Diesel Aircraft Engines: How They Work, Who Builds Them, and Why They Haven’t Taken Over

Yes, diesel aircraft engines exist, and you can buy a new airplane with one today. Continental, Austro Engine, DeltaHawk and SMA all build certified diesel piston engines that run on Jet A, the same kerosene fuel airliners burn.

Their appeal is simple. A diesel burns far less fuel than a gasoline engine of similar power, and it avoids 100LL avgas, the last leaded fuel in everyday US use.

They still haven’t taken over. Diesels are heavier, cost more up front, and Cessna has dropped its diesel plans more than once. Here is how they work, who builds them, and what is holding them back.

Engine	Power	Layout	Notable aircraft
Continental CD-135 / CD-155	135 / 155 hp	Turbocharged inline four	Piper Archer DX, Cessna 172 (STC), Diamond DA40 TDI
Continental CD-170	170 hp	Turbocharged inline four	Tecnam P2010 TDI
Continental CD-300	300 hp	Twin-turbo six-cylinder	Diamond DA50 RG
Austro AE300	168 hp	Turbocharged inline four	Diamond DA40 NG, DA42 NG
Austro AE330	180 hp	Turbocharged inline four	Diamond DA62 (two engines)
DeltaHawk DHK180	180 hp	Two-stroke inverted V4	Certified 2023, no factory airframe yet
SMA SR305-230	About 230 hp	Air/oil-cooled flat four	Cessna 182 (STC)

What Is an Aircraft Diesel Engine?

An aircraft diesel, or “aero diesel,” is a piston engine that ignites its fuel by compression instead of a spark. It turns a propeller like the gasoline engines in most small planes, but it runs on Jet A or road diesel. It is one of several types of aircraft engines, and the least common in service.

The cycle is the same four strokes as a car diesel. On intake, the cylinder draws in air only, with no fuel mixed in.

On compression, the piston squeezes that air until it gets extremely hot. Fuel is then injected at high pressure, and it ignites on contact with the hot air, driving the piston down. Exhaust clears the cylinder for the next cycle.

Modern aero diesels add three things a car does not need. A turbocharger keeps power up as the air thins with altitude. A reduction gearbox slows the engine’s high crankshaft speed to one a propeller can use.

The third is FADEC, or full-authority digital engine control. The pilot moves a single power lever and a computer manages fuel injection, turbo boost and propeller pitch. It replaces the separate throttle, propeller and mixture controls of a traditional piston engine.

Why Diesel? The Problem With Leaded Avgas

Most piston airplanes burn 100LL, a 100-octane “low lead” avgas. Its tetraethyllead additive raises the octane rating, prevents engine knock and helps lubricate the engine. 100LL can carry up to 2.1 grams of lead per US gallon.

The EPA finished phasing leaded gasoline out of US cars by 1996, but avgas kept its lead. That made piston aircraft the main remaining source of airborne lead.

On October 18, 2023, the EPA ruled that lead emissions from these aircraft endanger public health. On July 30, 2026, the FAA released its final plan to move the piston fleet to unleaded avgas by 2030, working with industry through the EAGLE initiative, with a separate transition for Alaska.

Unleaded replacements are coming, but slowly. As of January 2026, AOPA reported that GAMI’s G100UL, approved through an STC in 2022, was sold at only a handful of airports. The FAA is still testing three candidate fuels, and airports must keep selling 100LL until unleaded fuel is widely available.

A diesel avoids the whole problem. It burns Jet A, which contains no lead and is sold at almost any airport that serves turbine aircraft. Our guide to kerosene vs avgas covers how the two fuels differ.

Advantages of Diesel Aircraft Engines

Much lower fuel burn

Fuel efficiency is the headline benefit. AOPA measured a Continental CD-135 burning 5.8 gallons per hour at 75% power, against 8 to 10 gallons per hour for typical 160 to 180 hp gasoline engines.

The same pattern shows up in new aircraft. Tecnam quotes about 5.2 gallons per hour in typical cruise for its 170 hp P2010 TDI. Diamond quotes 8.0 gallons per hour at maximum range for the 300 hp DA50 RG. For comparison with other types, see how much fuel aircraft use.

Longer range

Lower fuel burn turns directly into range. The Tecnam P2010 TDI holds 63 US gallons (240 liters), and Tecnam quotes 1,300 nautical miles at 60% power with a 90-minute reserve. It can stay airborne for more than 14 hours.

Fuel you can find anywhere

Jet A is sold wherever jets and turboprops refuel, including remote parts of the world where avgas is scarce or expensive. That matters most to flight schools and operators outside North America.

