Ever since the news about the new unleaded fuel from General Aviation Modifications Inc. (GAMI) came out at EAA AirVenture Oshkosh 2021, many pilots believe that once that fuel becomes available, general aviation pilots will no longer be polluting the air.
That started me thinking it may be time to review the history of automotive emission and emission controls compared to that for GA piston engines.
The first emission controls on automobiles were in 1966 in California. These were just limits on carbon monoxide (CO) and unburnt fuel or Hydrocarbon (HC). These limits, which were expanded to all cars nationwide in 1968, were basically leaner carburetors and retarded ignition timing. There was also a requirement for positive crankcase ventilation (PCV) systems for all cars.
By 1970, the EPA realized that photochemical smog was a reaction of HC and oxides of nitrogen (NOX). And while the new emission controls on cars reduced the amount of HC and CO, they had increased the amount of NOX emitted.
In 1973 the EPA put limits on the amount of NOX that could be emitted. This resulted in exhaust gas recirculation (EGR) on almost every car.
The level of CO in the exhaust is directly related to the air/fuel ratio. This means that all car engines built since 1968 have been set to cruise lean of peak to reduce CO and HC emissions.
The NOX emission from an internal combustion engine is related to the peak temperature and pressure in the combustion cycle. The NOX level of exhaust can be reduced by reducing compression ratios or recycling exhaust gases, which reduce peak cylinder temperature and pressure. The EPA also put limits on evaporative emissions for all cars.
As time went on, the EPA kept lowering the limits for all three pollutants. By 1976 almost all vehicles had to be equipped with a catalytic converter to lower the emissions beyond that from engine controls. The fact that lead poisoned catalysis eventually resulted in its removal from automobile gas. That took about 20 years, with unleaded gas completely phased out by Jan. 1, 1996, for cars and other vehicles.
The use of converters continued and by the 1990s all automobile engines needed electronic fuel injection and ignition controls to get the even fuel distribution necessary to get to the low levels needed to meet the limits set by the EPA.
The lower limit also led to converters to reduce NOX and catalytic converters just for startup.
Then came the limits on fuel economy as part of the Corporate Average Fuel Economy or CAFÉ standard. And fuel economy is measured as part of the emission test procedure.
So what does this have to do with aviation?
It shows the distance the automotive world has gone to limit emissions. By comparison, the aviation community has done nothing in those same 50-plus years to control emissions.
And now that we have started to remove lead from our fuel, people think that the emissions for GA aircraft are all good.
Well, not really. Even without lead, the levels of CO, HC, and NOX are sky high.
Most people say that the size of the general aviation world is so small, it will not affect the overall emission picture.
You only need to look at California, where officials are considering plans to outlaw gas-powered lawn mowers and other lawn care equipment. Then compare the emissions from a 20cc four-cycle weed eater to that of a Cessna 421 with two GTSIO 520s putting out huge amounts of CO, HC, and NOX.
Then there is the practice of some general aviation pilots who sump their tanks, then throw the fuel out on the runway to let it evaporate.
That will have to change. In fact, there may be a lot of changes coming our way — and they may not all be good.
This is my last column for 2021. I wish all of you a great holiday season and a bright new year. As I listen to Christmas music, it is interesting to realize that the poem “The Night Before Christmas” was written 80 years before the Wright brothers flew.
I agree with your premise. Playing Devil’s Advocate on comparing emissions…how many 20cc four cycle weed eaters are there for every Cessna 421?
Sorry, GA aircraft are not large scale pollution producers, neither are automobiles. The Feds went after the auto industry because they figured the lowly owners were easier to mandate to, rather than Big Business with their smokestack emissions and Big Oil with their Big Money.
Sure it helped, and smokestack emissions have been lowered as well, but picking on GA is silly against the factory emissions levels that are still too high.
