Rolls Royce agree to power R66

[CRAN]

Taken from Rolls Royce website:
http://www.rolls-royce.com/media/showPR.jsp?PR_ID=40434
Rolls-Royce RR300 to power new Robinson helicopter
02 March 2007
Orlando, FL: Rolls-Royce, a world-leading provider of power systems and services, will supply a new turboshaft engine to power Robinson Helicopter Company’s new R66 rotorcraft, it was announced today at Heli Expo.
The new RR300 engine represents a major step forward in the helicopter industry by providing 300 shaft horsepower at takeoff, excellent hot and high performance and outstanding value. The RR300 makes Rolls-Royce turbine power available in the lower shp range.
The new R66 model, a five-seater, is Robinson Helicopter Company’s first venture into gas turbine-powered rotorcraft and will complement the company’s existing line of piston-powered aircraft.
Rolls-Royce expects FAA type certification by 2008 with full-rate production to follow. Under the agreement with Robinson Helicopter, Rolls-Royce will provide several hundred RR300 engines in upcoming years.
Rolls-Royce is the world-leading producer of light turbine engines in the helicopter market. The Model 250 line has produced nearly 30,000 engines, with approximately 16,000 currently in service worldwide in a wide range of aircraft styles.
The RR300 embodies new technology and advanced design methodology. The engine draws on the proven record of other Rolls-Royce turbine powerplants to deliver a powerful, dependable engine at a competitive price.
Key attributes of the RR300 include: lower acquisition and operating costs; low-weight, compact design; improved specific fuel consumption; an embedded engine monitoring system; and an optional, through-life, peace-of-mind maintenance program.
The new aircraft deal brings together two industry-leading rotorcraft companies.
Scott Crislip, President Helicopters & Small Gas Turbine Engines for Rolls-Royce, said, “We are honored to join with Robinson Helicopter Company on its first turbine-powered aircraft, the R66. We anticipate a great future partnership on this industry-changing aircraft. The RR300 engine represents the latest technology in turbine power and once again Rolls-Royce is leading the way. You will see big things from this small engine.”
Robinson Helicopter Company is the world's leading producer of civil helicopters and is known for its high performance, reliable aircraft.
Founded by Frank Robinson, the company sold 806 rotorcraft in 2005, the most civil helicopter sales of any company in the previous 25 years. The company has produced more than 7,000 helicopters overall.

http://www.rolls-royce.com/heliexpo2007/img/graphics/rr300_eng.jpg

And here's a link to the new engine:
http://www.rolls-royce.com/heliexpo2007/engines/rr300.htm

[Graviman]

I work out cruise consumption to be 255.4 g/kW-hour, which is pretty competetive. Only the latest diesels get down below 200 g/kW-hour. I guess cost savings are that the engine has not been optimised for minimum weight, which for cruise power is 1.69 kW/kg. Compared to A250 this is not so hot, but it blows any piston engine out of the water. Looks like Rolls intendeded the RR300 to compete against the Lycombing O-540 from the start.

Good on them, since O-540 is showing its design age - do you warm up / cool down your car engine during every trip?

Mart

[Graviman]

Well folks, it's about time i ate some humble pie:

Thanks Ian, this pm was so informative that it thought it unfair not to share it! Must admit i had noticed some similarity of RR300 with the 250...


Mart,

Don't want to flog this to death on a public forum, but you should probably take another look at your diesel vs. turbine calcs. The Thielert Centurion diesel (which Frank R. is reported to still be looking at) comes in at 0.32 lb/shp/hr, which equates to 110 g/kw/hr, not 200. The OPOC diesel is even more frugal.

The RR300 actually offers very little improvement over the Allison 250, which was already way behind newer designs from P&WC, Honeywell and TM in terms of SFC and MTBR. As I understand it, RR was originally intending to sell the C20 to Robinson (which has been in discussions with Allison since 2000/1), and it was the current President who decided to launch a whole 'new' engine as an ego trip to get some personal publicity (allegedly...). Which means that if/when Frank decides the R66 actually needs 400 shp, we'll either see a reversion back to the C20 or the development of another smoke & mirrors 'new' RR400.

Go figure !

I/C


Doing some proper bookwork, i find that aircraft fuels have a range of energy values:
Avgas: 42.0 to 43.71 MJ/kg
Diesel: ~42.6 MJ/kg
Jet A1: 42.5 to 43.23 MJ/kg

So if we choose roughly 43MJ/kg for all three fuels, this gives 100% engine efficiency with BSFC 83.7 g/kW-hour. Now the most efficient truck engine i know is about 45% efficiency, which corresponds to 186 g/kW-hour (200 g/kW-hour would be 42%).

