A magneto is an electromechanical device that provides the electrical energy needed to ignite the fuel-air mixture in aircraft internal combustion engines. They are critical parts in the ignition system, and are mainly used in piston aircraft engines.
Magnetos are composed of several essential elements, such as the rotor, the stator, the wire windings, the breaker or contacts and the distributor. Together, these components generate and distribute the electrical current to the spark plugs at the right time.
The interesting thing about magnetos is that they are a stand-alone system, i.e. they are not dependent on the aircraft’s electrical system. This means that if the electrical system should happen to malfunction or fail completely in flight, the engine can continue to operate normally.
Compared to a car’s battery and coil, the aircraft’s magnetos generate a higher spark intensity, which exponentially increases the efficiency of the engine.
In addition, the system starts working with the first crankshaft revolutions and will continue to do so for as long as it keeps turning.
Yes, we repeat ourselves a lot, but it’s the truth: aviation is the safest means of transport in existence, where every procedure has a plan B, and even a plan C. And further proof of this is the double magneto.
Aviation engines are equipped with two completely independent ignition systems, in order to avoid any possible engine failure. Each system consists of a magneto, distributor, wires and spark plugs.
Each cylinder is equipped with two spark plugs, which are fed by different systems, which greatly increases the safety of the system:
If you have seen the cockpit of one of our aircraft, you will have noticed that the key switch is very similar to that of a car, but how do they differ?
There are five different switch positions:
Once the propeller is turning, it is important to turn the key quickly to the BOTH position, as keeping the starter engaged can cause serious damage to the engine.
Despite the redundancy of the system itself, before every flight, an engine test is performed: a procedure in which everything is checked to ensure that all is working as it was intended.
Although the engine test procedure is included in the checklist for each aircraft, it can be roughly described as follows:
The RPM must not drop more than a certain number and the difference between the revolutions of one magneto and the other must not exceed a certain value. These differences are listed in the checklist.
Spark plugs are constantly in contact with the engine mixture, so they can sometimes become “greasy” and cause a sharp drop in revs or induce vibration.
This is why it is so important to adjust the mixture once we are in flight, as flying at high altitude and with the richest setting can cause a failure.
In our post about fuel mixture, we explained why it should be adjusted and how to do it correctly. Don’t miss it!
Undoubtedly, what is essential for the magnetos and the whole aircraft in general to work properly, is to have good maintenance.
And, at One Air, we can be very proud of this, as our own maintenance team ensures that our aircraft work perfectly.
In-house maintenance has many advantages, among which we can highlight: a reduction in work times and a great specialisation of the team.
Would you like to see the team at work? Here you have them on video!
We hope that, with this post, you have learned a little more about how general aviation aircraft engines work. If you want to continue learning and discovering new interesting facts, we recommend you to keep browsing our aviation blog.