Thanks for the great article and the points you make. I have an aircraft engine with FI and ECU (FADEC). It’s a newer design and very efficient. It want’s to burn Unleaded Fuel (UL94). But my FBO only sells 100LL. Even with lead scavenger additives the Tetra-Ethyl lead still fouled the spark plugs, valves and pistons. One of the keys to successfully weaning GA aircraft from lead is the existing infrastructure. I was reading about the early days of the automobile (1900) and how Standard Oil and others paid people to pump gasoline from drums to automobile drivers so that they could make trips out of the cities. This created gas stations and road maps and over time the highways and gas stations (infrastructure) we now take for granted. If we could convince the FBO’s in most airports to carry UL94 from Swift or Shell and push hard for UL100 I think that might be a solid step forward. Cats to come after perhaps.
Like everything it gets complicated. Many FBOs are insured by their fuel suppliers. Those same companies will not insure said FBO if they carry a different fuel. The FBO uses the “fuel supplier” insurance as it is often much less expensive than other options. There is also a full generation of aircraft owners and pilots that only know of 100LL . Many of them despite what their aircraft’s manual and placards may say, will not think of putting in anything other than 100LL.
I may be mistaken, but remember in the case of VW cheating on emissions…the additional NOX created was minimal when compared to the NOX generated by just one bolt of lightning.
It was stated that you could drive from NYC to LA and back in one of those VWs and still not create as much NOX as one bolt.
I’m sure aviation can leverage automotive technology to achieve lower emissions and maintain power. In fact, lean of peak operation is common. The big bugaboo,though, will be getting the FAA to buy off on it. An upside will be that our engines went longer use WWII technology. We’ll need to grandfather existing airplanes to make it acceptable.
EXCEPT FOR LEAD (PROBLEM?) THE START WAS THE CO2 + CH4, IT IS A NON-PROBLEM
(CAPS ARE MINE) …THE URBAN LEGEND OF 90+++ ? % OF ENVIROWACKO “SCIENETISTS AGREEE IS ABSOLUTELY DISENGENUOUS! (DISAGREE? PLEASE PROVIDE THE CITATIONS (SOURCE CAUSES .COM!). THIS MYTH BEGAN WITH THE IPCC REPORT BEFORE LAST WHEN 93% OF THER 47 EDITORS/AUTHORS OF THAT REPORT ACTUALLY AGREED WITH THE CONTENT OF THEIR OWN REPORT. …………………….. OPEN A WARM BEER AND A COLD BEER, HOW DOES THIS PROVE MAN IS NOT RESPONSIBLE FOR CLIMATE CHANGE. …………..
..”According to the EPA,……. most
man-made CO2 AND (H4) emissions come from the USE AND burning of fossil fuels such as oil, coal, and natural gas.”
TRUE BUT BY FAR:
MOST ATMOSPHERIC CO2 EMISSIONS COME FROM LITHIC AND ORGANIC DECAY, WARMING OF ORGANICS, THEIR MOISTURE, WATER INCLUDING ICE, LAKES, RIVERS. SEAS AND OCEANS DRIVES CO2 AND H4 OUT OF ALL OF THEM.
THE INCREASE IN CO2 IS ABOUT 150 PPM IN THE 150 YEARS AND H4, MUCH LESS SINCE THE L.ITTLE ICE AGE AND THE INDUSTRIAL REVOLUTION STARTED AND THE TOTAL IS ABOUT 400 PPM! SOUND LIKE A LOT???? LET’S COMPARE IT TO MONEY!! SO: 150 PPM = $150 COMPARED TO $1,000,000. IT IS NUMERICALLY WHAT $150 IS TO $1,000,000!
AND NOW, DRUM ROLL: THERE IS NO EMPERICAL OR EXPERIMENTAL EVIDENCE THAT THE INCREASE OF THE MINISCULE 150 PPM OF CO2 OR H4, HAS CAUSED ANY MEASURABLE INCREASE IN EARTHS ATMOSPHERIC TEMPERATURE.
SO WHAT HAS CAUSED THIS INCREASE IN CO2? NATURAL WARMING!
