4–2. LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)

TM 1-1520-238-T-4 4–3 4–2. LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont) 4–2 · Engine Exhaust Subsystem. Directs and cools engine exhaust gases and removes foreign particles from the engine. · Engine Ignition Subsystem. Described in TM 1-1520-238-23. · Engine Start Subsystem. Provides initial engine rotation to start the engines. · Engine Power Controls. Allows crew to regulate power output. · Engine Instruments. Informs crew of engine operating conditions (TM 1-1520-238-T-5). (1) Engine Cooling Subsystem. The major components of the engine cooling subsystem (fig. 4–2) for each engine include the louver assembly, the louver actuator, the directional control valve, the cooling doors, the cooling door actuator and the fixed louvers. (a) Louver Assembly. The louver assembly, a rectangular box frame with movable vanes, opens to allow airflow from main transmission area to the engine nacelles. (b) Louver Actuator. The louver actuator, a pneumatic actuator, is mounted on the rear of the left louver assembly and on the front of the right louver assembly. It opens the louver assembly for cooling airflow or closes the louver assembly to shut off airflow. (c) Directional Control Valve. The directional control valve is an electrically actuated, 3–way pneumatically controlled valve and is mounted alongside the louver actuators. The directional control valve controls pressurized air to the louver actuators. M58-067A COOLING DOORS FIXED LOUVERS CONTROL VALVE DIRECTIONAL COOLING DOOR ACTUATOR ACCESS DOOR LN4 (SHOWN OPEN) LOUVER ASSEMBLY LOUVER ACTUATOR Figure 4–2. Engine Cooling System