IGNITER PLUG - INSPECTION/CHECK
1. Igniter Plug Inspection
A. Examine Igniter Plug
(1)
Remove igniter plug from combustion chamber cap. Refer to Igniter Plug -Removal/Installation.
(2)
Examine ceramic parts of igniter plug for cracks or chipping.
(3)
Examine center electrode and outer shell for erosion. Igniter plug must be replaced if erosion is outside tolerances shown in figure 601.
(4)
Examine igniter plug barrel and threads for corrosion and damage.
(5)
Install igniter plug on combustion chamber cap. Refer to Igniter Plug -Removal/Installation.
500
Aug 15/72 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-41-51 Page 601
Igniter Plug Erosion Limits 500
49-41-51 Figure 601 Aug 15/72
Page 602
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
IGNITER PLUG - CLEANING/PAINTING
1. Igniter Plug Cleaning
A. Equipment and Materials
(1)
Solvent - Federal Specification P-D-680, or equivalent
(2)
Soft grit blasting equipment or brass bristle brush
NOTE: Suitable soft blasting materials are ground corn, apricot or peach pits, walnut shells, clover seeds, or cracked wheat.
B. Clean Igniter Plug
(1)
Remove igniter plug from combustion chamber cap. Refer to Igniter Plug -Removal/Installation.
(2)
Clean igniter plug with solvent and blow dry with clean compressed air.
(3)
Clean all deposits from igniter plug by blasting or brushing.
(4)
Blow off all loosened material with clean, dry compressed air.
CAUTION: DO NOT USE HARD GRIT BLASTING OR STEEL BRISTLE BRUSH AS THESE MATERIALS CAN SERIOUSLY DAMAGE IGNITER PLUG.
(5)
Install igniter plug on combustion chamber cap. Refer to Igniter Plug - Removal/Installation
500
Nov 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-41-51 Page 701
AIR - DESCRIPTION AND OPERATION
1. General
A. The APU air system consists of two systems: APU cooling air system and APU bleed air system. The APU cooling air system provides cooling air for the ac electrical generator, APU lubrication system, APU engine accessories, and APU shroud. The APU bleed air system provides pneumatic power for the airplane air conditioning system and for starting the airplane engines. For detail description of the air systems, refer to 49-51-0, APU Cooling Air System, and 49-52-02, APU Bleed Air System.
501
May 01/75 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-50-0 Page 1
APU COOLING AIR SYSTEM - DESCRIPTION AND OPERATION
1. General
A. The APU cooling air system provides forced air for cooling the ac electrical generator, APU lubricating oil, APU engine shroud, and engine accessories. The cooling air system consists of the accessory cooling air duct, cooling air fan, cooling air shutoff valve, pneumatic actuator, and cooling air crossover duct (Fig. 1). The cooling air is obtained from the torque box, passed through the ac electrical generator and the oil cooler to the inside of the engine shroud, and exhausted overboard.
2. Cooling Air Inlet Duct
A. The cooling air inlet duct supplies the static air on ground, or ram air in flight, to the cooling air fan. The duct is located between the torque box and the cooling air fan inlet flange, and is riveted to the upper shroud (Fig. 1).
B. An inlet air screen is attached to the cooling air fan housing. An inspection tube and cap assembly is attached to the inlet duct, providing visual access to the screen. The inspection tube protrudes through a lightening hole in the horizontal webbing above the upper shroud and is accessible from the compartment just aft of the aft pressure bulkhead.
3. Cooling Air Shutoff Valve
A. The cooling air shutoff valve stops the airflow through the cooling air inlet duct when the APU is not operating. The valve serves as a flame stop in event of an APU fire. The valve consists of a shaft-mounted butterfly installed in the cooling air inlet duct (Fig. 1). The valve is controlled by the pneumatic actuator.
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