FADEC is 1980s Technology

[spiderweb]

They still build new PC-12s... don't they? Single lever on that one.

You cheated! :wink2:

 

[Ted]

Sorry, going to agree to disagree. Every engine parameter is a compromise. If you've ever seen the intake on a O-470 head after >1200 hours you would see that there is sufficient overlap on the valves to put deposits in the intake. That is a function of the compromise needed to start an engine at 550RPM, and still run it at 2700. Also, most of us run our bigger engines at or very near full throttle, and control the speed with the prop. This is another situation where cam overlap will play a part in efficiency at any speed over 1800RPM. If we can alter the cam timing to perfectly match the induction parameters of the intake and carb/throttle plate for many different regions, we wouldn't have to compromise as much on duration and overlap.

Everything is a compromise, correct. But the reality from what I've seen is that, when you're looking at a 2200-3000 RPM engine, you don't need a lot of compromise. We're not talking about a 7,000 RPM engine (or, egads, 17,000 RPM like on some motorcycles) here. Yes, it's a compromise, but not enough of one to matter on our engines.

I'm fine with agreeing to disagree.

The question is, would those extra pounds, and complexity be worth it. So far, the answer has been no, but at some point I would like to see some work done with VVT on aircraft engines. Fixed cam timing and duration are always a compromise. Moreso for auto engines which generally operate over a wide range, but still true for aircraft engines.

I think the answer you'll find is no. For one, the pushrod arrangement of aircraft engines doesn't lend itself very well to variable timing, so you get significant compromises there. A DOHC setup like what works best with a variable valve arrangement adds a tremendous amount of weight, not to mention engine width. Given that we currently have remarkable efficiency in our 60-year-old engine design, the best place to spend money and effort (with no weight penalty, no less) would be combustion chambers.

 

[Ted]

Certification of what? I work on a helicopter with a FADEC. There is no manual backup. Period. There is a backup FADEC, but there is no backup manual control. If both FADEC channels for an engine fail, then that engine quits.

This is how most FADECs are certified. A mechanical backup would weigh a good bit.

AFaIK, the valve overlap and timing is optimized for cruise RPM and there's a slight loss of volumetric efficiency at takeoff RPM. I suspect that the only perceptible improvement that variable valve timing could offer would be smoother and more efficient idle.

That is correct.

 

[Ted]

They still build new PC-12s... don't they? Single lever on that one.

Is it? The PT-6s I've flown still have 3 levers per engine.

Of course, one of them is basically an "on-off" switch.

 

[Capt. Geoffrey Thorpe]

Certification of what? I work on a helicopter with a FADEC. There is no manual backup. Period. There is a backup FADEC, but there is no backup manual control. If both FADEC channels for an engine fail, then that engine quits.

That's why most people won't fly turbine powered aircraft. Piston engines with the mechanical systems are so much more reliable - you will probably never see turbines replacing the big radials in comercial transport aircraft in spite of the speed advantage.

 

[Henning]

That's why most people won't fly turbine powered aircraft. Piston engines with the mechanical systems are so much more reliable - you will probably never see turbines replacing the big radials in comercial transport aircraft in spite of the speed advantage.

FADEC is not an issue exclusive to turbines, nor are the majority of turbines even FADEC equipped.

 

[Dan Thomas]

Umm, unless you're only going part way on your "redundant" EFI, it weighs a lot more than you think. Every sensor must be redundant, as well as every wiring harness and every ground strap, the brain box and ignition computer. They must also have faults detected or the utility of redundancy is lost. How do you detect the loss of a ground strap when there is a redundant ground?

You also have to put all this stuff some place where it won't get melted or vapor locked, and still have some room for engine cooling.

I think you're very rapidly going to design a twin.

You'll gain some performance, but not nearly as much as you might with spark advance. EFI's big gain over carbs is with adaptivity, and even that is lost on an aircraft with a red knob. As an engineer, I insist on specifying benefits when considering increasing complexity. They seem limited in this case.

And for the SMA diesel, it would require another injector pump and complete set of injectors. Pretty heavy stuff. Not much room for it, either.

Dan

 

[Dan Thomas]

Certification of what? I work on a helicopter with a FADEC. There is no manual backup. Period. There is a backup FADEC, but there is no backup manual control. If both FADEC channels for an engine fail, then that engine quits.

OK, so you don't have a manual backup, but you have a second FADEC. Redundancy is the certification requirement, I suppose.

What happens if the electrics fail?

