(b)
If the EGT continues to rise with additional shaft load, the automatic temperature control system is not functioning correctly. 1) Pneumatic control pressure faulty. 2) Low spring tension in the APU bleed valve return spring. 3) Incorrect load control thermostat set point.
Item 20. RECORD APU EGT
CAUTION: TO AVOID DAMAGING APU, OBSERVE OPERATING LIMITS (AMM 49-11-0/201).
(a) Used to observe sensitivity of the APU bleed valve as a trend data value. Item 21. REMOVE THE ELECTRICAL LOAD FROM THE APU
(a)
No steps are necessary
(a)
No steps are necessary.
NOTE: Let the APU operate in the no-load condition for a minimum of 1 minute.
Item 22. DO THE APU USUAL SHUTDOWN
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Feb 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-11-0 Page 611
5. Inspection After an APU Power Plant Fire
A. General
(1) In the event of an APU fire, a complete cleaning and inspection of the APU Power Plant, APU components and the surrounding structural area should be performed.
B. Equipment and Materials
NOTE: The following equipment and materials are required for an inspection after an APU Power Plant Fire.
(1)
Vacuum -Source, 24 inch Hg minimum
(2)
G00034 Cloth, Process Cleaning Absorbent Wiper (Cheesecloth, Gauze) - BMS15-5
(3)
G02439 Brush, Nylon Bristle
(4)
G00110 Sponge, Silcone Rubber, Closed-Cell, General Purpose, Non-Solvent Use -BMS1-23
(5)
G50140 Gloves, Protective - Latex or Nitrile
(6)
G02418 Water - De-Ionized
(7)
B01023 Cleaner, Primary - Ardrox 6025
C. Prepare for the Inspection
(1)
Set the switch and the circuit breaker:
(a)
Set the APU MASTER SWITCH on the P5 forward overhead control panel to the OFF position and attach a DO-NOT-OPERATE tag.
(b)
Open this circuit breaker and attach a DO-NO-CLOSE tag: 1) E3-3 Electrical Self, APU Control Unit.
(2)
Open the APU cowl door:
(a)
Open the latches for the APU cowl door.
(b)
Open the APU cowl door.
(c)
Connect the door support rods.
CAUTION: BE CAREFUL WHEN YOU MOVE THE LOWER SHROUD. DAMAGE TO THE SHROUD DRAIN LINES CAN OCCUR.
(3) Remove the lower shroud:
(a)
Hold the lower shroud and open the shroud latches.
(b)
Remove the lower shroud.
D. Procedure
(1)
Visually examine the APU power plant for the cause of the APU fire, or an APU that became too hot.
(a)
If you find external damage to the APU, replace the APU (AMM 49-11-0/401).
(b)
If you do not find any external damage to the APU, refer to the Fault Isolation Manual for the APU fire detection system to find the cause of the high temperature indication.
(2)
Do these steps to visually examine the APU compartment, upper and lower shrouds and its structural components for signs of fire damage:
(a)
Visually examine the APU compartment and its structural components for signs of fire damage.
(b)
Visually examine the three APU engine mounts for signs of fire damage.
(c)
If any signs of fire damage are found in the APU compartment, and its structural components, contact BOEING SERVICE ENGINEERING for the disposition of the APU and the APU compartment structural components.
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NOTE: An APU fire will affect the safety and structural integrity of the airplane. Boeing engineering and structural repair personnel will review airline/operator-supplied information and provide recommendations on a case-by-case basis.
(3) Do these steps to remove and/or clean the fire extinguishing agent, used for the APU power plant fire, from the external surfaces of the APU and the APU compartment:
(a) Do these steps if foam was used as the fire extinguishing agent.
CAUTION: DO NOT LET THE FOAM GO INTO THE HOLES OF THE APU. FOAM THAT STAYS IN THE APU CAN CAUSE CORROSION OF THE POWER PLANT'S INTERNAL COMPONENTS.
1) Clean the areas of the APU and the APU compartment where the foam was used with clean water, cleaning cloth, brush, sponge, gloves or other equivalent equipment.
2) Make sure that all signs of the foam are removed from the APU and the APU compartment.
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