Mod 11.6 Cat B

Sparking in a DC generator could be caused by

• low spring tension

• bedding of brushes

• brushes on the Magnetic Neutral Axis

Answer explanation

If the brush tension is low then proper contact with the commutator segments may not be maintained, causing an air-gap and sparking

When installing multiple batteries on aircraft they are connected in:

• parallel

• series

• either parallel or series and switched between as an option

Answer explanation

Batteries may be connected in series to increase the voltage, or parallel to increase the capacity

In a carbon pile regulator the resistive element is

• in series with the field and changes resistance with changing length

• in series with the field and changes resistance with surface area contact

• in parallel with the field and changes resistance with changing length

In a transistor voltage regulator the voltage output is controlled by

• Transformers and transistors

• Thyristors and transformers

• Zener diodes and transistors

The main purpose of a CSD is to

• maintain a constant output voltage from the generator

• maintain a constant output frequency from the generator

• maintain  a constant load on the generator

Answer explanation

The CSD is used to maintain the Generator drive speed regardless of the engine speed, producing a constant frequency output

On a D.C. powered aircraft the battery charge current is determined by:

• the voltage regulator setting

• the battery voltage only

• both a) and b)

Answer explanation

The voltage regulator controls the output voltage from the generator. The charge current will be determined the Potential Difference between the generator and the battery

During servicing of an aircraft battery, leakage current is measured by connecting:

• a voltmeter across the battery terminals

• an ammeter between the positive terminal and the case of the battery

• an ammeter across the battery terminals

Answer explanation

An ammeter is used to measure current. If it was connected across the terminals maximum current would flow (short circuit). By measuring between the +ve terminal and the case we are checking for any damage to the case and any leaking electrolyte

When charging batteries, they may be connected:

• in series only

• in parallel only

• a.       in any combination of series and parallel

If a 40AH at the 1 Hr rate battery takes 62 minutes to discharge whilst on a capacity test:

• its capacity is 103%

• something was not done correctly during the test

• its capacity is 97%

Answer explanation

Read up on battery capacity testing. New batteries can have a capacity of greater than 100%

A lead acid battery is considered fully discharged when it has a:

• specific gravity of 1150 and a cell voltage of 1.8V

• specific gravity of 1150 and a cell voltage of 2.0V

• specific gravity of 1270 and a cell voltage of 1.8V