Dan

 

[Henning]

And for the SMA diesel, it would require another injector pump and complete set of injectors. Pretty heavy stuff. Not much room for it, either.

Dan

Not if they go to a common rail system, everything is pretty light weight.

 

[Ted]

That's why most people won't fly turbine powered aircraft. Piston engines with the mechanical systems are so much more reliable - you will probably never see turbines replacing the big radials in comercial transport aircraft in spite of the speed advantage.

 

[darrell]

OK, so you don't have a manual backup, but you have a second FADEC. Redundancy is the certification requirement, I suppose.

What happens if the electrics fail?

Dan

During normal operation, the FADEC is supplied with 28vdc from an engine-mounted alternator. The engine-mounted alternator only provides power to that specific engine's accessories. However, in the event of failure, the FADEC is also supplied with 28vdc from the aircraft electrical system, which includes two more generators and a battery.

But to specifically answer your question, if all electrical power is removed from the FADEC, then that engine will shut down.

 

[spiderweb]

So, basically what all of you are saying is that the ideal of an airplane without the hassle and worry of overpriming, choking, detonation, arguments about how and when and how much to lean, starting procedures, shut-down procedures, etc. etc.--an airplane without a need to consider all that crap, is too expensive and not practical to produce, unless I'm willing to move up to a FADEC turbine of some sort?

 

[Everskyward]

During normal operation, the FADEC is supplied with 28vdc from an engine-mounted alternator. The engine-mounted alternator only provides power to that specific engine's accessories. However, in the event of failure, the FADEC is also supplied with 28vdc from the aircraft electrical system, which includes two more generators and a battery.

But to specifically answer your question, if all electrical power is removed from the FADEC, then that engine will shut down.

The FADEC you are talking about doesn't have PMAs? All the electrical power could be removed from our airplane but the engines will keep running.

 

[denverpilot]

The cost gets passed onto the customer at overhaul, as well. 2x your overhaul cost sound good?

Fine if the FADEC provides better engine longevity, expressed in dollars enough to cover its keep.

(It won't. Unless the pilot is causing damage by negligence with knowing how to use the red knob.)

 

[Henning]

So, basically what all of you are saying is that the ideal of an airplane without the hassle and worry of overpriming, choking, detonation, arguments about how and when and how much to lean, starting procedures, shut-down procedures, etc. etc.--an airplane without a need to consider all that crap, is too expensive and not practical to produce, unless I'm willing to move up to a FADEC turbine of some sort?

Nope, I never said any of the above, in fact I said all of that is available currently for any plane that takes a TCM engine directly from TCM. You can have FADEC in a recip without having to spring for a turbine, whether it is 'too' expensive is your own call to make.

BTW, I can't ever recall seeing an airplane engine get 'over primed', typically it's the opposite problem.

 

[Ted]

Fine if the FADEC provides better engine longevity, expressed in dollars enough to cover its keep.

(It won't. Unless the pilot is causing damage by negligence with knowing how to use the red knob.)

Exactly. It won't provide any of the things people think it will (other than easier starting). So when one looks at the cost/benefit as a manager, it's hard to justify.

I've never been a fan of marketing departments, but they're the key to FADEC implementation.

 

[Henning]

Exactly. It won't provide any of the things people think it will (other than easier starting). So when one looks at the cost/benefit as a manager, it's hard to justify.

I've never been a fan of marketing departments, but they're the key to FADEC implementation.

Considering all the engine damage and wear and tear caused by the misuse of the red knob, not to mention the fuel wasted, I don't concur with you guys' findings on the whole or even average. IF most pilots actually understood how to work the red knob properly, I would concur. As it is though, I'd estimate payoff for converting to a FADEC installation will pay off in 2 engine cycles for the vast majority of pilots. FADEC will basically eliminate top end overhauls since they are typically a red knob missuse issue.

 

[Ted]

Considering all the engine damage and wear and tear caused by the misuse of the red knob, not to mention the fuel wasted, I don't concur with you guys' findings on the whole or even average. IF most pilots actually understood how to work the red knob properly, I would concur. As it is though, I'd estimate payoff for converting to a FADEC installation will pay off in 2 engine cycles for the vast majority of pilots. FADEC will basically eliminate top end overhauls since they are typically a red knob missuse issue.

You're not getting it.

The pilot operating the engine poorly doesn't convince management to undertake a new R&D project. Warranty claims from bad engine management aren't high enough to make that argument, and furthermore, I think your estimates are highly exaggerated.

