How Do Thielert Diesels Do It?

FLYING Staff

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

Verified

Key Takeaways:

Thielert GmbH manufactures liquid-cooled, geared turbo-diesel aircraft engines, based on Mercedes designs, for retrofitting existing aircraft (e.g., 135-hp for 160-hp Lycomings) and new Diamond airplanes.
These diesel engines utilize a high 18:1 compression ratio, operate without an air throttle (fuel flow controls power), feature a Full Authority Digital Engine Control (FADEC), and run on cheaper jet fuel or road diesel.
Despite offering lower nominal horsepower, Thielert-powered aircraft achieve comparable takeoff and climb performance due to the diesels' use of automatic variable-pitch propellers, which efficiently harness power.
The engines excel in cruise flight, providing superior fuel efficiency, flat-rated turbocharged performance at altitude, and significantly reduced direct operating costs, making them particularly attractive in regions with high 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.