(c) After performing an isolation procedure requiring opening a circuit breaker or disconnecting a connector, always restore the circuit to its initial condition before proceeding to the next procedure.
(4) In the AIRSTAIR RETRACTION sequence, the handrail extensions should be disengaged from the entry door and stowed.
C. When trouble shooting the airstair in manual operation, the following conditions should be in effect:
(1)
Electrical connector to airstair is disconnected from its receptacle.
(2)
Pinion drive is disconnected when moving the carriage on the aircraft rails.
(3)
Ladder drive shafts are disconnected when moving the ladder assembly in or out of the carriage.
CAUTION: AFTER ANY MANUAL EXTENSION OR RETRACTION, NO MATTER HOW SLIGHT, THE FORWARD AIRSTAIR SHOULD BE RESEQUENCED TO ENSURE THAT DAMAGE WILL NOT RESULT WHEN AUTOMATIC OPERATION IS RESUMED.
D. The following warning should be referred to frequently while trouble shooting the airstairs.
WARNING: IT IS DANGEROUS TO WORK BELOW CARRIAGE WHILE ELECTRICAL POWER IS ON THE AIRSTAIRS. UNEXPECTED RETRACTION OF THE UPPER STAIRS OR THE CARRIAGE COULD CAUSE SERIOUS INJURY.
ALL FORWARD AIRSTAIR CIRCUIT BREAKERS SHOULD BE OPENED WHILE WORKING ON THE AIRSTAIR, EXCEPT WHEN MAKING A SPECIFIC VOLTAGE CHECK. CIRCUIT BREAKERS SHOULD NOT BE CLOSED UNTIL ALL PERSONNEL ARE CLEAR OF AIRSTAIR AND CARRIAGE EXTENSION OR RETRACTION AREA.
E. The airstairs should not be fully extended when the airplane is on jacks or is about to be jacked. This is because the airstairs can be damaged by personnel using them while the lower end is unsupported. Also the airstairs, when fully extended, could be damaged when the airplane was lowered: an irregular ground surface might prevent the lower stairs feet from sliding away from the airplane as they normally do for small vertical movements of the airplane.
NOTE: When working with the ladder partially extended, it is recommended that some support be provided under the outboard end of the extended portion of the upper ladder. This will protect the carriage from the strains imposed by its cantilevered attitude, which may become exaggerated by personnel working with the ladder partially extended. A forklift truck with an empty pallet applying a light upward load would serve this purpose.
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52-61-0 Page 102 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Aug 15/69
2.
Door Opening Trouble Shooting Chart
3.
Airstair Extension Trouble Shooting Chart
4.
Airstair Retraction Trouble Shooting Chart
5.
Door Closing Trouble Shooting Chart
TROUBLE PROBABLE CAUSE ISOLATION PROCEDURE REMEDY
Airstair door will not open with NORMAL power Airstair door will not open with normal power and airstair attempts to extend into back of door Airstair door opens with normal power and motor continues to run Airstair door latch pin mechanism defective Normal door open limit switch defective Normal door open relay, normal door close relay or normal door motor is defective Normal door open limit switch defective Normal door open limit switch or door open relay is defective Check airstair door lock warning light is illuminated. If not, airstair door latch pin mechanism is defective Disconnect connector D4668P on junction box and check for 28 volts dc at pin 2 with airstair control switch in the extend position. If voltage is not present, switch is defective Disconnect normal door motor connector D912 and check for 28 volts dc at pin 4 with airstair control switch in extend position. If voltage is present, motor is defective. If voltage is not present, door open relay or door close relay is defective Disconnect airstair connector D934 and check for 28 volts dc at pin 5 on plug with airstair door control in the extend position. If voltage is present, switch is defective With door open, disconnect connector D4668P on junction box and check for 28 volts dc at pin 2 with airstair control in the extend position. If voltage is present, switch is defective. If voltage not present, relay is defective Replace or adjust door latch pin mechanism. Refer to 25-61-531, Adjustment/Test Replace or adjust switch. Refer to 52-61-611, Adjustment/Test Replace door open relay or normal door motor Replace or adjust normal door open limit switch Replace or adjust door open switch. Refer to 52-61-611, Adjustment/Test. Replace relay
