Thoughts about the RR250 Series?
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Thoughts about the RR250 Series?
My question to all your rotorheads is: What do you guys think of the Rolls Royce 250 series Turbo-shafts? I know they come in a wide range of aircraft. I'm sure many of you have a great deal of experience with them, as well as the other common powerplants used in rotorcraft. I only have exposure to the 250 series (I work at an overhaul facility) and I think highly of these engines. However, they are becoming a very old design and I'm surious as to everyones experience with them. Recently Robinson has announced that the 250 has been chosen to power the new r66 so maybe they're not as out dated as I think?
Comments and input appreciated.
Comments and input appreciated.
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I thought the new RR300 was the power plant for the R66?
I think the general consensus is that the 250 is actually a cheap gas turbine engine. It is however a brilliant design and well proven. Provides excellent power/weight and reliability.
MADY
I think the general consensus is that the 250 is actually a cheap gas turbine engine. It is however a brilliant design and well proven. Provides excellent power/weight and reliability.
MADY
I have been flying the 250-C30R/3 for 5 years now. I have flown it in civil and combat environments with zero complaints. the incorporated FADEC makes the engine very reliable and "almost" impossible to droop the rotor during flight withing aircraft envelope. when maintained properly it provides very rapid and predictable power and fuel burn. i wouldnt mind shedding some aircraft empty weight to take advantage of the power. but even running her at the 650 SHP limit, she runs smooth!
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The RR300 is "technically" a new engine. But the majority of the components are already in use in the smaller frame engines. 
The C30R/3's are mean engines. They make some GOOD power.IMO they are under rated from Rolls Royce.
The C30R/3's are mean engines. They make some GOOD power.IMO they are under rated from Rolls Royce.
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As with any engine there are good points and bad points. The RR 250, when properly maintained and flown is a reliable piece.
The good points are that it is well developed and runs just fine.
The bad points are that it has a lot of piece parts and these can wear and cause problems. You need to make sure the engine is overhauled properly and not just pulled apart and the apparent bad parts replaced. The turbine disks have a finite life and you have to respect those life limits lest you burst one and ruin your day.
The engine is old technology and sucks a lot of fuel for the power you get out of it.
The RR300 has a new compressor, but it has a lower flow and pressure ratio so even though the comrpessor efficiency is improved the SFC as % of power isn't better than the older engines. At the power point used in the R66 it is probably better than a 250 would be at that power, but it still sucks a lot of fuel for what you get out of it.
I don't know if they are still using the single channel FADECS. When those were working they were great, but the "reversionary mode" on the single channel system was dangerous.
The good points are that it is well developed and runs just fine.
The bad points are that it has a lot of piece parts and these can wear and cause problems. You need to make sure the engine is overhauled properly and not just pulled apart and the apparent bad parts replaced. The turbine disks have a finite life and you have to respect those life limits lest you burst one and ruin your day.
The engine is old technology and sucks a lot of fuel for the power you get out of it.
The RR300 has a new compressor, but it has a lower flow and pressure ratio so even though the comrpessor efficiency is improved the SFC as % of power isn't better than the older engines. At the power point used in the R66 it is probably better than a 250 would be at that power, but it still sucks a lot of fuel for what you get out of it.
I don't know if they are still using the single channel FADECS. When those were working they were great, but the "reversionary mode" on the single channel system was dangerous.
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The original idea of Compressor separated by the Engine Gearbox from the Turbine is a good practical idea for maintenance at base.
Either side can be inspected and repaired without disturbing the other half.
Old idea and I understand the latest models now have a single stage centrifugal compressor which saves much wieght from the axial/centrifugal of early days.
In fix wing applications the engine Hanging from the wing supports to the ER/GB certainly help maintenance.
john
Either side can be inspected and repaired without disturbing the other half.
Old idea and I understand the latest models now have a single stage centrifugal compressor which saves much wieght from the axial/centrifugal of early days.
In fix wing applications the engine Hanging from the wing supports to the ER/GB certainly help maintenance.
john
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What else is there for light helicopters except possibly Turbomeca? An old design, yes, but this means proven, with something like 30,000 engines built to date and 200 million flight hours. And parts and service widely available.
What's the difference between C30P and C30R ?
C30P 206 L1 (retro) thru L4
C30R/3 OH58D with a kind of Electronic governor?
Civil here
Military here
Knock yourself out!
All small turbines will always use a lot of fuel. Even supposedly modern engines have similar SFC to the old 250 series. Problem is in the tip clearance of such a small engine relative to its size. Yes you could improve it but at what cost and for how long?
As the engines get bigger they have a better SFC but it tends to be reflected in the price. Check out a GE T700/CT7 SFC.
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The C30P is a GA application
The C30R/3 is a military variant.
The C30P is a non fadec traditionally regulated turbine.
