can a rotary be rotated to meet this uber market plan?

Byron Head


Not FAA certified.

It could be certified in a heart beat if you equipped it with an
aircraft carburettor and aircraft magnetos. Of course you would have
to make all parts with a paper trail from the mine to the air that
includes the gear box.

Maybe if your name is Boeing.

Paul Lamar


I know this is a tough group, but you should know that an infrequent contributor here co-wrote a lot of the tech parts of that paper. It is properly a market plan, not an aircraft design, Uber is agnostic to the design if it meets the requirements — VTOL, quiet, safe, and cheap when mass produced. There are at least a dozen serious efforts around the world, a few of them of comparable size to Boeing, working on aircraft to be used in this scenario. Certifying a rotary engine would be trivial compared to the certification effort for the whole fly-by-wire aircraft, which they are taking as a given. When you have a customer like Uber committed to solving the rest of the service and market problems, and who would be using thousands of these aircraft, even an expensive certification effort becomes thinkable. It’s also easier for these aircraft which will have no single points of failure; think *many* redundant engines, props, batteries and *no* gearboxes. Once you have crossed the Rubicon (or is it the Styx?) to having the whole aircraft run by computers, all of the other assumptions change.

At least one of the companies is already considering a European rotary as a range extender engine, because no one is satisfied with the rate of progress in batteries. Another is looking at a generator with a turbine engine. Others not yet public could absolutely use mutliple small rotary engines without gearboxes. Even 20,000 rpm would not be too fast. 5-50 kW is a practical range for each powerplant, they can and should be tiny and spin fast. (Please do not ask me to explain why — take my comment at face value or ignore, for now.)

We have seen public announcements from Volocopter, Ehang (scaled up multicopters), Airbus and Joby (tilt rotor/wing multicopter), Lilium and Aurora (multiple small fans) and patents from people like zee.aero (multicopter lift rotors plus forward thrust props.) There are others in the works, some of which look entirely different from any of the above. And most are looking at rotary engines as potential power sources.

The powerplant has to be light, reliable and quiet. An electric turbo-compound as has been suggested here would be a great start. There will be a lot more news on this front later this spring. There is no funding that I’m aware of, but a lot of experimental efforts will be interested in buying engines with range extender generators in the near term. They don’t need to be certificated, as the whole aircraft doesn’t even have a certification basis yet. Discussions are well underway with FAA and other CAA’s and a lot of the potential makers, one of whom hired away one of the heads of FAA’s Small Aircraft Directorate a while ago to run their certification effort.

Woelfle/Engiro already have 20 and 40 kW range extender systems and other European rotary makers are in the game too. Rik DeDoncker from RWTH Aachen has a grant from DLR to work on it http://www.pt-em.de/en/1648.php ... Study those projects and do better.

David Josephson

Electric airplanes? What a joke :-) Hydrocarbons are unbeatable and always will be. Check the periodic table.

"We just have to invent a better battery. Thats all."

Good luck :-)

Every time you convert mechanical energy into electrical you lose 10 to 20 percent. Then back to mechanical
another 10 to 20% out the window.  80% times 80% is 64% You have now thrown out 36% of your available energy.

I told the Formula One engineers that but they did it anyway :-) Yes but better than no turbo compound.

Why? Because electric is politically correct.

I am still waiting for some one to pull their stupid head out of their liberal ass and build a pure mechanical turbo compound :-)

Paul Lamar


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