EXTENSION/RETRACTION SYSTEM–MAIN COMPONENTS
LANDING GEAR CONTROL PANEL (LGCP) AND LANDING GEAR
CONTROL LEVER (LGCL)
The Landing Gear Control Panel is located on the forward RH side of the
central console. The LGCP includes the controls and indications for:
• LG normal extension/retraction (LGCL and LG status annunciators)
• LG emergency extension (EMER DOWN guarded push-button switch)
• Nose wheel centerlock (pushbutton switch)
• Park brake handle
The LGCL has two positions: UP and DOWN to control the landing gear
control valve, LG normal retraction and extension. The control lever must be
pulled before operating it. The LG status annunciators show the LG position
with the following logic:
• 3 green lights for DOWN and LOCKED position with LGCL at DOWN
• all lights extinguished for LG in UP position with LGCL at UP
• 3 amber lights for any other condition (LG unsafe)
• Green/amber light to display the NLG center lock status
The LGCL locked in the DOWN position when the helicopter is on the
ground (WOW microswitch).
EMERGENCY DOWN (EMER DOWN) PUSHBUTTON SWITCH
An EMER DOWN guarded switch control the emergency section of the
Landing Gear Control Valve. The switch is able to move down the landing
gears in case of failure in the normal hydraulic circuit of the control lever. In
this case the emergency switch will be used to electrically actuate the
emergency spool of the Landing Gear Control Valve.
LANDING GEAR CONTROL VALVE (LGCV)
The Landing Gear Control Valve (LGCV) controls the hydraulic fluid flow
towards to the landing gear actuators. The LGCV comprises two solenoid
valves identified as UP and DOWN solenoid valves.
When the pilot moves the Landing Gear Control Lever to the UP or DOWN
positions, electrical power is supplied to the relevant solenoid valve that, in
turn, supply hydraulic power to the UP or DOWN circuit respectively.
The landing-gear control valve is connected to the hydraulic operated
components of the NLG and MLG via a manifold.
MLG EXTENSION / RETRACTION ACTUATOR (RA)
The extension/retraction actuator is an hydraulic actuator which, together
with the shortening actuator, extends and retracts the MLG according to the
pilot selection. The extension/retraction actuator is attached to a structural
element of the MLG (the trunnion).
The MLG RA has an internal mechanical locking device which is active when
the MLG is fully extended out of its bay.
The locking device is unlocked by hydraulic pressure.
MLG SHORTENING ACTUATOR (SA)
The main landing gear Shortening Actuator (SA) increases its length for the
retraction of the landing gear and decreases its length for the extension.
The MLG SA has an internal mechanical locking device which is active when
the MLG is fully extendeded (down and locked). The locking device is
unlocked by hydraulic pressure.
NLG EXTENSION / RETRACTION ACTUATOR (RA)
The NLG extension/retraction actuator is an hydraulic actuator which
extends and retracts the NLG according to pilot selections on the Landing
Gear Control Lever (LGCL).
The NLG RA has an internal mechanical locking device which is active when
the NLG is fully extendeded (down and locked). The locking device is
unlocked by hydraulic pressure.
POSITION MICROSWITCHES
Position microswitches monitor the extended, retracted and locked
conditions of each actuator of the MLG and NLG to control the normal
extension/retraction sequences and provide LG status indications on the
LGC