The C30R/3 has FADEC
Has anyone had an uncontained faluire of these turbines yet? I know an AD was issued for a containment ring, AD 2005-10-13. This only applies to the series 2 engines (ie, C20,B17,C20R ect). Which in theory, should have "contained" a falure of the hot section. Somehow I doubt this after inspecting a containment ring and doing some math on the rotating inertia of the turbine section.
Anyone had anything with the series 3 and 4?
The C30R/3 is a military variant.
The C30P is a non fadec traditionally regulated turbine.
The C30R/3 has FADEC
Has anyone had an uncontained faluire of these turbines yet? I know an AD was issued for a containment ring, AD 2005-10-13. This only applies to the series 2 engines (ie, C20,B17,C20R ect). Which in theory, should have "contained" a falure of the hot section. Somehow I doubt this after inspecting a containment ring and doing some math on the rotating inertia of the turbine section.
Anyone had anything with the series 3 and 4?
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It can be done, all it takes now is money
All small turbines will always use a lot of fuel. Even supposedly modern engines have similar SFC to the old 250 series. Problem is in the tip clearance of such a small engine relative to its size. Yes you could improve it but at what cost and for how long?
As the engines get bigger they have a better SFC but it tends to be reflected in the price. Check out a GE T700/CT7 SFC.
As the engines get bigger they have a better SFC but it tends to be reflected in the price. Check out a GE T700/CT7 SFC.
There have been two reseach engines that I know of that made around 750 hp and had an SFC at full power of under .45 lbs/hp hr (which is actually as good as the T700). The technology is out there to do it, and one of those engines was a low cost solution. Do some reasearch on the Army SHFE program.
All it takes is money to finish the development and certify the engines, but the technology is there.
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RVDT,
Have disagree with you on RR250 vs. T700/CT7 pricing. The T700 offers considerably more bang for the buck, especially now that GE Lynn and CCAD have got the TBOs under control.
T700-701Cs (and Ds) typically sell for $650K to the DoD, which equates to about $330 per shp. Rolls charges the DoD $560K for the 250-C30R/3, which equates to about $780/shp. Rolls' commercial pricing for spare C20/C30/C47 engines is even worse...not that Turbomeca is much better.
The sad thing is that we're still using what is at heart a late 1950s engine design. The NASA GAP program (remember that?) was supposed to give us a 250 successor in the shape of the TSX-2, but the technical problems encountered by Williams on the lead FJX-2 (FJ22/ER22) fan engine (mainly related to scaling issues and the complexity of the three-spool layout) killed the program.
Honeywell's Small Heavy Fuel Engine seemed like a potential successor-to-the-successor-to-the-250, and Honeywell says the engine has met most of its goals (testbed achievements including a 57% increase in power:weight, a 24% reduction in cost and an initial 13% reduction in SFC), but the DoD doesn't seem to be in any hurry to put the engine into production.
I/C
Have disagree with you on RR250 vs. T700/CT7 pricing. The T700 offers considerably more bang for the buck, especially now that GE Lynn and CCAD have got the TBOs under control.
T700-701Cs (and Ds) typically sell for $650K to the DoD, which equates to about $330 per shp. Rolls charges the DoD $560K for the 250-C30R/3, which equates to about $780/shp. Rolls' commercial pricing for spare C20/C30/C47 engines is even worse...not that Turbomeca is much better.
The sad thing is that we're still using what is at heart a late 1950s engine design. The NASA GAP program (remember that?) was supposed to give us a 250 successor in the shape of the TSX-2, but the technical problems encountered by Williams on the lead FJX-2 (FJ22/ER22) fan engine (mainly related to scaling issues and the complexity of the three-spool layout) killed the program.
Honeywell's Small Heavy Fuel Engine seemed like a potential successor-to-the-successor-to-the-250, and Honeywell says the engine has met most of its goals (testbed achievements including a 57% increase in power:weight, a 24% reduction in cost and an initial 13% reduction in SFC), but the DoD doesn't seem to be in any hurry to put the engine into production.
I/C
Problem is in the tip clearance of such a small engine relative to its size
falls off sharply when the average tip clearance becomes greater than about one percent of the blade height
Although RR is calling their new engine the "RR300," it is on the same type certificate as the 250 series. Kind of the same thing as Hughes calling the 369 the "500." Just some differences is all. I've got tons and tons of hours logged underneath 250's, and I'd fly 'em to the ends of the earth. And back. And I know they'd get me both ways.
Now, the engine I'm flying behind is a big, round, belching, farting, roaring, noisy, uncorrelated 700 h.p. seven-cylinder beast, and I dearly miss my relatively quiet little RR 250 sewing machine. The things we do for a living
Now, the engine I'm flying behind is a big, round, belching, farting, roaring, noisy, uncorrelated 700 h.p. seven-cylinder beast, and I dearly miss my relatively quiet little RR 250 sewing machine. The things we do for a living
.
