PART 1-DESCRIPTIVE
Page 16 17. Electrical system (24-volt)
A.L.3
(a) D.C. supply
(i) A single engine-driven generator supplies the whole of the
electrical system and charges two 12-volt batteries connected
in series.
(ii) A generator failure warning light is on the right of the instru-
ment panel. The warning light indicates when the generator
is not supplying power. Post Mod. FTC 104 the light will
only come on if the battery discharge rate exceeds 4-7 amps.
It will not illuminate when an external supply is used. It may
not come on prior to start-up until the flight instruments and
booster pump are switched on. It may come on in flight when
the throttle is closed.
(iii) Mod. 3378 introduces a voltmeter, fitted below the inverter
circuit breakers on the port instrument panel. With the
generator off-line the meter indicates battery voltage: with the
generator on-line the meter indicates generator output voltage.
In flight the voltmeter needle should normally be in the white
(25-29v) sector; in either red sector (15-22v or 30-35v) the
indication is that a generator output fault exists.
(iv) The Ground/Flight MASTER SWITCH (53) is below the
centre of the instrument panel. It should be pulled out for
Ground and pushed IN FOR FLIGHT. Two external sockets
are fitted, one on each side of the fuselage. The socket midway
along the starboard underside is for ground testing only.
The socket on the port side of the fuselage nose is for ground
test use. All electrical services (except automatic engine
starting) can be connected to the ground battery when it is
plugged into the port socket.
(vi) The Ground/Flight switch must be set in before electrical
power is available to the starting system from an outside source.
(b) A.C. supply
(i) Two type 101A inverters are fitted. No. 1 inverter normally
supplies the flight instruments and No. 2 acts as a standby to
meet the case of failure of No. 1 inverter.
(ii) Below the port instrument panel are two circuit breakers, one
for each inverter supply. A magnetic indicator (51) which
shows black when No. 1 inverter is supplying power, and white
when change-over to No. 2 inverter occurs or when electrical
supply is lacking, and a reset pushbutton (50) are on the star-
board instrument panel. The flight instruments switch (33)
is adjacent to the starter master switch.
(iii) When the FLIGHT INST switch is ON before
starting the engine,No. 2 inverter starts up and
supplies the artificial horizon and causes the Mark 4F
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