Diesel Engines for Aircraft

Recip Technology Progress made by one manufacturer on certifying a diesel engine By Joe Escobar Help wanted — diesel mechanics needed for aircraft repair facility. It is possible you may be seeing an ad like this within a few...


Recip Technology

Diesel Engines For Aircraft

Progress made by one manufacturer on certifying a diesel engine

By Joe Escobar

Help wanted — diesel mechanics needed for aircraft repair facility. It is possible you may be seeing an ad like this within a few years. A certificated diesel engine on an aircraft could be closer than you think. Although several companies have attempted to bring to market a diesel-powered piston engine for the aviation market, few have succeeded. One company, Racine, Wisconsin-based DeltaHawk Engines LLC is making progress toward certifying its diesel engine. Already available for experimental applications, it is working on certifying a two-cycle piston engine that will run on jet fuel. I visited them to learn more about the technology behind the engine. The following article gives some background into this unique powerplant.

Engine specifications
The DeltaHawk engine is a four-cylinder two-stroke diesel engine. It is set up in a “V” configuration vs. an opposed setup typical of gasoline-powered engines. The engine is designed to compete with the Lycoming IO-360 engine, so airframes with that engine could be candidates for future conversions. The engine will have two versions — a 160 horsepower, which would be non-intercooled, and a 200 plus horsepower that would be intercooled. The engine is currently in the testing and development stage with certification expected in a few years.

Piston crown, fire deck, injector, spring, and cylinder head cylinder head components installed on engine block
Clockwise from bottom left: Piston crown, fire deck, injector, spring, and cylinder head.
Cylinder head components installed on engine block.

Designing a diesel engine
DeltaHawk began from the ground up when designing its engine. The company felt that path would be better than trying to take an automotive diesel engine and modify it for aircraft applications. Diesel engines used in automobiles are not subjected to the same types of operating stresses those in aircraft would have to endure. Douglas Doers, vice president for DeltaHawk, explains. “A Cummins diesel engine doesn’t have the sustained high-power output that aircraft do. An aircraft engine may run at 80 percent or higher for hours — for however long you have fuel. A 275 horsepower truck engine may need to put out 275 horsepower when you step on it, but when you back down, you are operating at around 60 horsepower on the highway. That is a big difference. Consequently, there is a big difference in the way that you have to design your engine. That is the main reason why automotive versions don’t generally work in aviation. It takes so much development to make it work that when you’re done the cost of that $6,000 automotive engine is now $20,000. So why not start with a new design and have it do exactly what you want? And that’s exactly what we chose to do.”

As we look at some of the different components of the engine, there is one thing to keep in mind — pressure. Diesel engines operate at much higher pressures than gasoline engines. Peak pressure in the cylinders is around 2,000 psi. Because of this, numerous elements of the engine are designed to handle this intense pressure. Let’s take a closer look at some of engine components.

Engine Block Assembly
Engine Block Assembly
Engine block assembly.
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