Safer fuel, simpler cockpit

Jet A has a flash point of 100°F (38°C), so it does not ignite as readily as gasoline in a crash. And with FADEC, the pilot flies with a single power lever.

Why Aren’t Diesel Engines Used More in Aircraft?

Weight

Weight is the core problem. A diesel has to be built strong enough to handle very high compression, so it produces less power per pound. Engine maker UL Power notes that diesels of about 100 hp weigh about 220 pounds (100 kg) or more.

The fuel is heavier too. Jet A weighs about 6.84 pounds per US gallon (0.82 kg/L), against about 6.01 pounds (0.72 kg/L) for avgas. Fifty gallons of Jet A weighs roughly 41 pounds (19 kg) more than the same volume of avgas.

Together, these cut into payload. AOPA’s diesel-converted test aircraft could carry only 332 pounds (151 kg) with full fuel, 100 to 120 pounds (45 to 54 kg) less than comparable gasoline models.

Cost

Diesels are expensive to buy. AOPA priced a complete CD-135 retrofit kit, including propeller and engine computers, at $65,000 before labor.

Maintenance works differently too. Many Continental diesels have a “time before replacement” rather than an overhaul interval, so the whole engine is swapped at the limit. The CD-155’s limit is 2,100 hours. AOPA also reported a gearbox inspection at 600 hours that usually ends in a $3,500 to $4,500 replacement.

Technical trade-offs

Jet fuel lubricates poorly compared with road diesel, which adds wear to the high-pressure injection system. Diesels also need heavier starters and batteries to turn over against high compression, and can need extra help in cold weather.

UL Power also points to strong torque pulses that can damage propellers and parts designed for gasoline engines. That is part of why aero diesels need purpose-built gearboxes and propellers.

Diesel Aircraft Engine Manufacturers

Continental (formerly Thielert)

Continental has the largest diesel lineup of any maker here. Its line grew out of Thielert’s Centurion engines, which were based on heavily modified Mercedes-Benz car diesels. After Thielert went insolvent in 2008, the business passed to Technify Motors, owned by AVIC, and is sold under the Continental name.

The CD-135 and CD-155 are turbocharged four-cylinder engines with a 2,100-hour replacement interval. The CD-135 has been certified by EASA and the FAA since 2006, and its weight matches the older 1.7-liter Centurion, so it drops straight into existing installations.

The 170 hp CD-170 has a 1,800-hour interval and a helicopter version, the CD-170R. The 300 hp CD-300 is a twin-turbocharged, liquid-cooled six-cylinder engine with common-rail direct injection and a 2,000-hour interval.

Austro Engine

Austro Engine is Diamond Aircraft’s in-house engine maker, based in Wiener Neustadt, Austria, where its plant was built in 2007. When Thielert’s 2008 insolvency halted DA42 production, Austro’s engines became Diamond’s way forward.

Its AE300 four-cylinder diesel was certified by EASA and the FAA in 2009 and makes about 168 hp in the DA42 NG. The AE330 raises that to 180 hp and powers the twin-engine Diamond DA62.

DeltaHawk

DeltaHawk, based in Racine, Wisconsin, took a clean-sheet approach. The DHK180 is a liquid-cooled, two-stroke inverted V4 with both a turbocharger and a supercharger. DeltaHawk announced its FAA type certification in May 2023 after developing it since 2007.

The company says the 180 hp engine has 40% fewer moving parts than others in its class and is 40% more fuel efficient than avgas engines. It runs on Jet A or sustainable aviation fuel. At certification, DeltaHawk put the target price at $60,000 for the engine alone.

SMA (Safran)

SMA’s SR305-230 is unusual among modern aero diesels because it is an air- and oil-cooled flat four, the same layout as a traditional Lycoming or Continental gasoline engine. It was certified in Europe in 2001 and by the FAA in 2002. Its main use is as an STC conversion for the Cessna 182.

Diesel Aircraft You Can Fly Today

Diamond DA40 NG and DA42. Diamond offers more diesel models than any other planemaker on this list. The Diamond DA40 NG uses an Austro AE300 and earned European certification in 2010.

The twin-engine Diamond DA42 Twin Star first flew in December 2002 on Thielert engines. In August 2004, a DA42 flew non-stop across the North Atlantic in 12.5 hours, the first diesel-powered airplane credited with that crossing.

Diamond DA62 and DA50 RG. The seven-seat DA62 flies on two Austro AE330s. The five-seat DA50 RG, powered by the Continental CD-300, earned FAA certification on July 25, 2023.

