航空 发表于 2011-6-13 17:21:10

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航空 发表于 2011-6-13 17:24:25

<P>AIR - DESCRIPTION AND OPERATION<BR>1. General<BR>A. Engine compressor air is tapped for operating various engine accessories and airplane<BR>systems. Some bleed systems are basic with the engine as received from the engine<BR>manufacturer. Other engine bleed systems are installed by the airframe manufacturer. In<BR>addition to engine bleeds for accessory and system use, a compressor bleed system is<BR>incorporated to permit engine operational flexibility by allowing high compressor discharge air<BR>to bleed into the fan discharge duct.<BR>B. Those systems using engine bleed air and containing coverage within this chapter are as<BR>follows:<BR>SYSTEM SECTION<BR>Compressor Bleed 75-31-0<BR>Engine Anti-icing 75-11-0<BR>Engine Gravel Protection * 75-09-100<BR>Engine Nose Cowl Anti-icing 75-11-0<BR>Generator Cooling 75-21-0<BR>C. Those systems using engine bleed air and containing coverage in other chapters are as<BR>follows:<BR>SYSTEM CHAPTER<BR>Pneumatic Starting System 80<BR>Engine Fuel Deicing 73<BR>Pneumatic System 36<BR>* GJ ALL EXCEPT B-2509 AND B-2510<BR>PW 732, 742, 752, 761, 762 AND 772</P>
<P>ENGINE GRAVEL PROTECTION SYSTEM - DESCRIPTION AND OPERATION<BR>EFFECTIVITY<BR>GJ ALL EXCEPT B-2509 and B-2510<BR>1. General<BR>A. The engine gravel protection system is provided for the two engines to prevent dirt, gravel and<BR>other debris from getting into the engines. The system uses 13th stage engine bleed air ducted<BR>through the nose cowl and discharged at a point below the inlet of the engine through air<BR>nozzles (Fig. 1).<BR>B. The system uses 28-volt dc power from the P6 load control center.<BR>C. The system consists of a gravel protection boom, gravel protection valve, GRAVEL PROTECT<BR>or ENG ANTI-FOD light, and a pressure switch for each engine, and a GRAVEL PROTECT or<BR>ANTI-FOD switch for the two engines.<BR>D. The GRAVEL PROTECT or ANTI-FOD switch at the P5 overhead panel controls the operation<BR>of the system and permits testing valve operation during flight. System operation is indicated at<BR>the control cabin by the GRAVEL PROTECT or ENG ANTI-FOD light at the center instrument<BR>panel. A press-to-test feature checks the circuit continuity of the GRAVEL PROTECT or ENG<BR>ANTI-FOD light (Fig. 2).<BR>E. The landing gear module (M338) through the air-ground switch allows operation of the system<BR>while the airplane is on the ground. When the airplane lifts off the ground the system is<BR>automatically de-energized even though the GRAVEL PROTECT or ANTI-FOD switch is ON.<BR>2. Engine Gravel Protection Boom<BR>A. The engine gravel protection boom conveys bleed air from the engine and discharges it to the<BR>ground through nozzles located at its end. The boom is located below the nose cowl and<BR>extends from a point slightly forward of the aft end to a few inches beyond the inlet end. The<BR>boom has a forward strut support which is provided with internal air lines for anti-icing the strut<BR>(Fig. 1).<BR>B. The nozzles in the boom direct the air at an angle towards the rear of the engine. The high<BR>velocity air prevents dirt, gravel and other debris on the area below the engine inlet from being<BR>sucked into the engine.<BR>C. For removal/installation of the gravel protection boom, refer to Engine Nose Cowl, 71-11-31.<BR>3. Engine Gravel Protection Valve<BR>A. The engine gravel protection valve controls the flow of air that goes through the air nozzles in<BR>the gravel protection boom. It is a solenoid- piloted, pressure-actuated regulating valve.<BR>B. The valve is located below the engine just aft of the nose cowl. It is connected to the gravel<BR>protection air ducts by means of couplings.</P>
<P>C. The valve is opened by positioning the GRAVEL PROTECT or ANTI-FOD switch at the P5<BR>overhead panel to ON. This allows 13th stage engine bleed air to pass through the valve and<BR>then to the air nozzles in the boom. Air pressure downstream of the valve is monitored by<BR>means of an air sensing line tapped on the duct a few inches away from the outlet end of the<BR>valve and connected to the valve body. Air pressure beyond the minimum or maximum<BR>pressure limits at which the valve has been set will increase or decrease the opening of the<BR>valve thereby regulating the flow of air.<BR>D. The valve has an indicator which can be used in checking valve position during maintenance. A<BR>regulating screw on the valve permits adjustment of the downstream air pressure to the<BR>recommended value (Ref Adjustment/Test).