Yeah, I have driven some really amazing TD cars, but the laws of physics apply equally to all things (except the F22).

Wanna run JetA fine, buy a turbine. :ok:

Anything to do with how little power they produce when the turbo fails? :{

They belch black smoke distress signals and the fuel consumption goes into the ****ter, but generally they can keep running to a degree.

Yup. FADEC adjusts injectors for inlet pressure & temperature. To the maximum extent that it is programmed for.

If that happened over the mountains, I would ... increase power on t'other engine to compensate.

You wouldn't fly a single over the Rockies now would you Jaba? :p

Seriously though, once the bugs are ironed out of a new design (which will take several years to a decade) it is likely to be just as reliable as any other design. There is no evidence that a CI TC engine (to give it the strictly correct title) is intrinsically less reliable than an engine with spark plugs.

I can't see any difference really that all engines are compensates for altitude. Turbine or blown are all compensated can't see why this engine won't be any difference when it and if it get certified.
The test will be seen once it starts to fly. I'm sure there will be bugs it's going to be and if they can fix them.
Any one remember the hype over the thunder engine. It preformed better than the turbine engine in a 690 commander as I recall. Then sold some stc certified now gone and stc removed.

Time will tell.

Cheers

Andy
The inlet of a turbo scroll is convergent. This is before any gases are released across the turbine. Then the scroll continues to convergent path till the end this is to keep the velocity up across the whole of the disc to keep the forces equal across the centre bearing. Aircraft turbo centre bearings are made of aluminium any force that's not centralised will wear the bearing out extremely fast.

Px is distributed equally than as you say there would be no use for the scroll to continually decrease in size.

It dose not matter if it avagas engine Diesel engine or a gas turbine from an small Alison 250 to rb211 they all work on the small priceable velocity 1st the px change across the disc.

Now late model turbos in cars use variable vanes instead of a waste gate. The opening and closing of the vanes changes the velocity onto the disc.
In a gas turbine the same is used on the compressors to stop compressor stall on start up and low speed.

Cheers

Andy,

Ahh but the mixture knob fixes that ;) A sweep will find the best of a bad day. :ok:


Yr Right, have a think about what it takes to run a compression ignition piston engine at altitude and what happens with a substantial loss of boost from a simple coupling, not a turbo failure even.

Jabba
The penny has just dropped. Are you saying that at altitude not enough air means not enough compression to light the fire? Would sort itself out at lower altitudes but over the Seirra Nevada the silence would be frightening............

I think you will find the four stroke CI engine will drop off slower than a SI engine with a failed turbo.

I have heard that on the SMA it is possible for the diesel fire to go out on descent, which is why I believe they have a minimum descent power requirement.

On a liquid-cooled engine though, this is less of an issue because the cooling system can be thermostatically controlled to limit the rate of cool-down.

Having said that, since you can start and idle a modern diesel engine at the top of most mountains (FL100-120) I'd say the chance of losing ignition for a diesel engine because an inlet hose burst or fell off is pretty remote, especially under any reasonable power level that still remains. The beauty of a diesel engine though is that it doesn't rich misfire, hence the black smoke.

Well ive got to say ive never heard or seen an induction tube fail or come undone. That just comes done to simple maintenance procedures. Also never had a complete turbo failure ethier they give signs well before they die.
What may be interesting is if they able to put it in a px airframe and how they get a larger blower into the engine cowl.
and with one control it will be idiot prove lol
Cheers

Interesting, a question for those who have flown behind either the SMA or the Centurion. With engine control, is the engine speed governed by power settings or pitch settings? I have always assumed that governor settings would be controlled by fuel input. In effect, if you go from cruise to climb, engine senses rev change and automatically inputs more fuel. Till WOT, pitch remains at cruise setting until revs start to drop then pitch changes to maintain revs....automatically.....autothrottle for lighties?

I am an avgas fan and could not be botherd using google....so my question is....Can you run your Toyota Land Cruiser on JetA or could you run your PT6 on automotive diesel?

sms777:
In both cases, the answer is yes - but in both cases nearly all the manufacturers recommend against it.
It all comes back to the fact that each fuel is refined for a specific purpose, and refined to fuel specifications that apply to each type of fuel.

In the case of the Landcruiser - older diesel Landcruisers (with mechanical fuel injection) run quite happily on a mixture of kerosene and crankcase oil (not more than 5% oil).
However, newer models with electronic fuel injection have much tighter parameters for the fuel viscosity, and the ECU can sometimes reject the fuel once those parameters are exceeded. In other words, the engine will refuse to fire and a fault code will show.
I am not sure if JetA would be outside the viscosity parameters of regular road diesel in an electronically-injected Landcruiser. There is a difference in SG between the two fuels.

