(a)  
A center door is attached to the shock and the drag struts.

 (b)  
An outer door is hinged to the wing.

 (c)  
An inner door is hinged to the inboard edge of the center door.

 (2)  
The doors close the spanwise wing cavity when the gear is retracted.

 (3)  
No powered wheel well doors are installed since the wheel well is closed by the retracted gear tire and sealed by a blade-type seal.

 B.
Nose Gear Doors (Ref. 32-22-00)

 (1)  
The nose landing gear doors are single clamshell doors actuated by a pushrod linkage system slaved to the drag brace (Fig. 1).

 (2)  
The doors are open when the gear is extended and close after the gear is retracted.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
 52-00-00
 ALL  ú ú B01 Page 6 ú Nov 15/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 MAIN ENTRY DOORS - FAULT ISOLATION
__________________________________
 1.  General_______
 A.  This subject contains general fault-isolation steps for the four main entry doors. Refer to the appicable subject for special fault-isolation steps:
 (1)  
Refer to (AMM 52-11-00/101) for Forward Entry Door special fault-isolation steps.

 (2)  
Refer to (AMM 52-41-00/101) for Galley Service Door special fault-isolation steps.

 B.
Refer to the applicable door subject for component location information:

 (1)  
Refer to (AMM 52-11-00/001) for Forward Entry Door component locations.

 (2)  
Refer to (AMM 52-13-00/001) for Aft Entry Door component locations.

 (3)  
Refer to (AMM 52-41-00/001) for Galley Service Door component locations.

 C.  
Door Cycles

 (1)  
There are three separate cycles in the operation of the door (Fig. 101):

 (a)  
The Latch/Unlatch Cycle

 1)  In this cycle the door is latched or unlatched with the door handles. One end point of this cycle is when the latch rollers fully engage the latch fittings and the handle is at the limit of its movement. The other end point is when the latch rollers are fully out of the latch fittings and the gates are folded. The door should not have moved yet.
 2)  The door components used in this cycle are the door handle mechanism, the latch control rods, the latch torque tubes, latch cranks and rollers, the gate control rods and gates.
 (b)  The Cocking Cycle
 1)  In this cycle the door is turned in the cutout. One end point of this cycle is when the latch rollers are fully our of the latch fittings and the gates are folded. The other end point is when the door is in the cocked position.
 2)  The door components used in this cycle are the cocking crank pushrod, the guide arm, and the door hinge torque tube mechanism.
 (c)  The Open/Close Cycle
 1)  In this cycle the door moves toward or away from the fuselage cutout. No handle movement takes place. The door is either pushed or pulled through the cutout.
 2)  The door components used in this cycle are the body hinge torque tube mechanism and the hold-open lock.
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 52-01-00
 ALL  ú ú B01 Page 101 ú Mar 12/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 D.  Door Component Wear
 (1)  
The main entry doors are correctly adjusted when the airplane is new. The in-service operation of the doors creates worn areas on the door parts. It is the worn areas on the parts that affect the door operation. Most problems with door operation are related to worn parts, not door adjustments.

 (2)  
Door adjustments made because of worn parts will not supply a long term solution to a door problem. Identify the door adjustments that have been made because of worn parts. These adjustments are possibly not correct. The latch fittings and other door adjustment fasteners will have torque putty applied, which shows an initial adjustment.
　
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