10.  Door Warning System
A  The door warning system is an electrical circuit which provides the flight crew with a visual warning if certain doors are open or incompletely latched. The doors included in this system are the forward and aft passenger/crew entry doors, forward and aft galley service doors, forward and aft cargo compartment doors, lower nose compartment access door and the electronic equipment compartment external access door. The forward airstair door and the tire burst protector screen doors are also included in the system.
B.  The warning provided by the system consists of eight independent warning lights. The lower nose compartment access door, the electronic equipment compartment external access door and the left and right tire burst protector screen doors share the same warning light. The warning lights are mounted on the P5-20 Door Warning Module which is located on the overhead panel. The lights can be tested individually or by a master test switch that can simultaneously test all the warning lights. Each warning light is provided with an illuminated legend, which indicates the door, served by the warning light. The microswitch, or proximity switch, which is mounted on each door installation served by the door warning system, is included in the circuit served by the corresponding warning light. The circuits are similar for each warning light.
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C.  The microswitch or proximity sensor at each door is located so that the circuit to the corresponding warning light is de-energized when the door is closed and latched. When the door is unlatched and opened, the switch or sensor at the door activates the circuit from the power source through the corresponding warning light to ground and the circuit is energized. The warning light is then illuminated; visually warning the flight crew that the door served by the warning light is open or not latched.
11.  Landing Gear Doors
A.  The main landing gear doors (Fig. 1) consist of small door segments attached to the shock strut and actuated by pushrods slaved to the main gear at the lower side brace universal assembly and to an actuation fitting attached to a bracket on the trunnion link. The door segments close the spanwise wing cavity when the gear is retracted. No powered main body wheel well doors are installed since the wheel well cavity is effectively closed by the retracted gear tire and is sealed by a rubber seal.
B.  The nose landing gear doors consist of single clamshell doors actuated by a simple pushrod linkage system slaved to the drag brace (Fig 1). The linkage connected to the wheel well doors is arranged so that the doors open to allow the nose landing gear to leave the wheel well when the gear is extended and close when the gear is retracted. Each door is of epoxy reinforced glass fabric laminate-faced honeycomb construction. The skins, doublers, fillers, and blocks are of epoxy preimpregnated fiberglass fabric. The outer surface of the doors is coated with flame-sprayed aluminum.
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DOOR SEALS – APPROVED REPAIRS
1. General
A.  The silicone rubber seals used for pressure sealing doors and hatches are subject to three different types of failure or damage.
(1)  
Delamination of joints occurs where the mechanical bulb seal section joins the diaphragm seal section on the door seals. See Fig. 801 for this type of joint. The fabric-reinforced rubber which forms the joint peels loose from the mechanical or diaphragm seal. Primary cause of this failure is poor bonding.

(2)  
Cuts, nicks, splits or tears in the seal section are primarily a result of lack of care in handling and installation.

(3)  
Splice failure occurs on those continuous seals formed by splicing the ends of the extruded bulb section. The splices are reinforced with fabric. Delamination can occur as described in par. 1.A.(1). On emergency exit hatch seals, the ends of the seal are joined by a thick layer of vulcanized rubber. Flexing of the seal causes separation of the bond between this material and the ends of the extruded section.

B.  Seal repair procedure for the silicone rubber door and hatch seals may be divided into three general methods:
(1)  
Method A is a procedure for repairs in which the cut, delaminated or otherwise, separated surfaces are rejoined by adhesive only.

(2)  
Method B consists of repairs with an adhesive reinforced with open mesh Dacron D-117 or D-118 fabric. The fabric is embedded in the adhesive on the seal surface.

(3)  
Method C repair procedure comprises the replacement of a section of seal using adhesive, and when required, fabric cemented into place.
　
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