-
port B is the L/G lift line
-
port C is the hydraulic-reservoir return line.
(2) Operation
During a L/G normal extension and retraction operation, ports A and B are closed. The internal leakage vents to return through port C.
During a L/G free-fall extension, the operation of the vent valve opens ports A and B to port C so that hydraulic fluid returns to the reservoir.
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Vent Valve - Main Landing Gear (2516GM),
Nose Landing Gear (2532GM)
Figure 007
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1 1
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Vent Valve Main and Nose Landing Gear-Schematic
Figure 008
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7. Operation/Control and Indicating
________________________________
A. Operation/Control
A handle assembly on the cockpit center-pedestal controls the L/G free-fall extension. When operated, it starts (through a system of cables and mechanical links) the sequence that follows:
CONDITION ACTION
1. The cut-out valve operates - the pressure supply line closes
- the L/G hydraulic-supply system
is connected to return.
2. The NLG and MLG vent valves - the hydraulic fluid from the door
open actuator 'close' chamber and
the L/G actuator 'retraction'
chamber goes to the reservoir.
3. The L/G door uplocks release - the L/G doors open.
4. The NLG and MLG uplocks - the NLG and MLG extends.
release
5. The check valve operates - the supply of hydraulic fluid to
the L/G actuator 'extension'
chambers is increased, to prevent
cavitation.
After landing with free-fall extension, it is necessary to make the L/G and the L/G doors safe (Ref. 32-00-00).
With the aircraft in flight, the L/G system can be put back to its normal extension and retraction mode from a free-fall extension test. The L/G control handle must be set to DOWN and the L/G free-fall extension-handle put to its stowed position. The cut-out valve connects the green hydraulic supply to the landing gear selection manifold and the vent valves close ports A and B. Hydraulic power is therefore supplied for normal operation.
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There is no special indication for the position of the L/G in the free-fall extension mode. The L/G doors will show OPEN when the free-fall extension system is used. The other indications in the cockpit are the same as those for the normal extension and retraction system. These are:
-
the WHEEL page on the System Display (SD)
-
the L/G downlock indicator on panel 402VU
-
the light on the L/G control lever 6GA comes on (Ref. 32-61-00). If the WHEEL page is not shown on the SD at the start of a free-fall extension, it automatically shows after 30 seconds. When a free-fall extension is completed, the Engine Warning Display shows this data:
-L/G DOOR NOT CLOSED
-MAX SPEED 250 kt.
8. BITE Test_________
Not applicable
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_____________________________________
TASK 32-33-00-720-001
Functional Check of Free-Fall Extension
WARNING : PUT THE SAFETY DEVICES AND THE WARNING NOTICES IN POSITION BEFORE YOU
_______
START A TASK ON OR NEAR:
-
THE FLIGHT CONTROLS
-
THE FLIGHT CONTROL SURFACES
-
THE LANDING GEAR AND THE RELATED DOORS
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