PRIMARY LOCK SWITCHES_____________________ BIT __________ DESCRIPTION
___ BIT STATUS ___________ R BODY GR STRNG LEFT 26 1 LOCKED R BODY GR STRNG RIGHT 27 0 UNLOCKED L BODY GR STRNG RIGHT 28 0 UNLOCKED L BODY GR STRNG LEFT 29 1 LOCKED
(aa) Return the tiller of the captain to neutral.
(ab) Make sure that the BITS for label 271 are as shown in the table
that follows:
PRIMARY LOCK SWITCHES_____________________ BIT __________ DESCRIPTION
___ BIT STATUS ___________ R BODY GR STRNG LEFT 26 1 LOCKED R BODY GR STRNG RIGHT 27 1 LOCKED L BODY GR STRNG RIGHT 28 1 LOCKED L BODY GR STRNG LEFT 29 1 LOCKED
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747-400 MAINTENANCE MANUAL
(ac) Push the NEXT PAGE button. (ad) Make sure that the BITS for label 273 are as shown in the table that follows:
ALTERNATE LOCK SWITCHES_______________________ BIT __________ DESCRIPTION
___ BIT STATUS ___________
R BODY GR STRNG LEFT 26 1 LOCKED
R BODY GR STRNG RIGHT 27 1 LOCKED
L BODY GR STRNG RIGHT 28 1 LOCKED
L BODY GR STRNG LEFT 29 1 LOCKED
S 864-028
(16)
Put the tiller of the captain to neutral.
G.
Put the Airplane to Its Usual Condition
S 414-029
(1)
Connect the torsion links of the nose landing gear at the apex (AMM 32-21-03/201).
S 414-030
(2)
Connect the steering actuators of the body landing gear to the torsion link (AMM 32-53-11/201).
S 864-031
(3)
Remove the hydraulic power from system No. 1
(AMM 29-11-00/201).
S 864-032
(4)
Remove the electrical power if it is not necessary
(AMM 24-22-00/201).
S 094-033
WARNING:_______REFER TO AMM 32-00-30/201 FOR THE LOCK REMOVAL PROCEDURE. THE DOORS CAN CLOSE QUICKLY IF YOU DO NOT REMOVE THE DOOR LOCKS CORRECTLY. THIS CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
(5) Remove the door locks of the wing and the body landing gear
(AMM 32-00-30/201).
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747-400 MAINTENANCE MANUAL
LANDING GEAR POSITION INDICATION SYSTEM - DESCRIPTION AND OPERATION
___________________________________________________________________
1. General_______
A. The landing gear position indication system monitors the position of landing gear and landing gear doors. The landing gear indication system has proximity switch sensors and indication displays.
B. The proximity switch sensors are installed on the landing gear and the landing gear doors. The nose gear sensors monitor the up, lock, and compressed (squat) positions. The body and wing gear sensors monitor the up, down, and tilt positions. The system shows the state of landing gear and doors.
C. The indication is shown on the Engine Indication and Crew Alterting System (EICAS), in the flight deck. EICAS is a two display unit, main and auxillary.
2. Proximity Switch Sensors________________________
A. The proximity switch sensor is a field-producing coil-core mix in a dielectric gel. The sensor is inside a stainless steel case.
B. Function
(1)
All proximity switch sensors work the same. The landing gear indication system has two shapes of sensors, round and rectangular. Body and wing gear uplock sensors are round. All other sensors are rectangular.
(2)
The sensor is a two-wire device that is connected to a proximity switch card. The card is in the PSEU. A periodic pulse made in the proximity switch card supplies the sensor. The periodic pulse measures the inductance of the sensor. A specific inductance causes the proximity switch card to change state. A change in state occurs when a metal target comes in a specific distance to the sensor. The state also changes when a metal target goes away by a specific distance from the sensor.
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