APU FIRE EXTINGUISHING SYSTEM – TROUBLE SHOOTING
1.
General
à. Whenever the fire protection module (P8-1) is removed and replaced, a test must be performed on the APU fire extinguishing system (Ref 26-22-0, A/T).
2.
Equipment and Materials
A. Ohmmeter incapable of supplying more than 35 milliamperes.
WARNING: CURRENT FLOW EXCEEDING 35 MILLIAMPERES MAY DETONATE THE BOTTLE DISCHARGE SQUIB.
3. Trouble Charts
With all IND LIGHTS and SEC 5 circuit breakers on P6-3 closed.
APU BOTTLE DISCH LIGHT IS ON – Pressure is low. Replace bottle.
T52381
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APU FIRE EXTINGUISHING SYSTEM - ADJUSTMENT/TEST
1. APU Fire Extinguishing System Test
A. Tubing Leakage Test
(1) Do the Tubing Leakage Test for the Engine Fire Extinguishing System (Ref 26-21-0, Page 501).
B. Electrical Circuit Operation Test
(1)
Equipment and Materials
(a) Test box, Boeing F80229
(2)
Prepare Electrical Circuit for Test
(a)
Open APU access door and access door 3701.
(b)
Remove electrical connector D594 from bottle discharge plug.
WARNING: BOTTLE DISCHARGE PLUG CONNECTOR MUST BE DISCONNECTED. OPERATION OF FIRE SWITCH WILL DETONATE EXPLOSIVE CHARGE IF CONNECTOR IS NOT REMOVED FROM DISCHARGE PLUG.
(c)
Connect test box to electrical connector D594.
(d)
Connect electrical power to airplane (Ref 24-22-0, MP).
(e)
Check that EXTINGUISHER BOTTLES APU circuit breaker on panel P6-2 and all IND LIGHTS (3) and SEC 5 circuit breakers on panel P6-3 are closed.
(f)
Disconnect electrical connector Dl176 at APU bottle pressure switch.
(3)
Test Circuit Operation
(a)
Arm APU fire switch by pressing override button behind switch handle and pulling up on handle. 1) Make sure the APU LV light on the M238 panel comes on.
(b)
Turn APU fire switch clockwise as far as it will go. Hold in that position for approximately 5 seconds. Check that light on test box illuminates while discharge switch is held.
(c)
Repeat step (b) except turn APU fire switch handle counterclockwise.
(d)
Pull down on APU FIRE CONTROL handle on remote APU fire control panel in main wheel well.
(e)
Actuate BOTTLE DISCHARGE switch. Check that light on test box illuminates while discharge switch is held.
(f)
Jumper pins 1 and 2 of electrical connector D1176. Check that APU BOTTLE DISCHARGED light on P8-1 fire protection module illuminates.
(4)
Restore Airplane to Normal.
(a)
Reset APU fire switch to NORMAL.
(b)
Disconnect test box at electrical connector D594 and connect electrical connector to bottle discharge plug.
(c)
Connect electrical connector Dl176 to pressure switch.
(d)
Press TEXT EXT switch on P8-1. Check that APU, L and R lights illuminate and stay on until switch is released.
(e)
Remove electrical power if no longer required (Ref 24-22-0\MP).
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C. Squib Continuity Test
(1)
Prepare APU Fire Extinguishing System Squib for Continuity Test
(a)
Connect electrical power to airplane.
(b)
Check that EXTINGUISHER BOTTLES APU circuit breaker on panel P6-2 and all IND LIGHTS (3) and SEC 5 circuit breakers on panel P6-3 are closed.
(2)
Test Squib Continuity
(a)
Press TEST EXT switch on P8-1. Check that APU, L and R lights illuminate and stay on until switch is released.
(b)
Disconnect electrical connector D594 from bottle discharge plug and press TEST EXT switch. Check that APU light does not illuminate.
(3)
Restore Airplane to Normal.
(a)
Connect electrical connector D594 to APU bottle discharge plug.
(b)
Repeat step (2)(a).
(c)
Remove electrical power if no longer required.
