Aircraft Engine Induction Systems

From the beginning of our primary training, we learn how to check our airplanes fuel quantity and quality, and how to position various controls to ensure the engine starts and stays running. We know we can turn the fuel off and on, and perhaps select from which tank the engine will draw, but what happens after that often is a mystery. Whats going on between the fuel selector valve and the engine?

Editorial Staff

Wednesday, February 17, 2016 at 12:00 AM ET

Verified

Key Takeaways:

Aircraft piston engines use either carburetors or fuel injection systems to meter and mix fuel with air, both reliable but with distinct characteristics and operational quirks.
Carburetors are simpler, lighter, and less expensive, but are less efficient, generally produce lower power for the same displacement, and are notably prone to internal icing.
Fuel injection systems are more complex and costly, but offer greater power output, better fuel distribution, are largely immune to carburetor icing (though induction icing can occur), but can present challenges with hot starts.

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From the beginning of our primary training, we learn how to check our airplane’s fuel quantity and quality, and how to position various controls to ensure the engine starts and stays running. We know we can turn the fuel off and on, and perhaps select from which tank the engine will draw, but what happens after that often is a mystery. What’s going on between the fuel selector valve and the engine?

The quick answer is one of two things: The fuel either flows into a carburetor where it mixes with air and then is routed to each cylinder, or it moves through a more-complicated fuel injection system before getting to the cylinders. The air arrives separately. Both systems meter fuel and air to the engine, are reliable and work well. But they each have their quirks, and knowing how they work and can fail is critical to a full understanding of the airplane’s systems.