propeller operation and lubrication of the reduction
gearbox and engine bearings is supplied by an external
line from the high pressure pump. Two scavenge lines
return oil to the tank from the propeller reduction
gearbox. A noncongealing, external oil cooler keeps the
engine oil temperature within operating limits. The
capacity of each engine oil tank is 2.5 U.S. gallons. The
total system capacity for each engine, which includes the
oil tank, oil cooler, lines, etc., is approximately 3.5 U.S.
gallons. The oil level is indicated by a dipstick attached
to the oil filler cap. Oil grade, specifications, and
servicing points are described in Section XII, Servicing.
b. The oil system of each engine is coupled to
an oil cooler unit (radiator) of fin-and-tube design. The
oil cooler unit, located in the lower aft nacelle below the
engine air intake, is the only airframe mounted part of
the oil system. Each oil cooler incorporates a thermal
bypass valve which assists in maintaining oil at the
proper temperature range for engine operation.
2-28. ENGINE IGNITION SYSTEM.
a. Description. The basic ignition system for
each engine consists of a solid state ignition exciter unit,
two igniter plugs, two shielded ignition cables, pilot
controlled ignition and engine start switches, and the
auto ignition switches (fig. 2-15). Placing either ENG
START switch to START - IGNITION position will cause
the respective engine to motor and igniter plugs to spark,
igniting the fuel/air mixture sprayed into the combustion
chamber by the fuel nozzles. The ignition system is
activated for ground and air starts, but is switched off
after combustion light up.
b. Ignition and Engine Starter Switches. Two
three-position toggle switches, placarded #1 or #2 ENG
START, are located on the overhead control panel
(fig. 2-15). These switches will initiate starter motoring
and ignition in the START IGNITION position, or will
motor the engine in the STARTER ONLY position. The
START IGNITION switch position completes the starter
circuit for engine rotation, energizes the igniter plugs for
fuel combustion, and activates the respective #1 IGN ON
or #2 IGN ON annunciator on the annunciator panel. In
the center position the switch is OFF. Two 5-ampere
circuit breakers on the overhead circuit breaker panel,
placarded IGNITOR CONTR #1 and #2, protect ignition
circuits. Two 5-ampere circuit breakers on the overhead
circuit breaker panel, placarded START CONTR #1 and
#2, protect starter control circuits (fig. 2-9).
2-29. AUTO IGNITION SYSTEM.
If armed, the auto ignition system automatically
energizes both igniter plugs of either engine, should an
accidental flameout occur. The system is not essential
to normal engine operation, but is used to reduce the
possibility of power loss due to icing or other conditions.
Each engine has a separate auto ignition control switch
(fig. 2-15) and a green annunciator, placarded #1 IGN
ON or #2 IGN ON, on the annunciator panel. Auto
ignition is accomplished by energizing both igniter plugs
in each engine.
The system should be turned OFF
during extended ground operation to
prolong the life of the igniter plugs.
a. Auto Ignition Switches. Two switches located
on the overhead control panel (fig. 2-15), each placarded
-AUTO IGNITION - ARM, control the auto ignition
systems. The ARM position initiates a readiness mode
for the auto ignition system of the corresponding engine.
The system is disarmed when in the off position. Each
circuit is protected by the corresponding START CONTR
#1 or #2, 5-ampere circuit breaker on the overhead
circuit breaker panel (fig. 2-9).
b. Auto Ignition Annunciators. If an armed auto
ignition system changes from a ready condition to an
operating condition (energizing the igniter plugs in the
engine) the corresponding engine's green annunciator
will illuminate. The annunciator is placarded #1 IGN ON
or #2 IGN ON and indicates that the igniters are
energized. The auto ignition system is triggered from a
ready condition to an operating condition when engine
torque drops below approximately 20%. Therefore,
when an auto ignition system is armed, the igniters will
be energized continuously during the time when an
engine is operating at a level below approximately 20%
torque. The auto ignition annunciators are protected by
the 5-ampere IGNITOR CONTR #1 or #2 circuit
breakers, located on the overhead circuit breaker panel
2-30. ENGINE STARTER-GENERATORS.
accessory drive section of each engine. Each starter-
generator is able to function either as a starter or as a
generator. In the starter-function, 28 volts DC is
required to power rotation. In the generator function,
each unit is capable of 400 amperes DC output. When
the starting function is selected, the starter control circuit
receives power through the respective 5-ampere START
CONTR circuit breaker on the overhead circuit breaker
panel (fig. 2-9), from either the aircraft battery or an
external power source. When the generating function is
selected, the starter-generator provides electrical power.
2-31. ENGINE INSTRUMENTS.
The engine instruments are arranged vertically
near the center of the instrument panel (fig. 2-18).