P51 D Throttle working correctly in X-Plane settings and while on the ground (engine rpms increase and decrease with throttle movement) but when flying, the engine rpm goes to 3,000 and remains there no matter what the position of the throttle. Also, the sound does not change with the throttle position. The flight characteristic of the aircraft, however, react with the throttle position as expected i.e., throttle down - lose altitude, etc. while the rpms still show 3,000. Throttle appears to work correctly in other aircraft.