New 240hp turbine for light aircraft

[172driver]

Have a look at this baby (http://www.youtube.com/watch?gl=US&feature=player_embedded&v=NKVG1-mFlOI):

Interesting ?

PS: don't seem to be able to embed the video here

[Katamarino]

18 gallons an hour...ouch

[AdamFrisch]

Yeah, but at altitude that's probably 60% less in lapse rate, so not so bad. And in Europe where Jet A1 isn't taxed, this could quite quickly become cheaper to run than an Lycosaurus.

[B2N2]

DA42NG-V2? :}

I'll get my coat

[Denti]

Jet A1 is only tax free if it is used to fly commercial on international routes, at least in some countries in europe. Still cheap compared to avgas, but that is mainly because avgas is a rare and therefore expensive to produce fuel.

[peterh337]

16 USG/hr would be pretty reasonable for 240HP.

My IO540-C4 burns 23.5 USG/hr for 250HP, which is full rich, about 150F ROP and certainly not efficient.

The man presenting is Czech :)

[Noah Zark.]

Europe where Jet A1 isn't taxed,
How long would that be true if these (or any similar) engines began to be prolific?

[peterh337]

Jet A1 is now taxed for private use in the UK, on a self declaration basis. There are various exemptions e.g. training flights.

This tax has killed the case for diesel conversions instantly.

[VMC-on-top]

How much is tax on A1?

[silverknapper]

How long would that be true if these (or any similar) engines began to be prolific?

Sadly as mentioned above it isn't really true. Whilst in the UK the self declaration thing may not be strictly observed by some, in Europe the policy seems to be more charge first ask later. Add mineral oil tax etc and you're in to serious expense. Still not as bad as 100ll though!
In saying that as Peter says 18 per hour for 240hp seems fine. But if that's in the cruise as the guy said it will be 30gph or so at msl.
Could be an excellent unit for the right aircraft.

[mmgreve]

So they are claiming around 30mph speed advantage over a lycoming engine on the RV10

Wonder what they could acheive in a really efficient airframe, such as the planned Panthera from Pipistrel
Pipistrel Aircraft Panthera | Pipistrel (http://www.pipistrel.si/plane/panthera/overview)

Much lighter than the IO390 as well.

I guess it makes a lot of sense for longer missions where you plan to fly FL150 for long periods of time with the comfort of a turbine engine. Not ideal for a bimble just outside the circuit

[peterh337]

I don't see how they can claim a given speed.

So much depends.

With a turbine you do get a more efficient cowling shape, generally. But the fuel is heavier so you get less range even for the same SFC, and no turbine will match the SFC of a correctly leaned piston engine.

It's lighter but that merely severely screws up your W&B, requiring a very long mounting frame - see the Jetprop (http://www.jetprop.com) conversion. The resulting position of the nose gear could impact (pun intended) the prop clearance on grass :)

I'd like to see the real fuel flow at say 240HP, ISA. If they are doing 18USG/hr then they have a sterling proposition but I think they will have bent some rules of physics doing that because AFAIK nobody has got anywhere near that before.

[englishal]

Also turbines benefit from much higher TBO's - 3600 hrs or so. They cost more intially though, but are probably more reliable also.

[silverknapper]

Much more reliable. But the cost of the overhaul may not be for the faint hearted! And there's the hot section check to factor in also, again probably more costly than a new Lyco or Connie.
Maybe as its specifically aimed at light aircraft the costs will be more in line with reality. I hope so.

[achimha]

There's a rule of thumb saying that turbines start to make sense at 400BHP. I was told this is mostly a function of blade diameter as the main energy loss is due to the gap between the blade and the sheath and the larger the diameter, the smaller it is in relation to the whole thing.

One argument against turbines in single engine planes is that they stink and being placed in front of the cockpit, you get to breathe a lot of turbine exhaust. That alone would probably keep me from buying a single engine turbine.

[peterh337]

You should not be breathing anything at all. I have an electronic CO detector and it reads zero during normal ops. Sometimes, in slow flight, you get 10-30ppm and it goes off, and sometimes it picks up the exhaust from the plane that landed before me. But during flight, the reading is zero.

turbines start to make sense at 400BHP.

