While turbine engines dominate the rest of this list, the O-360 is the engine that most private pilots actually fly behind. Simple, air-cooled, and maintainable by any A&P mechanic, it defined the light aircraft experience for generations. The A1A was the first O-360 model certified, receiving approval in July 1955.
O-360-A1A Design and Operation
The primary subject of this technical guide focuses on the Lycoming O-360-A1A engine, engineered specifically for Horizontally Opposed 4-Cylinder, Air-Cooled Piston applications. Below is an essential digest of this powertrain configuration.
• 180 hp general aviation staple
• 361 cu in horizontally opposed
• First O-360 certified (1955)
• Air-cooled simplicity
O-360-A1A Core Specifications
361 cubic inches (5.9 L) from four horizontally opposed cylinders; 180 hp at 2,700 rpm; dry weight 258 lb; air-cooled with 8.5:1 compression ratio.
The O-360’s horizontally opposed layout keeps the engine compact and allows a streamlined nose profile on light aircraft. Air cooling eliminates coolant plumbing and reduces weight. The A1A variant used a carburetor and dual magnetos, with a 5.125-inch bore and 4.375-inch stroke. It’s not sophisticated, but parts are available everywhere and any mechanic can work on it—qualities that matter more than specific output in general aviation.
| Configuration | 4-cylinder, horizontally opposed |
|---|---|
| Bore | 5.125 in (130 mm) |
| Stroke | 4.375 in (111 mm) |
| Displacement | 361 cu in (5,916 cc) |
| Power | 180 hp @ 2,700 rpm |
| Compression | 8.5:1 |
| Weight | 258 lb (117 kg) |
| Fuel | 91/96 avgas minimum |
Aircraft Using the O-360-A1A
This engine model is deployed across various operational frameworks. Here is a breakdown of the typical machine or vehicle applications using this unit:
Cessna 172 (various variants), Piper PA-28 Cherokee, countless homebuilt aircraft
Pros & Advantages
Simple and reliable; easy to maintain; widely available parts; lightweight for its power class.
Cons & Disadvantages
Carburetor icing risk; requires avgas; lower specific output than modern designs.
Frequently Asked Questions (FAQs)
Q1: When was the O-360-A1A certified?
A1: The O-360-A1A was certified on July 20, 1955, making it the first O-360 model to receive approval.
Q2: What is the O-360-A1A’s displacement?
A2: 361 cubic inches (5,916 cc) from four horizontally opposed cylinders.
Q3: Is the O-360-A1A carbureted or fuel injected?
A3: The A1A is carbureted. The IO-360 designation indicates fuel injection.
A minimum grade of 91/96 avgas is specified, though 100LL is commonly used.