2.26.7 Fuel Pressure Warning System.
fuel pressure warning system for each engine consists of
a pressure switch that illuminates the FUEL PSI segment
on the pilot caution/warning panel. The FUEL PSI ENG 1
and FUEL PSI ENG 2 segments will illuminate when fuel
pressure drops below 9 psi.
2.27 ENGINE ALTERNATOR.
2.27.1 Engine Alternator
The engine alternator
(fig 2-16 ) supplies AC power to the ignition circuitry and
the ECU. It also supplies a signal to the NG speed indica-
tor. All essential engine electrical functions are powered
by the alternator. When the alternator power to the ECU is
interrupted, a loss of Np and torque indications will occur
on the affected engine(s), and the engine(s) will increase
to the maximum power. Percent Np/Nr will increase above
100% and T4.5 limiting will be inoperative. When the alter-
nator power providing the NG signal is interrupted, a loss
of NG indications will occur with a corresponding engine
out audio signal and warning light being activated. Actual
engine operation is unaffected. A complete loss of engine
alternator power results in affected engine(s) increasing
to maximum power with a loss of of Np, NG indication,
torque and engine out audio signal and warning light be-
ing activated, and by an inability to start the engine.
2.27.2 Engine Alternator
When the engine alter-
nator (fig 2-16 ) power supply to the DECU is interrupted,
400 Hz, 115 vac aircraft power is used to power the
DECU, therefore preventing an engine (high side) failure.
Np/torque indications will not be affected. When alternator
power supply for the NG signal is interrupted, a loss of the
associated engine NG indication and an engine out audio
signal and warning light will occur. Actual engine opera-
tion is unaffected. Complete failure of the alternator will
cause loss of NG indication, activation of an engine out au-
dio and warning light, and inability to start the engine. Op-
eration of the engine and all other indications will be nor-
2.28 ENGINE OIL SYSTEM.
Each engine is lubricated by a self-contained, pressur-
ized, recirculating, dry sump system. Included are oil sup-
ply and scavenge pumps, an emergency oil system, an in-
tegral oil tank, a filter, an oil cooler, and seal pressurization
and venting. A chip detector that illuminates the CHIPS
ENG 1 or CHIPS ENG 2 segment on the pilot caution/
warning panel is in line downstream of the scavenge
2.28.1 Emergency Oil System.
Small oil reservoirs,
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 differ-
ential across the filter increases, the first indication will be
a popped impending bypass button. As the pressure in-
creases 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 nor-
mal 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 in-
dicator has a thermal lockout below +38 C (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 accesso-
ry 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 de-
tectors are of the non-fuzz 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 al-
ternator. The MASTER IGN keylock switch on the pilot en-
gine PWR lever quadrant (fig 2-19) is an enabling switch
to the ENG START switches. When an