It will always be the Allison 250 series to me (old habits etc.) but .. one of the all time great general aviation turbines along with the PT6.
Thoughts about the RR250 Series
It will always be the Allison 250 series to me (old habits etc.) but .. one of the all time great general aviation turbines along with the PT6.
I think the RR250 technology is well past its used by date, but like Cessna, they build the same reliable airframe and keep on going, and get orders!
But preferably, I would rather operate the Turbomeca engines for their ease of start & reliability, and operate LTS101's for their cost effectiveness & simplistic approach of keep costs down during maintenance. Good performance figures for money too
Cheers, KP
But preferably, I would rather operate the Turbomeca engines for their ease of start & reliability, and operate LTS101's for their cost effectiveness & simplistic approach of keep costs down during maintenance. Good performance figures for money too
Cheers, KP
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The small GA aircraft turbine engine market is a tough business. It's expensive to develop, certify and tool up for a new engine design. The small turboshaft segment (ie. the RR250) is very few numbers and relatively low price, so it is difficult for an engine OEM to recover their non-recurring costs. That's why you see little significant (non-military) development occurring with these engines.
Even in the large commercial turbofan engine market, the OEM's don't make much profit on the sale of new engines. Most of their profits come from sales of spare/replacement parts.
Even in the large commercial turbofan engine market, the OEM's don't make much profit on the sale of new engines. Most of their profits come from sales of spare/replacement parts.
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But isn't this all a bit of inflating one's importance with turbines? Let's be honest here - they can charge these kind of money because they're on the type certificate as the only engine that particular aircraft can use. It's what is called a 'captive market'.
Engineering-wise, there is nothing today that suggests they would be that hard to make. The tolerances are far lower than in many other industries where none such price hiking appears. Let's not forget they were certified and approved when they were still hand made on lathe's and manual mills. Today we have robotic CNC vertical mill stations that have more productivity and much higher tolerances. Neither are the materials used very exciting or expensive. I don't believe for a second these aren't downright cash cows for RR, GE and P&W. Nobody can with a straight face tell me a 250 or a PT6 costs $600.000 to make. The R&D and the certification costs were recouped decades ago. What we're left with is corporate bullying.
The basics of capitalism apply here as everywhere else. The reason they're not selling very many of these engines and why their R&D costs are high per sold unit is - surprise! - because they're too bloody expensive. We could have had a myriad of small turboprops in every LSA and Cessna since the 60's, but they chose to ignore that because the times were good and the military could be relied on to overpay for their stuff - ever wondered why every aerospace manufacturer ever devised has gone after military contracts? One doesn't have to be a genius to figure that one out.
Make a certified 100-300shp turboprop and sell it for the same as a piston engine and you'd see massive sales. Bitching about how they don't make any money on their $30 million a pop GEnx engines for the 787 - excuse me if I don't immediately shed a tear and buy too much into that one (if you take future sales into account). If the RC guys at Jetcat, Wren and AMT can make working turbines in their sheds and sell them for $3000, the most certainly RR and the good old boys can make money selling theirs slightly bigger ones for $600K a pop. Yes, I know there are differences between the examples, but they're more similar than they are different.
Engineering-wise, there is nothing today that suggests they would be that hard to make. The tolerances are far lower than in many other industries where none such price hiking appears. Let's not forget they were certified and approved when they were still hand made on lathe's and manual mills. Today we have robotic CNC vertical mill stations that have more productivity and much higher tolerances. Neither are the materials used very exciting or expensive. I don't believe for a second these aren't downright cash cows for RR, GE and P&W. Nobody can with a straight face tell me a 250 or a PT6 costs $600.000 to make. The R&D and the certification costs were recouped decades ago. What we're left with is corporate bullying.
The basics of capitalism apply here as everywhere else. The reason they're not selling very many of these engines and why their R&D costs are high per sold unit is - surprise! - because they're too bloody expensive. We could have had a myriad of small turboprops in every LSA and Cessna since the 60's, but they chose to ignore that because the times were good and the military could be relied on to overpay for their stuff - ever wondered why every aerospace manufacturer ever devised has gone after military contracts? One doesn't have to be a genius to figure that one out.
Make a certified 100-300shp turboprop and sell it for the same as a piston engine and you'd see massive sales. Bitching about how they don't make any money on their $30 million a pop GEnx engines for the 787 - excuse me if I don't immediately shed a tear and buy too much into that one (if you take future sales into account). If the RC guys at Jetcat, Wren and AMT can make working turbines in their sheds and sell them for $3000, the most certainly RR and the good old boys can make money selling theirs slightly bigger ones for $600K a pop. Yes, I know there are differences between the examples, but they're more similar than they are different.
Last edited by AdamFrisch; 18th Jun 2011 at 08:10.