Let’s hear it for the Chinese and Germans. Continental, now Chinese-owned, acquired the bones of bankrupt German aircraft diesel engine manufacturer Thielert. The actual engines are based on a Mercedes car diesel engine, which is much heavier than the traditional aluminum air-cooled airplane piston engine, but is capable of burning jet fuel (much cheaper than Avgas in Europe and much more available at airports worldwide). Continental has been tracking the reliability of the engines they have produced. It turns out to be 3.3 inflight shut downs per 100,000 flight hours. Note that this would include, in a twin-engine plane, an intentional shutdown by a pilot who noticed a problem and decided to proceed with just one engine spinning.
Continental misleading cites some FAA statistics that older design engines experience 10 shutdowns per 100,000 hours. This could be true but those statistics include high-power engines and old engines. The proper comparison would be to relatively new engines with similar horsepower to the diesels. It is unfair to look at a 310-horsepower engine from 1990 that is past its 12-year recommended overhaul period and compare that to a two-year-old 135 hp diesel engine.
If these low-power piston engines can run for 30,000 hours before shutting down, what’s better? Supposedly the Pratt & Whitney PT6 has an in-flight shutdown rate of between 1 in 200,000 hours and 1 in 500,000 hours. The Honeywell turboprops (formerly Garrett) are somewhere in between.
Cessna seems to have given up on diesels (had an in-flight shutdown during late testing, the engine requires a 15min+ warm up): http://bit.ly/1PQtzMw
These guys (including Burt Rutan) http://eps.aero are in the middle of certifying a clean-sheet design diesel with: 350hp, 3000hr TBO, liquid cooling, single lever power, dual ECUs, modern steel alloys.
The progress that was made in jet engines in just a decade or two after they first flew was remarkable. The German wartime jets had MTBOs measured in minutes. The PT6 goes thousands of hours. The fundamental design did not change – it was mostly improvements in materials.
In Brazil, our social policies do not allow the use of both diesel in small vehicles, cars and small trucks are not allowed to use diesel because gasoline subsidizes diesel, that is, we pay dearly for a mess of and we can not use in order correct.