Mahindra GIPPSAERO GA8-TC 320 - Electrical Systems Malfunctions

Section 3
Model GA8-TC 320 Emergency Procedures
CASA Approved
Page 3-12 5 Feb 2009 C01-01-08
3.4.7. Electrical Systems Malfunctions
The operation of the electrical system is straight forward but to obtain the necessary degree of
reliability and redundancy the system must be operated correctly. Normal operation is with both
Master Switches in the ON position. Should the need to shed electrical loads arise the Bus 2
Master Switch, which controls the non essential electrical loads and the alternator, is switched
off and operation continued on the Bus 1 services utilising battery power alone. More severe
electrical system failures, such as those resulting in re, require both Master Switches to be
switched off.
WARNING:
DO NOT TAKE THE ALTERNATOR OFF LINE (EITHER BY TURNING OFF
THE BUS 2 MASTER OR BY PULLING THE ALTERNATOR FIELD CIRCUIT
BREAKER) IN FLIGHT EXCEPT IN AN EMERGENCY.
Usually battery power is required to initially excite the alternator. However, the GA8-TC 320
features a circuit incorporating a capacitor to provide an independent source of initial electrical
energy to the alternator should the battery fail. The capacitor circuit operates whenever the Bus
2 Master Switch is selected from OFF to ON. The alternator then provides the energy for the
eld current and recharges the capacitor.
In addition to the general guide above, specic failures may be dealt with as follows:
1. INSUFFICIENT RATE OF CHARGE If the ammeter indicates a declining or zero charge in
ight with electrical services switched on, minimal or no electrical power is being supplied by the
alternator. If the charge drops sufciently the alternator warning light will illuminate.
A possible cause of a zero charge indication is the over-volt relay tripping the alternator off line if
the alternator output voltage had exceeded approximately 16 volts due to a failure of the voltage
regulating system. The over-volt relay can be reset to check for this failure by turning the Bus
2 Master Switch OFF then ON again. If the over-volt relay trips the alternator off line a second
time it can be assumed that an over-volt problem denitely exists and the Bus 2 Master should
be switched off again. If the alternator comes back on line, be aware for further problems, as the
cause may be an internal alternator fault.
The opening of the alternator eld circuit eld breaker will also cause the alternator to go off
line. If the breaker is open, it may be reset, but only once. If the breaker opens again there is a
denite problem with the alternator circuit, and consideration should be given to landing at the
nearest practical aireld.
Another possible cause of a zero charge indication is the failure of the alternator or the alternator
drive belt. Provided the eventual total loss of electrical services will not affect the safety of ight,
the ight may continue.
A declining charge indication may be due to slipping of the alternator drive belt under increasing
electrical load, in which case the alternator will not be delivering it’s full output as additional
services are turned on.