Pilots will complain that the engine is less efficient. It won't end up being any more reliable than a current engine for the first decade or so until the bugs get worked out. Even if it was calibrated to make the engine be reliable (it won't - because airframers will make stupid requests just like the recommendation to run the Duke at 79% power and 1650 TIT or the Malibu at 1750 TIT), the new systems would cause issues at first.

It's a hard sell to management. It then becomes a harder sell to the customers. "Wait, you want me to pay more money for an engine that's less efficient?"

 

[Henning]

You're not getting it.

The pilot operating the engine poorly doesn't convince management to undertake a new R&D project. Warranty claims from bad engine management aren't high enough to make that argument, and furthermore, I think your estimates are highly exaggerated.

Pilots will complain that the engine is less efficient. It won't end up being any more reliable than a current engine for the first decade or so until the bugs get worked out. Even if it was calibrated to make the engine be reliable (it won't - because airframers will make stupid requests just like the recommendation to run the Duke at 79% power and 1650 TIT or the Malibu at 1750 TIT), the new systems would cause issues at first.

It's a hard sell to management. It then becomes a harder sell to the customers. "Wait, you want me to pay more money for an engine that's less efficient?"

Well, I'm not seeing your perspective since the R&D and certification of FADEC for GA recip is done and Continental has an entire line of FADEC engines ready to go into anything and Lycoming isn't far behind, they only need to do the certifications, the FADEC is already available for Experimental, I figure they're waiting to see how it pays for Continental. As for the reliability of the systems, they have been in use for decades on hundreds of millions of engines. There is no need to reinvent the EFI systems just because they are going on an airplane.

Why do you think FADEC would be less efficient? A FADEC engine can run at the brink of detonation safely because it can detect and adjust away the condition an a multiple time per second basis. This is as efficient as you can make a recip run.

 

[Ted]

Yeah, why would I know anything about the realities of a computer-controlled piston aircraft engine or the realities of R&D... Sigh...

Continental has had their computer-controlled engines out for years now. Wonder why Cirrus and others haven't used them. Must be a reason. Also must be a reason that the iE2 has been a hard sell. Hmm...

But to the reliability point: it's a new R&D effort, even if some of the parts are derived or taken directly from other areas. So there are new parts and then other things like software, etc that will have bugs. It's just the normal cycle. I'd expect it to take 10 years for GA to get fixes worked out.

But what do I know?

 

[wabower]

Average pilot's TTFL (for life) is less than a third of one engine, not multiples.

Considering all the engine damage and wear and tear caused by the misuse of the red knob, not to mention the fuel wasted, I don't concur with you guys' findings on the whole or even average. IF most pilots actually understood how to work the red knob properly, I would concur. As it is though, I'd estimate payoff for converting to a FADEC installation will pay off in 2 engine cycles for the vast majority of pilots. FADEC will basically eliminate top end overhauls since they are typically a red knob missuse issue.

 

[Henning]

Average pilot's TTFL (for life) is less than a third of one engine, not multiples.

Right, that is the primary issue, lack of use to make payoff, technically we are already there. It's the commercial users of the engines that will be the ones that prosper from FADEC because it can save their engines from ham fisted pilots.

 

[wabower]

Other than flight schools, which commercial operators fly them enough to care? Flight schools are the biggest users, but thinking they will pay for anything is folly, since their engines run forever anyway.

Right, that is the primary issue, lack of use to make payoff, technically we are already there. It's the commercial users of the engines that will be the ones that prosper from FADEC because it can save their engines from ham fisted pilots.

 

[Henning]

Other than flight schools, which commercial operators fly them enough to care? Flight schools are the biggest users, but thinking they will pay for anything is folly, since their engines run forever anyway.

The guys still flying the 400 series Cessnas and such is about it. We won't see FADEC popular in the GA market until it's fitted to aero motive Diesel engines. FADEC with gasoline doesn't provide enough savings to be worth the cost and downtime of conversion. Diesel however will provide a 30% fuel savings, and that makes it worthwhile for the flight schools as well, especially if Continental does like they say and price the Diesels same as the 100LL engines.

 

[LDJones]

Yep, and no reason not to have a redundant EFI system as well to provide yet one more buffer against failure. Two digitital and one analog backup that can be fed by a mechanical or electric pump to run the engine. One more rail worth of nozzles and boxes barely weighs enough to think about when considering it brings redundant capacity.

And twice the injector mx expense.

