Section 7 Pilot’s Operating Handbook
Description of Airplane and Systems EXTRA 500
7.18.a Starter-Generator
A starter-generator is mounted on the accessory gearbox of the
engine. It is a direct driven starter during engine start and a
DC generator driven by the engine during engine operation. Its
rated capacity is 200 A maximum for continuous operation. The
starter-generator is regulated by the GCU (Generator Control
Unit) to provide an output voltage of 28.5 V DC. The GCU is
controlled by the
GEN and GEN TEST switches located on the
MAIN section of the left side panel. Following engine start, the
generator delivers electrical power when the
GEN switch is
switched to
ON position.
In case the generator is not switched on or has failed the red
GENERATOR FAIL warning light on the annunciator panel
illuminates. The generator test switch (
GEN TEST, left side
panel) enables the pilot to test the overvoltage protection
function of the GCU (switch position:
OV-TEST). The TRIP
position of this switch gives the possibility to “trip” the
generator by momentarily interrupting its excitation. Both test
functions lead to disengagement of the generator from the
aircraft bus system. The momentary
RESET position of the
GEN switch enables the pilot to energize the generator field in
case problems have occurred trying to connect the generator to
the aircraft bus system (switching the generator
ON). Resetting
the generator is recommended in that case before trying to
switch the generator on again.
7.18.b Standby Alternator
In case of a starter-generator failure a gear driven standby
alternator provides an additional power source in excess to the
aircraft battery. The standby alternator is controlled by the
STDBY ALT switch in the MAIN section of the left side panel.
Switching it to the
ON position will command the alternator
regulating unit to regulate an alternator output voltage of
26 VDC. Therefore as long as bus voltage is higher caused by
an active generator the alternator load will be zero. As soon as
bus voltage tends to drop below the regulation voltage of the
standby alternator the alternator feeds to the bus system. Max.
rated current is 20 A which is available with N1 being at approx
7-50 26. January 2011
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