By Robert N. Rossier, EAA 472091
This piece originally ran in Robert’s Stick and Rudder column in the September 2025 issue of EAA Sport Aviation magazine.
Electrical system issues might not seem as urgent or consequential as engine failures or fires. However, accident data reveals that a lack of knowledge of an aircraft’s electrical system — its limits, operation, importance, and appropriate actions following a failure — can precipitate a serious or even fatal accident.
Not long ago, the pilot of a Beech A36 Bonanza was on a VFR flight when electrical system issues disrupted his plans. Following a normal start and run-up, the pilot departed Genesee County (KGVQ) in Batavia, New York, and climbed to cruise altitude. A short time later, a flashing message indicator on his GPS warned of an electrical system issue.
Heeding the warning, the pilot informed ATC that he would return to KGVQ to have the electrical system repaired. The airplane had just come out of maintenance. The pilot suspected a loose cable or unsecured wiring had caused a short and could possibly start a fire.
About 7 miles from the airport, the GPS and primary flight display began to flash. The pilot pulled the circuit breakers for the affected displays and set up for a straight-in approach and landing. At this point, the pilot might have thought the situation was well in hand, but he would shortly learn otherwise.
When it came time to descend, the flaps failed to deploy. He reset the pulled breakers, but the flaps still would not extend. Perhaps distracted or amped up from all the excitement, the pilot forgot to extend the landing gear and made a gear-up landing, resulting in substantial damage to the airplane.
After the accident, the pilot realized that his starting procedure had been interrupted for a quick maintenance check, and he had forgotten to turn on both the primary and standby alternator. Unknown to him at the time, he had departed on his flight operating the electrical system on battery power alone. And despite the indications, he had failed to recognize the problem and take appropriate actions to restore electrical power.
Clearly, it is important to be thorough when completing a checklist, but there’s more to keeping our electrical system in check. Since our ultimate safety might depend on a properly operating electrical system, consider the following tactics:
Read the signs — Resolving an electrical system problem requires prompt recognition of the situation, so we need to be monitoring the electrical system health. With the engine running, lights ablaze, and radios and electronic displays up and running, it’s easy to overlook the ammeter, load meter, or voltmeter and assume all is well. But those indicators monitor the heartbeat of the electrical system. They tell us where power is coming from and whether the alternator (or alternators) is keeping the system alive.
If we don’t catch those first clues to an electrical system malfunction, other symptoms may eventually evolve. The radios might become weak and scratchy, or we might notice a dimming of lights. We might get a warning light on the instrument panel or a message from our onboard electronics. By the time such signs appear, critical time has already been lost, and a complete electrical system failure might be soon to follow unless the condition is promptly corrected. Without a doubt, it’s time to consult the appropriate checklist.
Shed the load — One of the first steps in responding to an electrical system emergency (other than an electrical fire) is to shed the load. Reduce the demand on the electrical system to only essential items in order to prolong its operation. This requires us to have a good working knowledge of what does what, and the power demands of various items.
To start, the marking on the circuit breakers gives us a clue as to the potential load demanded by the items served by each circuit. A 20-amp breaker means the circuit can draw twice the electrical energy as a 10-amp circuit. And while that’s a good starting point, there’s more to it than what’s indicated on the breakers.
For example, incandescent lighting draws a lot of power, whereas LED lights draw little. Our old “steam gauges” and instruments draw relatively little, but modern electronics and glass cockpits can suck up the power like there’s no tomorrow. And not all items are needed all the time.
As part of our load-shedding strategy, we need to consider what is needed and when, and to distinguish between continuous and intermittent power needs. A typical radio draws 5 to 10 amps when transmitting, but uses only one-tenth of that when receiving. A gear, flap, or motor can draw 10 to 20 amps while operating but is only needed for a brief time. On the other hand, pitot heat typically draws a continuous 10 amps when turned on — and we’d better have it on if we’re in potential icing conditions.
We should land as soon as practical if we experience an electrical system failure, so we need to know how long we can operate on battery power alone. The time depends on several factors including the amp-hour rating of the battery, its age and condition, and the current being drawn. While a battery rated at 30 amp-hours can theoretically provide 30 amps for an hour, we should never expect our battery to have its full rated capacity available. Half is perhaps more likely.
What some pilots might not realize is that adequate voltage can also be essential to proper system operation. For example, low voltage might allow us to extend the landing gear but not be adequate to lock it into position. So, if we extend the gear while experiencing a compromised electrical system, we might need to follow up with some manual cranking to ensure it is down and locked. Some electronics may operate with power as low as 7 volts, for example, but will call it quits if voltage drops any lower.
Ring the bell — Another critical step in any electrical system failure is to let someone (ATC) know we have a problem. Our best tactic is to declare an emergency and divert to a nearby field — preferably a towered airport where assistance can be provided. Since we might be able to communicate by phone if our entire electrical system fails, we could give our phone number to ATC for in-flight emergency communication.
Additional considerations — For a night electrical emergency, we might rely on pilot-controlled lighting, so having an emergency handheld transceiver could be a lifesaver.
We might need extra power at the end of our flight to operate flaps, fuel pumps and gear, or make an instrument approach. If our alternate airport isn’t close by, we might shut off the master to conserve power and have a plan for when and where to turn it back on, so we can coordinate this with ATC.
In the meantime, we might need to rely on pilotage or dead reckoning for our navigation.
Besides having the requisite systems knowledge, consider carrying backup equipment to deal with an electrical system failure. Equipment should include multiple flashlights, a backup handheld radio, paper charts, a tablet with backup power, and a fully-charged phone.
Dealing with an electrical system malfunction or failure can present some serious challenges. However, if we maintain our knowledge and plan for such a scenario, we’ll be much more likely to have a successful outcome.
Robert N. Rossier, EAA 472091, has been flying for more than 40 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.