Aircraft ignition systems rely on similar instruments to what you would find in an automobile. Both are internal combustion engines that use spark plugs and some type of fuel monitoring network related to throttle position. However, rather than relying on a battery, planes employ a dual magneto model or self-contained electrical impulses to ignite the spark plugs and start their engines. In this article, you can read more about how aircraft ignition systems work, and gain a better understanding of whatever plane you are working with.
The Four Strokes of an Aircraft Engine
As with many other vehicles, aircraft engines are characterized by four stroke cycles: intake, compression, power, and exhaust. First, the fuel-air mixture is drawn into the cylinder as the piston moves downwards on its intake stroke. Then, the piston moves upwards with the valves closed to compress the mixture during the device’s compression stroke. Once compressed, the fuel is ignited, causing it to push the piston downward on the power stroke. Lastly, when the piston rises upwards again with the exhaust valve open, the exhaust stroke ends the four stroke cycle. Because aircraft engines use four or more cylinders, each igniting at different times, there is always one piston on a power stroke, and the process is continuous. However, there is also a crucial step that must happen before the four stroke cycle. In order to start the engine, a magneto system is used to create the initial sparks.
Dual Magneto Ignition
Most lawnmowers, chainsaws, and other small gas-powered engines do not require batteries. Instead, they use a magneto ignition system to generate their own power to start the combustion process. A magneto ignition system uses a rotating magnet (magneto) to generate electricity which can then be routed to power the spark plugs. When the magnet rotates past the primary and secondary coils, it generates a magnetic field. This field induces a small amount of current in the coils. As the magnetic field reaches its maximum, a switch in the system opens and triggers the circuit breaker. The circuit breaker stops the flow of current through the primary coil and causes a voltage spike (of about 200 volts). The second coil, which has 100 times more turns than the primary coil, amplifies the voltage to about 20,000 volts, and transfers it to the spark plugs. Then, just as in any combustion engine, the spark plugs create a spark at the required time to ignite the combustible mixture and start the movement of the engine.
In dual magneto ignition systems, two sets of rotating magnets and coils are used instead of one. Each magneto arrangement is then connected to its own collection of spark plugs so the two devices can work separately. Aircraft utilize dual magnetos for safety so that if one magneto fails in flight, the other magneto can keep the engine running with only a slight decrease in efficiency. In an effort to further safeguard the engine, the dual magneto system is completely separate to the aircraft electrical network so that the engine can start, even in the case of electrical failure.
Conclusion
Similar to many other vehicles, aircraft take advantage of a four stroke cycle in their engines that are powered by a mixture of pressure and the combustion of a specific air-fuel mixture. However, this process cannot simply start on its own, and instead, requires the use of spark plugs which are ignited by the electrical pulses given off from a dual magneto system. The development of these processes has been crucial to the efficiency and power of modern aircraft. As such, having a basic understanding of these mechanisms is not only essential for engineers, but also for pilots and other operators alike. Besides providing informational articles such as this, Sourcing Streamlined can offer you a range of premium-quality aviation, NSN, and electronic parts that you can confidently rely on. As an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited enterprise, we uphold strict quality-testing protocols for our parts, ensuring that our products fit the high standard expected within the aviation industry. Browse our catalog of available items on our website or send an Instant Request for Quote (RFQ) form today to get a response from our team of experts within 15 minutes!
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