<BR>4. Engine Gravel Protection Pressure Switch<BR>A. The gravel protection pressure switch in conjunction with the GRAVEL PROTECT or ENG<BR>ANTI-FOD light at the P2 center instrument panel indicates that the gravel protection system is<BR>operating (Fig. 2). The pressure switch is located downstream of the gravel protection valve.<BR>When the valve is opened, pressure developed downstream of the valve actuates the pressure<BR>switch which in turn closes the GRAVEL PROTECT or ENG ANTI-FOD light circuit and<BR>illuminates the GRAVEL PROTECT or ENG ANTI-FOD light. The pressure switch closes at a<BR>pressure of approximately 10 psi and opens when the air pressure goes below 5 psi.<BR>5. Operation<BR>A. The engine gravel protection system is operated on the ground by placing the GRAVEL<BR>PROTECT or ANTI-FOD switch at the P5 overhead panel to ON. This energizes the solenoid<BR>on the gravel protection valve of each engine which opens the valve. Opening the valve allows<BR>13th stage bleed air to go through the gravel protection air duct in the nose cowl and to the<BR>gravel protection boom below. The air goes through the gravel protection boom and is<BR>discharged through the air nozzles.<BR>B. Air pressure developed downstream of the valve actuates the pressure switch which causes the<BR>GRAVEL PROTECT or ENG ANTI-FOD light at the P2 center instrument panel to illuminate.<BR>Illumination of the GRAVEL PROTECT or ENG ANTI-FOD light in the control cabin indicates<BR>that the engine gravel protection system is operating.<BR>C. During flight when icing condition occurs, anti-icing of the gravel protection boom is done by<BR>placing the GRAVEL PROTECT or ANTI-FOD switch to ANTI- ICE/TEST. This operates the<BR>engine gravel protection system, allowing warm air to pass through the boom thereby<BR>preventing the formation of ice. Aside from anti-icing, this position of the GRAVEL PROTECT or<BR>ANTI-FOD switch may also be used to test system operation during flight or on the ground<BR>during maintenance.</P>
<P>ENGINE GRAVEL PROTECTION SYSTEM - ADJUSTMENT/TEST<BR>EFFECTIVITY<BR>GJ ALL EXCEPT B-2509 and B-2510<BR>1. Engine Gravel Protection Valve Test<BR>A. Equipment and Materials<BR>(1) Pressure gage, 0-100 psig, 8-inch dia., with 4-foot long high pressure hose extension and<BR>provided with a hook for attaching gage to engine<BR>B. Prepare to Test Engine Gravel Protection Valve<BR>(1) Check that GRAVEL PROTECT or ANTI-FOD switch is off and the following circuit<BR>breakers are open:<BR>(a) Applicable ENG GRAVEL PROTECT or ENG ANTI-FOD circuit breaker.<BR>(b) MASTER DIM BUS circuit breakers<BR>(c) DIM and TEST circuit breakers<BR>(2) Open left and right side engine cowl panels.<BR>(3) Check that engine gravel protection valve is closed.<BR>NOTE: An indicator on the valve will show valve position.<BR>(4) Remove tube cap from tee on air sensing line and attach end of pressure gage hose<BR>extension on tee.<BR>(5) Secure the pressure gage at a suitable place at the side of engine where it can be read at<BR>a safe distance.<BR>(6) Provide electrical power.<BR>C. Test Engine Gravel Protection Valve<BR>(1) Position GRAVEL PROTECT or ANTI-FOD switch to ON and close all circuit breakers in<BR>par. 1.B.(1).<BR>(2) Start the engine according to Chapter 71, Power Plant.</P>
<P>(3) With the engine running at the EPR setting listed in the following table, record pressure<BR>gage readings as regulated by the valve (Parker #F61D0236M Series).<BR>(4) If the recorded pressures are not within limits, run engine at idle and adjust valve to bring<BR>regulated pressure within tolerance. If pressure cannot be adjusted by moving upper<BR>adjustment screw 1/2 turn, replace valve assembly.<BR>NOTE: There are two adjustment screws on the valve, the lower and upper adjustment<BR>screws. Adjustment on this test should be made only to the lower adjustment<BR>screw.<BR>(5) Shutdown engine according to Chapter 71, Power Plant.<BR>(6) Position GRAVEL PROTECT or ANTI-FOD switch to OFF.<BR>D. Restore Airplane to Normal Configuration<BR>(1) Open MASTER DIM BUS, DIM and TEST circuit breakers.<BR>(2) Remove pressure gage connection at tee on air sensing line and install tube cap.<BR>(3) Close left and right side engine cowl panels.<BR>(4) Close MASTER DIM BUS, DIM and TEST circuit breakers.<BR>(5) If no longer required, remove electrical power from airplane.</P>

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