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FADEC - how exactly can it improve performance or fuel consumption on our piston engines

BackPacker wrote:

Anybody flying a diesel engine (e.g. Thielert 2.0) already has that.

Diesels work different from our gasoline aircraft engines, so it’s not comparable. But yes, the later Thielerts are great engines.

LeSving wrote:

You cannot optimize an engine for best economy, since that is dependent on aircraft speed, winds, and all kinds of things. An engine has best efficiency and max power.

Actually, economy is indeed the right word, as the aircraft engine has several efficiencies, depending on what you intend to describe (inner efficiency, outer efficiency, installed efficiency, total efficiency, etc.). That’s why engine manufacturers and aircraft manufacturers refer to “best economy cruise” in their manuals.

a_kraut wrote:

Wouldn’t it be simple to implement automatic leaning for best economy except when the throttle is put full forward in which case the engine is leaned to best power?

When I cruise a normal aspirated engine in FL80+, usually the throttle is at or near full forward. It’s more complex than that.

mh
Aufwind GmbH
EKPB, Germany

Peter wrote:

Even if you did it, almost nobody would buy it unless it is 100% standalone, like mags are. If it needs battery power etc etc, it’s a no-sell.

As I have said, I deliver development, certification, manufacturing and after market service :-)

If the majority here want’s these retrofit boxes so bad, there might be a market.

mh
Aufwind GmbH
EKPB, Germany

Silvaire,

well, there are more than one ways of doing these things. You can use stepper motors or you can do it all by wire. Boeing still moves their throttles Airbus don’t. With FADEC, I don’t actually see the need for keeping a direct connection other than for a backup.

The way you regulate them, also there different approaches, the way you said and others. In jets, you define the way you want to operate the airplane by cost index, which is a factor which will determine the speed and consumption you fly. For a GA plane, I’d say for pilots sake it would be easier to define a couple of power settings which then, via the FADEC, are translated to the engine.

When I take on a new POH to check out an airplane, I always split performance into high speed, normal and long range cruise. High speed optimizes on speed, normal is usually around 65% and long range would be the setting getting maximum range. To the pilot this could mean in one implementation that you can construct a throttle with 3 or 4 detents, one for MTOP, one for Climb, HSC, NCR and LRC. Or you go the Airbus way and have two detends (MTOP/CLIMB) and then select the desired power mode via a switch panel. Move it out of climb detent and it becomes a normal throttle.

The question of course is if our Lyco/Conti saurus plants are ideal for that. But I suppose with proper electronic ignition and translation of the FADEC output to the mechanical input of the engine, even those could be made to work for that. You’re right, that would probably require stepper motors or servos to do that.

LSZH(work) LSZF (GA base), Switzerland

mh wrote:

Diesels work different from our gasoline aircraft engines, so it’s not comparable. But yes, the later Thielerts are great engines.

Diesels require a less electronic complexity than a gasoline engine to achieve automatic engine management, but much more mechanical complexity than a similar low power level gasoline engine.

I love my simple planes, for their simplicity as much as their functionality, and nobody is ever in my lifetime going to add a bunch of engine management stuff to them.

FADEC in jets tends to have (after engine start) primary power from PMAs (permanent magnet alternators) which run off the accessory gearbox with ship’s power as standby.

Turbine stuff build quality is orders of magnitude better than GA build quality. We fly with crappy alternators from Ford trucks from the 1970s. And everybody in the market knows this, which is why IMHO almost nobody would buy a product for a Lyco/Conti which relies on “ship power”. Mags may be 19th century but the probability of losing both is really small (unless overhauled by the same dodgy shop, which I think happened to somebody on EuroGA recently ).

It would not be hard to develop self powered mag replacements, and if you can do that, you also have a solution for the D3000 single shaft dual mag market.

I think that very often the reason companies don’t develop some product is because deep down they know nobody would buy it, but they can’t say that because they don’t want to offend people who buy their existing products, so they blame certification costs.

If you are going to do a full FADEC (not just a mag replacement) then a marketable product would be a box which has all the electronics and HV generation, and the two mags would be replaced with two alternators which would provide a dual redundant power for this box.

When I cruise a normal aspirated engine in FL80+, usually the throttle is at or near full forward. It’s more complex than that.

Yes; it would have to be done transparently.

But it might be sub optimal. Currently, say I want to climb from FL100 to FL120. I can either do a max-perf climb (set 150F ROP and max rpm), or I can do a max-economy climb (just set +300fpm or so, and keep an eye on the CHTs). With FADEC you would not get this option, so it would have to go for the max-perf mode.

