HEADQUARTERS OH-58A, Technical Manual

Page: 63 / 292

TM 55-1520-228-10
2-10. ENGINE COMPARTMENT COOLING.
Openings are provided on both sides of the engine and
top cowling for compartment cooling. The center cowl
section houses the engine air inlet, the inlet bellmouth
and the forward firewall. Suspended below the engine is
a stainless fire shield. Below the fire shield is a titanium
floor which acts as a drip pan and also gives insulation
from heat.
2-11. INDUCTION SYSTEM.
The engine air inlet system consists of an induction
fairing with inlets on each outboard side. This fairing
provides mounting for the particle separator. The
particle separator removes dirt and other contaminates
from the incoming air and ejects the dirt out eductor
tubes on either side of the fairing. This allows cleaned
air to enter the engine compressor section. Removable
reverse flow inlet fairings may be installed over the air
inlets on modified induction fairings. These reverse flow
fairings minimize ram effect of falling or blowing snow,
thus permitting effective operation of the particle
separator and preventing engine flame-out caused by
ingestion of snow.
a. Intake Ducting. The engine air intake ducting
consists of louvered openings and a large circular air
inlet opening. The louvered openings are located on left
and right cowl panels.
b. Particle Separator. Foreign matter is removed
from the engine inlet air by a centrifugal-type particle
separator. The particle separator consists of a group of
separator tube assemblies arranged in rows and
positioned in a front and rear sheetmetal panel and a
scavenge system. The separator tube assemblies
consist of an inlet tube, a swirl tube which is bonded
inside the inlet tube, and an outlet tube. The scavenge
system consists of a bleed air manifold, bleed air
nozzles, and ejector tubes which are contained in two
ejector boxes located beneath the separator tube
assemblies. The bleed air manifold is attached to the
ejector boxes and is connected directly to the engine
compressor scroll with bleed air inlet fittings. Air enters
the inlet tube and is spun by the swirl tube. Clean air
then enters the engine inlet plenum chamber through the
outlet tube while foreign material is centrifuged into the
scavenge system. The foreign material is ejected
overboard by the vacuum-cleaner effect created by
engine bleed air as it is discharged through venturies in
the eductor tubes. Reverse flow inlet fairings may be
attached to the engine air inlets. These sheet metal
fairings make it impossible for air to enter the plenum
chamber without first making two 180° turns. These
abrupt changes in airflow greatly reduce the probability
of engine flame-out associated with snow ingestion.
2-12. ENGINE INLET ANTI-ICING SYSTEM.
The compressor inlet guide vanes and front bearing
support hub are the only engine components with ant-
icing provisions. Anti-icing is provided by the use of
compressor bleed air. Anti-icing is actuated by placing
ENG DEICE switch on overhead console (figure 2-12) to
ENG DEICE position.
2-13. ENGINE FUEL CONTROL SYSTEM.
The system controls engine power output by controlling
the gas producer speed. Gas producer speed levels are
established by the action of the power turbine fuel
governor which senses power turbine speed. The power
turbine (load) speed is selected by the operator and the
power required to maintain this speed is automatically
maintained by power turbine governor action on metered
fuel flow. The power turbine governor lever schedules
the power turbine governor requirements. The power
turbine governor schedules the gas producer speed to a
changed power output to maintain output shaft speed.
a. Deleted .
b. Throttle. Rotating the throttle (figure 2-4) to the
full open position allows the power turbine governor to
maintain a constant rpm. Rotating the throttle toward the
dosed position will cause the rpm to be manually
selected instead of automatically selected by the power
turbine governor. Rotating the throttle past the engine-
idle stop to the fully dosed position shuts off fuel flow. A
manually operated idle stop is incorporated to prevent
inadvertent throttle closure. The idle stop is controlled
by the engine idle release control (figure 2-4).
Change 10 2-21