FADEC is 1980s Technology

spiderweb

spiderweb

Final Approach
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Ben
Even in the Cirrus I'm flying, you still have to carefully tend to that red lever. Priming, flooding, detonation, fouling of spark plugs, using the lean-assist.

This is ridiculous. You have an aircraft with a sophisticated, extremely clean design, with cutting-edge avionics, and even a whole-aircraft parachute. What's with the 1970s engine technology?
 
This thread makes me laugh.
 
1970s? You're giving it about 50 years too much credit.

The answer is that, once you factor in certification and all that fun, the cost is extremely high, and you end up with something whose primary advantage is removal of a red lever and easier hot starting. More power? Nope. More efficiency? Nope.

But hey, nobody on here has believed me before, I doubt if they'll start now.
 
By the way, that's not to say I disagree. I think that there should be FADECs in modern aircraft. We can do it, we have the technology.

But, we don't want to spend a lot of money. That's the rub. An experimental system could be done cheaply, and it would be about an 80% solution. Throw in certification and all the required protections, etc for the 100% solution and the cost will go up. Silly, but that's how it is. Our best hope of FADEC is in the diesels of the future.
 
spiderweb said:
Even in the Cirrus I'm flying, you still have to carefully tend to that red lever. Priming, flooding, detonation, fouling of spark plugs, using the lean-assist.

This is ridiculous. You have an aircraft with a sophisticated, extremely clean design, with cutting-edge avionics, and even a whole-aircraft parachute. What's with the 1970s engine technology?
Click to expand...

Maybe shoulda bought a Diamond DA42 :)
 
They can't afford to put FADEC on a half million dollar Skylane.

(That's either sarcasm, or truth... You decide. Either way, it's sad.)
 
I think of it in a much simpler way. My plane isn't going anywhere unless the power-tow starts. The selector must be manually moved to the "choke" position (from the "stop" position that was required to turn it off) in order to start, usually on the the first or second pull. The selector must then be moved to "run" in order to continue making noise and move the plane from the hangar.

Whenever I find myself unable to successfully fire up the tow-motor, I'll assume that the operation of the red knob on the panel has also exceeded my capabilities. So far, so good.
 
Modern ignition systems produce a longer duration, or series of sparks that can be delivered very accurately on a CDI system. This can allow for a significant LOP operation, much like modern cars use. The modern injectors found on cars now produce a better spray pattern at higher pressure as well. It would be even better if we could get cam timing adjustments as well, but I'd settle for some advancements in ignition and fuel maps.

http://www.lightspeedengineering.com/Products/IgnitionIII.htm

Right now, my best BSFC for the Conti I run at LOP is about 0.45. Modern engines are getting below .4, and in some cases mid .3s. There's efficiency improvements to be had, and not with that much work either.
 
denverpilot said:
They can't afford to put FADEC on a half million dollar Skylane.

(That's either sarcasm, or truth... You decide. Either way, it's sad.)
Click to expand...

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

docmirror said:
Modern ignition systems produce a longer duration, or series of sparks that can be delivered very accurately on a CDI system. This can allow for a significant LOP operation, much like modern cars use. The modern injectors found on cars now produce a better spray pattern at higher pressure as well. It would be even better if we could get cam timing adjustments as well, but I'd settle for some advancements in ignition and fuel maps.

http://www.lightspeedengineering.com/Products/IgnitionIII.htm

Right now, my best BSFC for the Conti I run at LOP is about 0.45. Modern engines are getting below .4, and in some cases mid .3s. There's efficiency improvements to be had, and not with that much work either.
Click to expand...

That Lightspeed system is garbage, at least it was the last time I worked with it. Maybe they've improved it, but the last iteration I saw had an MTBF that could be measured on one hand. While I believe that modern ignition systems should be better than magnetos as far as spark production goes, I just haven't used one that actually measures up as far as showing a real improvement as advertised.

That said, I would actually take the minor efficiency hit I've seen from electronic ignition to be able to source my parts from the Ford dealer and what I suspect would be a reliability improvement.

Adjustable cam timing on an aircraft engine is rather useless given the small RPM range we run, but that would add significant weight to the engine, making it a better boat anchor. Modern injectors, while they may have an improvement over the mechanical ones we use now, aren't at the point to matter. It's actually surprising how bad your spray pattern can be on these engines and really not matter from an efficiency perspective.
 
