Turbine development

[keithmiller]

I was watching you tube channel yesterday and ran across some interviews about new products during Oshkosh . One of these was a new turbine from Rolls Royce.during the interview he mentioned working with Mooney but development had been slower than expected. One thing that caught my attention was the engine weights also half of the piston ! Has anyone heard anything dealing with this ? 

[KSMooniac]

Mooney was working with them before the 2008 crash if my memory is correct. I believe the intent was for a Jet A powered plane for the world market where 100LL is scarce. It would be optimized for flight in the mid teens, and likely slower than an Acclaim but with higher fuel consumption.

We all dream of a TP Mooney, but it doesn't make a lot of sense on an M20 that cannot be pressurized to get high enough where fuel consumption is reasonable.

If they can improve BSFC it might get attractive for us, but I don't think the physics work out with current tech.

Sent from my LM-V405 using Tapatalk

[A64Pilot]

While it’s true most turbines love altitude, turbines have done very well down low for a long time. Turbines do burn more fuel, but the fuel costs less and the weight of the turbine somewhat offsets the fuel burn. Helicopters and crop dusters both work almost exclusively at low altitudes, and both do very well with turbines.

Operational cost per hour of a turbine are actually lower than a piston, or not almost every crop duster built in the last few decades would have been almost all turbines.

‘What is the killer for innovation is the cost when spread over a production rate of likely less than one a month, probably takes 10 a month min to be profitable with realistic sales prices and 20 a month to really be real viable.

[carusoam]

There was a turbine in search of interest around here recently…

Could be the same?

Best regards,

-a-

[EarthboundMisfit]

These guys were at Oshkosh this year, and their engine is still being developed - https://turb.aero/

Some videos on YouTube of their engine too.

 

[aviatoreb]

16 hours ago, EarthboundMisfit said:

These guys were at Oshkosh this year, and their engine is still being developed - https://turb.aero/

Some videos on YouTube of their engine too.

 

It looks more efficient than I would guess - it says 

Specific fuel consumption
0.56 lbs/hp/hr
Fuel flow @ 150hp @ 10,000'
12.6gph / 47 litres p.h

I read somewhere what is it for a continental reciprocating - .49 lbs/hp/hr?  .45?  So if yes that would be 10.1gph for the same hp so the same cruise.

This is a 200hp turbine.  Its not for speed or for efficiency but you do get reliability and also jet a is easier to find around the world.  Its lighter too so that makes up the gap a bit on the extra fuel you need to carry.

[Schllc]

Their website says 150-300hp so it would seem they plan to have variants of the engine. 
I be ok never hearing or feeling another piston burp in my Mooney again. 

[keithmiller]

That would be nice ! 

[carusoam]

350hp would be nice….

with a prop that can be slid into beta….

This would make the short field performance a piece of cake…. 

Go Turbine Mooney!

Best regards,

-a-

[Will.iam]

Also you could do the chop and drop from altitude without the shock cooling worry and get very big drop if you put the prop in beta. 

[Hank]

1 hour ago, Will.iam said:

Also you could do the chop and drop from altitude . . . and get very big drop if you put the prop in beta. 

Is beta mode supposed to be used in flight???

[A64Pilot]

2 hours ago, Hank said:

Is beta mode supposed to be used in flight???

Depends on the aircraft, the Pilates Porter is Certified for Beta use inflight, normal pilot won’t carry Beta to short final, this guy doesn’t for example, but I have seen it done one by the French Military at an Airshow in Dax France, it’s incredibly impressive.

There are many Videos of a Porter descending pretty much vertical with sky divers, of course they have to be in Beta to descend as slow as a skydiver.

 It’s not uncommon for the Porter to beat them to the ground.

Its not uncommon for Crop Dusters to use Beta on short final. but they shouldn’t, they have not  been yet flown and Certified to do so.

It’s very possible for Beta to block airflow over the tail, and if that happens of course the result is an immediate dive, if your close to the ground, we’ll, that’s bad.

 

Edited September 14, 2021 by A64Pilot

[A64Pilot]

Be careful if you choose to try beta in flight, I have had a prop inadvertently go into Beta when I went I went to idle on downwind, what happened was it began to Autorotate, overspeed, prop governor suddenly caught it with a bang, then let go of course as RPM dropped within limits and prop began to autorotate again, I added throttle and it stopped.

Prop min pitch was set too fine, you can adjust a turbines prop min pitch to fine tune descent and this one was set too fine.

[philiplane]

Back in 2007-2008, Mooney contemplated a 500 HP version of the RR250 (420 hp) engine.