That's perhaps true for the 1960s Allison heli engines whose business Rolls Royce bought, and are trying to flog a 450HP one with a prop shaft on the end. There are some interesting developments now - example (http://www.bladonjets.com/). I have no financial interest in that venture but know the people behind it well.

But no turbine will match a piston engine for SFC. Even the huge and state of the art engines on a 787 only just about match a piston engine for efficiency.

[achimha]

You should not be breathing anything at all. I have an electronic CO detector and it reads zero during normal ops.

CO doesn't stink :) Every time I was on a single engine turbine aircraft, I noticed strong exhaust smell in the cabin, especially during ground operations. Turbine exhaust is oily and has a much stronger smell than petrol engine exhaust. In a multi engine turbine, you are not seated directly behind the turbines so it's less of an issue.

[peterh337]

What type of a/c was that?

I've been in a Jetprop (http://i101.photobucket.com/albums/m74/peterh337/jetprop.jpg) and flown a TBM850 (http://www.peter2000.co.uk/aviation/tbm850/index.html) for 1.5hrs but never smelt anything.

I know CO doesn't smell but if exhaust was entering the cockpit then CO would register on a decent meter - unless you are running peak-EGT or LOP in which case there shouldn't be any, but you won't be doing that during high AoA flight.

[Flaymy]

Stink? It's a wonderful smell, burnt Jet A1!

[AdamFrisch]

There's nothing inherently difficult in the design and manufacture of turbines with todays CNC machinery. It's got fewer parts than a piston. Therefore, it is possible to design a turbine that would cost less than any piston engine. All it takes is one visionary and it could be reality tomorrow. Don't expect it from the old guard, tho - they're to comfy with their overpriced military contracts to do an about face. It will have to be an outsider.

If this is the company, I don't know.

[abgd]

CNC's great for intricate shapes, but what of the exotic materials and techniques used to make large-scale engines operate at high enough temperatures to be efficient? (single crystals, cooling channels inside blades etc).

[peterh337]

You can't CNC machine flat-disk compressor or turbine disks.

The material ends up too thin.

Spark eroding is the way that Bladon do it, and they have patents on it.

Crude centrifugal compressors can be diecast or even sandcast, but engines that use those have poor efficiencies.

[AdamFrisch]

Peter - every single turboprop on the market has a simple one stage or two stage centrifugal compressor doing the majority of the work. The P&Ws, the Garrett's, the Allison/RR's. Exactly the same ones you find in turbos. Yes, the turbine side needs to be able to deal with the heat, but there are alloys that can readily do so without complicated cooling channels. You could make a simple power turbine with just one moving part.

Axial compressors are more complex, for sure, but you won't find them much on turboprops. OK, the Allison and the PT6 has a short, cold stage just before the centrifugal one, but they're only two stages or something and deal with completely cold air, so could probably be machined out of aluminium!

We have been fed so much b****it over the years, we don't know truth from fiction. Like the geared Lycoming and Continentals - remember those? "Oh, don't buy a geared engine whatever you do, the gearbox breaks down and that's why they have such short TBO". Funny, how the reduction gearboxes on turbines never do that, right? In fact, a PT6 has a TBO of 3600hrs and the Garrett TPE 331 has 5400hrs. How come those reduction gearboxes don't break down?

[abgd]

My understanding is that any fool can make a jet engine, but it's not so easy to develop a good one.

A compression ratio of 7 as the PT6 uses should still heat the air to about 200 degrees, which is above the temperature most aluminium alloys are comfortable at. Googling around suggests that the compressors are made of titanium and stainless steel.

As for the turbine stage... The higher the temperature it works at, the more efficient the engine can be. So of course it's possible to make an engine that works at a low temperature without using exotic and costly technology, but the chances are it won't work very efficiently.

[achimha]

"Oh, don't buy a geared engine whatever you do, the gearbox breaks down and that's why they have such short TBO". Funny, how the reduction gearboxes on turbines never do that, right? In fact, a PT6 has a TBO of 3600hrs and the Garrett TPE 331 has 5400hrs. How come those reduction gearboxes don't break down?

