Robinson R44 Diesel

[CRAN]

It looks to me that the R44 Diesel might not be far off...

I’ve just noticed an updated version of the SMA305 Diesel engine is being marketed by Continental with a rating of 287hp at 2700rpm and a package weight of 200kg.

http://www.continentalmotors.aero/uploadedFiles/Content/Engines/Diesel_Engines/CD200-SpecSheet.pdf

Reading the specs, the engine has a 12-year or 2200hr TBO...hmmm 😉. That engine would also allow the gross weight of the machine to be increased to 2700lb, if necessary or desired. Seems like a great fit for the R44, so long as the torsional vibrations can be handled.

At cruise that engine would only burn 12 US Gals per hour of JET A1.

Would be exciting if they can get it to market and would have amazing performance. Hopefully they can keep costs under control.

CRAN

[Agile]

Must have been crossing Bruno's mind for a G4.
The Diesel EC120 showed that it was possible to dampen the torsional vibration using a torsion shaft.

[mini]

I see there are three different displacement figures for the same bore/stroke dimensions, is this a typo or am I missing something? (I calculate the displacement as 4989.6cc)

Sorry for the slight drift.

[Spunk]

:oh:In my country they start to ban Diesel cars from the city due to high NOx and elements of fine dust. So does that mean that a helicopter Diesel would have to comply with European emission standard 6?

[WillyPete]

:oh:In my country they start to ban Diesel cars from the city due to high NOx and elements of fine dust. So does that mean that a helicopter Diesel would have to comply with European emission standard 6?

likely not considering the regular engine doesn’t have any catalytic converters or similar requirements that non-diesel vehicles have .
The volume of aircraft using this engine would simply be negligible compared to vehicles.

[gg17]

Must have been crossing Bruno's mind for a G4.
The Diesel EC120 showed that it was possible to dampen the torsional vibration using a torsion shaft.

The guys at Guimbal already have a G2-based UAV which runs on a diesel powerplant (currently flown with a safety pilot). Their main issue with it is cooling.

Robinson have been experimenting with three different powerplants for the past few years, and the issues that they have been facing are the vibrations mentioned above and increased powerplant weight. A potential solution to the weight issue might be to roll out the first R44 Diesel as a Cadet, with payload restrictions.

[RMK]

Regarding weight, the Raven II's Lycoming IO540-AE1A5 engine is 447lbs (203kg) - I Googled this; my memory is not that sharp.

So this seems to be more power for same weight, reduced fuel burn (and cheaper by the litre)

Could someone elaborate more on the problems regarding torsional vibrations of a diesel engine in a helicopter.

[Spunk]

The volume of aircraft using this engine would simply be negligible compared to vehicles.

It's not the amount of vehicles, it's the amount of emission the individual vehicle produces. One cruise ship visiting a city produces by far more fine dust than all the cars in the same city.
Do I sound like a greeny now?:confused:

[whoknows idont]

Well the fact that they still let us fly around with leaded AVGAS decades after it was prohibited for road use shows that there are different measures applied for GA. I'm certainly no chemistry guy, but looking at how things developed on the roads I would expect TEL to be a far bigger problem than NOX.

[CRAN]

RMK,

When people refer to torsional vibrations in Diesel engines, is relates to the (lack of) smoothness with which the engine delivers its torque. Every time a cylinder fires it issues a big thump of power to the crankshaft. These torque pulsations are extremely damaging to the helicopters dynamic components and rotors or the propellers of aeroplanes.

The reason for the pulsations is the fact that in a Diesel engine the combustion process is more
of a spontaneous combustion everywhere in the cylinder rather than a the gentle propagation of a flame front that occurs in a spark ignition engine leading to a nice smooth torque delivery. This sudden spontaneous combustion leads to very high transient peak cylinder pressures and hence torque spikes as the crankshaft rotates.

Modern Diesel engines go a long way to improve this characteristic by delivering multiple little pilot injections in quick succession rather than the traditional one big squirt provided by the old mechanical injection systems.

CRAN

[CRAN]

In terms of emmissions, the requirements on light aircraft are a lot less onerous than for road vehicles, largely since there are so few light aircraft that their impact is simply not significant.

[Robopilotforeever]

This sounds like a great idea!