Here's the thing - FADEC is necessary in automotive engines, which constantly change power levels at any given time, even down a straight road. In an aircraft, you are changing power settings three times in a typical flight. There isn't a huge benefit to automatic mixture adjustment.

Other aspects of modern technology such as EFI, and digital spark control would be pretty significant advances for piston aircraft engines though.
 
Ted DuPuis said:
That Lightspeed system is garbage, at least it was the last time I worked with it. Maybe they've improved it, but the last iteration I saw had an MTBF that could be measured on one hand. While I believe that modern ignition systems should be better than magnetos as far as spark production goes, I just haven't used one that actually measures up as far as showing a real improvement as advertised.

That said, I would actually take the minor efficiency hit I've seen from electronic ignition to be able to source my parts from the Ford dealer and what I suspect would be a reliability improvement.

Adjustable cam timing on an aircraft engine is rather useless given the small RPM range we run, but that would add significant weight to the engine, making it a better boat anchor. Modern injectors, while they may have an improvement over the mechanical ones we use now, aren't at the point to matter. It's actually surprising how bad your spray pattern can be on these engines and really not matter from an efficiency perspective.
Click to expand...

I must admit I've never had any experience with the Lightspeed unit, so it could be as you say. I do know that modern CDI systems have reliability factors that are far higher than any mag or points/coil system. Sadly, converting production quality from engineering quality make a CDI system very challenging.

As for cam timing, the new Porsche centrifugal units look promising. We do spend a lot of quality time at 50-75% of max power so it may not be that useful, but the cost in part count and weight for a very modest improvement in fuel econ might be worth it. Also, there's the factor that we can up the effective HP or decrease the engine volume if some of these things are used. I would like to have a 470CI engine produce more than a paltry 260HP. 300HP is not a difficult thing given our 100 octane fuel and RPM limitations but creativity is sorely lacking in aviation engines.
 
docmirror said:
As for cam timing, the new Porsche centrifugal units look promising. We do spend a lot of quality time at 50-75% of max power so it may not be that useful, but the cost in part count and weight for a very modest improvement in fuel econ might be worth it. Also, there's the factor that we can up the effective HP or decrease the engine volume if some of these things are used. I would like to have a 470CI engine produce more than a paltry 260HP. 300HP is not a difficult thing given our 100 octane fuel and RPM limitations but creativity is sorely lacking in aviation engines.
Click to expand...

The purpose of adjustable anything is because you're trying to run at more than one operating a point. If you have effectively one operating point (which we do), adjustable cam timing or anything won't help. You can optimize everything for steady state operation just fine.

As far as making more power goes, it would be (and is) easy enough to get more power out of these engines, even without increasing RPM. That's a whole other debate, though, and doesn't require any fancy technology.
 
Ted DuPuis said:
The purpose of adjustable anything is because you're trying to run at more than one operating a point. If you have effectively one operating point (which we do), adjustable cam timing or anything won't help. You can optimize everything for steady state operation just fine.

As far as making more power goes, it would be (and is) easy enough to get more power out of these engines, even without increasing RPM. That's a whole other debate, though, and doesn't require any fancy technology.
Click to expand...

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.

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.
 
FADEC. You keep using that word. I do not think it means what you think it means.

True full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an EEC or ECU. An EEC, though a component of a FADEC, is not by itself FADEC. When standing alone, the EEC makes all of the decisions until the pilot wishes to intervene.

For a piston engine to have a FADEC, it implies that there is no mechanical link to the throttle of the engine (also no mechanical mixture or rpm). The only control link would be between the pilot and the FADEC, and the FADEC would decide what the engine will do based on what the pilot wants as an end result.
 
darrell said:
FADEC. You keep using that word. I do not think it means what you think it means.
Click to expand...

To whom are you referring when you say 'You'? I've reviewed my posts, and no where do I use FADEC.
 
docmirror said:
To whom are you referring when you say 'You'? I've reviewed my posts, and no where do I use FADEC.
Click to expand...

1) It's a quote from a movie (replace "FADEC" with "inconceivable"), but is also apropos to this thread.

2) You say you didn't use the term, therefore my only answer to the question "to whom are you referring" is "not you".
 
darrell said:
1) It's a quote from a movie (replace "FADEC" with "inconceivable"), but is also apropos to this thread.