It needed too much fuel, cost too much, and required a tail redesign for the added HP, for starters. 

It would have been more viable on the M22 airframe. although a PT6 would have been perfect for that. 

https://www.avweb.com/air-shows-events/mooney-rolls-royce-look-at-turbine-single/

And shortly after, the bottom dropped out.

Edited September 14, 2021 by philiplane

[A64Pilot]

The Allison 250 was actually a Detroit Diesel built engine circa 1959 or so for the US Army to power a light observation aircraft. 

‘It’s a simple ancient design that wasn’t overly concerned with fuel consumption, and of course ended up primarily powering mostly light helicopters like the OH-6 and OH-58. We have come a long way since then with turbine design and especially materials 

The VLJ market exists in my opinion because the DOD funded development of a small turbine to power a cruise missile, it took tax payer money to get there, but that’s always been the case.

I don’t believe anyone will spend the $$ to develop a modern small turbo shaft engine, unless hopefully the DOD decides it needs or wants one for a small drone or something.

If that happens, then maybe we will get a small, modern, efficient turbo shaft for little airplanes.

The capability of greatly decreasing fuel consumption via a modern design exists.

When I worked at the Army test activity, they had put a T-800 engine in a Huey just to put time on the engine I guess, but the thing we pilots never thought about was that when they did the old Hubert went from a 2 plus hour endurance to an almost 6 hour endurance, the decrease in fuel consumption from the old Lycoming 1950’s T-53 to the modern T-800 was amazing.

The T-800 was meant for the Comanche. which was never built as after the fall of the Soviet Union, it was determined that we had no need for a super expensive aircraft to operate in an environment that no longer existed. that was a very efficient air defense which the Soviet’s had.

I don’t know what happened to the T-800.

Edited September 14, 2021 by A64Pilot

[philiplane]

The fuel efficiency problem with a turbine engine is insurmountable. Intermittent combustion (piston) engines handle low power situations more efficiently than continuous combustion engines. Turbine engines are suited for operations that Mooneys are not designed for. Mating the two just turns into massive compromises with disappointing results. 

[A64Pilot]

48 minutes ago, philiplane said:

The fuel efficiency problem with a turbine engine is insurmountable. Intermittent combustion (piston) engines handle low power situations more efficiently than continuous combustion engines. Turbine engines are suited for operations that Mooneys are not designed for. Mating the two just turns into massive compromises with disappointing results. 

It’s not really, turbines are relatively inefficient at part power, so if sized and designed for the mission they do relatively well.

But you can’t expect a 500 HP turbine to develop 250 HP efficiently, it won’t.

The difference in fuel cost also negates a lot of the increased burn

It’s entirely possible to design an efficient turbine that will operate a Mooney at lower then the flight levels and do so efficiently.

The materials exist now to do it, even the lowly PT-6 now uses single growth crystal compressor turbine blades, the secret to efficiency is an efficient compressor and very high operating temps, we can do both now, it just takes $$$, and the GA market simply doesn't support that kind of expense

[Jerry 5TJ]

3 hours ago, A64Pilot said:

But you can’t expect a 500 HP turbine to develop 250 HP efficiently, it won’t.

Isn’t it true that if you run the 500 hp turboprop engine at an altitude where it produces 250 hp while running near 100% RPM and near max ITT limit it approaches its best efficiency?  
 

[A64Pilot]

2 hours ago, Jerry 5TJ said:

Isn’t it true that if you run the 500 hp turboprop engine at an altitude where it produces 250 hp while running near 100% RPM and near max ITT limit it approaches its best efficiency?  
 

Yes, but it’s not a 500 HP engine at those altitudes, and it’s actually more of an airframe loss of drag that makes the aircraft efficient more than any increase in engine efficiency

‘For example the TBM 850 or whatever with its -66 Pratt is an 850 HP engine, gearbox limited

‘But the -67F meant for large crop dusters has the same engine “core” but it’s a 1700 HP engine, the difference is of course altitude, the -F model engine at altitude due to its larger gearbox meant to hold 1700 HP won’t make quite as much power as the -66 in the TBM at altitude.

So that’s largely the point, size an engines “core” to operate at the altitude the aircraft is meant to and your will gain a lot of efficiency that way.

P&W Canada for example has a line of Ag engines meant specifically for the Crop Dusters, so they have relatively large gearboxes and small cores, so they actually follow HP production pretty close to what a NA piston does, meaning they do well at seal level, but are dogs in the flight levels.

