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built into the engine oil sumps, are kept full during normal
operation by the oil pump. If oil pressure is lost, oil
will bleed slowly out of these reservoirs and be atomized
by air jets thus providing an oil mist lubrication for
the engine bearings for thirty seconds at 75% NG. An
OIL PSI ENG 1 or OIL PSI ENG 2 light on the pilot
caution/warning panel will illuminate when oil pressure
drops below 20-25 psi.
2.28.2 Oil Tank. Pertinent oil grades and specifications
are in table 2-7. The filler port is on the right side
of the engine (fig 2-16). The oil level is indicated by a
sight gage on each side of the tank. Oil is supplied to
the oil pump through a screen. The scavenge pump returns
oil from the sumps to the oil tank through six
scavenge screens.
2.28.3 Oil Cooler and Filter. Scavenge oil passes
through an oil cooler (fig 2-16) before returning to the
tank. It is cooled by transferring heat from the oil to
fuel routed through the cooler. If the oil cooler pressure
becomes too high, a relief valve will open to dump scavenge
oil directly into the oil tank. Oil discharged from
the oil pump is routed through a disposable element filter.
As the pressure differential across the filter increases,
the first indication will be a popped impending
bypass button. As the pressure increases further, the
OIL BYP ENG 1 or OIL BYP ENG 2 segment on the
pilot caution/warning panel will illuminate. During engine
starting, with oil temperature below the normal
operating range, pressure may be high enough to close
the oil filter bypass sensor switch. In this situation, the
caution light or lights will remain on until the oil
warms up and oil pressure decreases. The impending
bypass indicator has a thermal lockout below +38 0C
(100 °F) to prevent the button from popping.
2.28.4 Chip Detector. Each engine chip detector (fig
2-16) is mounted on the forward right side of the accessory
gearbox. It consists of an integral magnet, electrical
connector, and a housing. A removable screen surrounds
the magnet. The detector attracts magnetic
particles at a primary chip detecting gap. If chips are
detected, a signal is sent to the pilot caution/warning
panel to illuminate a CHIPS ENG 1 or CHIPS ENG 2
segment. These chip detectors are of the non-fizz burning
type.
2.29 ENGINE IGNITION SYSTEM.
Each engine has an ignition exciter unit with two igniter
plugs. The exciter unit receives power from its engine
alternator. The MASTER IGN keylock switch on
the pilot engine PWR lever quadrant (fig 2-19) is an enabling
switch to the ENG START switches. When an
2-28
TM 1-1520-238-10
ENG START switch is placed to START, pneumatic
motoring of the engine starter takes place and the ignition
system is energized. Ignition cutout is automatic
after the engine starts. Following aborted starts (Chapter
9, Emergency Procedures), the engine must be motored
with the ignition system disabled. This is done by
placing the ENG START switch to IGN OVRD. Chapter
5 contains the starting cycle limitations.
2.30 ENGINE STARTING SYSTEM.
The engine uses an air turbine starter (fig 2-16) for engine
starting. System components for starting consist
of the engine starter, a start control valve, an external
start connector, check valves, controls, and ducting.
Three sources may provide air for engine starts: The
shaft driven compressor (SDC) (normally driven by the
APU for engine starts), No. 1 engine compressor bleed
air, or an externally connected ground source. In any
case, the start sequence is the same. With the ENG
FUEL switch ON and MASTER IGN switch ON, placing
the ENG START switch momentarily to START
will initiate an automatic start sequence. This will be
evidenced by the illumination of the ENG 1 or ENG 2
advisory light above the ENG START switch on the pilot
PWR lever quadrant. Compressed air is then directed
through the start control valve to the sir turbine
starter. As the air turbine starter begins to turn, an
overrun clutch engages which causes the engine to motor.
The starter turbine wheel and gear train automatically
disengage from the engine when engine speed exceeds
starter input speed. At approximately 52% NG,
air to the starter shuts off, and ignition is terminated. If
the engine does not start, the PWR lever must be returned
to OFF and the ENG START switch must be
placed at IGN OVRD (which aborts the automatic engine
start sequence) momentarily before another start
is attempted. Chapter 8 explains abort start procedures,
and Chapter 5 contains the start cycle limits. If
　
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