-370 mph (= slower by 20-60 mph). Many of them were ill armed to really harm the Hellcat. Hellcat also engaged plenty of bomber and attack aircraft, unlike the Mustang that mostly engaged fighters. Against the IJN, the USN have had, in time Hellcat was aboard, far more numerous and better led fighter force, backed up by radar assisted command and control network.
By the end of the war in Europe the Luftwaffe had large amounts of barely-trained kids, same as the Japanese.
The Japanese started to scrub the barrel already in late 1942, due to the efforts of Allied forces both on the ground, air and on ships. Japanese can also blame themselves for that, of course.
The LW was in that state maybe at mid, or late 1944?