As for using diesel in a PT6 - yes, you can, but most manufacturers do not recommend it, because of the high possibility of the diesel fuel gelling or freezing.
Diesel fuel can be used in low level aviation operations, if the engine manufacturer approves.
JetA has lubricity improvers for improved aviation engine life, and other additives that allow it to still function satisfactorily as a fuel at the extremes of temperatures encountered in aviation at higher altitudes.
This question has been discussed before at length, on this forum - http://www.pprune.org/tech-log/444111-diesel-fuel.html

The Su-25 could run on diesel for up to 4 hours. From what I understand it had a toolkit that allowed the pilot to make off field alterations to facilitate this to allow unscheduled front line landings (assuming on roads) to refuel from vehicle diesel and limp home. I don't think many commercial jets or turboprops would have this ability.

If you can burn it you can run it in a turbine. Some aircraft with pt6 alow you to run Avgas for a short time. This limits however the o/h periord but

I've seen a Alison 250 modified to run on coal dust. Not for aircraft use but
Cheers

FADEC might be the temporary saviour of traditional engines, but as I see it, there will be a day where the oil companies simply refuse to manufacture a fuel that sells in miniscule volumes compared to Jet A and even automotive fuels. On top of that you need special distribution systems. I can see Avgas being priced out of the market in my life time.

In many countries you cannot get Avgas at any price. In that regard I think diesels are the only way forward. Aerodiesels are still in their infancy today, but I believe given enough time and money the problems will be resolved. They simply have to be.

Many engines will run on anything combustible, the real issue is how long it will put up with it, what affect it will have on it, how practical is the fuel, such as power output, supply, weight etc... The GE LM2500 is a derivative of the CF-6, it's used in the ANZAC frigates, but it is modified for this use with marine fuels.

As with any other piston engine, engine speed and propeller RPM are tied together. But I think you're asking more than that!

The FADEC controlled manifold pressure (via turbo wastegate), fuel flow (via injector timing) and propeller pitch (via oil valve). From memory there were about sixty inputs into the FADEC to tell it what was going on in & around the engine.

The power lever angle is resolved into an electrical signal, so the FADEC knows what power is being requested. Each power setting is associated with a particular RPM, so the propeller control valve would move to change blade angle to change RPM to match the target value. Entering a climb, reducing speed, would cause the FADEC to command a smaller blade angle to maintain RPM. That doesn't set power however. The FADEC could set power independently of RPM, by adjusting MAP and injector timing.

Fuel flow would be set by the FADEC according to a specific schedule - obviously depending on inlet manifold temperature & pressure, fuel type (diesel, JetA, JetA1 etc), and many other variables. The FADEC would adjust fuel flow and manifold pressure to maintain the commanded power setting at any given TAS, altitude and RPM.

It worked very much more smoothly than traditional engines with three levers.

I once had a propeller control valve malfunction in flight. RPM was cycling between about 1200 and 2300 RPM, with a period of 20 seconds or so. At first I thought it was a sputtering engine, but power output was rock steady and there was no yaw. Strange feeling! But it illustrates the relative independence of RPM and power output in these engines.

Obviously I would be more impressed by an engine that didn't fail at all. But, given that was early days of the Thielert engine, things have improved since. It is IMO the way of the future.

MMMM Fadec $$$$$$$$$$$$$$$$$$$$$$


Remember kiss
keep it simple stupid


Cheers

yr right - I for one, also love the KISS principle. Unfortunately for us dinosaurs, substantial amounts of electronics that control a wide range of engine control inputs are here to stay.
If it wasn't for modern electronics, engines would still be relying on very imprecise engine fuelling setups, imprecise and less reliable ignition systems, and an inability to adjust a wide range of other important combustion controllers.

The main problems with electronics come with the "cheapest arrangement we can purchase" mentality, and the lack of knowledge of actual operating conditions by engine designers which results in poor positioning of electronics, and less-than-ideal-design wiring connectors and wiring harnesses.

Electronic components often have a huge profit margin in their selling price that is designed to recoup design and research costs.
If competition via aftermarket manufacturers is introduced, prices rapidly fall to realistic levels.
Unfortunately, aviation is still full of the "captive customer" or "captive market" production principle, that ensures high costs for owners.

Remember flat screens TVs that where upwards of 20k when it's first here now you can get them for $100. Now why is that. Mass production. Aviation isn't like that. It's a unequivocal low production where 500 aircraft is a great deal.
Now nothing in aviation is cheap. Nor dose it ever get cheaper. Litagation insurance is the main reason. Yet what is developed in aviation finds it's way to the greater public in other areas. Carbon fibre is a prime example.
I change a turbine disc just recently. At $2000 each turbine blade and 54 in a disc they use to be around $550 ea. that's over 100k just in blades.

Fadec fine but in GA I have to ask why. What happens when it stops. Now remember it breaks. Who has spares. Equipment to look after it. Who then pays for that. What happens if it stops in the middle of no where. I'm not against change but the cost is going to hurt. I've heard flying schools removing glass screens and going back to dials because they can't afford the cost of a break down at arond $25k a hit for a replacement. Won't hurt my pocket but may hurt yours.

onetrack

A good simple carby setup is more efficient than a good EFI set up in a modern car. Only problem is the carby set up will go out of tune quicker. Manufacturers plump for the less efficient EFI as it helps guarantee them a known state of tune and therefore known level of emmissions. Electronics are not universally better. Yr right makes some very good points as well.

