FI engines- Mixture

[Jaybird180]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

 

[dmccormack]

Care to build one, go through certification process, market it, and then provide all the necessary indemnification?

If not -- that's why.

 

[Capt. Geoffrey Thorpe]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

My Rotax has neither a mixture control or a processor...

Altitude compensated carburetors have been around, like, forever...

But, I think Mr. McCormack came pretty close to hitting the nail on the head. The other bit would be market resistance to anything electronic - really.

 

[Lance F]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

When I first got into power flying, I asked the EXACT same question. You will learn; you will learn

 

[vontresc]

My Rotax has neither a mixture control or a processor...

You have the samne Bing constant vacuum carbs I have on my BMW airhead. They use a diaphragm, and a needle valve to meter the the fuel flow based on airflow (vacuum) in the carb. Pretty elegant little system to manage the mixture. At least until the diaphragms crack and fail

More info on the Bing CV carb.. http://www.omnilex.com/public/bmw78/cvcarb.pdf

 

[dmccormack]

My Rotax has neither a mixture control or a processor...

My 1940 Lycoming O-145-b2 with Stromberg MA-4 Carb has no mixture control either.

"Full rich" is how it is all the time.

At first I wondered abouty this shortcoming, then realized:

• Who's flying a Chief at high altitude?
• Gas was cheap in 1940
• Labor was cheap, too, so pulling and cleaning plugs was no big deal

 

[Baron2PG]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

Three reasons: F.A.A.

The FAA is keeping us safe from pesky new technology by making the certification process overly onerous. When you have a very small number of aircraft to amortize a large and risky investment it just doesn't make sense. Add to that our litigious society and you've pretty well killed new technology investments.

 

[gismo]

You have the samne Bing constant vacuum carbs I have on my BMW airhead. They use a diaphragm, and a needle valve to meter the the fuel flow based on airflow (vacuum) in the carb. Pretty elegant little system to manage the mixture. At least until the diaphragms crack and fail

More info on the Bing CV carb.. http://www.omnilex.com/public/bmw78/cvcarb.pdf

I don't see how that carb could compensate for air density changes. It looks to me that it responds to air volume not air mass.

 

[Tom-D]

Precision airmotive Eagle EMS

http://www.precisionairmotive.com/

the FAA has stone walled them for certification with a unreasonable testing requirement.

I was told (by a trusted source) that it was over a million flight hours.

I believe that the FAA caved to the pressure from companies like Kelly, unison, TCM, (bendix)
and others that rebuild fuel systems, and accessories. because this system if it gains direct replacement status will put the whole fuel system industry out of business.

 

[dmccormack]

I was told (by a trusted source) that it was over a million flight hours.

Ted has these installed on the AzTruck?

 

[Dan Thomas]

Continental's injection system has an aneroid on some installations that adjusts the mixture for altitude, but that thing has a habit of sticking. The problem is that such a mechanical device is expected to respond to very small changes in pressure but still be able to move a mechanism to adjust fuel flow. And it makes no compensation for temperature, only pressure, yet temperature affects density as well. And it can't make adjustments for power demand, where the mixture needs to be richer at higher power settings to control detonation and CHT.

Electronics can do it and Lycoming, I think, has it beat with their new IE2 engine, but certification is expensive, and parts and maintenance won't be cheap either. Not many of us will be flying behind it.

The real problem is that too many students these days don't want to learn anything more than they absolutely have to. The solution to mixture control is to learn how an engine works, what importance mixture has, and how to operate things properly. It's not difficult at all; just takes a little time and effort.

Dan

 

[steingar]

It is certainly not hard to adjust mixtures, and there is nothing wrong with it. It is a pity, however, that aviation technology stays rooted in the past. It is supposed to work the other way around.

That, and I'll bet there are all sorts of ways developed in the last 50 or so years to make engines more efficient that we can't use on aircraft. An even greater pity, since the price of fuel isn't going down in the foreseeable future.

 

[taters]

Im sure there will be an Iphone app soon.

I am happy knowing I have manual control of a mixture lever. Nothing wrong with simple proven systems.

 

[Tom-D]

Ted has these installed on the AzTruck?

I have no clue as to what Ted has, but these are EXP at the moment.

 

[Tom-D]

Continental's injection system has an aneroid on some installations that adjusts the mixture for altitude, but that thing has a habit of sticking. The problem is that such a mechanical device is expected to respond to very small changes in pressure but still be able to move a mechanism to adjust fuel flow. And it makes no compensation for temperature, only pressure, yet temperature affects density as well. And it can't make adjustments for power demand, where the mixture needs to be richer at higher power settings to control detonation and CHT.

Electronics can do it and Lycoming, I think, has it beat with their new IE2 engine, but certification is expensive, and parts and maintenance won't be cheap either. Not many of us will be flying behind it.

