TM 1-1520-238-T-4
4–5
4–2.
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)
4–2
(2) Engine Anti–Ice Subsystem.
Major components of the engine anti–ice subsystem (fig. 4–3) are the
thermostatic switch, the anti–ice valve, the NGB heater blanket and the bleed air tubes.
(a) Thermostatic Switch.
The thermostatic switch, mounted in the bleed air tube between the inlet
anti–ice valve and the engine inlet fairing, senses a change in the temperature of the air in 40 seconds or less.
(b) Anti–Ice Valve.
The anti–ice valve, an electrically controlled pneumatic valve, spring–loaded to the
open position and closed by a solenoid, controls anti–icing airflow to the engine inlet fairings.
(c) NGB Heater Blanket.
The NGB heater blanket includes a control unit and heater elements. The
control unit consists of a control sensor and a safety sensor. The control unit is a non–repairable unit. The heater
elements are 115/200 VAC, 400 Hz heaters.
(d) Bleed Air Tube.
A bleed air tube connects the thermostatic switch and anti–ice valve to the engine
and a second tube connects them to the engine inlet cowling.
(3) Engine Exhaust Subsystem.
Major components of the engine exhaust subsystem (fig. 4–4) are the
primary exhaust nozzle, the rim clenching clamp, the secondary exhaust nozzle and an air duct assembly.
(a) Primary Exhaust Nozzle.
The primary exhaust nozzle, attached to the engine exhaust frame by a
rim clenching clamp, provides a path for engine exhaust gas airflow.
(b) Rim Clenching Clamp.
The rim clenching clamp is an adjustable tension v–band coupling clamp.
(c) Secondary Exhaust Nozzle.
The secondary exhaust nozzle has three curved finned nozzles and
is attached to the rear of the nacelle structure. It mixes gases from the engine with ambient air for exhaust gas
cooling.
(d) Air Duct Assembly.
The air duct assembly, attached to an adaptor on the primary nozzle and the
secondary nozzle support assembly, provides an exit for foreign objects from the inlet particle separator and
additional cooled air for engine exhaust gas temperature.
(4) Engine Ignition Subsystem.
The engine ignition subsystem is described in TM 1-1520-238-23.
(5) Engine Start Subsystem.
The major components of the engine start subsystem (fig. 4–5) are the
starter speed cutout switch, the regulating valve, and an engine air starter.
(a) Air Turbine Speed Cutout Switch.
The air turbine speed cutout switch is a sealed electronic unit
installed on the the aft section of the electrical power distribution box behind the pilot station. It holds and
maintains the engine start circuit energized until the engine has started and reached a self–sustaining speed.
(b) Regulating Valve.
The regulating valve, coupled to the engine air starter, is an air–actuated,
solenoid–controlled valve. It provides required air from the pressurized air system (PAS) to the engine air starter.
(c) Engine Air Starter.
The engine air starter is mounted on the right side, rear of the accessory
gearbox and consists of a turbine wheel, reduction gears, clutch and an output shaft. Lubrication oil is supplied
from the oil sump in the starter case. The engine air starter rotates the compressor through the accessory
gearbox until the engine reaches a speed that permits it to be self–sustaining.
