Forward Airstair Component Location 500
52-61-100 Figure 1 (Sheet 1) May 15/67
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
500 Forward Airstair Component Location
May 15/67 Figure 1 (Sheet 2) 52-61-100
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. The upper ladder consists of two side beams that are connected by step risers and treads. Each side beam has a pair of rollers mounted on the outside surface near the upper inboard end that support the upper ladder in the carriage track. Ball screws, which drive the upper ladder along the carriage track, are attached to the inside surface of each carriage side beam. Each upper ladder side beam supports two stanchions, a handrail and the mechanism for raising and lowering the handrail and folding and unfolding the lower ladder.
C. An additional roller is attached to each inboard support roller by a link to form a truck. The trucks remain horizontal in the carriage tracks when the ladder outboard support rollers extend over the curved end of the track at the limit of travel. A trunnion attached to each truck supports a pivot mounted ball bearing nut, which engages the corresponding ball screw in the carriage. The ball screw and ball bearing nut make up the drive mechanism for extension and retraction of the stair. The trucks are connected to the handrail operating mechanism, and to the gears that operate the lower ladder, by a series of bell cranks and pushrods. When the upper ladder outboard support rollers extend over the curved end of the carriage track, the upper ladder begins to rotate down toward the ground and the trucks maintain a horizontal position in the carriage track. The relative angular motion between the trucks and upper ladder cause bellcranks to turn which in turn operate pushrods. The pushrods cause the lower ladder to unfold from under the upper ladder and the handrails to raise to the erect position.
D. The lower ladder is hinged to the outboard end of the upper ladder, folds under the upper ladder during the retract cycle and unfolds from under the upper ladder during the extend cycle. The ladder consists of two side beams connected by fixed treads and risers. Each side beam supports a handrail stanchion. The lower end of each beam has a wheel and shoe installed. The shoe provides for stability by making firm contact with the ground when load is placed on the stair. The wheel provides for rolling action at the start of retraction cycle and end of extension cycle.
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52-61-100 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 15/67
5. Handrails
A. The handrails are of tubular construction and rise automatically to an erect position during the airstair extend cycle and lower automatically to the stowed position during the retract cycle. (See detail B, figure 1.)
B. The handrails are supported by stanchions attached to the upper and lower ladders. The two upper powered stanchions are raised and lowered by a series of cranks and linkages actuated by the relative angular movement of the upper ladder with the upper ladder trucks. The lower end stanchions are not powered.
6. Handrail Extensions
A. Each handrail has an additional section of rail that can be manually extended to close the gap between the erected handrails and the forward entry doorway. (See detail C, figure 1.)
B. Each extension has a slide fitting which fits over the handrail. The slide fitting allows the lower end of the extension to slide along the handrail as the upper end of the extension is pulled up into the opening of the forward entry door. The upper end of each extension is then attached to a support bracket mounted on the passenger compartment interior panels. The support brackets are spring hinged and when not in use are stowed against the panels.
7. Actuation System
A. The airstair actuation system consists of a control assembly, motor-driven actuator, right angle gearboxes, ball screws, pinions and various shafts and couplings.
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