The Pratt & Whitney R-2800-5 engines were reliable, but the Curtiss electric pitch change mechanism in the propellers required impeccable maintenance, not always attainable in the field. Human error and some failures of the mechanism occasionally placed the propeller blades in flat pitch resulting in an overspeeding propeller, sometimes known as a "runaway prop". Due to its sound and the possibility that the propeller blades could disintegrate, this situation was particularly frightening for aircrews. More challenging was a loss of power in one engine during takeoff. These and other malfunctions, as well as human error, claimed a number of aircraft and the commanding officer of the 22nd Bombardment Group, Colonel Mark Lewis.