The Lycoming O-320 is a large family of naturally aspirated, air-cooled, four-cylinder, direct-drive engines produced by

Lycoming Engines Lycoming Engines is a major American manufacturer of aircraft engines. With a factory in Williamsport, Pennsylvania, Lycoming produces a line of horizontally opposed, air-cooled, four, six and eight-cylinder engines including the only FAA-certi ...

. They are commonly used on light aircraft such as the Cessna 172 and Piper Cherokee. Different variants are rated for 150 or 160 horsepower (112 or 119 kilowatts). As implied by the engine's name, its cylinders are arranged in

horizontally opposed A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, wh ...

configuration and a displacement of 320 cubic inches (5.24 L).

Design and development

The O-320 family of engines includes the carbureted O-320, the fuel-injected IO-320, the inverted mount, fuel-injected AIO-320 and the

aerobatic Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...

, fuel-injected AEIO-320 series. The LIO-320 is a "left-handed" version with the crankshaft rotating in the opposite direction for use on twin-engined aircraft to eliminate the critical engine. The first O-320 (with no suffix) was FAA

certified Certification is the provision by an independent body of written assurance (a certificate) that the product, service or system in question meets specific requirements. It is the formal attestation or confirmation of certain characteristics of a ...

on 28 July 1953 to CAR 13 effective 5 March 1952; this same engine was later re-designated, without change, as the O-320-A1A. The first IO-320 was certified on 10 April 1961, with the AIO-320 following on 23 June 1969 and the first aerobatic AEIO-320 on 12 April 1974. The LIO-320s were both certified on 28 August 1969. The O-320 family of engines externally resembles the Lycoming O-235 and O-290 family from which they were derived. The O-320 shares the same stroke as the smaller engines, but produces more power with the bore increased to . The design uses hydraulic tappets and incorporates the provisions for a hydraulically controlled propeller installation as well. The controllable-pitch propeller models use a different crankshaft from those intended for fixed-pitch propellers.Christy, Joe: ''Engines for Homebuilt Aircraft & Ultralights'', pages 77-80 TAB Books, 1983. The O-320 uses a conventional wet sump system for lubrication. The main bearings, connecting rods, camshaft bearings, tappets and pushrods are all pressure lubricated, while the piston pins, cylinder walls and gears are all lubricated by spray. The oil system is pressurized by an accessory-drive mounted oil pump. A remotely mounted oil cooler is used, connected to the engine by flexible hoses. The versions of the carbureted O-320, are approved for the use of 87 AKI automotive gasoline. Models with 9.0:1 compression ratio are not approved, such as the H2AD model. All other 0-320s are approved for 91 AKI. Airframe approval is also necessary to use automotive gasoline in any

aircraft. The factory retail price of the O-320 varies by model. In 2010 the retail price of an O-320-B1A purchased outright was USD$47,076

Variants

O-320 series

;O-320 (No suffix) later redesignated O-320-A1A : at 2700 rpm, Minimum fuel grade 80/87

avgas Avgas (aviation gasoline, also known as aviation spirit in the UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in motor vehicles, w ...

, compression ratio 7.00:1. Provisions for a controllable-pitch propeller and 25-degree spark advance. ;O-320-A1B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A1A but with straight riser in oil sump and -32 carburetor. ;O-320-A2A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A1A but with fixed-pitch propeller. ;O-320-A2B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A2A but with straight riser in oil sump and -32 carburetor. ;O-320-A2C : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A2B but with retard breaker magnetos. ;O-320-A2D : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E3D but with conical mounts. ;O-320-A3A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A1A but with 7/16" prop bolts. ;O-320-A3B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A3A but with straight riser in oil sump and -32 carburetor. ;O-320-A3C : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A3B but with retard breaker magnetos. ;O-320-B1A : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as A1A but with high compression pistons. ;O-320-B1B : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B1A but with straight riser in oil sump and -32 carburetor. ;O-320-B2A : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B1A but with fixed-pitch propeller provisions. ;O-320-B2B : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B2A but with straight riser in oil sump and -32 carburetor. Robinson R22 engine detail

