The Lycoming IO-720 engine is a large displacement, horizontally opposed, eight-cylinder aircraft engine featuring four cylinders per side, manufactured by Lycoming Engines.
There is no carburated version of the engine, which would have been designated O-720 and therefore the base model is the IO-720. The IO-720 and the Jabiru 5100 are the only flat-eight configuration aircraft engines currently in production.
Design and development
The engine has a fuel injection system which schedules fuel flow proportionally to the airflow, with fuel vaporization occurring at the intake ports. The engine has a displacement of 722 cubic inches (11.8 litres) and produces 400 hp (298 kW). The cylinders have air-cooled heads cast from aluminum alloy with a fully machined combustion chamber.
The first IO-720 was type certified on 25 October 1961 to the CAR 13 standard as amended to 15 June 1956 including 13-1, 13-2, 13-3, 13-4.
In 2009 a new IO-720-A1B cost US$113,621, with a rebuilt engine retailing for US$75,435 and a factory overhaul priced at US$66,289.
IO-720-A1AEight-cylinder, horizontally opposed, air-cooled direct drive, fuel injection, internal oil jet piston cooling, 722 cubic inches (11.8 litres), 400 hp (298 kW), certified 25 October 1961
IO-720-A1Bfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -A1A except equipped with Bendix S8LN-1208 and S8LN-1209 magnetos, certified 22 February 1971
IO-720-A1BDfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -A1B except has a dual magneto, certified 30 December 1976
IO-720-B1Afuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -A1A except for top exhaust cylinders and offset exhaust valve shroud tubes, certified 4 November 1965
IO-720-B1Bfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -B1A except equipped with Bendix S8LN-1208 and S8LN-1209 magnetos and Bendix RSA-10ED1 fuel injection, certified 22 February 1971
IO-720-B1BDfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -B1B except has a dual magneto, certified 30 December 1976
IO-720-C1Bfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -A1B except that it has up-exhaust cylinder heads, certified 22 December 1971
IO-720-C1BDfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -C1B except has a dual magneto, certified 28 January 1977
IO-720-D1Bfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -A1B except has a rear type air inlet housing instead of a front inlet, certified 29 October 1973
IO-720-D1BDfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -D1B except has a dual magneto, certified 28 January 1977
IO-720-D1Cfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -D1B except equipped with an angled fuel injector adapter, certified 15 April 1982
IO-720-D1CDfuel-injected, 722 cubic inches (11.8 litres), 400 hp (298 kW), same as -D1C except has a dual magneto, certified 10 June 1977
IO-720-A1ANorthwest Ranger - factory installationPiper Comanche 400 - factory installationIO-720-A1BBeechcraft 80 - Excalibur and Queen Air conversionsHelio Courier - Helio Courier H-800 factory installationPacific Aerospace FU-24-954Piper PA-36 Pawnee Brave - Johnson Aircraft conversionIO-720-A1BDBarr 6IO-720-B1ANorthwest Ranger C-6 - factory installationIO-720-B1BAero Commander - MR. R.P.M. conversionIO-720-B1BDAero Commander - MR. R.P.M. conversionIO-720-D1BEmbraer EMB 202 Ipanema - factory installationIO-720-D1CPiper PA-36 Pawnee Brave - Johnson Aircraft conversionIO-720-D1CDPiper PA-36 Pawnee Brave - Johnson Aircraft conversionData from Lycoming Specialty Datasheet and TYPE CERTIFICATE DATA SHEET NO. 1E15, Revision 6
Type: 8-cylinder fuel-injected horizontally opposed aircraft engineBore: 5.125 in (130.18 mm)Stroke: 4.375 (111.12 mm)Displacement: 722 in³ (11.8 litres)Length: 46.41 In (117.88 cm)Width: 34.25 in (87.00 cm)Height: 22.53 in (57.23 cm)Dry weight: 597 lb (271 kg) dryFuel system: Bendix RSA-10AD1 fuel-injectionFuel type: 100LL avgasCooling system: air-cooledPower output: 400 hp (297 kW) at 2650 rpmSpecific power: 0.55 hp/in³ (25.2 kW/L)Compression ratio: 8.70:1Power-to-weight ratio: 0.67 hp/lb (1.10 kW/kg)