 

[Henning]

And twice the injector mx expense.

Let's see, injector MX expense, how much do you spend on injector maintenance on your car? What is there to maintain with solid state FI and ignition systems?

 

[wabower]

So the answer is never. Why are we beating this horse?

The guys still flying the 400 series Cessnas and such is about it. We won't see FADEC popular in the GA market until it's fitted to aero motive Diesel engines. FADEC with gasoline doesn't provide enough savings to be worth the cost and downtime of conversion. Diesel however will provide a 30% fuel savings, and that makes it worthwhile for the flight schools as well, especially if Continental does like they say and price the Diesels same as the 100LL engines.

 

[Henning]

So the answer is never. Why are we beating this horse?

Because FADEC does not only apply to gasoline engines.

Besides, planes are still being produced new which could have FADEC gasoline engines already on them as the Bonanza, Cirrus and Corvalis really should because it DOES make a difference in the ongoing cost of operations and longevity of the engine by severely reducing cabon deposits. Just because it's not economic to convert doesn't mean it's not economic to initialize with.

 

[wabower]

If it were really important, wouldn't somebody already be doing it?

Because FADEC does not only apply to gasoline engines.

Besides, planes are still being produced new which could have FADEC gasoline engines already on them as the Bonanza, Cirrus and Corvalis really should because it DOES make a difference in the ongoing cost of operations and longevity of the engine by severely reducing cabon deposits. Just because it's not economic to convert doesn't mean it's not economic to initialize with.

 

[Henning]

If it were really important, wouldn't somebody already be doing it?

You mean like Continental? Besides, your supposition is invalidated by your own arguments that maximum profit is the route for business to take. Since all these planes are already certified with non FADEC installations with no competition taking business away from them with FADEC, under your auspices of bottom line trumps all, it would be negligent of the company with regards to the bottom line to incur the certification expense of getting a model flying with FADEC. It's all about valuing the quantity of cash more than the quality of the product.

 

[Capt. Geoffrey Thorpe]

Yeah, why would I know anything about the realities of a computer-controlled piston aircraft engine or the realities of R&D... Sigh...

But what do I know?

Apparently, not much. After all, we all know that the average pilot knows more about how to lean their engine than some control system design engineer.

Pilots have rules of thumb to work with. Engineers are stuck with dynamometer data.

 

[wabower]

What arguments are you talking about?

Based on your typically flawed logic, no products that require development expenses would have ever been introduced.

You mean like Continental? Besides, your supposition is invalidated by your own arguments that maximum profit is the route for business to take. Since all these planes are already certified with non FADEC installations with no competition taking business away from them with FADEC, under your auspices of bottom line trumps all, it would be negligent of the company with regards to the bottom line to incur the certification expense of getting a model flying with FADEC. It's all about valuing the quantity of cash more than the quality of the product.

 

[Ted]

Apparently, not much. After all, we all know that the average pilot knows more about how to lean their engine than some control system design engineer.

Pilots have rules of thumb to work with. Engineers are stuck with dynamometer data.

I hate having data. It makes it hard for me to ignore reality.

 

[Henning]

What arguments are you talking about?

Based on your typically flawed logic, no products that require development expenses would have ever been introduced.

That's not true, if a development cost leads to increased sales that more than offset the cost, or if the savings in manufacture will offset the costs the development fits current business models.

 

[Capt. Geoffrey Thorpe]

I hate having data. It makes it hard for me to ignore reality.

 

[spiderweb]

BTW, I can't ever recall seeing an airplane engine get 'over primed', typically it's the opposite problem.

It happens a lot in the injected Cessnas. The amount of prime time (haha) recommended in checklists is generally too long.

 

[Ted]

It happens a lot in the injected Cessnas. The amount of prime time (haha) recommended in checklists is generally too long.

So? Mixture to idle cut-off and crank longer.

 

[spiderweb]

That's not true, if a development cost leads to increased sales that more than offset the cost, or if the savings in manufacture will offset the costs the development fits current business models.

That's why I was hoping that at least by now, we could rent and own FADEC equipped airplanes, and just concentrate and enjoy the freaking flying.

 

[spiderweb]

So? Mixture to idle cut-off and crank longer.

Just like the 1970s. Yay.

 

[wabower]

I only flew them for 27 years without using the factory recommendation and can't ever remember any starting issues? What particular problems have you noticed?

It happens a lot in the injected Cessnas. The amount of prime time (haha) recommended in checklists is generally too long.