Yr right - you're right. The cost is going to hurt, and it'll hurt more if an integrated circuit board dies in the middle of nowhere.

However, it's the way of the future. AFAIK, general aviation is now the only place where we buy 1950s technology with 2010s dollars. No disrespect intended to that technology of course - it's rugged and durable. But cars, boats, trucks, racing cars, all have moved to fuel injection, electronic ignition, hi-tech fuel economy, replace-it-don't-fix-it.

It's getting harder to buy avgas too, although that's a different argument.

FADEC is used quite successfully on light turbine helicopters, operating in very remote locations.
The EPS Vision 350 engine has a bosch general aviation technology control system so backup shouldn't be an issue.

CI is the way to the future, as long as initial costs can be lowered.

Do you have a source for this?

A carby has a better mixture of the fuel to the air. That's why a 500ci prostock car can run at over 200 mph and mid 6 sec runs. This is not new information just everyone thinks cause it the latest it must be the greatest


cheers

I have heard that about NASCAR engines from several engineers, but cant get my head around it. Obviously the NASCAR engines are built to perform well at a precise rpm and have a very narrow operating rpm range. Below 4000 rpm they buck like horses but come on song at 7500. The intakes, heads and valves are optimised for a specific rpm.

So why wouldn't fuel being squirted through an injector at 27,000 psi atomise even better than a simple pressure drop through the venturi of a carburettor?

Plus the carby engine has the added advantage of being immune to carburettor icing ! Makes you wonder why they ever mucked about with this new dangled fuel injection stuff in the first place:p

Constant Mass Flow
 

A carby is very good at mixing fuel and air at the appropriate ratio when mass flow is constant, eg an aircraft engine at constant RPM. When you change the RPM constantly such as in a car in traffic the carby cant keep up and this is when fuel injection comes into its own.

I would be interested to see if petrol direct injection would improve combustion/atomisation/metering over a carby in an aircraft engine

It does, unless you're a luddite, in which case it doesn't

yr right is spouting so much ignorant ****e here, I'm surprised that everyone didn't pick up on 27/09's subtle satirical post...

Yr right...now you're gilding the Lilly! You know full well the only reason that prostocker is running a carbie is because the rules tell them to!

I can tell you it used to take me half a morning and two runs for a plug chop to get my 250ci tripple SU powered XP hardtop to run into the 13s...with a little nitrous...any late model car will stay in tune months longer. Mine would change with the weather! My son's car will run tens any day of the week on a factory turbo and electronics with only a different wastegate and intercooler.
To quote a movie line..."His grandmother wouldn't be scared to ride in it" where my car ran a huge cam solid lifters and a 9inch that was more locked than it needed to...electronics are the go!

Bus driver having crewed on a pro stock car I know the rules. Yes that is true but then have a look at any other class and then look at what is achived with just 8 thoarts. Mid 6s at over 200 mph I think it's impressive then consider what initro cars where running with them times. A carby tune at the right end will produce more power than an injection in a N/A environment.

Cheers

Yes, it is impressive what performance can be had out of a carbie that resembles four buckets tied together and over 500cubes of highly tuned induction system...enough to suck the air out of a 20ft container in a minute.

Okta, thanks for that. Pilots are so use to revs held static by the prop and having to watch manifold pressure where diesels fuel up the instant the load comes on...counterintuitive.

So no one has a source for this.

I went to a lecture by a Rover engineer some years ago who stated that they got more performance out of a 3500 (V8) SD1 car with Weber carbs than with the best EFI set up. The car buying public was clamouring for injected cars at the time though, so the Rover Vitesse was injected, simply because that was what would sell.

Going back to aero-diesel engines, mechanical injection is simple and reliable, however it is common rail (electronic) injection which gives the real gains in performance, economy and engine longevity, as the forces in the engine can be controlled so much better.

Piezo injectors give even better control and can allow more power to be extracted from an engine, but are, or at least were recently, prone to unreliability.

With electronics on a diesel aero engine, you have a choice between mounting the electronics on the engine or engine mount and have them shake around with the engine, or mount them in the airframe and run the risk of the wires fatiguing with the relative movement to the engine.

The reason for a carby preformance is it better atomises the fuel into the whole volume of intake air. It's down size is it harder to control than efi.
It the hymomics of the desiel that's the worry for me.

Bet you can't run this diesel Lean Of Peak (LOP) :E

No but im sure they will try cant run a turbine lop but they try that as. then they get a nice bill ti replace the blades etc and don't touch it again


cheers

There is no basis in fact for this claim. The only advantage it might have is when the carb is positioned way upstream giving the fuel more time and surface area for vaporization. On F1 engines in the past, the injector was placed at the inlet bellmouth entry for this very reason. Of course it doesn't come without penalty, which is increased air-fuel ratio excursions during transient operation.

Most phased port injection systems are injecting on the back of a closed inlet valve - immediately after valve closing for sequential systems - so a large part of mixture preparation is by evaporation.

You worry about some strange and irrelevant stuff...