The real problem is that too many students these days don't want to learn anything more than they absolutely have to. The solution to mixture control is to learn how an engine works, what importance mixture has, and how to operate things properly. It's not difficult at all; just takes a little time and effort.

Dan

the only thing wrong with these systems is, there is an idiot at the controls.

 

[Anthony]

How about mechanical fuel injection like the ME-109 had? How did that work? They did not have the inverted flight worries like the carbuerated engined planes had.

 

[steingar]

the only thing wrong with these systems is, there is an idiot at the controls.

Though there is nothing inherently wrong with them, there are more sophisticated systems available that would exhibit superior function in the aviation environment. It is a pity that such technologies cannot be exploited by the utterly moribund aviation community. We use technology from the fifties and wonder why no one wants to fly small planes.

 

[jesse]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

It's coming. Lycoming is working on certified FADEC systems and they've existed in the experimental world for some time now.

More info, Lycoming iE2:
http://www.lycoming.textron.com/news-and-events/pdfs/iE2_Engine.pdf
http://www.<b>lycoming</b>.textron.com/news-and-events/pdfs/<b>iE2</b>_Engine.pdf

 

[Capt. Geoffrey Thorpe]

But, I think Mr. McCormack came pretty close to hitting the nail on the head. The other bit would be market resistance to anything electronic - really.

Im sure there will be an Iphone app soon.

I am happy knowing I have manual control of a mixture lever. Nothing wrong with simple proven systems.

Q.E.D.

 

[Dan Thomas]

How about mechanical fuel injection like the ME-109 had? How did that work? They did not have the inverted flight worries like the carbuerated engined planes had.

Mechanical fuel injection is found on Lycomings and Continentals and has been for several decades. No carb, but the fuel tanks aren't invertable unless they're designed for it.

Dan

 

[flyingcheesehead]

Why do airplane engines have mixture control? Why not have a simple processor monitor and constantly adjust mixture considering that it can do a better job than a human.

Until it breaks or malfunctions.

The beauty of the mixture control is that it's dirt simple, and thus not very prone to failure.

 

[poadeleted20]

Precision airmotive Eagle EMS

http://www.precisionairmotive.com/

the FAA has stone walled them for certification with a unreasonable testing requirement.

"Unreasonable" tends to be a very subjective judgement.

I was told (by a trusted source) that it was over a million flight hours.

When you have that from two independent sources with no vested interest in the result, let us know.

I believe that the FAA caved to the pressure from companies like Kelly, unison, TCM, (bendix) and others that rebuild fuel systems, and accessories. because this system if it gains direct replacement status will put the whole fuel system industry out of business.

Would you care to share with us the evidence on which you have developed that belief?

 

[spiderweb]

Why don't cars have mixture levers?

 

[Skip Miller]

Why don't cars have mixture levers?

Electronic fuel injection. -Skip

 

[Tom-D]

"Unreasonable" tends to be a very subjective judgement.

It has been availiblle for 10 years, do you see it certified?

When you have that from two independent sources with no vested interest in the result, let us know.

Those who have no vested interest have no interest.

Would you care to share with us the evidence on which you have developed that belief?

a simple knowledge of the industry will give you the insight to know a better system will make the rest obsolete, allowing the better system to take over the market.

common sense.

 

[Tom-D]

Why don't cars have mixture levers?

When the car first came west over the high country, the driver had to lean the carbs by adjusting the mixture by twisting the screw for that purpose.

plus the new cars have a electronic engine control, operated by a computer. and adjust the mixture as needed.

 

[spiderweb]

Electronic fuel injection. -Skip

Exactly. So, what baffles me is why FADEC is such a big deal. I mean, haven't we had this technology for awhile? Is this just another example of the regs and cert requirements being too onerous?

 

[spiderweb]

When the car first came west over the high country, the driver had to lean the carbs by adjusting the mixture by twisting the screw for that purpose.

plus the new cars have a electronic engine control, operated by a computer. and adjust the mixture as needed.

I heard about that on "Car Talk!"

So is FADEC just the aviation world following the automotive world 30 years later?

 

[Dan Thomas]

Why don't cars have mixture levers?

As one has said, they have electronic injection, and adjustments are made according to air pressure and temperature, coolant temperature, exhaust gas oxygen levels, and a few other factors. Older carbureted cars sometimes had aneroids to adjust mixture for altitude, some had a power enrichment valve to help prevent detonation, but most had no mixture adjustment at all. Most of those old cars never strayed too far from sea level and those that did get up high often ran poorly due to too much fuel.

Dan

 

[Tom-D]

I heard about that on "Car Talk!"

So is FADEC just the aviation world following the automotive world 30 years later?

My Sister has the car below, after it was restored they drove it out to see us. and had to adjust the carb on the way.

