DOOR - OVERPRESSURE RELEASE, APU COMPARTMENT - DESCRIPTION AND OPERATION
________________________________________________________________________
 1.
 General

_______ The overpressure release door is installed in the upper left side of the APU compartment between FR83 and FR84. It prevents damage to the fuselage tailcone if there is a sudden increase of pressure in the APU compartment. If a sudden increase of pressure occurs (e.g. a leak at a bleed-air line) the door opens, it closes automatically when the pressure decreases. A drive lever keeps the opening of the door to a limit. A hinge connects the door to the fuselage structure. When the door is closed it is level with the fuselage contour. Tension springs keep it in the closed position.

 2.
 Component Description

_____________________ (Ref. Fig. 001) The door is made of aluminum alloy. It has seven louvered openings which are for ventilation. Screws attach the hinge to the inside of the door. Rivets connects the hinge on the fuselage structure at FR83. A bonding strap is attached to the hinge and to the fuselage structure. The tension springs are installed between a bracket on FR84 and an attachment fitting on the door. The bracket and the attachment fitting are made from aluminum alloy. A slot in the drive lever lets the door move out and in. The tension springs are loaded to 11.7 +0.5 -0.5 daN (26.3026 +1.1240 -1.1240 lbf). A nut (installed at the end of the tension springs) lets you adjust the tension in the spring.

 3.
 Operation

_________ If there is an overpressure in the APU compartment a force is applied to the overpressure release door. When the force is more than 11.7 daN (26.3026 lbf) the door opens and the overpressure is released into the open area. The door closes automatically when the pressure decreases.
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 Overpressure Release Door - Component Location
 Figure 001
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 DOOR - OVERPRESSURE RELEASE, APU COMPARTMENT - INSPECTION/CHECK
_______________________________________________________________
 TASK 52-92-00-210-001 Visual Inspection of the APU Compartment Overpressure Release Door WARNING : DO NOT TOUCH THE APU UNTIL IT IS SUFFICIENTLY COOL TO PREVENT BURNS
_______ WHEN YOU DO THE MAINTENANCE TASK(S).
 1. Reason for the Job
__________________
 To make sure that the force to open the overpressure release door is
 correct.

 2. Job Set-up Information
______________________
 A. Fixtures, Tools, Test and Support Equipment
 -------------------------------------------------------------------------------REFERENCE QTY DESIGNATION -------------------------------------------------------------------------------
No specific circuit breaker(s) safety clip(s)
 No specific spring scale with a range up to 12.5 daN (28.101 lbf)
 No specific access platform 5.0 m (16 ft. 5 in.)

 B. Referenced Information
 -------------------------------------------------------------------------------REFERENCE DESIGNATION -------------------------------------------------------------------------------
52-92-00-991-001 Fig. 601
 3. Job Set-up
__________ Subtask 52-92-00-941-050
 A. Aircraft Maintenance Configuration
 (1)
 Put the access platform in position below the APU compartment.

 (2)
 Put the warning notice in the flight compartment to tell persons not to start the APU.

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 B. Open, safety and tag this(these) circuit breaker(s):
 -------------------------------------------------------------------------------PANEL DESIGNATION IDENT. LOCATION -------------------------------------------------------------------------------121VU APU/APU/CTL 2KD L42 121VU APU/ECB/SPLY 1KD L41
 Subtask 52-92-00-010-050
 C. Open the APU access doors 315AL, 316AR.
 4. Procedure
_________ (Ref. Fig. 601/TASK 52-92-00-991-001) Subtask 52-92-00-220-050
 A. Measurement of the Force to Open the Door
 (1)
 Attach the spring scale with a range up to 12.5 daN (28.101 lbf) (3) to the hole of the overpressure release door (2).

 (2)
 Make sure that the force which is necessary to open the overpressure release door (2) is 11.7 +0.5 -0.5 daN (26.3026 +1.1240 -1.1240 lbf). Pull at a right angle to the door.

 (3)
 Release the overpressure release door (2) and remove the spring scale (3).

 (4)
 If necessary, adjust the tension of the springs with the nut (1) in the APU compartment.
　
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