The Aircraft Magneto

Guides · 4 min read · Oct 17, 2021
Magneto airplane

A magneto is an electrical device that behaves as a self-contained generator and, is used to produce periodic pulses of alternating current. Magneto behaves as a generator for producing electricity and uses permanent magnets for producing AC. Magneto is one of the earliest electrical systems having multiple applications in the modern world due to its reliability and simplicity. It is an essential component of engines in small aircraft.

What are airplane magnetos?

An aircraft magneto is an electrical generator driven by an engine shaft to produce high voltage. This high voltage is utilized in operating spark plugs for the ignition of fuel in the combustion chamber. Airplane magnetos are constructed with permanent magnets and abundantly applied in the ignition system of most reciprocating aircraft engines.

Airplane magnetos are reliable and easy to maintain. They are used in pairs to ensure the continuous combustion of fuel in the combustion chamber. Aircraft magneto does not require any external electrical source to operate and due to less physical contact in moving parts and, easier installation, it is one the most reliable source of producing high voltages for aircraft piston engines.

Usually, there are two magnetos on each cylinder of the piston engine of aircraft so that if one aircraft magneto fails in flight, the other Magento keeps the piston working by continuing the combustion process.

A passenger aircraft ready to land at an airport on a cloudy day.

The function of aircraft magneto ignition system

Magnetos are widely used in general aviation airplanes, specifically piston engines. In such engines, magneto consists of a rotating magnet nearby a high-output coil. Magnet starts spinning by using the engine’s rotating shaft and starts producing electricity in the primary coil.

When voltage output is sustained between 20,000 to 30,000 volts a distributor provide the path to the amplified current towards the spark plug. High voltage electric current generated induces a high-intensity spark inside the combustion chamber to ignite the fuel-air mixture and the resulting energy pushes the piston to operating movement.

Ignition redundancy using two spark plugs

The aviation industry believes in a fail-safe concept while designing a critical component in an aircraft. The same concept is applied in the combustion process of an aircraft engine. Piston engines for light aircraft are designed with two independent magneto ignition systems. Each cylinder is equipped with two spark plugs and two magnetos, one installed on each side. Then left magneto fires one plug while the right magneto fires the other, this arrangement ensures continuity in the working of the aircraft engine thus eliminate risks about consequences of aircraft magneto failure.

Voltage creation

In airplane magnetos, each magneto consists of a permanent magnet on a rotor that spins in close proximity to a high-output voltage coil with two windings. First is the primary winding that is made with heavy copper wire and the other one is the secondary coil which is enclosed with a high number of turns. When a magnet rotates, magnetic flux lines pass through the primary winding, it creates magnetic flux linkage, changes in these flux linkages induce voltage.

Electrical spike

The voltage created by primary winding is not enough for application in piston aircraft engines so this voltage is created on the secondary winding by connecting with the primary winding. When connected, the magnetic field in the primary coil collapses and induces a large fluctuation in magnetic flux linkages.

This spike in electricity passes on to the secondary winding and amplifies it significantly between 20,000 to 30,000 volts. At the moment when the secondary coil releases this higher voltage a high-intensity spark is produced by a spark plug which is enough to ignite the fuel mixture in the combustion chamber of the cylinder.

Parts of Magento

The basic configuration of aircraft magnetos includes magneto housing, a rotating magnet, contact points, pole shoe, and coil. Additional parts in aircraft magneto include a permanent-magnet rotor, a primary winding with less number of turns, and another winding with a high number of turns commonly referred to as the secondary winding, a parallel-connected capacitor with a series of the magneto to reduce noise, and a circuit breaker.

Types of aircraft magnetos

There are three different kinds of aircraft magnetos, each having its qualities and advantages depending on usage. Each type of Magento is discussed below to make it easy for the operator in selecting the most appropriate for use. Every airplane magneto is designed for a specific purpose according to the design and operational requirements of the aircraft type. For example, single aircraft magnetos are designed to output high voltage and facilitate aircraft in flying at higher altitudes.

Slick Magneto

A central image of a slick aircraft magneto.

These aircraft magnetos are smaller and lighter than other types and it is also it is easy to install and remove due to their lightweight. Slick magnetos are comparatively less noisy thus eliminate the need for magneto filters. These are engineered with a balanced wear design which allows parts to wear and tear evenly. This is a very useful feature in predictive maintenance and contributes to reducing the overall maintenance cost. These are manufactured by Champion Aerospace.

Dual Magnetos

A central image of a dual aircraft magneto arrangement.

This type is a dual Magento arrangement in which left and right aircraft magnetos are housed in a single casing. Both side Magnetos are operated by a single magnet rotor and engine-driven shaft. This arrangement shows improvement in weight reduction and space occupation in comparison with single magnetos. These magnets are also cost-friendly in maintenance as they require less time and this design allows a reduction in the number of moving parts exposed to wear and tear. Dual magnetos were produced by Teledyne Continental Motors.

Single Magnetos

A central image of a single aircraft magneto system.

Single aircraft magneto is known for being lightweight, decent size, reliable, and comparatively high output. These can be impulse coupled or driven directly with engine drive. In a series combination of magnetos, a capacitor is connected to reduce radio noise developing from magnetos. Single magneto can reach high voltages which allow uninterrupted functionality at higher altitudes.


What happens if a magneto fails?

If an aircraft magneto fails during flight, the engine will keep running because of the other magnetos. However, engine power will be slightly reduced and the engine gauge will identify rpm drop.

Why do planes have two magnetos?

Airplanes have two magnetos so that if one magneto fails the other keep the combustion process running in the cylinder by providing ignition to spark plugs. This is done to reduce the safety risk during flight.

What are magnetos used for?

Magneto is an electrical generator that runs on engine power. They are used to supply electrical current to spark plugs to ignite the mixture of fuel in the piston cylinder.

What is the difference between a magneto and an alternator?

A magneto is an electrical generator that works on permanent magnets to produce AC while alternators are the same but they use field coils instead of permanent magnets.

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Aeroclass Team
A team of professionals with a deep passion for the aviation industry bringing you the newest and the most striking industry-related news and content.

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