The L/G doors and the L/G have uplocks that lock the components in the retracted position. Geometric (overcenter) downlocks lock the L/G in the extended position.
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An anti-retraction baulk in the L/G control lever prevents an UP
selection when:
-all three L/G shock absorbers are not fully extended (weight off the ground)
-the nose wheels are not in the center position.
B. Free Fall Extension System
The free-fall extension system includes a control handle. When rotated, it operates a mechanical control system, which releases the MLG and NLG door and gear uplocks. The mechanical system also causes the cut out valve (in the RH MLG bay) and a vent valve (in the LH MLG and NLG bays) to move in sequence.
The cut out valve isolates the L/G hydraulic system from the Green hydraulic power supply (Ref. 29-11-00). The vent valves let the hydraulic fluid move between some components to prevent cavitation and hydraulic locks. They also let the unwanted fluid go back to the Green hydraulic system return.
4. Power Supply____________
A. Electrical Power Supplies
The normal extension and retraction system gets a 28V DC power supply
from these busbars:
-401PP ESSENTIAL BUS
-601PP SERVICE BUS.
The free-fall extension system is mechanically operated and has no
electrical power supplies.
B. Hydraulic Power Supply
The Green hydraulic power system (Ref. 29-11-00) supplies the normal
extension and retraction system.
The free-fall extension system is mechanically operated and has no
hydraulic power supplies.
5. Interface_________
(Ref. Fig. 002)
The extension and retraction system connects with the systems that follow:
-
the normal extension and retraction system
-
the free-fall extension system.
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Extension and Retraction - Interface Figure 002
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6. Component Description_____________________
Not applicable
7. Operation/Control and Indicating________________________________
R **ON A/C 001-049, 101-149, 151-199, 201-299,
(Ref. Fig. 003)
**ON A/C 051-099,
(Ref. Fig. 003A)
R **ON A/C 301-399,
(Ref. Fig. 003B)
R **ON A/C 401-499,
R (Ref. Fig. 003C)
**ON A/C ALL
The L/G control and Indication have two operation procedures: - normal - free-fall.
A. Normal Extension and Retraction
When the L/G control lever is put in the UP position, it sends a signal to the active LGCIU. A baulk device in the control lever prevents this if the aircraft is not in the correct configuration. The LGCIU sends a signal to the L/G and the L/G door selector-valves to move the doors and gears in this sequence: - the door uplocks release and the doors open fully - the L/G downlocks open
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Landing Gear - Control and Indication
Figure 003
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R Landing Gear - Control and Indication
R Figure 003A
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Landing Gear - Control and Indication
R Figure 003B
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Landing Gear - Control and Indication
R Figure 003C
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INTENTIONALLY BLANK
R 1 1
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-
the L/G's retract and lock
-
the doors close and lock.
The proximity sensor signals supply the necessary position data to the LGCIU. If the aircraft is in the correct configuration, a DOWN selection of the L/G control lever starts this extend sequence:
-
the door uplocks release and the doors open fully
-
the L/G uplocks open
-
the L/Gs extend and lock
-
the doors close and lock.
The control of the operation of the retraction and extension sequence changes from one LGCIU to the other. This occurs after each retract/extend cycle (when the landing gear control lever is moved away from the DOWN position). If a failure occurs in the active LGCIU, the standby LGCIU becomes active. The LGCIU also sends L/G configuration data to other aircraft systems.
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