Saab340 AutoCoarsen and CTOT的功能说明

The AutoCoarsen system was designed into the aircraft per single-engine climb certification requirements. With the autocoarsen computer turned on for takeoff and landing (in event of go-around), should an engine failure occur, the airplane will automatically “coarsen” the pitch of the inoperative engine’s propeller to a mimimum drag setting (not completely feathered).

The CTOT is a fancy little system to meter fuel during takeoff and during an autocoarsen event. Turboprops can be finicky about setting takeoff power due to “torque bloom” as the airplane accelerates. The CTOT, or Constant Torque on Takeoff, lets us undershoot the torque setting with the power levers and let the torque motor add addional fuel to command and contol a constant torque as set into the CTOT control panel. As an added bonus, the CTOT system also has an APR, or Automatic Power Reserve switch postition that, in the event of an autocoarsen, will boost the operating engine’s power by 7% torque to provide the required performance for continued climb.