GO STUDY THE CARBON CYCLE (THERE ARE NICE PICTURES!)
SO WHY IS IT WARMER? THE CURRENT WARMING /CLIMATE CHANGE HAS BEEN GENERALLY GOING ON FOR ABOUT THE LAST 22,000 YEARS AS WE HAVE BEEN COMING OUT OF THE LAST ICE AGE AND MORE RECENTLY WARMING FOR THE LAST 150 YEARS COMING OUT OF THE L ITTLE ICE AGE!
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The California problems, which in many ways are Colorado River problems, will go away when the water runs out in the Southwest. The water situation is slowly worsening and the swamp critters can’t even have an intelligent discussion of how it might be dealt with.
The lawless behavior on the left coast will also self correct. The left coast libs are almost ready to do something about having their luxury cars damaged and stolen. Two words for the fix. Guns ammunition.
What would happen to the left coast if the electricity were to simply go away??
There is a Colorado scenario from law enforcement that would cause the SW to simply go away in any area depending primarily on the Colorado for water. This is a scenario that would take 24 hours, not months or years to occur.
Hav been reading a lot about the switch to electric planes lately. Seems to me that there are many restrictions to this approach, one being lack of range especially the higher you climb the colder it gets which batteries are not to fond of, the modern tech/electric panels a lot of people are upgrading to love power . Weight/power/range ratio just isn’t there and doesn’t look close either. One other concern is there any health issues being this close to such large amounts of power? Like in high power lines . Just a thought
No matter the reality vs the misconceptions, and speaking as someone immersed in automotive service for more the half a century, anything in aviation beyond unleaded fuel is going to cost a fortune if retro fits are required. Much like hush kits put many commercial aircraft out of service, think about a primarily hobby market.
Another thought provoking article full of informative that few pilots are aware of. Thanks Ben.
So, if they take the lead out of the fuel, and there are still many many many airplanes that will continue to require the lead so they don’t burn up their motors, what will they do? I’m assuming a lead additive would easily fix that problem. I checked prices on the best lead additives and it would seem that it should only add about .02 cents per gallon. Not horrible….But these idiotic Liberal ideas, because of imagined global warming will net nothing. The lead will still be in these planes, causing little to no damage at all to our environment. I was living in CA when they did this to marine fuel. I needed lead in my twin 302 Ford engines. I had to use a lead additive. Then they banned 2 stroke motorcycles for off-road riding. Geographically, California is probably the most beautiful and diverse states we have. Occupied by Chicken Little Liberals and run by Lame Brained Criminals. This is simply a new chapter in a Eden turned Hell State. They’ve lost millions in population and lost, I believe 2 Electoral votes for loss of population. People need to stand up or they will take everything from you. That goes for the rest of the country too. I run MOGAS in my plane. I don’t need lead. But, I’m standing up for all my friends that do need it to fuel their passion. This is wrong on so many levels.
Yes, there might be some work, some innovations still to come for aviation engines; but we also might take a big step forward with renewable fuels. Read more about renewable fuels in general on this nonprofit educational site: http://www.AdvancedBiofuelsUSA.org and find some specific articles about renewable, sustainable aviation fuel (mostly jetfuel) here: https://advancedbiofuelsusa.info/category/aviation/
The new service bulletin for lycoming engines in Cessna and Beech singles covers a lot of aircraft and is a step if not a big step forward. Full rich on takeoff is where the most noted lead deposits were forming on the ground path. The reason we only generally had one aviation fuel is because it was approved for just about everything even though not ideal for all applications and in the big picture, piston aviation fuel was a small percentage of that distillate.
Operation at recommended lean while not having the same lower emissions as a autos cat. converter is helpful as well.
So after 50 years of government controls of auto emissions, we have more auto pollution now then in the 60’s. Maybe we are controlling the wrong thing.
Maybe less politicians, less people,
Maybe less power plants and more electric cars and airplanes. Maybe more people in the USA and then complain about how little water we have. Maybe less manufacturing here and more in the uncontrolled manufacturing in China.
