The drag created by the nil or negative thrust produced by propellers set in the beta/ground idle range is very useful in controlling taxi speed on the ground without wearing out the wheel brakes, but it can transform an aircraft’s aerodynamic efficiency to that of a grand piano when selected in flight.
Thus, a variety of mechanical latches, locks, levers and detents have been devised to prevent the power levers, which contribute to propeller control, from being moved into beta/ground idle mode at the wrong time, such as on short final approach.
Like other aircraft manufacturers, Xian went one step further in its MA60 twin-turboprop transport by incorporating an electromechanical lock as a backup to the mechanical stops that help prevent the power levers from being moved aft of flight idle in the air.
The electromechanical lock is designed to release automatically when the weight-on-wheels system is triggered on touchdown, allowing the pilot flying to subsequently release th…