2) You say you didn't use the term, therefore my only answer to the question "to whom are you referring" is "not you".
Click to expand...

Your "only" answer? Sorry, I missed that movie as well. Hey - and thanks for all your contribution to this thread. :D
 
Ted DuPuis said:
By the way, that's not to say I disagree. I think that there should be FADECs in modern aircraft. We can do it, we have the technology.

But, we don't want to spend a lot of money. That's the rub. An experimental system could be done cheaply, and it would be about an 80% solution. Throw in certification and all the required protections, etc for the 100% solution and the cost will go up. Silly, but that's how it is. Our best hope of FADEC is in the diesels of the future.
Click to expand...

-Sigh- This about sums up what I've thought was going on.
 
P2006T, Da 42, Rotax LSA, New Skylane

Your decision. Anything else is uncivilized! :yes:

The problem is when you need a 6 seater... They are all relics. :mad2:

Come on Europe release some 4 seaters worth a darn.
 
spiderweb said:
Even in the Cirrus I'm flying, you still have to carefully tend to that red lever. Priming, flooding, detonation, fouling of spark plugs, using the lean-assist.

This is ridiculous. You have an aircraft with a sophisticated, extremely clean design, with cutting-edge avionics, and even a whole-aircraft parachute. What's with the 1970s engine technology?
Click to expand...

You do not have FADEC in a Cirrus to the best of my knowledge, you have a mechanical interconnect to the prop on the single lever.
 
Sac Arrow said:
Other aspects of modern technology such as EFI, and digital spark control would be pretty significant advances for piston aircraft engines though.
Click to expand...

I've done some thinking about that, and I don't think so.

Why? What happens in your car when you break a ground wire? Your engine quits. Instantly. No partial power, no warning, no "check engine light," it just quits with no spark. How likely is this? In a three year old car, not very. In a 20 year old car -- well, let's put it this way -- I've repaired a heat-driven ignition failure on every vehicle I've owned of that age, except for the 1972 Chevy (which doesn't have electronic ignition -- that came in 1973).

That's why magnetos are used rather than ignition coils and distributors, and it's why electronic fuel injection is much more difficult for aircraft than it is for cars. The failure modes are highly problematic. With a high pressure solenoid fuel injector, what should its failure mode be, if a solenoid were to fail (and I've seen this happen as both an open circuit and a dead short -- the latter takes out all the other injectors in the same circuit, often half of them)? Closed? The engine quits. Wide open? It floods then, and either quits or limps. Both are very serious problems for an aircraft. As a shadetree mechanic, I spend a lot of time replacing wires and connectors. They don't last, and they cause occasional serious drivability issues you wouldn't have with a simpler control system.

The flip side of adaptivity is that it hides warning signs you might otherwise get. That is, with a little bit of a problem, you adapt it away and don't notice anything. You might set a warning light if the problem is detected (and a lot of people overestimate just how reliable that is -- there is a LONG list of problems that don't set the light). With a big problem, it doesn't run. If you're lucky, it's a no-start.
 
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jmp470 said:
P2006T, Da 42, Rotax LSA, New Skylane

Your decision. Anything else is uncivilized! :yes:

The problem is when you need a 6 seater... They are all relics. :mad2:

Come on Europe release some 4 seaters worth a darn.
Click to expand...

Anything that takes a Continental engine you can have in FADEC with digital injection according to the TCM guy I talked to at OSH, and IIRC they are ready to run on 94UL. If I run into problems with Mogas or 94UL I'll just blend in some Sunoco racing fuel. They already make a product that would likely fill the bill. Thing is, Sunoco doesn't want anything to do with Avgas. Now, let's go down the river to the other bank where Delta Airlines has just opened their refinery could take some of the light end stuff they're trading for Jet A and they can reset to produce a usable Avgas solution from across the river.
 
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The way I would do EFI is with a system like a pressure carb such as the PS-5C found on many older Bonanzas. The EFI system would be fully independent of the existing low pressure fuel system. The low pressure pump would Tee off and feed the pressure carb, and also the EFI high pressure pump(s). The mixture control for the pressure carb, which is actually a throttle body FI would remain in the full lean/mixture cutoff position at all times unless the EFI system faulted. As long as the EFI were working off the controller map, the pressure carb would remain off, and it would only modulate the air intake. In the event of a failure of the EFI system, one of the emer procedures would be 'mixture rich'. If the low pressure pump failed, maybe have a backup engine driven pump just like they do now. Not much weight added over a throttle body only system.
 