 

The “altitude” turbines are not much more than simply derating an engine, if for example you fly the TBM low, it’s eats fuel like it was free, because the core is at about 50% output.

 

Or said another way, the closer to full output you operate a turbine. the more efficient the engine becomes, largely due to the hotter its running. Raising the ITT limit with improved cooling, single growth crystal blades and ceramic coating is so that you can run them hotter, hotter means both more power and less fuel consumption.

Add in multiple stage compressor turbines ($$$) and variable inlet guide vanes (more $$$) and you get quite efficient, probably way more than GA could possibly justify, so unless the taxpayer funds it through the DOD, it’s not likely to happen

This explains a lot of it 

https://www.americanscientist.org/article/each-blade-a-single-crystal

Edited September 15, 2021 by A64Pilot

[carusoam]

The nifty turbine pulling Tom’s Lancair IVPT…. Built in the Czech republic… now owned by GE…

750hp Walter (?)

Great climb rates… but, if you don’t throttle back after reaching altitude….  Vne may become a problem….

Climbing too high in an unpressurized cabin can cause some serious O2 delivery/TUC issues…. Spend a lot on the primary and secondary O2 supply… 

NA PP thoughts only… not a turbine guy yet…

Best regards,

-a-

 

[Jerry 5TJ]

10 hours ago, A64Pilot said:

So that’s largely the point, size an engines “core” to operate at the altitude the aircraft is meant to and your will gain a lot of efficiency that way.

I know that at low altitudes my PT6A-35 (750 hp gearbox & about 900 hp sea-level thermal limit) with its fixed blade compressor stages dumps a lot of high pressure air out of its bleed air exhaust valve.  That’s not an efficient use of the engine.  
At 27,000’ it is much more efficient and the bleed air valve is closed so all of the compressor output is used.  Up there engine delivers about 325 hp to the propeller shaft while the core ITT is around 700C, near the limit. FF is 30-32 GPH.  
GE is developing a new version of the Czech turboprop design.  It is closer in size to the PT6A-67 series but it claims 10-20% improvement in SFC.   If those figures are achieved in the field that engine will be an impressive upgrade for TBM and PC12 sized turboprops.  It will be far too large for a Mooney airframe, alas.   
All that is nice, but when ATC holds you at 8,000’ the engine’s high altitude efficiency does you no good.  

[EricJ]

4 hours ago, Jerry 5TJ said:

I know that at low altitudes my PT6A-35 (750 hp gearbox & about 900 hp sea-level thermal limit) with its fixed blade compressor stages dumps a lot of high pressure air out of its bleed air exhaust valve.  That’s not an efficient use of the engine.  
At 27,000’ it is much more efficient and the bleed air valve is closed so all of the compressor output is used.  Up there engine delivers about 325 hp to the propeller shaft while the core ITT is around 700C, near the limit. FF is 30-32 GPH.  
GE is developing a new version of the Czech turboprop design.  It is closer in size to the PT6A-67 series but it claims 10-20% improvement in SFC.   If those figures are achieved in the field that engine will be an impressive upgrade for TBM and PC12 sized turboprops.  It will be far too large for a Mooney airframe, alas.   
All that is nice, but when ATC holds you at 8,000’ the engine’s high altitude efficiency does you no good.  

Is your air conditioning an air cycle machine or vapor phase?   Sounds like you'd be getting a/c for free with an ACM.

[A64Pilot]

Most engines bleed valve close on the ground at  well less than 100%, usually mid 80’s Ng to maybe low 90’s Ng 

‘I know of no engine this isn’t true, especially a PT-6, the bleed valve exists for acceleration from low RPM, but is fully closed way before takeoff power at seal level

Google PT-6 coke bottle test. it’s the ground test where you determine RPM that the bleed valve is fully closed.

http://blog.covingtonaircraft.com/2015/08/11/pt6a-engine-maintenance-basic-stuff-compressor-bleed-off-valve/

[A64Pilot]

The GE H series engine is the one I Certified in an aircraft and have a lot of experience with, it’s really just a Walter with a good compressor, the rest of the engine is the same, but it greatly improved the hot and high performance of a Walter.

‘GE has been for a few years building it’s big brother, it will still be manufactured in Czech, but it’s a pretty clean sheet design, it’s meant for the Cessna Denali.

‘One neat thing about the new GE engine is that quite a lot of it is 3D printed.

‘New engine is the Catalyst. I retired four years ago and expected it by now, so I don’t know where it is 

https://en.wikipedia.org/wiki/General_Electric_Catalyst