ENGINE STARTING
Recommended Start Methods
Aircraft power alone .........LO START
External power
..............HI START
In-air restart
................HI START
LO START. The two aircraft batteries perform the start sequence in parallel.
HI START. Though HI START results in faster light off, cooler starting
temperatures, and lower stresses on the engine, it depletes the batteries
more quickly. The Master Control Unit (MCU) initiates the start with the two
batteries in parallel and then, as the starter current decays to a pre-determined
value, the batteries are switched into series to feed the starter. The resultant
48 volts appear only at the starter and nowhere else in the electrical system.
The inrush current and impact torque on the accessory gears is signicantly
reduced and the engine acceleration is faster, which results in reduced peak
inter-turbine temperatures at startup.
If a ground power unit is available, an external power start should be
performed on the rst ight of the day or if maintenance has been performed
on the aircraft involving the use of the aircraft electrical system. Even if
24 volts is shown on the voltmeter, the battery condition may be less than
desired.
If a ground power unit is not available, a LO/MOTOR START should be
selected on the rst ight of the day, or if maintenance has been performed
on the aircraft involving the use of the aircraft electrical system. LO/MOTOR
START should also be selected and is recommended if a HI START is
attempted without successful light-off, and no external power is available.
The LO START cycle does not consume as much battery power for continued
attempts to start the engine.
Checklist Procedures for Engine Starting
The Engine Starting Checklist procedures must be followed closely to assure
satisfactory starting of the engine.
• With the Battery Master Switch ON, check the buss voltages for a reading
of 24 volts minimum. If the battery voltage is lower than 24 volts, external
power should be used to start the engine. If the low-voltage problem
persists, the problem should be determined and remedied prior to
attempting an engine start.
• Verify the Emergency Power Lever is secured in its NORMAL position.
• Actuate the Auxiliary Fuel Pump switch and verify the AUX PUMP ON
annunciator is shown on the PFD, the
FUEL PRESS LOW annunciator is
not shown on the PFD, and there is no indication of fuel ow.
• The ignition switch may be placed in the OFF position when starting the
engine in HI START mode, as the igniters are automatically excited when
the starter switch is actuated. The ignition switch must be placed in the ON
position for a LO/MOTOR start.
• Actuate the starter switch to HI for a HI START or LO/MOTOR for a LO
START.
• Verify the IGNITION ON annunciator is illuminated, Engine Oil Pressure is
rising and the gas generator RPM (
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