52-11-00
 ALL  ú ú B01 Page 9 ú Nov 12/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (2)  
The trigger includes a cam that engages the stowing latch lever link on the opposite side of the guide arm. The trigger holds the stowing latch lever in the unlatched position until a tang on the upper radius link sweeps over the stowing latch lever, returning it to the normal position.

 F.  
The hole on either side of the guide arm roller is slotted so that manual depression of the stowing latch lever causes the collar and latch pin to be pulled down sufficiently against the spring force to clear the stop hole in the roller guide plate, permitting door closing to be started.

 6.  Lower Hinge Assembly____________________
 A.  The lower hinge arm (Fig. 1) is bolted to the hinge pin which is located in two plain bushings in the lower hinge support. A seal for pressurization is located between the hinge pin and the hinge support. Two stop plates are mounted at the lower hinge position on the forward frame of the door opening. A radius link, including a stop pin, is located between the stop plates. The lower hinge arm is attached to the radius link and stop plates by the lower hinge spigot. A door snubber is located at the lower hinge assembly. Both ends of the snubber contain a spherical-type bearing. One end is bolted to the lower hinge support and the other end is bolted to the radius link.
 7.  Spring Assist Torque Tube_________________________
 A.  A spring-loaded torque tube assembly (Fig. 2) is mounted in the right side of the door frame. The upper and lower hinge arms have a smooth oval cross-section which mates with a hole in the hinge arm. The upper spigot is connected to the torque tube by the upper spring attachment nut and bolt. The lower spigot is splined to the lower end of the torque tube. Three springs are mounted on the torque tube. The upper and lower springs are connected to the structure and torque tube to assist the initial 60 degrees of door closing from the door "stowed open" position. The center spring is connected to the torque tube and the structure to assist the door opening from the "door cocked" position to the balanced position, which is approximately 60 degrees from the door "stowed open" position. Spring-loaded retainers support seals at the upper and lower spigots to prevent pressurization losses.
 8.  Door Lining and Insulation__________________________
 A.  The entry door panels are decorative linings made of vinyl-aluminum or tedlar-aluminum laminate with an insulation blanket cemented to the outboard side of each panel. The entry door has an upper panel and a lower panel. The inboard window is removable without removing the panel.
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 52-11-00
 ALL  ú ú B01 Page 10 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 9.  Operation
_________
 A.  The door is opened from the airplane interior by rotating the inside handle counterclockwise (Fig. 3). Initial rotation of the cam plate transmits angular movement to the latching crank assembly. The control rods at each end of the latching crank turn the latch rods and withdraw the latch rollers from the latches, allowing the door to move inward. When the door moves inward, the proximity switch in the door warning circuit closes and the door warning light comes on (Ref 52-71-00). The latch rods also operate the control rods attached to the upper and lower gates, causing the gates to fold inward and push the stop rods away from stops. Further rotation of the handle to full travel of 180 degrees allows the cam plate to transmit angular movement to the cocking crank assembly. The cocking crank operates the pushrod connected to the torque tube crank. Movement of the pushrod is resisted by the torque tube, causing the door to rotate on the hinge arms and pivot about the torque tube axis. This motion is due to the change in relative positions of the hinge arm and guide arm at the upper hinge, and the hinge arm and snubber at the lower hinge. Tracking of the door is controlled by the guide arm roller in the roller guide plates. As the door rotates to the cocked position (step 3), the guide arm and snubber deflect the upper and lower hinge flaps inward on the hinges. The door is swung through the opening by means of the assist handle. The outward lateral travel of the hinge arm transmits motion through the radius link to the guide arm which in turn causes the door to rotate in an outward direction about the pivot axis of the torque tube. The inside handle on the door automatically rotates approximately 45 degrees clockwise during final movement of the door to the open latched position (step 6). This is due to the change in relative position of the hinge arms, guide arm, and snubber passing beyond 180 degrees from the door cocked position and causing the door to counter-rotate and operate the cocking crank and cam plate in reverse. When the door is approximately parallel with the airplane exterior, the stop pin contacts the stop plate and prevents further movement of the door. The door is latched in the open position by the latch pin engaging the latch pin hole.
　
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