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Example: Landing Flaps Drive System

We have developed the entire drive system for the Fowler landing flaps of a business jet aircraft. The landing flaps drive system consists of:
  • the two motors with the central reduction gear box
  • the four actuators with worm gears and ball screw spindles
  • the four flexible shafts between the central gear box and the actuators
The key features are:
  • actuation force: approx. 12 kN = 2700 lbf (each actuator)
  • actuation stroke: approx. 220 mm = 87 in
  • actuation time: approx. 20 s

The systems engineering is according to the conditions of RTCA (DO-160).


The kinematic layout diagram shows the general layout with two motors attached to a common main gear unit, from where the four actuators are driven.

The photograph shows the central drive unit (consisting of the two motors and the main gear box) and the four actuators.

Not shown are the flexible shafts (several meters long) between the main gear box and the actuators.

Drive unit

On both sides of the gear box a motor is attached in the middle. The two outputs for the flexible shafts are on the outer corners.


In the actuator acts a worm gear for the additional increase in torque. The conversion from rotational motion to linear motion is made by a ball screw spindle.