;O-320-B2C : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B2B but with retard breaker magnetos. ;O-320-B2D : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as D1D but with conical engine mounts and no propeller governor. ;O-320-B2E : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as B2B except the carburetor is in the same location as the O-320-D models. ;O-320-B3A : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B1A but with 7/16 inch propeller bolts. ;O-320-B3B : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B1A but with 7/16 inch propeller bolts, a straight riser in oil sump, and -32 carburetor. ;O-320-B3C : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B3B but with retard breaker magnetos. ;O-320-C1A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B1A. ;O-320-C1B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B1B. ;O-320-C2A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B2A. ;O-320-C2B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B2B. ;O-320-C2C : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B2C. ;O-320-C3A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B3A. ;O-320-C3B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B3B. ;O-320-C3C : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Low compression version converted through field conversion of B3C. ;O-320-D1A : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as B3B but with Type 1 dynafocal mounts. ;O-320-D1B : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as D1A but with retard breaker magnetos. ;O-320-D1C : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as D2C but with provisions for a controllable propeller, ;O-320-D1D : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as the D1A but with Slick instead of Bendix magnetos and a horizontal carburetor and induction housing. This model was used in the Gulfstream American GA-7 Cougar twin. ;O-320-D1F : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as E1F except with high compression pistons. Lycoming O-320-D2A engine A

;O-320-D2A : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as D1A but with fixed-pitch propeller provisions and 3/8 inch attaching bolts. Used in the Symphony SA-160. ;O-320-D2B : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as D2A but retard breaker magnetos. ;O-320-D2C : at 2700 rpm, Minimum fuel grade 100/130 or 91/96 avgas, compression ratio 8.50:1. Same as D2A except -1200 series magnetos. ;O-320-D2F : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as E2F except with high compression pistons. ;O-320-D2G : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as the D2A except with Slick instead of Bendix magnetos and 7/16 inch instead of 3/8 inch propeller flange bolts. ;O-320-D2H : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as the D2G except with a O-320-B sump and intake pipes and with provisions for AC type fuel pump. ;O-320-D2J : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1.Similar to the D2G but with two Slick impulse coupling magnetos and the propeller governor pad, fuel pump and governor pads on the accessory housing all not machined. Used in the Cessna 172P. ;O-320-D3G : at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as the D2G but with 3/8 inch propeller attaching bolts. ;O-320-E1A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A3B but with Type 1 dynafocal mounts. ;O-320-E1B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1A but with retard breaker magnetos. ;O-320-E1C : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1B. ;O-320-E1F : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1C but with propeller governor drive on the left front of the crankcase. ;O-320-E1J : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as the E1F but with Slick magnetos. ;O-320-E2A : at 2700 rpm, or at 2450 rpm Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1A but with fixed-pitch propeller, 3/8 inch attaching bolts and an alternate power rating of . ;O-320-E2B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2A but with retard breaker magnetos. ;O-320-E2C : at 2700 rpm, or at 2450 rpm Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2A but -1200 series mags and an alternate power rating of . ;O-320-E2D : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Similar to E2A but with Slick magnetos and O-235 front. Used in the Cessna 172 I to M models. ;O-320-E2F : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1F but with fixed pitch prop provisions. ;O-320-E2G : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2D but with O-320-A sump and intake pipes. ;O-320-E2H : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2D but with S4LN-20 and -21 magnetos. ;O-320-E3D : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2D but with 3/8 inch propeller flange bolts. ;O-320-E3H : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E3D but with S4LN-20 and -21 magnetos. ;O-320-H1AD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Integral accessory section crankcase, front-mounted fuel pump external mounted oil pump and D4RN-2O21 impulse coupling dual magneto. ;O-320-H1BD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Same as H1AD but with a D4RN-2200 retard breaker dual magneto. ;O-320-H2AD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Same as H1AD but with provisions for a fixed-pitch propeller. This was the troublesome engine that was installed on the 1977 to 1980 Cessna 172N Skyhawk. Cessna Aircraft: ''Pilot Operating Handbook 1977 Skyhawk Cessna Model 172N'', page 1-3. Cessna Aircraft, 1976. It was notable from all other Lycoming models by incorporating hydraulic lifters that were barrel shaped instead of mushroom type, in an attempt to make the lifters possible to be serviced without having to disassemble the entire engine case, but the higher load on the cam lobes resulted in severe

spalling Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball ...

. Multiple service bulletins and airworthiness directives have been issued regarding this specific model, and multiple modifications exist to attempt to mitigate its design defects. ;O-320-H2BD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Same as the H2AD but with a D4RN-2200 retard breaker dual magneto. ;O-320-H3AD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Same as the H2AD but with 3/8 inch propeller flange bolts, in place of instead of 7/16 inch. ;O-320-H3BD : at 2700 rpm, Minimum fuel grade 100LL avgas, compression ratio 9.00:1. Same as H3AD but with a D4RN-2200 retard breaker dual magneto.