I know, let’s defund the police, complain about crime then have the Federal Government pay the cities that defunded the police, with the entire US taxpayers money, so the idiots can now solve the problem they created by defunding the police.
We need to elect, then support new leaders of our country. Then replace them every other election cycle so they can’t get rich at our expense. Lifetime politicians need to go.
On your comment of ‘ more auto pollution than in the 60’s, is not correct.
When I brought my 2, 60’s cars to California in the 70’s, the HC emissions were tested in the 600 ppm range.
Our newer cars test at 2-3 ppm HC, so there has been a huge improvement in smog forming emissions, like 200 x.
If you are referring to CO2, it is NOT a pollutant. The increase has improved food crop yields by 15+%, solely due to the higher CO2 level.
The levels that are harmful to humans is in the 50,000 ppm, about what we exhale .!
BTW, the typical CO2 levels on US submarines is usually in the 4,000-5,000 ppm level.
On the ‘political’ side , you get what you vote for, assuming the politicians aren’t lying to you.?
I was referring to the total pollution, the aggregate pollution of today. No matter where it comes from. The pollution, visible and not visible. 50 years ago we could see the Rockies from 100 miles away. Now you can’t see them 20 miles away. So no matter how you cut it, the pollution is worse today than 50 years ago.
Crops are more productive today solely because of our soil being poisoned with chemicals. You can’t even raise honey bees today because of agriculture poisoning. The only bug that survives is the mosquito.
I have to RO my water to remove all the nitrates so it’s safe for drinking and cooking.
You are correct in we get what we vote for. That is why no one should be in office long enough to get rich. And that goes for all political parties.
I don’t know what you mean by ‘total pollution’.
If you are referring to Colorado, it still has 9 coal fired power plants, generating 45% of the electricity. If all of the fly ash isn’t scrubbed there is that and a few radioactive elements emitted.
Auto engines are very much ‘cleaner’ emitting mostly CO2 and water vapor.
Where I live in Northern California I can see Mt. Diablo, 92 miles south.!!
CA has no coal power plants, but way too much solar and wind, which has caused major power shut-offs due to insufficient electrical generation in the last 2 years.
Total pollution from cars, power plants, wood fire places, home heating, ect. More people more pollution.
California imports about 85,000,000 MWs of electricity and exports nothing. California is connected to Colorado, Utah, Arizona and most states west of Nebraska. The western grid. So California may not have any power plants but do use and pollute their neighbor states that do have coal plants.
Colorado is in the process of closing all their coal fired plants with no good back up plan that is affordable. Although the power companies are installing wind generation in eastern Colorado so the front range can have their power. 95% of Colorado s population lives along the east side of the mountains from Pueblo to Cheyenne Wy. And most of the wind home companies are not US. Companies. The Colorado power companies just purchase the out put.
I would go along with wind if the companies that make a huge profit would put enough money in escrow to completely remove all the tower and the huge concrete and rebar base when the profit is gone and we are left with the mess.
Next?
Yup, Ca imports 30% of it’s electricity , on average. The stupid CA PUC tells the power companies what to do , and they do it….They don’t care, as long as they make the profits that they are guaranteed.
Most wood stoves here are damped down too much and produce huge amount of smoke- unburned hydrocarbons.
All the other sources you mentioned produce water vapor and CO2; both invisible emissions.
ok, so the water vapor is visible until it cools.
Here’s my fear with all this crap. If the government would just get out of the way and quit regulating everything we do in life, we would figure it out
The government keeps subsidizing with our tax dollars things that we would never buy.
There is a natural progression to things like cars, then roads, then gas stations, then better roads. Small towns with gas stations, full service, motels, restaurants with no tax dollars, just entrepreneurs putting their work and money at risk
Then the interstate highways and most of the small towns are ghost towns. Not that interstates are bad, just not for small America.
