>>As usual, I cannot recall the source. But I remember reading that the contrarotating propellers were used on an the initial prototypes. The engine was unusually large and powerful for a Japanese fighter of the time, and the propellers were intended to allay fears about torque effects on the small airframe.
>So the contra rotating propellers were used on what Ki-44 model? And is there a performance sheet on it?
As Blackkite notes, it was one of the early prototypes. To the best of my knowledge, it was a predecessor of the operational Ki-44s, not a development of them. So it would not be the Ki-44-III, even though, as Windswords notes, the propellers could, perhaps, appear to be a single four-blade unit.
Contrarotating propellers were developed as insurance against potential handling problems during takeoff and landing. The engine was large and powerful for a Japanese fighter of the time and for a relatively small, closely coupled airframe. Given lack of experience with designs of this type, the developers explored contrarotating propellers as a way of correcting any torque-related controllability issues that might emerge during later flight testing. The contrarotating props worked. But in the event, the handling improvements did not prove significant enough to offset the added weight and complexity. So all subsequent Ki-44s had single propellers.
Since it was an early, pre-production prototype, I imagine that the contra-prop airplane would have had the same armament as the initial production models, had it gone into production. I also doubt that speed, altitude, or range performance would have been signnificantly different from the standard aircraft peformance.