IO-320 series

;IO-320-A1A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Base model with a Bendix RSA -5AD1 fuel injection system. ;IO-320-A2A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A1A but with provisions for fixed-pitch propeller. ;IO-320-B1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1A but with the fuel injector offset toward the engine's fore and aft centerline. ;IO-320-B1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1A but with an AN fuel pump drive. ;IO-320-B1C : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the B1A but with an adapter for mounting the fuel injector straight to the rear. ;IO-320-B1D : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the B1C but with S-1200 series high altitude magnetos. ;IO-320-B1E : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the D1C except with a horizontal fuel injector. ;IO-320-B2A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the BIA but with provision for a fixed-pitch propeller. ;IO-320-C1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the B1B except it has features making it suitable for adding a turbo-supercharger via a Supplemental Type Certificate This engine has internal piston cooling oil nozzles. ;IO-320-C1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the C1A but with a horizontal rear-mounted fuel injector. ;IO-320-D1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the B1D but with Type 1 dynafocal mounts, S4LN-1227 and S4LN-1209 magnetos and the fuel injector mounted vertically under the oil sump. ;IO-320-D1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the D1A but with the propeller governor drive on the left front of crankcase instead of on the accessory housing. ;IO-320-D1C : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the D1B but with Slick Magnetos. ;IO-320-E1A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2A but with provision for a controllable-pitch propeller. ;IO-320-E1B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E1A but with Slick 4050 and 4051 magnetos. ;IO-320-E2A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as A2A but with Scintilla S4LN-20 and S4LN-21 magnetos, straight conical mounts, and the fuel injector mounted under the oil sump. ;IO-320-E2B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as E2A but with Slick 4050 and 4051 magnetos. ;IO-320-F1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the C1A except with a Type 1 (30°) dynafocal mount attachment instead of Type 2 (18°) mount attachment.

LIO-320 series

;LIO-320-B1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as B1A except with counter-clockwise engine rotation and reverse rotation of accessories. It uses a modified starter ring gear, crankshaft, cam shaft, accessory housing and oil pump body. This engine is usually paired with an IO-320-B1A on a twin-engined aircraft. ;LIO-320-C1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as C1A except with the same changes as the LIO-320-B1A. It has provisions for adding a turbo-supercharger. This engine is usually paired with an IO-320-C1A on a twin-engined aircraft.

AIO-320 series

;AIO-320-A1A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the IO-320-B1D but this model permits installation and operation of the engine in the inverted position. The differences include a front-mounted propeller governor, two dry oil sumps, dual external oil scavenge pumps, an oil tank, three options for the position of the fuel injector and a Type 1 dynafocal mount. ;AIO-320-A1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1A but with one impulse coupling magneto. ;AIO-320-A2A : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1A but with provision for a fixed-pitch propeller. ;AIO-320-A2B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1A but has one impulse coupling magneto and a fixed-pitch propeller. ;AIO-320-B1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the A1B but with a front-mounted fuel injector. ;AIO-320-C1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the B1B but with the fuel injector vertically mounted on bottom of the oil sump in the front position.

AEIO-320 series

;AEIO-320-D1B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the IO-320-D1B but with an inverted oil system kit to allow aerobatic flight. ;AEIO-320-D2B : at 2700 rpm, Minimum fuel grade 91/96 or 100LL avgas, compression ratio 8.50:1. Same as the AEIO-320-D1A but without provisions for a propeller governor. ;AEIO-320-E1A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as the IO-320-E1A but with an inverted oil system kit to allow aerobatic flight. ;AEIO-320-E1B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as the IO-320-E1B but with an inverted oil system kit to allow aerobatic flight. ;AEIO-320-E2A : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as the IO-320-E2A but with an inverted oil system kit to allow aerobatic flight. ;AEIO-320-E2B : at 2700 rpm, Minimum fuel grade 80/87 avgas, compression ratio 7.00:1. Same as the IO-320-E2B but with an inverted oil system kit to allow aerobatic flight.

Applications

Specifications (O-320-A1A)

References

Notes

Bibliography

* Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989.

External links

Lycoming – O-320 page
{{US military piston aeroengines Boxer engines O-320 1950s aircraft piston engines 1953 introductions