History repeats
Good conversation
Thanks
Shouldn’t the government regulate bad things like Pb that kills brain cells in kids?
To what extent should the government get involved?
On a federal level, no
On a local level, the local government should solve the problem and the local taxpayers should vote to finance the repairs/replacement of lead pipes for water distribution
I did not create the Flint Michigan problem ad I don’t want to finance the repairs. Not my problem
They normally ban my comments when I speak the truth here….👍
We’ve got three problems.
First, we constantly call attention to ourselves because our engines are far from quiet. Every time an airplane goes past, it is yelling “Hey! Look at ME!!” If our airplanes were quieter, far fewer people would even pay attention – out of sight, out of mind.
The second problem is that beyond the arcane and glacially slow efforts towards an unleaded aircraft fuel, we are essentially making NO efforts to reduce pollution from our aircraft. While we are a very very small part of the problem, we are a very very visible part of the problem. We could add PCV valves easily, we could vent the fuel tanks to the inlet tract to take care of evaporative emissions (with a spring loaded valve to let air back into the tanks on descent), we’re talking a $10 valve at an auto parts store and several feet of tubing (and when the FAA is done, it’ll be $10,000 per Cessna 150).
If we did just those few small things, we could show that we are trying to be part of the solution, we are at least trying to help.
The third problem is that most of our piston aircraft engines are totally obsolete technology. We’re stuck with them because nobody is going to create a complete line of contemporary engines with modern IC technology to retrofit all our airplanes – development costs would be astronomical, STC costs would be even worse, and nobody is going to buy a pair of $100,000 (each) new-tech low emission, reliable engines to put into a Piper Apache, or even one of them to put into a high-time Tomahawk.
The long-term future of GA is going to have to be electric. Quiet, no pollution, no leaky plumbing or exhaust systems, no dedicated supply system to ensure no cross-contamination with car gas, and nobody sumping the tanks and throwing it in the grass – even though MOST of us don’t do that any more.
The big iron piston aircraft are mostly either in museums or make appearances at airshows. Nobody uses a P-51 or B-25 for regular transportation any more. The medium piston twins will be endangered from the top by single engine turbines, and from the bottom by (eventually) more and more capable electric aircraft. They will also be endangered from the middle due to their high operating costs.
Personally, I don’t care what makes my airplane go – gasoline, diesel, electricity, pixie dust – as long as it will do what I need and want. Progress marches on inexorably. The only constant is change.
Correct me if I’m wrong, wasn’t lead added to fuel to increase the octane rating ? The more lead added the higher the octane in that fuel. When auto fuel went to unleaded fuel for smog control the lead was left out so as to rid of burning lead and having some control of the smog contributions. So why is it all of a sudden a monumental task of getting the lead out of avgas other than to continue ripping off the users of avgas !!! It is all a matter of money (greed) that’s all this is, it always has been and still is, We the users are still getting it in the shorts by our lovely powers to be. What a crock!! This should of been taken care of as fast as it was to add the lead in the first place. Printing all this information that no one understands is nothing but smoke and mirrors to keep ripping off the users of this fuel.. Bad arithmetic.
The simple answer;
– auto gas octane is now 87 to 93, vs with TEL it was as high as 130 for the 11:1 compression ‘muscle cars ‘ of the ’70s
– TEL was initially replaced with MTBE, but it was found to contaminate ground water if it leaked from the tanks. So, we now have ethanol in autogas to get 93 octane.
– the aviation fuels were reduced to 100/130 octane with the elimination of the lower grades.
– most certified engines and airframes cannot tolerate alcohol with the aluminum tanks and lines, since it is corrosive to aluminum.
So, the need for a fuel like G100UL.
Once G100UL is approved for all engines, there may be some interest in applying closed loop multi-point EFI for certified engines, since O2 sensors will survive with unleaded fuel exhaust.
There are a number of EFI and electronic ignition system available now for experimental aircraft, and a few Mag replacements.
But certified engines require FAA certification, at huge cost, and with the low volumes, not likely to happen.