This has all been solved in cars. They tend to go very rich when you put your foot right down; there is no effort to do anything lesser. But in a plane at FL080+ the throttle is already wide open, so the only usable input would be the selected VS or pitch.

You can use stepper motors or you can do it all by wire

The stepper motor thing is a redherring. It is just a servo motor, with the advantage that it gives you high torque at rpm down to zero, and avoids the need for a tacho. It would still need a gearbox, and you would not be able to overpower it unless a slipping clutch is provided (as in King autopilot servos).

Adding servo drive to throttle, rpm and mixture would be a huge STC – bigger than anything we have ever seen in GA. And different for every aircraft type, because they all have different layouts and dimensions.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

This has all been solved in cars. They tend to go very rich when you put your foot right down; there is no effort to do anything lesser. But in a plane at FL080+ the throttle is already wide open, so the only usable input would be the selected VS or pitch

The throttle control would direct the engine management to a certain power level. Pre determined maps based on altitude and outside air temp would select the most fuel efficient way to generate that power level. You’d still have to know when max power selection would result in a lower efficiency than a lower power selection, and maximizing mechanical efficiency does not regardless maximize overall aircraft efficiency.

The advantage of throttle by wire is that the computer can reduce rpm to minimum and throttle/lean to a selected percentage power at low altitude, then as the plane climbs with unchanged percentage power demand setting the throttle will open automatically (first) and then the prop speed will increase. All without pilot control.

Airspeed and cowl flaps could be mapped into the solution for a given power level, to control CHT.

Why anybody would want to own something with all that crap on it is however beyond me.

Last Edited by Silvaire at 31 Mar 19:17

I think the only advantage of FADEC is it works better than the average pilot for engine lifecycle and fuel economy, you will get less variance between “good engine” and “low hours” in service, this is not the case when you put a human hand behind the engine….

On new touring aircrafts that have FADEC engines, they tend to be designed for max economy in their POH figures and aerodynamics (that is what you sell)

Paris/Essex, France/UK, United Kingdom

mh wrote:

as the aircraft engine has several efficiencies, depending on what you intend to describe (inner efficiency, outer efficiency, installed efficiency, total efficiency, etc.)

The obvious parameter here is fuel efficiency. You want to know the points where the engine produces most HP per unit fuel for a given RPM, throttle position and inlet air density.

Peter wrote:

One would also need to bring CHT into it, which you probably don’t need to do with a watercooled engine (well assuming the cooling system is correctly sized).

You only need CHT if the heads are not properly cooled. ULPower has huge fins and also dedicated oil cooling of the heads. Rotax has water cooled heads. Lycoming relies on the pilot adjusting the mixture to cool the heads. This works with minimum engineering of proper cooling, but at the expense of poor fuel economy among other things.

Peter wrote:

But in a plane at FL080+ the throttle is already wide open, so the only usable input would be the selected VS or pitch.

You forget that you have FADEC. There is no reason why WOT needs to equal max power. WOT only means WOT.

EASA has already certified the Lycoming TEO-540 for the Tecnam P2012. FADEC, turbo, single lever control. Looks cool, but I wonder what it costs

The elephant is the circulation
ENVA ENOP ENMO, Norway

LeSving wrote:

Lycoming relies on the pilot adjusting the mixture to cool the heads. This works with minimum engineering of proper cooling, but at the expense of poor fuel economy among other things.

Actually this results from good airframe engineering to minimize cooing drag at the higher speeds associated with higher powered and/or more aerodynamic aircraft. The cooling system is not designed for the limited period during which the plane is climbing at lower speeds, and as a result the plane is faster and/or lighter. For low powered aircraft that have a narrower speed range, this is not an option.

My Lycoming powered plane is relatively slow, 120 kts indicated with climb at 80 kts, so CHT is not an issue at any time. Assuming a sea level takeoff, I’m progressively leaning from 1000 ft agl upward. If the same engine were installed in a faster cruise speed plane, you’d need to watch CHT on climb.

Last Edited by Silvaire at 01 Apr 01:45

That Lyco PDF linked by LeSving IOM_TEO_540_C1A_pdf is worth a read.

The list of sensors is impressive


This thing does 375HP!

The fuel flow is interesting; the linearity suggests they run the engine stochiometric, all the time there is enough cooling

I calculate 280 lb/hr to be 46.8 USG/hr and this is at 375HP.

It is interesting to relate the fuel flow at around 160HP (a typical IO540 65% cruise) to this. I make it about 17 USG/hr which seems way too high.

A lot of R&D has gone into this… I wonder who the launch customer was?

Administrator
Shoreham EGKA, United Kingdom
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