According to Wikipedia the Hirth engine weighs 38kg, but the Rotron weighs 23. The engine block is only about 12, and very compact. I wouldn’t buy one on the grounds that it’s too early to know how it’s going to be supported, but if it works out there’d be a lot to like.
Some of their larger drone engines run on heavy fuel and have dual ignition, but they seemed to have no plans to sell them for manned aircraft.
They also say they have no plans to supply the engine (the e-go engine) for any other light aircraft projects.
Hirth F23 LW:
Engine 22 kg + PSRU 4.17 kg + electric starter 2.36 kg = 28.5 kg (50 HP air cooled)
Rotron:
Engine 12 kg + PSRU 2.6 kg + electric starter 3.2 kg + generator 0.7 kg + water pump 0.25 kg + radiator 1.14 kg + oil tank 0.5 kg + ECU 0.4 kg + throttle body 0.3 kg = 21 kg. And you need oil, hoses/fittings and water and end up at at least 25-30 kg. But this is only 30 HP. Both engines also need exhaust at 3-4 kg all in all.
OK, I think we can say they weigh roughly the same, but the Hirth is considerably more powerful. The Hirth can also be made heavier with a heavier gearbox and ECU etc. Both engines are only suitable for a very small niche of tiny aircraft, and the trend there is to use small industrial 4 stroke engines. Those engines are heavier, but on a different level regarding reliability and they are also much cheaper.
I think they are both cool though.
Probably because they know that UAV has no “man’s wife” to sue after the EFATO accident!
Alas if I were in their position, that would be my take on the matter too.
but they seemed to have no plans to sell them for manned aircraft.Quote
Probably because they know that UAV has no “man’s wife” to sue after the EFATO accident!
How did Thielerts ever get certified, when a total electrical failure shuts down both engines on a DA42? I know it’s unlikely to happen, but it’s been (very famously) done.
That happened very early during the initial deployment and was to my knowledge corrected. It had to do with power instability, not a total failure. I do remember an article about this accident and the follow up a few years after it happened and how it was dealt with. I believe the ECU is now running with a backup battery.
It is however interesting to see how such old accidents influence public perception of such engines or airplanes for that matter. Only recently I heard someone tell me that he would never fly a Bonanza because they tend to loose their tails. That this problem was addressed in the mid 1960ties and is no factor anymore today does not seem to have had any effect on a lot of people….
Re Innovation and new technologies, I believe the main problem in that is the enormeous cost of certification and the resulting enormeous cost for the end user of a product which would cost maybe half that price if it were being certified to reasonable standards rather than gold plated 10 year processes which makes a lot of people go uncertified or bancrupt. If you look at the difference in price between certified and uncertified aviation material no matter if engines, avionics or what else, it appears to me that certification cost outweighs the actual material cost by far. And you get the absurd situation that in certified aviation we have to contend with age old technology whereas really nice stuff appears in the uncertified market, works just as well but has NO test standards at all.
Nice would be an in-between for materials used on airplanes below somewhere like 2.5 tons and max 6 seats, to the effect that certification for those components can be realistically achieved in a reasonable time frame and cost which make it worthwile.
Having said that, I still do believe that the Diesel engines now in production and having been taken out of amateur hands into a large manufacturers sale/support network are the way forward in GA, certainly for new planes. It will be very interesting how the M10J fares in that regard, as a fast and economic 2-3 seat traveller. Certainly Diamond with their diesel products have set a certain amount of standard there. Of course diesel has the definite advantage that fuel is available basically everywhere, as opposed to Avgas.
Re UL91, it is a step in the right direction I believe. Many of the low compression engines were actually made to do with a lot less than 100 Octane and many engines actually suffer from spark plug fouling as a consequence. The big advantage is also that most airplanes can use UL91 without any paperwork, certifications or anything by the end user, the fact alone that the engine is certified is sufficient. The disadvantage is that UL91 is even less established and available than Avgas 100LL. So while it allows a way out in case of an Avgas ban, it does not solve the problem of availability. Last time I looked, UL91 is about 10-15% cheaper where it is available than Avgas.
That is the big problem with MOGAS. While it is cheaper, it is the question how long you have to fly to make the certification if it works worthwile and it does work only with a number of engine/airframe combinations.
fuel efficient small turbine
I would consider the above statement to be an Oxymoron 
According to Wikipedia the Hirth engine weighs 38kg, but the Rotron weighs 23. The engine block is only about 12, and very compact. I wouldn’t buy one on the grounds that it’s too early to know how it’s going to be supported, but if it works out there’d be a lot to like.
Some of their larger drone engines run on heavy fuel and have dual ignition, but they seemed to have no plans to sell them for manned aircraft.
For the e-go engine the TBO is 500 hours, not 50.
That remains to be seen. They state 10-50 h for their drone engines. Why the e-go designers chose a completely unproven rotary engines instead of a well proven Hirth F23 is hard to understand. The F-23 is lighter, and has more HP. It also has 1000 h TBO. Hirth also makes drone engines for several drones. The smallest are literally model aircraft gas engines of the sort you find in any larger model airplane 50-250 cc. They also have larger engines based on their 2 stroke aircraft engines. This engine runs on Jet fuel, but is “ordinary” 2 stroke (not a 2 stroke diesel) and has 60 HP. Looking at these drones though, it seems to me if the power is more than 100 HP or something, they use turbines instead.
That Hirth jet fuel engine could be cool for a small aircraft, but the engine already exist for small aircraft, only it uses gasoline. A small turbine could of course be cool, but then the price would be 100-200k instead of 10-20k.
All in all I don’t think drone engines are very interesting for small aircraft, except maybe a fuel efficient small turbine gets developed.
I wonder if the first one is peak or LOP?
Best economy – so peak EGT.
My IO540-C4 would be burning about 9 USG/hr for that HP, but that’s a bigger engine.
Yours is a 6 cylinder as opposed to 4 cylinders for the DA40’s IO360. So more internal friction.
Except perhaps for the really large ones, drone engines seems to be light and powerful 2 strokes made to be constantly maintained, model airplane engines essentially. Also, the rotary engine is technically a 4 stroke, but practically a 2 stroke regarding lubrication.
The best known US government funded UAVs have Rotax 914 engines with modified ancillary systems. They’ve been that way for over 20 years but new production has now made the inevitable cost/capability climb to turboprops. Army funded tactical UAVs used Thielert diesels but with the change to Chinese company ownership that must be ending, which was I imagine the reason for the Lycoming/VM diesel demo. Who knows where that is going.
For the e-go engine the TBO is 500 hours, not 50.
I had a long chat with them at Farnborough and the ‘overhaul’ for the e-go engine seemed relatively straightforward – primarily a bearing change. They seemed very helpful, and some of the larger engines seemed very attractive (ran on Jet-A). Of course, the real question will be how they perform in service but with the number of hours drones are putting in, some of these companies will be getting real-world experience.
