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Can You Legally Fly with One Magneto?

Published in Aircraft Malfunction Procedures 4 mins read

Yes, you can legally continue a flight with one inoperative magneto if it malfunctions during flight, provided the remaining magneto is functioning correctly and you are proceeding to the nearest suitable airport for repairs. This is an accepted procedure when experiencing an in-flight mechanical issue.

Understanding Aircraft Magnetos

Most piston-engine aircraft are equipped with a dual ignition system, typically featuring two independent magnetos. Each magneto provides sparks to a set of spark plugs (usually two per cylinder, with each magneto firing one plug per cylinder). This dual system offers significant redundancy and improved combustion efficiency.

Why Two Magnetos?

  • Redundancy: If one magneto fails, the other can continue to power the engine, ensuring the aircraft can safely reach an airport.
  • Reliability: Independent systems reduce the chance of a single point of failure affecting ignition.
  • Performance: Two spark plugs per cylinder generally lead to more complete combustion and smoother engine operation.

In-Flight Magneto Malfunction

Should a magneto fail during flight, it is a common and manageable emergency. Identifying a single bad magneto typically involves observing how the engine performs when switched between ignition positions. If the engine runs poorly when switched to one magneto position (e.g., "Left" or "Right") but runs well and smoothly on the other, it indicates a problem with the magneto that caused the rough running.

In such a scenario, it is certainly all right to continue your flight on the single functioning magneto to an airport where necessary repairs can be made. The primary goal is to safely land the aircraft at the nearest suitable airfield.

Regulatory and Safety Considerations

While continuing a flight on one magneto is permissible in the event of an in-flight malfunction, it's crucial to understand the context:

  • In-Flight Emergency/Malfunction: This allowance applies to situations where equipment becomes inoperative during a flight. It does not generally permit initiating a flight with a known inoperative magneto unless explicitly authorized by a Minimum Equipment List (MEL) specific to the aircraft type or a special flight permit (ferry permit).
  • Pilot in Command Authority: Federal Aviation Regulations (FARs) grant the Pilot in Command (PIC) the authority and responsibility to act during an emergency. Safely landing the aircraft following an in-flight malfunction falls under this discretion.
  • Reduced Redundancy: Flying with only one functioning magneto eliminates the backup system. This increases the risk if the remaining magneto were also to fail. Therefore, proceeding directly to the nearest suitable airport is paramount.

Practical Steps When a Magneto Fails

If you experience a magneto malfunction during flight, consider the following actions:

  • Confirm the Malfunction: Perform a magneto check (as per your aircraft's Pilot's Operating Handbook/Aircraft Flight Manual (POH/AFM)) to confirm which magneto is at fault.
  • Maintain Engine Operation: Switch the ignition to the working magneto position. The engine should run smoothly on the single operational magneto.
  • Adjust Mixture: You may need to lean the mixture slightly to achieve the best power on one magneto, as it can sometimes run a bit richer.
  • Proceed to Nearest Airport: Immediately divert to the nearest suitable airport for landing and repairs.
  • Communicate: Inform Air Traffic Control (ATC) of your situation and intentions. This allows them to provide assistance and prioritize your landing.
Action Item Description
Identify Faulty Mag If the engine runs rough on one magneto switch position but well on the other, that's your faulty unit.
Select Operating Mag Keep the ignition switched to the magneto that provides smooth engine operation.
Lean Mixture Optimize fuel-air mixture for best power/smoothest operation on the single magneto.
Divert to Nearest Airport Prioritize landing at the closest suitable airport for maintenance.
Communicate with ATC Declare your situation and intentions to ATC for assistance and priority.
Consult POH/AFM Always follow your specific aircraft's emergency procedures.

Conclusion

While dual magnetos are a critical safety feature, the operational design allows for continued safe flight in the event of a single magneto failure. The focus shifts to safely concluding the flight at the nearest suitable airport for repair, ensuring the safety of the aircraft and its occupants.