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float ball is at the top of the sight glass. Oil grades and specifications are prescribed in Section XV of this 2-27. STARTER.
chapter. a. Starter Switch. The START switch is located on
d. Cooler. The engine oil cooler is located directly the pilot collective control head. The switch is springaft
of the engine and above the oil cooler blower. The loaded and must be positioned and held for engine
oil cooler blower is an integral part of the tail rotor drive start. The ignition keylock switch must be in the ON
system. Air is discharged from the blower upward position to complete the starter ignition circuit. Refer to
through the engine oil cooler. Chapter 8 for switch operation.
(1) General. Engine oil can bypass the oil b. Starter-Generator. The starter-generator (7, fig.
cooler by two methods. When the engine oil is cold, the 2-11) is located on the aft right side of the power and
oil cooler is bypassed through a valve located on the accessories gearbox. Access to the starter-generator is
right side of the oil cooler. This mechanical valve is gained through the right engine compartment access
controlled by the temperature of the oil flowing through door. A start counter is provided, for recording each
it. When the oil is cold, the valve is closed allowing oil time the exciter is energized, and is located on the
to bypass the cooler. The valve starts to open as the oil lower, left side of the power and accessories gearbox.
temperature reaches 71 °C (160 °F). At 81 °C (178 °F)
or higher, the valve is completely open allowing oil to
flow through the cooler. 2 - 2 8 . E N G I N E I N S T R U M E N T S A N D
INDICATORS.
(2) Functional Description. The second source
of oil cooler bypass is the oil cooler bypass valve a. Vertical Scale Display Subsystem (VSDS). The
mounted on the back side of the aft engine firewall. VSDS consists of the multiparameter display (MPD),
This electrically operated valve is powered through the dual tachometer, and TGT/TRQ (turbine gas
DC emergency bus and controlled by the ENG OIL temperature/mast torque indicators (fig. 2-6). These are
BYPASS switch located on the forward overhead vertical scale type displays, either alone or in
console panel (fig. 2-8) in conjunction with engine oil combination with digital readouts. The vertical scale
quantity. When the ENG OIL BYPASS switch is in the displays are color coded and have range markings and
OFF position, a low engine oil quantity condition will symbols to show operating limits, cautions limits, and
illuminate the LOW OIL QUANTITY ENG caution avoidance areas. Refer to Section XIV for additional
message on the MFD but the oil cooler will not be descriptive data.
bypassed. With the ENG OIL BYPASS switch in the
AUTO position, a low engine oil quantity condition will b. Turbine (Ng and Np) Speed Monopole Pickup
illuminate the LOW OIL QUANTITY ENG and OIL BYP Units. The turbine speed indicating components are
ENG caution lights and the oil cooler will be bypassed. two monopole pickup units installed on the power and
At normal engine oil quantity, placing the ENG OIL accessories gearbox. The power turbine (Np) monopole
2-31
TM 1-1520-248-10
pickup unit is located on top of the power and NOTE
accessories gearbox. The gas producer (Ng) monopole
pickup unit (4, fig. 2-11) is located on the upper right In order for the the TGT caution timers to be
portion of the power and accessories gearbox. reset after the limit threshold is exceeded,
TGT must be lowered 30 °C below the
c . T u r b i n e G a s T e m p e r a t u r e ( T G T ) threshold. For the 30 minute range, TGT
Measurement. Turbine gas temperature (TGT) is must be reduced below 686 °C to reset the
measured at four thermocouple probes located around timer. (CDS2) For the 5 minute range, TGT
the power turbine section. These signals are processed must be reduced below 755 °C to reset the
through the MCPU and MPD and then sent to the TGT timer.
indicator where TGT is displayed in degrees Celsius.
Signals are also processed through the MCPU to the
caution, warning, and advisory system for overtemp
conditions.
SECTION IV. FUEL SYSTEM
2-29. FUEL SYSTEM. The pump pressurizes the fuel inlet line and assists the
engine-driven suction pump at its critical operating
The fuel system consists of a crash resistant, self- periods: during start, at very low fuel levels, and during
sealing fuel cell, one engine driven fuel pump, one fuel high altitude operation.
cell mounted priming/boost pump, quantity indication
system, emergency shutoff valve, drainage provisions,
low level warning system, filter, filter bypass indicator, c. Emergency Fuel Shutoff Valve. A manually
and breakaway valve. Refer to Section XV for usable operated emergency fuel shutoff valve is provided to
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TECHNICAL MANUAL OPERATOR’S MANUAL FOR ARMY OH-58D HELICOPT(17)
