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4.  Engine Gravel Protection Pressure Switch
A.  The gravel protection pressure switch in conjunction with the GRAVEL PROTECT or ENG ANTI-FOD light at the P2 center instrument panel indicates that the gravel protection system is operating (Fig. 2). The pressure switch is located downstream of the gravel protection valve. When the valve is opened, pressure developed downstream of the valve actuates the pressure switch which in turn closes the GRAVEL PROTECT or ENG ANTI-FOD light circuit and illuminates the GRAVEL PROTECT or ENG ANTI-FOD light. The pressure switch closes at a pressure of approximately 10 psi and opens when the air pressure goes below 5 psi.
5.  Operation
A.  The engine gravel protection system is operated on the ground by placing the GRAVEL PROTECT or ANTI-FOD switch at the P5 overhead panel to ON. This energizes the solenoid on the gravel protection valve of each engine which opens the valve. Opening the valve allows 13th stage bleed air to go through the gravel protection air duct in the nose cowl and to the gravel protection boom below. The air goes through the gravel protection boom and is discharged through the air nozzles.
B.  Air pressure developed downstream of the valve actuates the pressure switch which causes the GRAVEL PROTECT or ENG ANTI-FOD light at the P2 center instrument panel to illuminate. Illumination of the GRAVEL PROTECT or ENG ANTI-FOD light in the control cabin indicates that the engine gravel protection system is operating.
C.  During flight when icing condition occurs, anti-icing of the gravel protection boom is done by placing the GRAVEL PROTECT or ANTI-FOD switch to ANTI- ICE/TEST. This operates the engine gravel protection system, allowing warm air to pass through the boom thereby preventing the formation of ice. Aside from anti-icing, this position of the GRAVEL PROTECT or ANTI-FOD switch may also be used to test system operation during flight or on the ground during maintenance.
5C8 
Oct 20/83  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  75-09-100 Page 3 

K92341
Engine Gravel Protection System Schematic  5C8 
75-09-100  Figure 2  Oct 20/83 
Page 4 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ENGINE GRAVEL PROTECTION SYSTEM - TROUBLE SHOOTING

EFFECTIVITY
GJ  ALL EXCEPT B-2509 and B-2510

5C8
Oct 20/85 75-09-100 Page 101
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

5C8 
75-09-100 Page 102  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Oct 20/83 

ENGINE GRAVEL PROTECTION SYSTEM -ADJUSTMENT/TEST
EFFECTIVITY
GJ ALL EXCEPT B-2509 and B-2510
1.  Engine Gravel Protection Valve Test
A.  Equipment and Materials
(1)  Pressure gage, 0-100 psig, 8-inch dia., with 4-foot long high pressure hose extension and provided with a hook for attaching gage to engine
B.  Prepare to Test Engine Gravel Protection Valve
(1)  
Check that GRAVEL PROTECT or ANTI-FOD switch is off and the following circuit breakers are open:

(a)  
Applicable ENG GRAVEL PROTECT or ENG ANTI-FOD circuit breaker.

(b)  
MASTER DIM BUS circuit breakers

(c)  
DIM and TEST circuit breakers

 

(2)  
Open left and right side engine cowl panels.

(3)  
Check that engine gravel protection valve is closed.

NOTE: An indicator on the valve will show valve position.

(4)  
Remove tube cap from tee on air sensing line and attach end of pressure gage hose extension on tee.

(5)  
Secure the pressure gage at a suitable place at the side of engine where it can be read at a safe distance.

(6)  
Provide electrical power.

C.  Test Engine Gravel Protection Valve
(1)  
Position GRAVEL PROTECT or ANTI-FOD switch to ON and close all circuit breakers in par. 1.B.(1).

(2)  
Start the engine according to Chapter 71, Power Plant.

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(3)
With the engine running at the EPR setting listed in the following table, record pressure gage readings as regulated by the valve (Parker #F61D0236M Series).

(4)  
If the recorded pressures are not within limits, run engine at idle and adjust valve to bring regulated pressure within tolerance. If pressure cannot be adjusted by moving upper adjustment screw士1/2 turn, replace valve assembly.

NOTE:  There are two adjustment screws on the valve, the lower and upper adjustment screws. Adjustment on this test should be made only to the lower adjustment screw.
　
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