07 Electrical System

Compared with the current flow through the starter circuit, which connects the battery to the starter motor, the current flow through the starter switch in the start position is:

• Much higher.

• The same.

• Much lower.

• Alternating.

A fully charged battery:-

• Is capable of supplying the total electrical load of an aircraft for one hour or more.

• Has an electrolyte with a specific gravity of 1.3.

• Will have an off load voltage of 2.0 Volts per cell.

• Will never fail.

Connecting two 12 volt, 40 ampere-hour, capacity batteries in series will provide a battery of:

• 12 volts and 80 ampere-hours capacity.

• 24 volts and 40 ampere-hours capacity.

• 24 volts and 80 ampere-hours capacity.

• 12 volts and 40 ampere hours capacity.

A fully charged lead acid battery has a specific gravity of approximately:

• 1.350

• 2.275

• 1.170

• 1.300

A 100 Ampere-Hour battery:

• Will, in theory, supply 20 Amps for up to 5 hours.

• Must be used in parallel with another similar battery.

• Supplies the bus-bars through a 45 Ampere circuit breaker.

• Takes 100 hours to charge.

If a fuse blows during flight it:

• Should not be replaced until after landing.

• May be replaced in the air once only, by one of the same value.

• May be replaced by a fuse of a higher rating to ensure that it will not blow again.

• May be replaced as often as required.

In the event of an alternator or generator failure during flight the:

• Flight may be continued normally because the battery supplies all electrical loads.

• Electrical loads should be reduced to a minimum and a landing made as soon as safely practicable.

• Alternator master switch should be turned off and flight continued normally without electrical power.

• Battery master switch should be turned off and flight continued normally without electrical power.

The diagram shows a light aircraft electrical power system, which employs a centre-zero reading ammeter. In flight with the battery fully charged and the battery switch ON, you would expect the ammeter to be:

• In the centre-zero position.

• To the right showing a large positive reading.

• To the left showing a negative reading.

• Fluctuating, but mainly showing a negative reading.

The diagram shows a light aircraft electrical power system. In flight if the loadmeter reading drops to zero, the most probable cause is that the:

• Battery has been fully charged.

• Alternator has failed.

• Battery is flat.

• Bus-bar is overloaded.

The main advantage of an alternator over a generator is that:

• An alternator will give almost full power at engine idling speed.

• A generator can only produce alternating current.

• The output of a generator fluctuates too much.

• An alternator produces direct current from its armature.