(a)
Alternate extend system faults are shown by an EICAS LDG GEAR MONITOR status message and a R GEAR DOWN maintenance message.
(b)
The ALT EXT CONT LATCH RELAY and the hydraulic pressure switch control the time that the power pack operates. When the power pack has been started, it will not stop until the conditions that follow have occurred:
(c)
Output from the PSEU (Proximity Switch Electronics Unit), right main gear, system 2, down and locked signal is sent through the normally closed contact of the latch relay to the EICAS computer. When the latch relay is energized, (power pack in operation), the PSEU signal cannot get to the EICAS computer.
(d)
EICAS compares system 1 and system 2 signals from the PSEU to see if they agree. If the right gear down and locked signal does not agree for more than 30 seconds and the landing gear is down and locked, EICAS LDG GEAR MONITOR status message and R GEAR DOWN maintenance message will be shown.
(e)
Normally only about 10 seconds or less is necessary for the power pack to put out the pressure that is necessary to open the hydraulic pressure switch. Thus, the EICAS LDG GEAR MONITOR or R GEAR DOWN messages will not be shown during normal power pack operation.
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757 MAINTENANCE MANUAL
LANDING GEAR ALTERNATE EXTENSION - MAINTENANCE PRACTICES
________________________________________________________
1. General_______
A. This procedure contains instructions to open and lock the landing gear doors. It is used for ground maintenance when the alternate extension system does not operate.
TASK 32-35-00-862-001
2. Open the Landing Gear Doors (Fig. 201, 202)___________________________
A. References
(1)
AMM 29-11-00/201, Pressurize/Depressurize Main Hydraulic System
(2)
AMM 32-00-15/201, Landing Gear Door Locks
(3)
AMM 32-00-20/201, Landing Gear Downlocks
B.
Prepare to Open the Doors
S 862-002
(1)
Make sure the downlocks are installed on the nose and main landing gear (AMM 32-00-20/201).
S 862-003
(2)
Pressurize the left hydraulic system (AMM 29-11-00/201).
C.
Open the Doors
S 862-004
WARNING: MAKE SURE PERSONS AND EQUIPMENT ARE CLEAR OF THE MAIN AND NOSE
_______ LANDING GEAR AREAS. THE DOORS WILL OPEN QUICKLY WHEN THE CONTROL LEVER FOR THE LANDING GEAR IS MOVED AND CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
(1) Push the lock override and momentarily move the control lever to UP to release the lock on the landing gear doors.
S 862-005
WARNING:_______DO NOT MOVE THE CONTROL LEVER TO DN. THE DOORS ARE NOT IN A SAFE CONDITION. THEY WERE OPENED WITH THE NORMAL SYSTEM AND NOT BY THE DOOR GROUND RELEASE. THE DOORS WILL CLOSE QUICKLY IF THE LEVER IS MOVED TO DN AND CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
(2)
Move the control lever to OFF and attach a DO-NOT-OPERATE tag.
S 862-006
(3)
Remove the pressure from the left and right hydraulic systems (AMM 29-11-00/201).
S 862-007
(4)
Do the steps that follow to close the safety valve:
(a)
For the main landing gear doors, manually pull the safety valve control rod down until the safety valve cam turns and latches.
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757
MAINTENANCE MANUAL
SEE A
VALVE SAFETY DOOR
INTERLOCK ACTUATOR DOOR RELEASE
VALVE CONTROL ROD DOOR SAFETY
DOOR ACTUATOR DOWN PULL
FWD RELEASE ACTUATOR DOOR LOCK
A
Main Gear Door Lock Release Mechanism
Figure 201
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本文链接地址：757 AMM 飞机维护手册 起落架 CHAPTER 32 - LANDING GEAR 2(94)
