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
-----------------------------------------------------------------------
BTW Our Mazda time to climb engine is a world wide record power to
weight ratio engine
at 650 HP and 200 pound weight. The fuel burn with no turbo compound is
2/3 that of
a PT6 turbo prop engine and half to one third the weight. Aircraft that
lift people
need engines with good power to weight ratios. Hybrids engines DO NOT
have good
power to weight ratios!
On top of that we are throwing away a lot of exhaust energy. We have a
waste gate and
a 1.5 inch HOLE in the exhaust manifold ALWAYS wide open. There is still
so much excess
energy in the exhaust we have had to add a manifold pressure blow off
valve. Otherwise
the engine will run away with the boost heading towards infinity. Very
little weight
would be needed for a small gear box to feed that excess energy back
into the prop
shaft further reducing the fuel burn by another 30%.
All we want to do is get the absolute world record prop driven time to
climb record
and not explore the ultimate mechanical limits of the Wankel engine.
(Not in sight yet!)
We are going to run it again tomorrow and fly it again very soon.
Paul Lamar
There is no question that the Wankel rotary configuration would be great
for a turbo-compound engine. The weak link of the turbo-compound R3350
was the poppet type exhaust valve. In 1962 I was an engineering
technician at McCulloch ADD and I worked on a two-stroke cycle, five
cylinder aircraft engine that used piston ports and direct injection.
Cylinder charging was accomplished with a regenerative type air pump and
turbocharger. At the higher outputs the regenerative pump became a
turbine thus making this a turbo-compound engine. The SAE paper on this
engine was published in 1965 and the report number is:660173.
The architecture of this engine was not satisfactory but the concept was
sound. It eventually morphed into a four cylinder diesel engine that
performed well and the only example is on display at the Pima Air Museum
in Tucson, AZ.
With todays electronic fuel controls the original spark engine concept
could be explored and prove to be viable. The injection pressure of the
1962 engine was only about 600psi and today gasoline direct injection is
applied to many modern cars.
The architecture of the original engine contained too many joints
resulting in many leak paths for the coolant and in the diesel version
those leak paths were eliminated.
Robert Young
I think have that paper some place. I recall seeing it. McCulloch was on
Sepulveda Blvd very close the LAX
also as I recall. I lived in Manhattan Beach at the time.
Paul Lamar
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