The Lycoming IO-540 series is a family of air-cooled, horizontally opposed, six-cylinder aircraft engines produced by Lycoming Engines. These engines are widely used in general aviation aircraft, particularly in single-engine and twin-engine planes. The IO-540 series is known for its reliability, power output, and versatility, making it a popular choice for a variety of aircraft applications.

• Horizontally opposed (flat-six) configuration
• Six cylinders, air-cooled

541.5 cubic inches (8.87 liters)

• Ranges from 235 to 300 horsepower depending on model
• Turbocharged versions available for higher power outputs

Fuel-injected (denoted by "IO" for "fuel-injected, opposed") providing better fuel efficiency and performance compared to carbureted engines

Approximately 320 to 350 pounds (145 to 159 kg), depending on model and accessories

• Known for durability and long service life when properly maintained
• Regular maintenance and adherence to manufacturer guidelines critical for optimal performance

• Cessna 182 Skylane
• Cessna T206H
• Piper PA-32 Cherokee Six
• Van's RV-10
• Robinson R44
• Gipsaero GA8
• Kitty Hawk LE500
• Aerostar 600
• Lancair IV

• Regular oil changes, inspections, and adherence to service bulletins essential
• Proper break-in procedures critical for new or overhauled engines
• Monitor engine parameters (oil pressure, temperature, etc.) during operation

• Smooth operation and consistent power delivery
• Fuel-injected models offer better altitude performance and fuel efficiency
• Turbocharged versions (e.g., TIO-540) available for high-altitude operations

The Lycoming IO-540 series remains a cornerstone of general aviation, offering a balance of power, reliability, and efficiency for a wide range of aircraft.