Piper Archer DX. Piper’s diesel trainer pairs the classic Archer airframe with a Continental CD-155 and Garmin G1000 NXi avionics. Piper quotes a 123-knot cruise and an 845-nautical-mile range.

Tecnam P2010 TDI. Tecnam’s four-seat high-wing runs the Continental CD-170 on Jet A, Jet A-1 or road diesel. Tecnam calls it the longest-range, lowest-consumption aircraft in its fleet.

Cessna 172 and 182 conversions. Owners can still convert a Cessna 172 Skyhawk with Continental’s CD-155 STC, or a Cessna 182 with the SMA engine.

Military drones. The US Army’s General Atomics MQ-1C Gray Eagle uses a Centurion 1.7 heavy-fuel engine, a diesel that burns jet fuel.

A Brief History of Diesel Engines in Aircraft

Diesel flight is nearly a century old. On September 18, 1928, a Stinson SM-1DX Detroiter, registered X7654, made the first successful flight of a diesel-powered aircraft. Its engine was the 225 hp Packard DR-980, the first successful diesel designed specifically for aircraft.

Germany’s Junkers built the most successful early aero diesels. The Jumo 205 was a two-stroke with 12 opposed pistons in six cylinders and two crankshafts geared together. About 900 were built, for the Ju 86 bomber, the Blohm and Voss BV 138 and BV 222 flying boats, and Dornier’s Do 18 and Do 26.

The Jumo 205 was efficient at cruise but proved too unresponsive for combat and liable to fail at maximum power. That flaw kept diesels out of fighters.

Airships used diesels too. The Hindenburg and Graf Zeppelin II flew on reversible diesel engines, and Britain’s ill-fated R101 airship used the Beardmore Tornado, a diesel developed from a railcar engine. The Soviet Petlyakov Pe-8 bomber was built with Charomskiy ACh-30 diesels, which were replaced after the war.

After World War II, better gasoline engines and turbines pushed diesels aside for decades. The modern revival came in the early 2000s, led by Thielert’s car-based Centurion engines and SMA’s SR305.

Diesel Aircraft Engines: Future or Fad?

Diesels are no longer an experiment. Certified engines from four makers are flying in new Diamond, Piper and Tecnam aircraft, in retrofitted Cessnas and in military drones.

They are also not about to replace gasoline. Weight, purchase price and a thin US market have held them back, and Cessna’s retreat shows how hard the sale is in North America.

The deciding factor may be avgas itself. If unleaded 100-octane fuel spreads smoothly before 2030, gasoline engines keep their edge. If it does not, a diesel that already burns lead-free, widely available Jet A becomes a much easier case to make. For a wider look at the fuels involved, see our guide to sustainable aviation fuel.

FAQ

Are there any diesel aircraft engines?

Yes. Continental builds the CD-135, CD-155, CD-170 and CD-300, Austro Engine builds the AE300 and AE330, DeltaHawk builds the DHK180, and SMA builds the SR305-230. All are certified and run on Jet A.

Why are diesel engines not used more in aircraft?

Mainly weight and cost. Diesels produce less power per pound than gasoline engines, Jet A is heavier than avgas, and a diesel conversion kit can cost $65,000 before labor. Weak demand in North America also led Cessna to drop its diesel Skyhawk in 2018.

How much does a DeltaHawk diesel engine cost?

When the 180 hp DHK180 was certified in May 2023, DeltaHawk put its target price at $60,000 for the engine alone. Installation and propeller costs come on top, so check with the company for current pricing.

Can a diesel aircraft engine run on jet fuel?

Yes, that is the whole point. Jet A is chemically very close to road diesel, and engines like the Continental CD-155 and CD-170 are approved to run on Jet A, road diesel, or a mix of the two.

Can you put a diesel engine in a Cessna 172?

Yes. Continental sells the CD-155 as an STC conversion for the Cessna 172. Cessna built a factory diesel version, the Turbo Skyhawk JT-A, but discontinued it in May 2018.

How much fuel does a diesel airplane burn?

Far less than a comparable gasoline airplane. AOPA measured a Continental CD-135 at 5.8 gallons per hour at 75% power, against 8 to 10 gallons per hour for similar gasoline engines, and Tecnam quotes about 5.2 gallons per hour in cruise for the P2010 TDI.

What was the first diesel-powered airplane?

A Stinson SM-1DX Detroiter made the first successful diesel-powered flight on September 18, 1928. It used a 225 hp Packard DR-980 engine.

Is Jet A safer than avgas?

In terms of fire risk, generally yes. Jet A has a flash point of 100°F (38°C) and does not ignite as readily as gasoline, which is one of the safety arguments for diesel aircraft engines.