Diesel In The Sky: Aviation And The Diesel Engine

DeltaHawk mounted inverted in the “A” position

The diesel engine has long been a mainstay in industrial power. Heavy equipment like tractors, excavators, earth movers and other utilitarian machines rely on compression ignition power for many reasons. But, what about the opposite end of the spectrum? The very light, delicate, and graceful forms common to the general aviation community are embracing this versatile powerplant. The application of diesel in aircraft is nothing new, in fact it has been in use for nearly 80 years. When considering the flying machine has only been with us for about 112 years, diesel has been a neglected fuel of aviation from the beginning.

However, diesel fuel is making a comeback in modern aircraft. The advantages are becoming more and more obvious as fuels requiring increased refining grow in price, and scarcity. At Diesel Army we are interested in diesel culture as a growing community, and aviation is one of the fastest growing markets. We hope to give you a retrospective on the history of diesel in airplanes, and introduce some of the new powerplants breaking into the market. The next time you look overhead you just may hear the familiar sound of a diesel engine.

Advantages Of Diesel

The primary reasons for diesel’s explosion into the aviation market are the availability and affordability. Light aircraft operating in remote regions of the world are often challenged by a lack of availability when it comes to fuel. Traditionally, piston-engine powered aircraft run on Avgas, a gasoline-based fuel engineered to perform in the specific application of aviation.

Avgas is generally a tetraethyl lead enhanced fuel — like race gasoline. Most general aviation engines are air-cooled to reduce weight, and therefore run higher cylinder head temperatures. The availability of Avgas is variable in countries with less infrastructure. Aide, or humanitarian flights in and out of the continents of South America, Africa, and Australia are often dictated by fuel planning. This limits the reach of said operations.

Diesel fuel is widely available, and if aircraft can be retrofitted to operate on it, the radius of range will increase such that almost anywhere is reachable. Diesel engines are known for their robust design and reliable operation. The number-one paramount of aviation engines is reliability. If your car stops running you pull over and get out, but this is not usually an option in aircraft. Two-stroke diesel engines eliminate the need for a valve-train. This simplification alone cuts the number of moving parts down to around half.


Modern Aircraft

Modern diesel aircraft are sometimes the products of retrofits, and others are purpose-designed to employ these non-conformist engines. When we think of diesel, grace and flowing form are not the usual knee-jerk associations. Companies like Diamond Aircraft Industries has been working to reverse that stereotype. The DA42 Twin Star is a diesel-powered aircraft that looks just as deserving as any other high-end private aircraft when it comes to aesthetics.

DA42PanelThis twin-engined, four-place aircraft features a modern composite construction and a fully electronic “glass” cockpit from Garmin. With touches like these, one expects the powerplant to be something equally exotic.

Powering the DA42 are a choice of engines. Replacing the conventional Lycoming IO-360 gas engines are either a pair of Thielert Centurion 2.0-liter diesels, or in 2007 and up models, the Austro AE-300 engines. The advantages of these engines over their gas contemporaries are hard to argue against. Incredible fuel efficiency is possible at 3.2 gallons per hour, and the comfort of a quiet ride will make the interior that much more luxurious for the few who can afford the $600,000 price tag.



DeltaHawk Diesel engines are some of the most exotic and forward thinking of the powerplants we will examine. Arranged in a “V” configuration these two-strokes are available as four-cylinder engines to replace the flat 360, but according to Diane Doers, CEO of DelatHawk, “We are going to be doing a six-cylinder, and eight-cylinder to take us to the 250 horsepower, [and] 420 horsepower.”

These liquid-cooled diesels feature redundant forced-induction systems. A turbocharger will feed a supercharger for extra security if a system failure were to happen. The oiling system of the DeltaHawk engines is a particularly interesting feature. Two-stroke diesels do not employ oil-fuel mixtures to lubricate the internal components the way gasoline engine do, this engine features a drysump system that allows mounting of the engine as a “V” or “A.” That’s right, you can mount this engine upside down if your packaging needs are restrictive.

DeltaHawk has thought beyond the needs of the general aviation consumer. The engines it produces have been developed for use in UAV (unmanned arial vehicles), ground power units (GPU), and other applications.

​For the full article, visit Diesel Army.