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A.  Disconnect pneumatic pressure line from valve actuator. Cap/plug fittings.
B.  Remove nuts and washers securing valve to top of upper shroud.
NOTE: Bolts are secured to inner surface of upper shroud.
C.  Lift valve from cooling air duct and remove through opening in horizontal web.
4.  Install Cooling Air Shutoff Valve
A.  Insert valve through opening in horizontal web, aligning bracket holes with bolts protruding through upper shroud.
B.  Install nuts and washers. Make certain valve fits snugly over cooling air duct.
C.  Check operation of valve (Ref 49-51-21, Adjustment/Test).
5.  Restore Airplane to Normal Configuration
A.  Close access door to horizontal stabilizer jackscrew compartment.
B.  Close circuit breaker on M280 module-APU accessory unit on E3-3 electrical shelf.
C.  Close horizontal stabilizer trim control circuit breaker on P6 panel and remove placard.
D.  Check that BATTERY SWITCH is ON and rotate horizontal stabilizer trim to neutral position.
E.  Remove placard from APU START switch.
F.  Position BATTERY SWITCH to OFF if power no longer required.
575 
Feb 15/79  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-51-21 Page 401 

G00578
Cooling Air Shutoff Valve Installation  575 
49-51-21  Figure 401  Feb 15/79 
Page 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

COOLING AIR SHUTOFF VALVE - ADJUSTMENT/TEST
1.  Cooling Air Shutoff Valve Test
A.  General
(1)  The APU cooling air shutoff valve test is performed to test the operation of the pneumatic actuator, and to check the valve for binding.
B.  Equipment and Materials
(1)  
Pressurized air supply capable of supplying up to 7 psig

(2) 
 Pressure gages

C.  Prepare for Cooling Air Shutoff Valve Test
(1)  
Position BATTERY SWITCH and APU MASTER SWITCH to OFF and placard that APU maintenance is "in work."

(2)  
Open the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.

(3)  
Gain access to compartment immediately aft of pressure bulkhead.

(4)  
The pneumatic actuator is accessible through the lightening holes in the horizontal web above the APU.

D.  Test Cooling Air Shutoff Valve (Fig. 501.)
(1)  
If aircraft pneumatic pressure line is attached, disconnect and attach air line from portable air source.

(2)  
Apply 7.0 +0.5 psi air to pneumatic actuator air inlet port. Valve should open to fully open position without binding.

(3)  
Remove air supply. Actuator spring should return valve to closed position without binding.

(4)  
Disconnect portable air source pressure air line and reconnect aircraft pneumatic pressure line to pneumatic actuator fitting. Tighten coupling nut.

E.  Restore Airplane to Normal Configuration
(1)  
Close the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.

(2)  
Remove placard from APU MASTER SWITCH.

(3)  
Start APU (Ref 49-11-0, Maintenance Practices).

(4)  
Visually check that cooling air valve and actuator function properly.

(5)  
Shut down APU (Ref 49-11-0, Maintenance Practices).

(6)  
Position BATTERY SWITCH to OFF if power no longer required.

(7)  
Close access door to compartment aft of pressure bulkhead.

504 
Jun 20/83  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-51-21 Page 501 

Cooling Air Shutoff Valve -Adjustment/Test  501 
49-51-21  Figure 501  Feb 15/79 
Page 502 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

COOLING AIR SHUTOFF VALVE PNEUMATIC LINE FILTER - REMOVAL/INSTALLATION
1.  Prepare for Removal
A.  Position BATTERY SWITCH and APU START SWITCH to OFF and placard that APU maintenance is in work.
B.  Open the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
C.  Open APU compartment access door latches and open access door.
2.  Remove Pneumatic Line Filter (See figure 401.)
A.  Disconnect pneumatic pressure line from reducer and remove reducer from filter. Discard gasket.
B.  Remove filter from air bleed duct. Discard gasket.
3.  Install Pneumatic Line Filter (See figure 401.)
　
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