|Type||Piston Aircraft engine|
|National origin||United States|
|Major applications||Piper PA-31 Navajo
Socata TB-30 Epsilon
The Lycoming O-540 is a family of six-cylinder, horizontally opposed fixed-wing aircraft and helicopter engines of 541.5 cubic inch (8,874 cc) displacement, made by Lycoming Engines. The engine is a six-cylinder version of the four-cylinder Lycoming O-360.
Design and development 
Generally these engines produce 230 to 350 horsepower. They are installed on a large number of different aircraft types. Their main competitive engine is the Continental IO-520 and IO-550 series.
The AEIO version was developed for high-performance competition aerobatics aircraft. Starting at 260 hp (190 kW), the power was then improved to 300 hp (220 kW). The AEIO-540 family has achieved tremendous results in competition aircraft such as the Extra 300, CAP 232 and Zivko Edge 540.
All engines have an additional prefix preceding the 540 to indicate the specific configuration of the engine. There are also numerous engine suffixes, denoting different accessories such as different manufacturers' carburetors, or different magnetos.
- Standard, direct-drive, normally aspirated Opposed engine, equipped with a carburetor.
- Normally aspirated engine with fuel Injection.
- Normally aspirated engine with fuel injection and inverted lubrication for Aerobatic use.
- Turbocharged and fuel-injected.
- Turbocharged with independent Electronic sensors and fuel injection controls for each cylinder which manage detonation and exhaust gas temperature making the engine compatible with a range of fuel compositions producing up to 350 horsepower.
- Left-hand (opposite-direction) rotation, turbocharged, fuel-injected; used as the right-hand engine on Piper PA-31-325 Navajo C/Rs and Piper PA-31-350 Chieftains to prevent critical engine control issues. Also used for the left hand side of the Aerostar 700P.
- Gearbox at the front end of the crankshaft to drive the propeller fewer revolutions per minute than the engine, normally aspirated with fuel injection. Dry sump engine built specifically for the Aero Commander 560F.
- Supercharger driven by the engine, gearbox to drive propeller, and fuel injection (up to 380hp).
- Vertically mounted engine for use in a helicopter, normally aspirated and equipped with a carburetor.
- Normally aspirated engine with fuel injection, mounted vertically for use in a helicopter.
- Turbocharged engine equipped with a carburetor, mounted vertically for use in a helicopter.
- Turbocharged engine with fuel injection, mounted vertically for use in a helicopter.
- Helicopter engine mounted horizontally as in fixed-wing aircraft, normally aspirated with fuel injection; not used in any fixed-wing aircraft.
- AAC Angel
- Aero Commander 500 series
- Akaflieg München Mü30 Schlacro
- Barrows Bearhawk
- Bellanca Viking 300 (17-31 and 17-31TC)
- Bellanca 17-31ATC Turbo Viking
- Britten-Norman Islander
- Britten-Norman Trislander
- Brantly 305
- CallAir A-9
- Cessna 182
- Dornier Do 28
- Dream Tundra
- Embraer EMB 202 Ipanema
- Enaer T-35 Pillan
- Evangel 4500
- Gippsland GA8
- Gippsland GA200
- Lancair ES
- Lasta 95
- Helio/Maule M5-235
- Mooney M20
- Moynet 360-6 Jupiter
- MSW Votec 252T
- Murphy Moose
- Neiva Universal
- PAC CT-4E/F
- PAC Super Mushshak
- Piaggio P.166
- Piper Aerostar
- Piper Aztec
- Piper Saratoga
- Piper PA-24 Comanche
- Piper PA-25 Pawnee
- Piper PA-31 Navajo
- Pitts Special variants
- PZL-104MA Wilga 2000
- Raven 2XS
- Ravin 500
- Robinson R44
- Rockwell Commander 114
- Sharp Nemesis NXT
- Socata TB-20
- Socata TB-30 Epsilon
- Team Tango Foxtrot
- Utva 65
- Van's Aircraft RV-10
- Zlin Z-143
- Zlín Z 50
Specifications (IO-540-K1A5) 
Data from FAA Lycoming IO-540 Series Type Certificate. Retrieved: 1 September 2008.
- Type: Six-cylinder air-cooled horizontally opposed engine
- Bore: 5.125 in (130.2 mm)
- Stroke: 4.375 in (111.1 mm)
- Displacement: 541.5 in³ (8.9 L)
- Dry weight: 438 lb (199 kg)
- Valvetrain: Two overhead valves per cylinder
- Fuel system: Fuel injection
- Fuel type: 100 octane rating gasoline
- Cooling system: Air-cooled
- Power output: 300 hp (223 kW) at 2,700 rpm at sea level
- Specific power: 0.55 hp/in³ (25.14 kW/L)
- Compression ratio: 8.7:1
- Power-to-weight ratio: 0.68 hp/lb (1.12 kW/kg)
See also 
- Related development
- Comparable engines
- Related lists
- Lycoming (2005). "540 Series" (PDF). Retrieved 2009-01-10.
- Page listing all variants of the Lycoming O-540 series. Retrieved: 1 September 2008.
- Lycoming TEO-540-EXP press release
- FAA Piper PA-31-300/325/350 Type Certificate. Retrieved: 1 September 2008.
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