WINDSHIELD WIPERS SYSTEMS

Windshield Wipers Systems

Windshield wipers for aircraft are similar to those used on automobiles except they must be able to withstand the air loads caused by the high speeds of operation. A rain control panel of a large transport aircraft is shown in Figure 7.1. Electri­cal windshield wipers are usually operated by a two-speed DC motor that drives a converter. This converter changes the rotary output of the motor into the reciprocating motion needed for the wiper blades. When the windshield wiper switch is turned OFF, the control circuit is open, but the motor continues to run until the blades are driven to the PARK position. The motor then stops, but the control circuit is armed so the motor will start when the windshield wiper switch is turned to either the FAST or SLOW position. Some installa­tions have a separate position on the speed selec­tor switch that allows the pilot to drive the wiper blades to the PARK position before putting the switch in the OFF position.

illustrates a typical installation of a wiper system showing the wiper, wiper electric motor (actuator) and the control panel on an aircraft. The wiper blades are driven by electric motors. Each windscreen has one electrically operated wiper. A motor–converter assembly that changes the rotary motion to operate the wiper arm drives each wiper. A shaft protruding from the assembly provides an attachment for the wiper arms.