The Stromberg carb used on the Wright 3350 was a version of a manual and automatic variable mixture carb. It was a single point fuel injected carb that fed fuel to the center of the super charger impeller, the mixture could be changed by the handle in the cockpit, or as auto rich or auto lean. which used 4 chambers separated by rubber diaphragms, guiding a needle valve to change the mixture.

 

[elmetal]

Exactly. So, what baffles me is why FADEC is such a big deal. I mean, haven't we had this technology for awhile? Is this just another example of the regs and cert requirements being too onerous?

Fuel Injections can't adjust fast enough. It can easily adjust to a 5000 foot difference in the time it takes you to drive it... But it can't handle sea level to 5000 in 5-10 minutes like most aircraft can climb.

That's the basic idea behind not using electronic fuel injections in the plane.

not the mention if a fuel injection acts up, we just pull over, but in the air what can we do?

 

[spiderweb]

My Sister has the car below, after it was restored they drove it out to see us. and had to adjust the carb on the way.

The Stromberg carb used on the Wright 3350 was a version of a manual and automatic variable mixture carb. It was a single point fuel injected carb that fed fuel to the center of the super charger impeller, the mixture could be changed by the handle in the cockpit, or as auto rich or auto lean. which used 4 chambers separated by rubber diaphragms, guiding a needle valve to change the mixture.

Wow. What a beautiful car!

 

[spiderweb]

Fuel Injections can't adjust fast enough. It can easily adjust to a 5000 foot difference in the time it takes you to drive it... But it can't handle sea level to 5000 in 5-10 minutes like most aircraft can climb.

That's the basic idea behind not using electronic fuel injections in the plane.

not the mention if a fuel injection acts up, we just pull over, but in the air what can we do?

Ah good point!

So does that mean that FADEC (aside from managing the prop) have a faster "reaction time" to altitude changes?

 

[Tom-D]

Wow. What a beautiful car!

Its a 20 year old restoration, and starting to show its age, we used it when we were home this fall.

 

[spiderweb]

Its a 20 year old restoration, and starting to show its age, we used it when we were home this fall.

Just beautiful.

 

[Capt. Geoffrey Thorpe]

Fuel Injections can't adjust fast enough. It can easily adjust to a 5000 foot difference in the time it takes you to drive it... But it can't handle sea level to 5000 in 5-10 minutes like most aircraft can climb.

That's the basic idea behind not using electronic fuel injections in the plane.

not the mention if a fuel injection acts up, we just pull over, but in the air what can we do?

NFW...

Sometimes I wonder where you people come up with this stuff...

 

[Dan Thomas]

Fuel Injections can't adjust fast enough. It can easily adjust to a 5000 foot difference in the time it takes you to drive it... But it can't handle sea level to 5000 in 5-10 minutes like most aircraft can climb.

That's the basic idea behind not using electronic fuel injections in the plane.

not the mention if a fuel injection acts up, we just pull over, but in the air what can we do?

First time I've heard that FADEC can't make rapid adjustments. I guess the FAA-certified FADEC on the FAA-certified SMA diesel we have here in the FAA-certified Cessna182 can't do it either...

Honestly. The real reason we don't see electronic injection in light aircraft is due to the propensity of electrical systems to fail. Without a supply they die. It's the reason we use magnetos, too. Just ask any pilot of any experience just how often aircraft electrical systems make trouble. 90% of all problems tend to be electrical in nature, and that applies to cars, too. Unless any manufacturer of an aircraft electronic ignition or fuel control can prove to the FAA that loss of aircraft electrical supply won't kill the engine, they won't get certification. The SMA's FADEC has a mechanical override, whereby the fuel control is mechanically shifted by a separate lever from the computer's control directly to the power lever; that lever normally just works a potentiometer. Works fine with diesel but it ain't gonna work with electronic gasoline fuel injection.

Dan

 

[Tom-D]

but it ain't gonna work with electronic gasoline fuel injection.Dan

My 07 jeep JK works great with multi port FI. and fly by wire computer.

 

[Jack Spectre]

Though there is nothing inherently wrong with them, there are more sophisticated systems available that would exhibit superior function in the aviation environment. It is a pity that such technologies cannot be exploited by the utterly moribund aviation community. We use technology from the fifties and wonder why no one wants to fly small planes.

EXACTLY.

Does anyone wonder how something like the ICON A5 generates so much interest among non-pilots? Look at this cockpit...I'm not saying ICON is the answer, but they are sure barking up the right tree.

 

[dmccormack]

Does anyone wonder how something like the ICON A5 generates so much interest among non-pilots? Look at this cockpit...I'm not saying ICON is the answer, but they are sure barking up the right tree.

That's a mock up -- it will change after certification.

We all need to face a startling fact -- flying requires specialized skills that people of a somewhat above average combination of intelligence and physical dexterity -- with the desire and enough hubris to ignore certain risks -- can only obtain with enough time and money.