4N Emergencies - Electrical

Question 0

2. Interpret the following ammeter indications. (POH)

Answer 0

a. Ammeter indicates a right deflection (positive).
After starting—The power from the battery used for starting is being replenished by the alternator. Or, if a full-scale charge is indicated for more than 1 minute, the starter is still engaged and a shutdown is indicated.
During flight—A faulty voltage regulator is causing the alternator to overcharge the battery.
b. Ammeter indicates a left deflection (negative).
After starting—Normal during start. Other times indicates the alternator is not functioning or an overload condition has occurred in the system. The battery is not receiving a charge.
During flight—The alternator is not functioning or an overload has occurred in the system. The battery is not receiving a charge.

Question 1

1. What recommended procedure should be used in resetting a tripped circuit breaker? (FAA-H-8083-30; AC 120-80)

Answer 1

A tripped circuit breaker should not be reset in flight unless doing so is consistent with procedures specified in an approved AFM, or unless, in the judgment of the PIC, resetting the breaker is necessary for safe completion of the flight. Repeated resetting of a circuit breaker can lead to circuit or component damage, or worse, the possibility of a fire or explosion.

Question 2

3. What action should be taken if the ammeter indicates a continuous discharge (left needle) while in flight?

Answer 2

The alternator has quit producing a charge, so the master switch and the alternator circuit breaker should be checked and reset if necessary. If this does not correct the problem, the following should be accomplished:

a. The alternator should be turned off; pull the circuit breaker (field circuit will continue to draw power from the battery).
b. All electrical equipment not essential to flight should be turned off (the battery is now the only source of electrical power).
c. The flight should be terminated and a landing made as soon as possible.

Question 3

4. What action should be taken if the ammeter indicates a continuous charge (right needle) while in flight (more than two needle widths)? (POH)

Answer 3

If a continuous excessive rate of charge were allowed for any extended period of time, the battery would overheat and evaporate the electrolyte at an excessive rate. A possible explosion of the battery could result. Also, electronic components in the electrical system would be adversely affected by higher than normal voltage. Protection is provided by an overvoltage sensor which will shut the alternator down if an excessive voltage is detected. If this should occur the following should be done:

a. The alternator should be turned off; pull the circuit breaker (the field circuit will continue to draw power from the battery).
b. All electrical equipment not essential to flight should be turned off (the battery is now the only source of electrical power).
c. The flight should be terminated and a landing made as soon as possible.

Question 4

5. If the low-voltage warning light illuminates, what has occurred? (POH)

Answer 4

Illumination of the low-voltage light along with a discharge indication on the ammeter can occur during low rpm conditions with a full electrical load on the system. This event usually occurs on the ground with low rpms while taxiing. Another possibility is the alternator has been shutdown; the airplane is equipped with a combination alternator/regulator high-low voltage control unit which, when an over-voltage condition occurs, will shut down the alternator and illuminate the warning light. The battery is now supplying all current to the electrical system. The ammeter will indicate a discharge.