The Airbus A320 has a hand crank on the center pedestal that allows the flight crew to extend the landing gear if the aircraft loses hydraulic systems or electrical power (Gravity extension).
If the normal system fails to extend the landing gear hydraulically, the flight crew can use a crank to extend it mechanically.
To put the landing gear down by gravity, the flight crew must pull the gear crank out, then turn it clockwise for 3 turns. When the flight crew operates the crank handle, the cutout valve shuts off hydraulic pressure to the landing gear system and depressurizes it.
When a crew member turns the crank, it :
- Isolates the landing gear hydraulics from the green hydraulic system
- Unlocks the landing gear doors and the main and nose main gear
- Allows gravity to drop the gear into the extended position.
Locking springs help the crew to crank the main gear into the locked condition, and aerodynamic forces assist in the locking of the nose gear.
The gear doors remain open.
The flight crew can reset the emergency extension system in flight after using it for training (if green hydraulic pressure is available).