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Malfunctions in the electrical power supply system can be detected by periodic monitoring of the ammeter, however, the cause of these malfunctions is usually difficult to determine. A broken alternator drive belt or wiring is the most common cause of alternator failures, although other factors could cause the problem. A damaged or improperly adjusted voltage regulator can also cause malfunctions. All electrical problems of this nature constitute an electrical emergency and should be dealt with immediately. Electrical power malfunctions usually fall into two categories:
After periods of heavy electrical usage (such as starting and taxiing), the battery condition may be low enough to accept above than normal charging during initial flight. However, after 30 minutes of cruising flight, the ammeter should be reading normal. If the charging rate remains above normal on a long flight, it is possible that the battery will overheat. In addition, electronic components could be adversely affected by the higher than normal voltage if a faulty voltage regulator setting is causing the overcharging. To preclude these possibilities, the alternator side of the split Master switch should be turned “OFF”. The flight should be terminated and/or the current drain on the battery minimized as soon as practical because the battery can supply the electrical system for only a limited period of time. If it becomes apparent that the battery voltage is getting too low to operate the electrical system, the alternator switch can be turned on for several minutes at a time until the battery is partially recharged. If the emergency occurs at night, the alternator switch should be returned to the “ON” position just before landing lights will be required for landing.
If the ammeter indicates a continuous discharge rate in flight, the alternator is not supplying power to the system and should be shut down, since the alternator field circuit may be placing an unnecessary load on the system. All non-essential equipment should be turned “OFF” and the flight terminated as soon as practical.
In the event of an electric trim “runaway” malfunction, immediate corrective measures are required as follows:
A slight engine roughness in flight may be caused by one or more spark plugs becoming fouled by carbon or lead deposits. This may be verified by turning the ignition switch momentarily from “BOTH” to either “LEFT” or “RIGHT” position. An obvious power loss in single ignition operation is evidence of spark plug or magneto trouble. Assuming that spark plugs are the more likely cause, lean the mixture to the normal lean setting for cruising flight. If the problem does not clear up in several minutes, determine if a richer mixture setting will produce smoother operation. If not, proceed to the nearest airport for repairs using the “BOTH” position of the ignition switch unless extreme roughness dictates the use of a single ignition position.
A sudden engine roughness or misfiring is usually evidence of magneto problems. Switching from “BOTH” to either “LEFT” or “RIGHT” ignition switch position will identify which magneto is malfunctioning. Select different power settings and enrichen mixture to determine if continued operation on “BOTH” magnetos is practical. If not, switch to the good magneto and proceed to the nearest airport for repairs.
Failure of the engine-driven fuel pump will be evidenced by a sudden reduction in the fuel flow indication prior to a loss of power, while operating from a tank containing adequate fuel.
In the event of a pump failure during take-off, immediately switch on the auxiliary fuel pump switch until the aircraft is well clear of obstacles, after which, maneuver the aircraft for landing.
If low oil pressure is accompanied by normal temperature, there is a possibility that the oil pressure gauge or relief valve is malfunctioning. A leak in the line to the gauge sensor is not necessarily cause for an immediate pre-cautionary landing because an orifice in this line will prevent a sudden loss of oil from the engine sump. However, a landing at the nearest airport would be advisable to inspect source of the trouble.
If a total loss of oil pressure is accompanied by a rise in oil temperature, there is a good reason to suspect an engine failure is imminent. Reduce the engine power immediately and select a suitable forced landing field. Leave the engine running at low power during the approach, using only the minimum power required to reach the desired touch down spot.
Before attempting an “off airport” landing, one should drag the landing area at low altitude to inspect the terrain for obstructions and surface conditions, proceeding as follows:
If an engine stoppage occurs, establish a flaps-up glide at 85 mph. If time permits, attempt to restart the engine by checking for fuel quantities, proper fuel selector valve position and mixture control setting. Also check that the ignition switch is in the correct position. If all attempts to restart the engine fail and a forced landing is imminent, select a suitable field and prepare for the landing as follows:
Upon entering the clouds, and immediate plan should be made to turn back as follows:
The initial indication of an electrical fire is the odor of burning insulation. The immediate response is to turn the master switch “OFF”. Then close off ventilating air as much as practical to reduce the chances of a sustained fire. If electrical power is indispensable for the flight, an attempt may be made to identify and cut off the defective circuit as follows:
An unexpected icing encounter should be handled as follows: