WARNING: WHEN OPERATING AIRSTAIRS FROM INTERIOR CONTROL PANEL, OPEN ENTRY DOOR TO COCKED POSITION TO ALLOW CLEAR VISIBILITY OF AREA OUTSIDE AIRPLANE TO PREVENT INJURY TO PERSONNEL. DO NOT OPEN DOOR BEYOND COCKED POSITION WHILE OPERATING AIRSTAIR OR EQUIPMENT MAY BE DAMAGED.
CAUTION: TO PREVENT POSSIBLE DAMAGE TO AIRSTAIR, CHECK THAT HANDRAIL EXTENSIONS ARE PROPERLY STOWED BY PULLING ON HANDRAIL EXTENSIONS PERPENDICULAR TO THE HANDRAILS.
(3) Position interior normal control to RETRACT or exterior control to NORMAL RETRACT and hold in that position.
(a)
Positioning of the controls to retract the airstair provides power to energize the retract relay of the stair motor which operates the airstair actuator. The actuator drives the carriage pinions that cause the carriage to travel inboard on the rail assemblies. Ball bearing nuts attached to the upper ladder and driven by the ball screws attached to the carriage beams retract the upper ladder into the carriage.
(b)
The initial motion of the airstair retract cycle causes the extend switch to move to the not-extend position which will illuminate the STAIRS OPERATING light on the interior control panel and cause the stair tread lights to go out.
(c)
As the upper ladder begins to rotate up from the ground, the handrail mechanism within the upper ladder side rails will lower the handrails down against the ladders and the lower ladder will fold up under the upper ladder.
(d)
When the lower ladder is completely folded, the lower ladder retract switch is actuated, for normal system only, to allow retraction of the upper ladder into the airstair carriage. The lower ladder is held in place by a mechanical lock mechanism.
(e)
The upper ladder retracts inboard into the carriage and the carriage retracts inboard on the rails until it reaches the limit of travel and the airstair retract switch is actuated. Actuation of the retract switch will stop the actuator motor and transfer power through the airstair door close switch, which is in the door not-closed position, to the door close relay. The airstair is prevented from moving while in the retracted position by the motor brake and is stabilized in flight by inflight supports.
(f)
When the door close relay is energized, power is provided to operate the door motor, which rotates the door actuator. The actuator operates the jackscrew connected to the door carriage. The door travels upward and outboard in the door and carriage tracks to the close d position. When the doorstops are seated properly, the door close switch is actuated to the closed position to stop the door actuator motor, and the STAIRS OPERATING light on the interior control panel will go out.
(g)
When retract cycle is complete, position interior control to OFF or exterior control to the neutral position.
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NOTE: If the forward entry door is open, the airstair door latch pin is not engaged and the AIRSTAIR door warning on the control cabin forward overhead panel will be illuminated. If the forward entry door is closed, returning the exterior control handle to the neutral position will automatically engage the airstair door latch pin and cause the AIRSTAIR door warning light to go out.
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Nov 15/68 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 52-61-0 Page 15
E. Forward Airstair Retraction - Standby Operation (Fig. 6)
NOTE: In the event of an electrical failure in the normal system, the standby system is provided to operate the airstair. This system operates from 28-volt dc airplane power or if airplane power is not available, airplane battery power is used to operate the airstairs.
Operating the standby system from outside the airplane is identical using either power source. However, the airstair can be operated from inside the airplane only if airplane dc power is available.
Either the interior or exterior controls may be used to retract the airstair. Whichever control is used, the control must be held in the position required to retract the airstair until the entire retract cycle is complete.
CAUTION: NO SAFETY SWITCH IS PROVIDED IN THE STANDBY SYSTEM. ENSURE THAT HANDRAIL EXTENSIONS ARE RETRACTED AND PROPERLY STOWED BEFORE ATTEMPTING RETRACTION. FAILURE TO DO SO MAY RESULT INSTRUCTURAL DAMAGE.
(1)
Disengage handrail from support brackets just inside forward entry doorway (Ref. Forward Airstair Retraction - Normal Operation).
(a) The support brackets are spring loaded and fold vertically against the passenger cabin interior panels when not in use.
(2)
Retract handrail extensions and stow on handrails (Ref. Forward Airstair Retraction -Normal Operation).
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