How Do Thielert Diesels Do It?

FLYING Staff

Saturday, October 09, 2004 at 08:00 AM ET

Verified

Key Takeaways:

Thielert diesels are Mercedes-based, liquid-cooled, geared turbo-diesel engines certified for aircraft retrofits (e.g., Cessna 172, Piper Warrior) and new aircraft like the Diamond Star/TwinStar.
Despite lower horsepower than gasoline engines they replace, Thielert engines achieve comparable takeoff and climb performance, mainly attributed to their use of automatic variable-pitch propellers, not superior torque.
In cruise, Thielert diesels offer significant advantages, including a Full Authority Digital Engine Control (FADEC), greater fuel efficiency due to high compression, ability to run on cheaper jet fuel, and improved high-altitude performance due to turbocharging.
Their higher cost and complexity are offset by lower operating costs, making them particularly attractive in markets like Europe with higher aviation fuel prices.

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One reader castigated me for not paying enough attention to Thielert diesels. Another inquired whether the just-certified Diamond TwinStar would have superior climb performance because of the great torque of its Thielert diesel engines. A critical mass of Thielert interest has evidently been reached.

Thielert GmbH is located at the small town of Lichtenstein in the former East Germany (not to be confused with the principality of Liechtenstein, wedged almost invisibly between Switzerland and Austria). The company produces, among other things, liquid-cooled geared turbo-diesel aircraft engines based on Mercedes automotive designs. A 1.7-liter, 135-hp four-cylinder is currently certified for retrofit to Cessna 172s and Piper Warriors originally equipped with the 160-hp Lycoming O-320 engine. The Austrian firm of Diamond offers its single-engine Diamond Star with one of the engines, and the upcoming TwinStar has two. More than a hundred Thielert-powered airplanes are now flying, and the company expects to certify a 4.0-liter, 310-hp V-8 this year.