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Example: Elevator Trim Drive System

We have developed the elevator trim drive system for a business jet. It consists of:
  • two motors with a central summing gear
  • two actuators with worm gears and trapezoidal thread spindles
  • flex shafts between the main drive unit and the actuators
  • position sensors and switches (attached to the summing gear and the actuators)
  • slip clutches at the motor output shafts and the actuator input shafts
The elevator trim drive system is a "fly-by-wire" design without any mechanical connections between the cockpit and the elevator. So special reliability requirements apply.

Kinematic Layout

The central drive unit drives two (practically identical) actuators by flex shafts. The reliabiliy is guaranteed by key components (position sensors, slip clutches).

Drive Unit

The drive unit consits of the motors, the spur gears and the safety components.

Actuator with worm gear and trapezoidal thread spindle

The (practically identical) actuators have a high gear ration and are therefore self-locking (worm gear, trapezoidal thread spindles). There are also safety components to detect mechanical failures (e.g. rupture of the drive train).