LANDING GEAR

The green hydraulic system provides power for landing gear extension and retraction. In case of hydraulic, electrical or mechanical failure the gear can be extended by gravity using a hand crank that physically disengages the up-locks, opens the gear doors, depressurizes the system and allows the gear to free-fall. The hand crank, located aft on cockpit pedestal, must be rotated three full turns to enable the gravity extension. The nose wheel steering, normally powered by the green hydraulic system, will be lost after gravity extension and the doors will remain open.

LANDING GEAR CONTROL AND INTERFACE UNITS (LGCIU) 

Electrical signals are provided for gear and door actuation by two LGCIUs. The LGCIUs receive information from the landing gear, cargo door and flap systems. They then process gear and door position, sequencing, control and gear lever selection. The LGCIUs also send information and signals to the ECAM and other aircraft systems regarding the ground or flight mode; for example the active LGCIU will signal that the aircraft is on the ground and landing gear retraction will be inhibited; another example would be the inhibition of flap extension during cargo door operations on the ground. In the air, examples would be the inhibition of reverser operation or the closure of the hydraulic safety valve above 260 knots, preventing the gear being extended above this speed. There are at least 37 LGCIU outputs which are obviously beyond the scope of these notes; for more information see FCOM 1.32.10. p8.

• LGCIU 1 provides landing gear position information to the landing gear indicator panel (next to the gear lever) and the ECAM. LGCIU 2 only provides this information to the ECAM, so if you lose LGCIU 1, you will loose the landing gear position information on the indicator panel. On the SD (WHEEL page) each landing gear position is indicated by two triangles. Each triangle is controlled by one LGCIU. 

• A green triangle indicates that its respective LGCIU detects a landing gear downlocked. 

• A red triangle indicates that a landing gear is in transit 

• No triangle indicates that a landing gear is uplocked 

• Amber crosses indicate an LGCIU failure

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