C. The motor-driven actuator contains the transmission which transmits power through drive shafts to the carriage pinions and through drive shafts to the right angle gearboxes for the ball screws, which drive the upper ladder in the carriage tracks.
D. From the motion imparted to the carriage and upper ladder by the actuator, the carriage step, the lower ladder and the handrails are operated by a series of cranks, linkages and gear throughout various phases of the extend and retract cycles.
8. Electrical System
A. The airstair electrical system consists of a normal system ac stair motor, a standby system dc stair motor, relays, switches, circuit breakers, stair tread lights, controls, and swing arms. (See 52-61-0, figures 2 and 3.)
B. The motors are equipped with brakes that allow stopping the retract or extend cycles at any point in the cycle while preventing creep of the stair mechanism.
C. The relays and switches are used to provide power to the system components in the proper sequence to perform smooth operation of the airstair.
D. The circuit breakers in the airplane provide a means of power disconnect at the power bus to isolate the airstair circuits.
E. There are 22 lights provided to illuminate the stair treads. The lights are controlled so they will illuminate automatically when the airstair is fully extended and automatically go out when it starts to retract. The lights may be manually turned on or off when the airstair is in any position. The tread light control switch is located on the attendants forward auxiliary panel.
F. Swing arms are provided to give protection and support to the electrical cabling between the rails and carriage and between the carriage and upper ladder. The swing arms are of tubular construction with a coil spring center segment to provide flexibility when the carriage is in motion, relative to the rails, and when the upper ladder is in motion relative to the carriage.
500
52-61-100 Page 6 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 15/67
FORWARD AIRSTAIR -MANUAL OPERATION
EFFECTIVITY
Standard Passenger Airplanes
1. General
A. The airstair should not be operated manually except for maintenance or emergency purposes. Manual extension will cause airstair to be out of sequence, necessitating manual retraction of the airstair followed by the performance of a resequence operation prior to power operation of the airstair.
2. Equipment and Materials
A. No. 1 Rig Pin - 0.4980 +0.0005/-0.0010-inch diameter by 4.0 inches long
B. No. 2 Rig Pin - 0.2480 +0.0005/-0.0010-inch diameter by 2.50 inches long
3. Extend Forward Airstair
A. With airstair door open, open forward airstair system circuit breakers on circuit breaker panel P6.
B. Gain access to airstair area through electronics compartment access door.
C. Disconnect airstair electrical connector (1, Fig. 201) and tag connector with a note stating DO NOT OPERATE. AIRSTAIR OUT OF SEQUENCE.
D. Partially extend carriage.
(1)
Remove lockwire from carriage pinion disconnect lever (5) 201) and move to unlocked position.
(2)
Move airstair outboard until inboard edge of carriage step (6) is immediately below upper sill of airstair door opening. Stop airstair movement short of point where carriage step starts to rise.
(3)
Engage carriage drive pinions by moving carriage pinion disconnect lever to locked position.
E. Extend ladders.
(1) Disconnect dog coupling (10) on actuator drive shaft (11) by gaining access through drain pan hatch if installed.
CAUTION: DO NOT ATTEMPT TO MOVE SWING ARM OUT OF WAY OR USE SWING ARM AS HANDHOLD OR SWING ARM MAY BE DAMAGED.
5C8
Feb 20/84 52-61-100 Page 201
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Forward Airstairs Manual Operation and Resequencing 500
52-61-100 Figure 201 (Sheet 1) Feb 15/68
Page 202
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
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