Stephen W. B. wrote us: I continue to appreciate your reporting on the progress of aero-diesel engines into the general aviation market, however, increasingly, most of the news is from "across the pond" manufacturers. What happened to DeltaHawk? The website, though sporadically updated once or twice a year offers very little insight on the progress of certification. I am not being jingoistic. I would buy the best value product the market offers but, with the Euro being so strong against the dollar, the cost of a Thielert or SMA has been pushed into the realm of not providing a reasonable time for return on investment. The Thielert replacement for a run-out Lycoming in a 172SP is about $70,000 (parts and labor). Did the Thielert and SMA STCs take this long to get through the FAA or were their tribulations as difficult but unobserved by me? Given the favorable exchange rate for American products it seems that DeltaHawk could make great strides in GA market share if they could get out of the starting blocks. Any insight on their progress (especially Cessna 172 STC)?

Andre answers: What I notice is that manufacturing plans are more and more transoceanic. The D-Air opposite piston 2-stroke engine has been acquired by a US firm and is inspiring the Gemini on both sides of the pond. IndUS Aviation assembles in the US a US designed Thorp made in India and plans to put in it a UK Wilksch WAM 120 engine, which may be soon manufactured in the US. Thielert acquired Superior Engines already some time ago. We may hear one day that Raytheon, Teledyne or SNECMA has acquired a controlling interest in Thielert. Etc. Remember: The famous North American P51 Mustang, so dear to the heart of so many jiongoist American aviation enthusiasts, was designed by Elgar Schmoed, an Austrian engineer sent to the US in 1929 to manage the Fokker New Jersey facility, and eventually flew with a British designed Rolls-Royce engine; and the Republic P47 Thunderbolt was the work of engineer Georgiu Hartveli from Russian Georgia, himself hired by entrepreneur Alexander de Seversky, a white Russian WW1 ace who escaped to the US during the Russian revolution. But this must not make us forget that all modern all-metal planes to this day are derived from the 1929 Jack Northrop cantilever wing, which was the real breakthrough; and Northrop was a red-blooded American born in Newark NJ. DeltaHawk seems to be doing well thanks to the DoD market (drones) and slowly moving towards offering their engine for STC retrofit. It takes time because I understand they still have cooling issues (every aircraft/engine design since the Wright Brothers had to cope with cooling issues, which always conflict with weight problems. You can improve the cooling of any aero engine: All you have to do is add weight!) And they have limited resources. Buying a diesel has nothing to do with return on investment because what you get is a different plane altogether, not simply a savings on fuel. DieselAir has elaborated on this many times here. Both Thielert and SMA will end up manufacturing in China, India, Mexico or similar. And, yes, both SMA and Thielert had to go through an extremely lengthy process imposed by FAA, not by bad will, but because FAA itself lacks resources to undertake testing!