C42E 540kg LSA POH Issue 3 China
15.03.2016
Page 26 of 36
7.3
Instrument panel
Battery
A small lightweight lead acid battery is installed beneath the instrument panel for engine starting. It has
a capacity of 5 amp hours and very high current capability. No maintenance is required, apart from
keeping the contacts clean and dry. The battery is charged from the engine’s in-built alternator, via a
rectifier-regulator unit.
The engine ignition system is independent of the rest of the electrical system and does not require the
battery to operate.
Fuses
Fuses are provided to protect wiring to all the electrical services with the exception of the starter motor.
If a fuse blows, it is important to determine the cause of the failure before replacing the fuse. Under no
circumstances replace the fuse with one of a higher rating.
Instruments
A variety of electrical instrument configurations is available, with an essential minimum as follows:
Fuel gauge
Oil Temperatur gauge ( Oil-T )
Oil Pressure gauge ( Oil-P )
Cylinder Head Temperature gauge (CHT)
*
Tacho ( rpm )
Compass
*
Note: there may be a significant difference between the CHT reading and that of the coolant
temperature, with the CHT gauge likely to read low, and to have a slower response. Although the
CHT gauge may indicate an acceptable temperature, it must not be assumed that the coolant
temperature lies within limits.
Switches
A master switch provides isolation of the battery from the main bus.
The master switch must be closed
(on) before attempting to start the engine, and must remain on to ensure that the battery is charged
properly.
Separate isolating switches are provided for the remaining services or groups of services. Where a radio
is installed, it is wise to turn off the radio switch before starting to reduce the risk of high spurious voltages
damaging the radio.
NOTE: - The ignition switches stop the engine by grounding the ignition circuit. The engine is
started and runs with the switches open, and is stopped by closing the switches. The ignition
switches are therefore mounted in the reverse sense to the other switches to enable the normal
aviation switch sense to be maintained. ie. up for ON, down for OFF.
It is also important to note that disconnection of the ignition switch wires, by accident or during
maintenance, renders the engine live. Great care must be exercised in this case to ensure that
the engine cannot be started accidentally. Normally remove the spark plugs’ caps.