It's not that easy, really. From a gearbox point of view, reciprocating piston engines are much more demanding than smooth turning turbines with contant torque. The fewer cylinders, the more changes in torque, i.e. vibration on the gearbox. In a 4 cylinder 4-stroke engine, you only get one torque impulse every 180°. Diesel engines with their high compression are a lot more challenging.

[S-Works]

I can echo the comments about the smell of exhaust. Once of the turbines I fly is a Walther powered single knocking out 800shp. After a days flying I stink of Jet A1 from the exhaust. We don't get any in when in flight and but on the ground a spinning turbine is still running at around 60% on the gas generator which is a loit of exhaust swirling around and everything stinks from it.

I would imagine the same effect in converting a light aircraft and with a low wing one you have the issue of where to direct the exhaust to, pointing down will burn the floor and backwards the wing or doors canopy. One of SET's had to have the side windows replaced from heat bubbling before they redesigned the exhausts to point at a different angle.

Turbines may be the fantasy of the average GA pilot but in reality they are not that well suited to light GA flying and as Peter rightly states for that type of flying a piston engine is way more efficient.

[peterh337]

What you get from a turbine is great reliability.

I vaguely recall NTSB data showing a SE turbine being 5x less likely to go down than a piston twin.

Turboprops are unfortunately massively expensive - a TBM700 PT6 costs US$300k to overhaul, and while for that you get 3600hrs it is still a huge bite.

It's probably fine in a pressurised hull because you cannot smell anything when on the ground. I think this is why the Cessna Caravan's PT6 has the weird modified single exhaust which takes the gases underneath the cabin.

[Flaymy]

Peter

I thought that was to avoid great soot stains down the sides ...

AdamFrisch

Having shredded a GTSIO-520 because my then employer had me fly it beyond the 1600-hour TBO into the extension period, against all advice, I can say that is no fiction that you should be wary of these. Great engine when treated with respect and care. Smooth power, wonderful sound of the lazy 1700 RPM turns of a 7' prop. Not an engine for amateurish pilots or careless crews.

[AdamFrisch]

Yes, you are right about the piston engines being harder on the gear box. But still...

What I don't get is why they don't make gear reductions today with belt drives. They absorb a lot more jerkiness, have no life limits, need no lubrication, much lighter and are super reliable. Would be ideal to pair with piston engines. In fact, the Schweizer 300 helicopter have had them in the main drivetrain since the 60's. Rotax and Austro?

Flymy - the GTSIO, GSO's and the GTSO's were a bit of a special breed as they were so very highly strung. They pulled a lot of horse power from something rather small as to compete with turbines. This never is good for longevity. At the Aero Commander forum all the 685 owners with the GTSIO-520K's all complain about them and how they rarely make 1000hrs with at least something done to the top. But if you pull 435hp out of an engine that would normally give about 300hp, it's not really a surprise. Don't think the gearbox is the culprit here, it's the power. Still cheaper to run than a turbine, I suppose. Same performance, more or less.

I baby my geared engines and fly strictly adhering to the geared engine guru's recommendations - never touch the props on final, always keep the props running the air and not the other way around. Will see if it helps.

[englishal]

Peter, I vaguely recall reading that the B200 can have the engines zero timed for about $120,000 a side...Is the TBM really $300k ?

My TO360 cost about ~$45,000 to zero time, and if you divide that by the TBO I get $25 per hour. For a turbine based on the above (B200) and TBO of 3600, I get $33 per hour so not horrible costs.

[peterh337]

That's what Socata in France told me.

A TBM700 with a runout engine is about $900k. Engine overhaul is $300k, which sets the base price for an old TBM at $1.2M.

I would investigate further if I was in the market :)

[S-Works]

Our Walter G92 engines cost us about €180k to overhaul. They go to full life and there is no hot section inspection on them at anytime unlike the PT6. Life is 3000hrs. Its a constant production line in the maintanance hangers swapping them out!!