Radial Aircraft Engine

An aircraft needs some form of power to keep it flying, to postpone the inevitable return to mother earth. Since the first flights by the Wright Brothers numerous types and models of engines have been developed. Some successful others less. Not all engine types are suitable for the LSA or experimental type aircraft. Big four row seven cylinder engines like the Pratt & Whitney Wasp Major are not commonly seen on homebuilt aircraft.
Although smaller versions like the M-14 nine cylinder radial by the Vedeneyev Design Bureaux are available to aircraft builders.

On this page we discuss the two broad type of engines: piston and turbine engines.

Piston engines

Aircraft piston engines can be divided in two fuel types, diesel and avgas. Both can be found in the same basic form or shape: radial, horizontally opposed (boxer), inline (sometimes inverted) and V setting (inverted too: Deltahawk engines).

In WW-II and shortly thereafter, piston powered engines peaked power, performance and complexity wise. Power went up to over 4000 bhp for large multi-row radial engines. Only to be defeated by the jet engine, developed by (among others) Germany's Dr. Hans von Ohain and seperately in the UK by Sir Frank Whittle.

These days, piston engines in aircraft can be found in configurations of two cylinders inline up to eight cylinder opposed and nine cylinder radials also in diesel and with fuel injection (diesel or avgas) or carburetted (avgas) fuel systems. Engine cooling is usually by air or a mix of water and glycol which means that hoses and a radiator are applied to dump the excess heat in the atmosphere.

Engine manufacturers
There are a number of manufacturers for the experimental and general aviation market: Rotax Bombardier, Jabiru, Hirth, Lycoming, Teledyne Continental, Superior / Mattituck and radial types from Vedeneyev and Rotec Engineering. Each of these companies have their own line of engines ranging from 50 bhp to 400 bhp.

Some are installing car engines (or converted types) in their aircraft, engines like VW and Chevy are used for these, usually one time installations. One successful converted car engine and sold commercially is the Subaru H6 from Eggenfellner Aircraft, available as four and six cylinders with an turbo as option. These beautiful created engines are able to run on autofuel. As are the Rotax and Jabiru's.

Piston powered engines are normally used in the lower altitudes, unless fitted with a turbocharger. Turboprops are much less efficient at these altitudes due to thicker air, they usually can be found from 10000 ft and up. Turbofans are used from roughly 25000 ft and higher, same reason as for the turboprop.

Turbine engines

These come in a number of models: turbojet, -prop, -shaft and turbofan. We will concentrate on the turboprop and turbofan engines as you will see these types more than the other two in our part of the aviation community.

Turbofan engines
These engines consist of an multistage compressor fan, combustion chambers and exhaust turbine which is connected throug a shaft to the compressor. Engine core design can be one or multiple shafts. The compressor fan directs air around and through the engine (bypass) and this bypass air is used to cool the engine and generate a large amount of thrust. This cool air surrounds the very hot exhaust and this results on lower noise emitted by the engine. Turbojet engines do not have this bypass air.

Turboprop engines
The turboprop engine has the same basic parts as the turbofan less the fan in front. There is a gearbox connected which drives a propeller and other things like a propeller rpm control, generator/starter, oilpump etc.

Innodyn
Been under development since 1997, the Innodyn turboprop engine is a direct spooled and has a centrifugal compressor and a radial inflow turbine. The fuel system is FADEC controlled and accepts diesel, JET, biodiesel and kerosene. Full installed weight is 188 Lbs and maintenance is really low: change gear oil every 500 hours, the spark plugs bianually and inspect the turbine for damage. Propeller is an electric controlled type.
The engines have a power range between 165 bhp and 255 bhp.

Pratt & Whitney

Pratt & Whitney PT6 series engine A widely known turboprop engine from Pratt & Whitney Canada is the PT6 series engines. It is a reverse flow, free turbine and a very reliable engine and installed on a multitude of aircraft.

Walter M601
This commonly known turboprop engine (from the Czech Republic) is used in numerous aircraft commercial and experimental, for example, the Turbine Legend uses the Walter M601-D. It has 675 bhp. Lately the Honeywell Garrett TPE331-10 engine is installed for extra climb performance and speed at altitude, this engine has about 1070 bhp.

The Walter M601 is a dual-shaft reverse-flow free turbine turboprop engine made by Walter Engines a.s.. The gas generator section consists of two axial and one centrifugal compressor stages, an annular combustion chamber, and a single stage axial compressor turbine. The power section consists of a single stage axial power turbine, exhaust system, and a two stage planetary reduction gearbox (15:1) with torque meter.
You will see this engine in a number of aircraft like the Lancair IV-P, Comp Air turbo models, Murphy T-Moose and many more.

Honeywell Garret
In contrary to the Walter and the PT6, the Garret is not a free turbine engine. The core shaft is direct connected to the propeller through a gearbox. When shutdown you can see that easily as the propeller blades are in flat (fine pitch) position, the free turbine engine has the blades in full coarse pitch when shutdown.

Sources claim that an aircraft with the Garret engine runs with less fuel than one with a Walter or Pratt & Whitney PT-6 turboprop and this is with the same speed/power setting. Noise level seems to be higher on the ground but lower when flying.