Light Aircraft Association

Please can anyone tell me the TBO of a Midwest rotary power unit and the likely fuel burn .
Many thanks,
Mike

Mike,
I only have early experience of MidWest. When they were at Staverton. I installed a single rotor 50hp unit in a Shadow. It was crap, however, the twin rotor units have proved pretty reliable and very smooth. A number of years development have passed since my effort (engine returned and refund received) so it would be unfair to judge on my experience.

Rotary engines are turbine like in smoothness, but there doesn't seem to be any such thing as an economical wankel unit (don't really know why).

I think one or two have found their way into ARV2s? Hopefully one or two others on here can update you.

Have a look at uavenginesltd.co.uk

I think the 'one-trip lethal' is an interesting concept that is ok for a UAV but less attractive for flying behind or in front of.

Over here in Ireland there is a Bede BD5 based at Waterford fitted with a twin rotor Mid West rotary engine. Apparently at some point Mid West were taken over by a German co. and the BD5 owner said all spares are now in Switzerland and difficult/expensive to get.
The BD5 is probably smaller than many UAV's!

Thanks for the gen folks,

regards Mike

Nigel Ramsay wrote:I think one or two have found their way into ARV Super2s.

MidWest engines were indeed installed into three ARV Super2s, one of which is now in the USA.
The UK aircraft are G-ORIX & G-BWBZ. PM me if you would like more information.

Mike Fawdrey wrote:Please can anyone tell me the TBO of a Midwest rotary power unit and the likely fuel burn.

Fuel burn in an ARV with a fuel-injected Midwest engine is between 14 & 18 lph, typically averaging 15-16 lph.

xair899 wrote: Apparently Mid West were taken over by a German co. and the BD5 owner said all spares are now in Switzerland and difficult/expensive to get.

Not quite! MidWest was bought by Diamond in Austria:
Diamond Aircraft Industries | N. A. Otto-Straße 5 | A-2700 Wiener Neustadt | Tel: +43 2622 26700 | Fax: +43 2622 26780 | [email protected]

I got interested in buying an engine not long ago. A couple of previous operators of the engine very kindly ga v e me some feedback. None of it was very positive unfortunately.
Diamond have zero interst in the engine - so if you need parts, camping on their doorstep seems the only option.

Fuel consumption - much more than the equivalent Rotax, gthe figures given would be for 50% power or something similar. The basic problem with the Wankel is that the combustion chamber is long and narrow - which gives poor combustion - they actually need dual ignition to give combustion. That translates into poor fuel consumption and poor emissions - not an issue presently with aircraft but indicative of performance.

When they run, very smooth. Tip seal life? Big issues with many of the car and bike engines, so far not an issue with the aircraft ones - probably due to the warm-up period and lack of over reving.

With Diamond owning the rights to this engine you might have thought if the engine had any real merit they would have continued to build it. They did not - although they have managed to produce a certified diesel in under a year. Granted there was considerable commercial pressure on them to produce the diesel - but it is indicative of their engineering ability. The Wankel is sitting there, ready to exploit, but they have chosen not to bother........... Wankel engines have caused serious financial harm to NSU, Citroen, Norton and Mid-West.

UAVs and the military seem a good place for them.

gasax wrote: The basic problem with the Wankel is that the combustion chamber is long and narrow - which gives poor combustion - they actually need dual ignition to give combustion.

Wankels DO run with a single spark plug per rotor; but the MidWest has two, side-by-side, to comply with aviation dual-ignition requirements. Madza have found that having three plugs per rotor is ideal, and it gives much improved combustion & economy, even when using peripheral exhaust ports. (The MidWest has perheral intake and exhaust ports). Madza have also found that side inlet ports give smoother idling; but this is of real benefit to road vehicles only. Peripheral ports, as on the MidWest, give better power.

When they run, very smooth. Tip seal life? Big issues with many of the car and bike engines, so far not an issue with the aircraft ones - probably due to the warm-up period and lack of over reving.

Quite! A Wankel's massive rotors need to be properly warm before applying full power, which is why I feel they are not ideal engines for road vehicles. But they ARE excellent engines for racing, light-aviation and military use.

With Diamond owning the rights to this engine you might have thought if the engine had any real merit they would have continued to build it. They did not. .... The Wankel is sitting there, ready to exploit, but they have chosen not to bother........... Wankel engines have caused serious financial harm to NSU, Citroen, Norton and Mid-West.

Why Diamond have chosen not to exploit their engine is a bit of a mystery. I suspect they are holding it in reserve. Note that the Norton road bikes were very good, but did not sell well. By contrast, Norton's racer was very successful; and the newly reborn Donington Norton is producing a new twin-rotor racing engine. It seems to me it would be well-suited for development as a lightweight aviation engine giving about 125bhp. see: http://www.lightaircraftassociation.co. ... php?t=1954

gasax wrote: Diamond have zero interst in the engine - so if you need parts, camping on their doorstep seems the only option.

The same method seems to be needed to get parts for thier aircraft. Our club got rid of the Katana because of the spares situation.

There are many reasons why Diamond my have brought the rights.
The deal may have includes a patent they wanted to apply elsewhere.
They saw it as a threat and wanted to remove competition.
or they see it as a future investment, but have other priorities to deal with.
Take your pick

Ian Melville wrote:There are many reasons why Diamond may have bought the rights.
The deal may have included a patent they wanted to apply elsewhere.
They saw it as a threat and wanted to remove competition.
Or they see it as a future investment, but have other priorities to deal with.
Take your pick!

Any would-be manufacturer must obtain a Wankel licence before they can produce a rotary engine. I somehow doubt that the MidWest had any special patents, as their engine was based so closely on the Norton motor (although, unlike the Norton, the Midwest does not burn the very hot air that has just cooled the rotors, but dumps it overboard). Instead, for better volumetric efficiency, the MidWest engine induces cool air into the combustion chamber. Also, nothing unusual about the excellent MidWest gearbox (2.96:1), as it is "merely" a bigger version of the Hewland engine's box; although the rubber doughnut damper is rather novel.

MidWest posed absolutely no threat to Diamond, who were not engine manufacturers at the time. Rather, I suspect that they were anxious that Rotax might hike the price of their 912 even higher, and Diamond wanted control of an alternative engine supply. But, if I am correct in thinking that Diamond still make the single-rotor version for motor-gliders, why on earth did they stop production of the twin-rotor version just as it was fully sorted?!