I'd just run twin EFI systems in parallel at 50% until fault is detectected then the remaining fills in the required capacity. One can also have a standby emergency mechanical injection system as triple redundant. Any EFI system though has to be a tuned port high pressure system.
 
That's another way to go. Dual systems with 50% normal duty cycle, with the ability to take over should one of them fail.
 
darrell said:
FADEC. You keep using that word. I do not think it means what you think it means.

True full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an EEC or ECU. An EEC, though a component of a FADEC, is not by itself FADEC. When standing alone, the EEC makes all of the decisions until the pilot wishes to intervene.

For a piston engine to have a FADEC, it implies that there is no mechanical link to the throttle of the engine (also no mechanical mixture or rpm). The only control link would be between the pilot and the FADEC, and the FADEC would decide what the engine will do based on what the pilot wants as an end result.
Click to expand...

The SMA diesel has FADEC, with a manual backup in case the computers goof off. You pull an emergency lever, which disengages the FADEC's servo motor from the fuel controller and clutches the control to the throttle lever directly. It's one of those things that certification demands.

Dan
 
Dan Thomas said:
The SMA diesel has FADEC, with a manual backup in case the computers goof off. You pull an emergency lever, which disengages the FADEC's servo motor from the fuel controller and clutches the control to the throttle lever directly. It's one of those things that certification demands.

Dan
Click to expand...

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.
 
Well, the pressure carb is well proven, and ultra low tech reliability. This is why I would do it with the single EFI and a known backup. If elec power failed for some reason, the plane would still remain in the air provided it had one mag. going all electronic presents an interesting SPOF equation.
 
Henning said:
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.
Click to expand...

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.
 
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Dan Thomas said:
The SMA diesel has FADEC, with a manual backup in case the computers goof off. You pull an emergency lever, which disengages the FADEC's servo motor from the fuel controller and clutches the control to the throttle lever directly. It's one of those things that certification demands.

Dan
Click to expand...

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.
 
MAKG1 said:
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.
Click to expand...
. Not at all. With EFI systems you can have detonation sensors which allow the engine to be operated at peak efficiency without melting down.
 
docmirror said:
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.

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.
Click to expand...

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.
 
Henning said:
You do not have FADEC in a Cirrus to the best of my knowledge, you have a mechanical interconnect to the prop on the single lever.
Click to expand...
More of a LAMLEC. Limited authority, mechanical linkage, engine controller.
 
Henning said:
You do not have FADEC in a Cirrus to the best of my knowledge, you have a mechanical interconnect to the prop on the single lever.
Click to expand...

You're absolutely correct.

In an aircraft otherwise so technically cutting-edge, why is the fuel metering system so Leave it to Beaver era?
 
MAKG1 said:
I've done some thinking about that, and I don't think so.

Why? What happens in your car when you break a ground wire? Your engine quits. Instantly. No partial power, no warning, no "check engine light," it just quits with no spark. How likely is this? In a three year old car, not very. In a 20 year old car -- well, let's put it this way -- I've repaired a heat-driven ignition failure on every vehicle I've owned of that age, except for the 1972 Chevy (which doesn't have electronic ignition -- that came in 1973).

That's why magnetos are used rather than ignition coils and distributors, and it's why electronic fuel injection is much more difficult for aircraft than it is for cars. The failure modes are highly problematic. With a high pressure solenoid fuel injector, what should its failure mode be, if a solenoid were to fail (and I've seen this happen as both an open circuit and a dead short -- the latter takes out all the other injectors in the same circuit, often half of them)? Closed? The engine quits. Wide open? It floods then, and either quits or limps. Both are very serious problems for an aircraft. As a shadetree mechanic, I spend a lot of time replacing wires and connectors. They don't last, and they cause occasional serious drivability issues you wouldn't have with a simpler control system.

The flip side of adaptivity is that it hides warning signs you might otherwise get. That is, with a little bit of a problem, you adapt it away and don't notice anything. You might set a warning light if the problem is detected (and a lot of people overestimate just how reliable that is -- there is a LONG list of problems that don't set the light). With a big problem, it doesn't run. If you're lucky, it's a no-start.
Click to expand...

Thanks for this post. A lot I never considered!
 
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