52-32-00
 ALL  ú ú 03 Page 13 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 (2)  Close door electrically.
 NOTE: The door is closed electrically by holding the control
____ switch in the CLOSED position until the door is fully closed and power to all mechanisms is shut off, then closing the latch lock handle. The sequence of events during door closing are as follows:
 (a)  
When either control switch is placed in the CLOSE position, power is provided through de-energized door down relays (K1 and K2) and energized hook open relays (K8 and K9) to the lift power unit to closed the door. As the door moves away from the full up position, one set of contacts in the door up switches close to permit door operation to be reversed at any time. The other set of contacts open to turn off the DOOR OPEN lights.

 (b)  
On the door closing cycle, the pawls of the gearbox and brake assemblies engage ratchet teeth on the brake housing to prevent rotation, forcing the lift power unit to drive against slipping brake disks to close the door. This equalizes the power required to open and close the door, and ensures the door will remain in position if power were lost or a failure were to occur.

 (c)  
When the hooks contact the hook pins on door closing, door movement is stopped, but the lift power unit continues to operate until the door down switches close, energizing the door down relays (K1 and K2). Overtravel of the lift mechanism is provided for by slip joints in the rotary actuator links. Continued rotation of the rotary actuator arms after door movement is stopped causes the rotary actuator links to extend at the link slip joints.

 (d)  
If the latch cams are not in the fully open position as the door closes, flanges on the midspan latch cams will contact the latch pins and hold the door open far enough to prevent engagement of the hooks with the hook pins. The lift mechanism will continue to operate because of the slip joint in the rotary actuator links, and the hooks will rotate to the closed position even though the hooks do not engage the hook pins.

 (e)  
When both door down relays (K1 and K2) are energized, power is removed from the lift power unit and transferred to the hook actuators. As the hooks rotate away from the full open position, the hook open switches open, de-energizing hook open relays (K8 and K9) to permit door operation to be reversed at any time. On the hook closing cycle, the restraint solenoids are de-energized and the restraint arms ride over the stops on the hook torque tubes. As the hooks close the door, the rotary actuator links are compressed at the slip joint to a point within the limits of slip to unload the link.

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 52-32-00
 ALL  ú ú 05 Page 14 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
 (f)

(g)

(h)

(i)

(j)

(k)

(l)

A
747-400
MAINTENANCE MANUAL

When the hooks reach their fully closed position, the hook closed switches close, energizing the hook closed relays (K6 and K7). When both relays are energized, power is removed from the hook actuators. At the same time, the door will have reached the fully closed position and closed the door closed switch. Power is then supplied through the energized hook closed relays (K6 and K7), door closed switch and de-energized latch closed relay (K5) to the latch actuator.The door closed switch sends a signal to the door warning system that the door is closed.As the latch cams rotate away from the open position, the midspan latch open switches and latches open switch open, de-energizing the midspan latch open relays (K3 and K4) and the latches open relay (K10) to enable door operation to be reversed. When the latch cams reach the fully closed position, the latch closed switch is closed, energizing the latch closed relay (K5) to remove power from the latch actuator and turn on the LATCHES CLOSED lights. The door down relays (K1 and K2), hook closed relays (K6 and K7) and latch closed relay (K5) remain energized until the master latch lock handle is closed.The door latched switch sends a signal to the door warning system that the door is latched.When the manual master latch lock handle is latched into its housing, the latch lock sectors extend to interfere with the latch cams to lock them closed. As the lock sectors extend, the master latch lock switch opens to prevent electrical operation of the door and turns off the LATCHES CLOSED lights. The POWER ON lights remain on as long as the control circuit breaker is closed.When the manual handle is rotated fully up and locked, the pressure relief doors close. At the same time, the door warning switch sends the door warning system a signal that the door is locked.The door warning system gets signals from the door closed, door latched and door warning switches. When the door is closed, latched and locked the DOOR SIDE CARGO warning message does not show on EICAS.
　
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