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## Alternator/Generator Failure 

Depending upon the aircraft being flown, an alternator failure is indicated in different ways. Some aircraft use an ammeter that indicates the state of charge or discharge of the battery. [Figure 11-4]  A positive indication on the ammeter indicates a charge condition; a negative indication reveals a discharge condition. Other aircraft use a loadmeter to indicate the load being carried by the alternator. [Figure 11-4] 

Sometimes an indicator light is also installed in the aircraft to alert the pilot to an alternator failure. On some aircraft, such as the Cessna 172, the light is located on the lower left side making it difficult to see its illumination if charts are open. Ensure that these safety indicators are visible during flight. 

When a loss of the electrical charging system is experienced, the pilot has approximately 40 minutes of battery life remaining before the system fails entirely. The time mentioned is an approximation and should not be relied upon as specific to all aircraft. In addition, the battery charge that exists in a battery may not be full, altering the time available before electrical exhaustion occurs. At no time shoul d a pilot consider continuing a flight once the electrical c harging system has failed. Land at the nearest suitable airport. 

## Techniques for Electrical Usage 

## Master Battery Switch 

One techn ique for conserving the main battery c harge is to fly the aircraft to the airport of intended landing while operating with minimal power. If a two-position battery master/alternator rocker switch is installed, it can be utilized to isolate the main battery from the electrical system and conserve power. [Figure 11-5] 

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## Operating on the Main Battery 

While en route to the airport of intended landing, reduce the electrical load as much as practical. Turn off all unnecessary ele ctrical items, such as duplicate radios, non-essential lig h ting, etc. If unable to turn off radios, lights, etc., manually, consider pulling circuit breakers to isolate those pieces of eq u ipment from the electrical system. Maximum time of useful voltage may be between 30 and 40 minutes and is influenced by many factors, that degrade the useful time. 

## Loss of Alternator/Generator for Electronic Flight Instrumentation 

With the increase in electrical components being installed in modern technically advanced aircraft, the power supply an d the charging system need increased attention and 

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