272 Ki-61-II-KAI airframes sitting forlorn at Kagamigahara were converted to take the Ha-112 engine, and the aircraft was formally accepted for service as the Army Type 5 Fighter Model Ia (Ki-100-Ia). Soon ground crews and pilots alike were singing the praises of the Goshikisen (simply, “Type 5 Fighter”) as the best, most reliable, and easiest-to-fly of all operational JAAF fighters. It was so easy to handle, even the greenest Japanese flyers, with fewer than 100 flight hours before arriving at their new units, were soon flying the Ki-100-Ia like masters. JAAF pilots flying the Goshikisen came to look upon the US Navy’s formidable F6F Hellcat carrier fighter as a relatively easy kill; indeed, the first time the Ki-100 ever encountered the F6F, the Japanese shot down 14 Hellcats without loss. It proved quite capable of intercepting B-29s as well. But the hardest test came with the arrival of the P-51D Mustang in Japanese skies, flying from bases on the newly-captured island of Iwo Jima. Mustang-vs.-Goshikisen dogfights were ferocious affairs. The Mustang was faster, and could engage and disengage at will, but if the American chose to stay and fight, he would have a real hurricane on his hands. The two enemies were so evenly matched in a dogfight, usually, only pilot skill would determine the winner, not the capabilities of the plane alone.
Ki-84
It was in the Philippines, however, where the Ki-84’s weaknesses were discovered. In the furious rush to produce them in great numbers and attempt to replace the older Ki-43, the Hayates, flying under primitive conditions, suffered from faulty engines that could lose oil and/or fuel pressure disconcertingly in combat. They also had poorly designed and unreliable hydraulic systems, and their landing gear legs could snap during rough landings on jungle airfields, due to poor hardening of the steel used.
The Allies must’ve counted themselves very fortunate, indeed, that the Hayate was plagued by poor workmanship and an unreliable engine that limited the type’s serviceability under combat conditions.