This also give a figure for the RR300, with its cruise consumption of 255.4 g/kW-hour, of 32.8% efficiency. In fairness this is probably comparable to the Lycombing O-540, but not vastly better. The Thielert Centurion diesel, at 110 g/kw/hr, is thus running at 76% efficiency!

There was me being all cynical about CO2. :ok:

Mart

[moosp]

Disclaimer. I only fly them I do not design them.

With the RR300 coming in at 300shp at take off and 240 in max cruise, it seems to me that Frank's engineers will have difficulty getting the machine down to a mass where it can handle a commercial load.

The Arrius 2F in the EC120 gives 504 shp at take off and 450 in cruise, and even that is not quite enough for five blokes + toys + sensible fuel on a summers day.

Do you designers have a rule of thumb for SHP per pound empty weight or Kw per kilo max t/o mass or similar, which gives you a down and dirty look at whether a machine is viable? :confused:

[Graviman]

moosp,

This can be done using idealisations about the airflow through the rotor. If you ignore fuselage aerodynamics and lump rotor performance into a figure of merit (efficiency), the ideal hover power in kW is:

Hover Power = ( Weight*SQRT( Disk Loading / 2*rho )) / 1000*Figure of Merit

Where rho is air density, take as 1.1681kg/m^3 from this source
http://en.wikipedia.org/wiki/Density_of_air
Clearly altitude can be seen to increase power requirement.

This calc is converted to SI units from Prouty, so a quick check of my maths is in order! A Bell 206 at MUAM is ~1882kg or 18462N weight, with a rotor of 5.64m radius, produces a disk loading of 184.7 N/m^2. Guess rotor FM of 0.7, then plug these into equation:

Hover power = 18462 * SQRT( 184.4 / (2 * 1.1681)) / 1000 * 0.7 = 234 kW

or 312 BHP - this compares with 307BHP using Prouty formula directly, so he
probably uses a more accurate air density figure.

In general, power requirement explains why A250-C30 with 692HP TO, or 456HP cont, is required in the 206 (you want to manouvre, right?). Don't have numbers for R66, but assuming it is similar to Bell 206 power requirements will be similar. Hmmm...

Mart

[CS-Hover]

Hi

only a kick question about physics (not intended to go off topic....)

it's about units of weight, mass, definitions, and all around...

graviman said "A Bell 206 at MUAW is ~1882kg or 18462N"

but we know that in MAUW, the "W" stand for weight (in JAA land they chanced everything with W, to M (they call it mass..) . ok until now!! :ok:

but when you put an helicopter over a scale, what it gives me?? weight, right?? :rolleyes:

and for units, if you read a BES units flight manual, it will show the "weights" (or mass, as the JAA definitions..) in lbs, that seems to be the unit for force (as the weight can be defined) in that units standard (if i remember right, mass unit will be the unit "slug"), on the other way, if the flight manual is in the SI system, the same "weight", will be show in kg (as force in that standard is newton..)

so, the question!! is mass or weight, that we should use in the definitions? (MTOW or MTOM)

thanks

[Graviman]

CS-Hover, that raises an interesting question. Speaking only as an engineer i would say that mass is the correct unit to use. Why? Because the weight is only defined when static on the ground at 1g. Once airborn any manouvre will affect g loading, hence weight, while aircraft mass remains constant (ignoring fuel burn).

For calcs Prouty uses Imperial units, which causes me a headache! Slugs are things that ruin my side salad, and poundals are what my computer gets when it crashes. SI units are generally fairly good for spotting errors, and for mental calcs, but this is just my experience.

Mart

[diethelm]

Lets try another way. I do not remember the exact numbers but the lycoming in the Raven II is derated to 240hp and is approximately 225 pounds heavier. So 60 more hp and 225 less pounds?

[Graviman]

diethelm, this is very true. So it would make suitable replacement for the R44 engine, and may just be able to squeeze in an extra pax. The reduced engine mass would allow the extra person, while the extra horses would fly the additional fuselage mass/drag. Worth considering though that 300SHP is 5 mins power, so is nibling at Nick's bean jar ;) , and cont power is still only 240SHP.

Robinson seem to specialise in squeezing acceptable performance out of acceptable costs. Perhaps the RR300 should be seen as a derated 250, with extra life from all components. So the machine can nibble at 206 territory, slightly undercutting operating costs for slightly lower performance.

Does this seem like a fair analysis?

Mart