So, the 200k+ existing aircraft will continue to fly without major modifications for a long time.
And, aircraft emissions from air cooled engine will remain high due to the oil burned, with loose piston/cylinder clearances.
Auto engine technology was driven by federal legislation, once TEL was removed from auto gas, adding the cat. converter, variable valve timing, etc….
The millions of engines produced annually allowed the development and EPA certification costs to be amortized easily, vs the few 100s of new piston aircraft annually,
Comparing general aviation (piston) emissions to the emissions generated by automobiles and presuming that equivalent steps are “required” or appropriate is hopelessly lacking in context and sense of scale.
Sure, there are elements of automotive technology that could benefit aircraft engines, but the ones worth chasing are the ones that increase fuel efficiency for a given power output, (further) simplify operation, increase TBO, or reduce maintenance. Most of the emissions equipment is there on car engines to deal with portions of the operating range that aircraft engines only briefly (if ever) enter like idling (once at operating temperature), low-power (low manifold pressure) highway cruise, and coasting/deceleration (even lower manifold pressure). (Even modern cars’ emissions systems do surprisingly little for at least a few minutes at cold start and at full power.) So, if foisted on aircraft, they would just bring unnecessary weight, complexity, cost, and potential failure modes to little actual benefit.
Moreover, and perhaps more importantly, the general aviation piston fleet accounts for a minuscule amount of the fuel burned each year, so the resulting emissions are (logically) also exceedingly small as a percentage of internal combustion emissions. So, taking the simplistic approach of just-do-what-the-car-manufacturers-did is akin to hiring a team of plumbers to fix a dripping faucet by ripping all the pipes out of your walls and starting over inside, while ignoring the cracked, gushing supply line outside at the curb, and then patting yourself on the back for saving water.
I genuinely hope unleaded avgas opens the door for aviation piston engines to benefit from some (more) of the impressive advances in automotive engine technology. But, those of us concerned with it had better ensure that we choose wisely from the menu of (real, relevant) benefits, rather than giving politicians and special interests a blank check to mandate whatever tickles their fancy.
Otherwise, I suspect we may be ushering in an end to general aviation as we once knew it and finally, completely turning our sky over to the airliners, rich jet setters, “urban air mobility” startups, and Amazon delivery “drones”. In fact, I think that outcome may actually be the real goal for some of those special interest lobbyists and their pet politicians, regardless of how they label it for now.
All new piston aircraft should have fuel injection, tuned for low emissions.
If we don’t take some action the result will be airport closures , like the current one in San Jose Ca- using the pollution as the lever to appeal to the public.
Fuel injection does NOT automatically mean lower emissions, though. Cars benefit from fuel injection because they must and do operate at a wide variety of throttle settings and loads, which made effective mixture control a compromise without continuous and wide ranging adjustment made possible by automated, closed-loop engine management.
Aircraft engines don’t and don’t need to operate over the side varied envelope. Except for fairly brief periods of operation at low power, they spend most of their lives at a handful of high (compared to cars) power settings. This, ironically, makes mixture settings pretty constant and (so) trivial to manage. That’s why you don’t really have to fiddle with the mixture once you are established at cruise.
Really, what is a bigger driver in our emissions (and fuel consumption) is the fact that we rely so much on fuel for cooling at high power. Adding fuel injection won’t change that. (Go check with the experimental guys.) And, unfortunately, that dependency is very unlikely change without liquid cooling.
My point is that electronic fuel injection isn’t the promised land for emissions and fuel economy in aircraft. It might make for easier starting, it may simplify engine management during flight, it might even make it easier to run lean of peak (which is the big savings source). But, compared to an otherwise same engine, also running lean of peak, the benefit will be marginal. Meanwhile it will come at the price of weight, complexity, cost, and more potential failure modes.
In my mind, you will see much more benefit from electronic ignition systems that allow variable ignition timing.
Like anything involving control of others life, it is never what it appears to be.
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