Electrical Failure

Electrical Failure

An electrical failure can take several forms: an electrical fire or broken alternator are the two most common. A pilot’s reaction to an electrical emergency is dependent upon several factors including the type of failure, weather, and airplane. A fire, for example, warrants a more rapid response than an alternator failure, because the fire has a much higher potential to do damage.

Lesson Notes

Any electrical emergency will likely require load shedding — turning off non-essential equipment to reduce electrical load or turn off malfunctioning equipment. Load shedding increases the life of our battery by running only essential equipment. The nuance in an electrical emergency is determining which equipment is essential and which is not.

This requires some common sense and thinking from the pilot. If, for example, an airplane in IMC experiences an electrical failure, there is probably quite a lot of essential equipment needed to fly an instrument approach and land at the nearest airport. By contrast, flying on a clear sky day, a pilot may elect to turn off nearly all electrical equipment. Pilots can also consider options like keeping a radio on but limiting transmissions which are power intensive.

Electrical equipment which can be turned off may include:

• Communication radios
• Navigation radios
• GPS units
• Primary or Secondary Flight Displays (PFD/MFD)
• Transponder
• Lights
• Fuel pumps
• Master switch (whole system)

If a pilot experiences an electrical fire, they will likely turn off everything they possibly can without compromising their ability to get back on the ground. If they experience an alternator failure, they will likely load shed more judiciously, perhaps turning off a transponder if it is not required, but still turning on a fuel boost pump on approach.

It’s worth noting that alternator failures in most airplanes are not like alternator failures in cars. Because the magnetos operate independently of the electrical system, the engine will continue to run without electrical power. In fact, there are many vintage light airplanes (e.g. Piper J-3 Cub) that have no electrical system at all.

Additional Resources