In fact the HPH 304S is certified with a 80 lbf jet engine..So let's sum up - We have a engine that offers less time between OVERHAULS than most engines do between OIL CHANGES. It's got a TBO of 25 hours, which is 1500 minutes - less than the number of HOURS that most aircraft engine manufacturers allow.
So yes, its lifespan is measured in minutes.
And I know it's not a new idea - at least TWO!!! human-carrying aircraft have been powered by these engines. But that doesn't mean it's a practical - or even good - idea.
I am sure more airplanes will be built with these engines. But I'm also sure they'll be just novelty* acts for the foreseeable future.
2) The jet cri-cri uses almost 5lb of fuel PER MINUTE at full throttle. It's fuel load is barely FAA-legal.
And though maintenance is an issue it's much less than it is on comparable two-strokes, TBO's are unknown to me, but certainly way less than a certified two-stroke.
Sure, 1.1 litre a minute is a good 5 gph, but don't forget that at typical flying speeds (100 kts) that's 27 true HP (comparable to 34 installed hp. Though that's not too much, the installed engine weight certainly pays off with only 12 lbs total...
A rather bad idea for going XC, but a significant part of the pilot population just want to fly around and for that application it's more than interesting