32-30-00  EXTENSION AND RETRACTION Back

A. System Function

The extension and retraction system controls and operates the landing gear. It moves the landing gear between the extended and the retracted positions and gives an indication of the position of each landing gear leg.

B. System Components(Ref. Fig. 1)

The primary components of the system are the:
  • Landing-gear control unit
  • Landing-gear control valve
  • Pressure release valve
  • Retraction actuators
  • Downlock units
  • Uplock units

C. System Operation

The system has two modes of operation:
  • The normal mode (which uses the main hydraulic system)
  • The emergency mode (which uses the emergency hydraulic system)
In usual conditions of operation, the pressurized hydraulic fluid (from the main hydraulic system) moves the landing gear. It automatically operates locks to make sure the landing gear is held safely in the set position. When the main hydraulic system is not available, the emergency system is used to extend and lock the landing gear. The emergency system cannot be used to retract the landing gear.

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