Definition
A four-cylinder, horizontally opposed, fuel-injected aircraft piston engine manufactured by Lycoming, with a displacement of approximately 360 cubic inches. It is widely used in single-engine general aviation aircraft and typically produces between 180 and 210 horsepower depending on the variant.
Plain English
A specific model of small aircraft engine made by the Lycoming company. It has four cylinders arranged flat and opposite each other, uses fuel injection instead of a carburetor, and is about 360 cubic inches in size. You'll find it in many common training and personal aircraft.
Context Anchor
You may see this term in an aircraft manual, maintenance record, engine logbook, or aircraft specification sheet.
Derivation
The model code tells you the engine: 'I' stands for Injected (fuel injection), 'O' stands for Opposed (cylinders arranged flat opposite each other), and '360' is the approximate displacement in cubic inches. So 'IO-360' literally describes the engine layout.
Why Pilots Care
Pilots need to know the exact engine model to follow correct operating procedures, fuel requirements, and performance charts.
Intuition Check
Do not read “IO” here as the computer term “input/output.” In this engine name, it identifies the engine as fuel-injected and horizontally opposed.
Example Sentence 1
The Piper Arrow in our flight school is powered by a Lycoming IO-360 producing 200 horsepower.
Example Sentence 2
The pilot reviews the Lycoming IO-360 operating limitations before the flight.