Passing gas


It’s all Tom Midgely’s fault, so quit knocking him for ridding us of the knock.

That was the problem a chemist named Thomas Midgely was tasked to resolve in the early 1900s. His bosses at General Motors were making better engines with higher compression and higher horsepower output. Unfortunately, the gasoline going into those engines was little better than crude coming out of the ground. Pre-detonation, backfiring in plumes of acrid black smoke, and generally acting like a lope-eared jackass in heat plagued the early automotive engine. But knocking was the thing that irritated drivers most. It just didn’t sound right and, what’s more, it seemed like a bad thing to have in a device with hundreds of moving parts.

Midgely’s peers tried ethyl alcohol, but it was expensive and hard to blend. Then came iodine, red dye, and even organic derivatives from plants, but nothing seemed to help. What’s more, the additives stunk so badly that most drivers would rather stand next to an open septic tank than near an exhaust pipe.

Then in 1921 Midgely added a small dose of tetra-ethyl lead. Bingo! No knock and the engine purred like a kitten. It even smelled strangely nice. Lead became known as the “anti-knock” cure.

By this time the ratio of how much gasoline could be compressed before ignition occurred had been defined as “octane.” If compression causes ignition prior to the spark plug firing, you’ve got knock and probably a lower octane rating. But add some lead and voila!, the potential for higher octane with no knock. Adding lead allowed for cheap grade gas to be boosted to a higher octane and — under most circumstances — the higher the octane, the better the engine performs.

While auto engines were advancing in the 1920s, aircraft engines lagged behind with most, such as the Curtiss OX-5, putting out an anemic 90 hp. The compression was so low that anything from tractor gas to dandelion wine would do the trick. About 10 years after Midgely put the knock to rest, aircraft engines caught up quickly thanks to the air racing craze of the 1930s. Pratt & Whitney, Curtiss-Wright, and Lycoming were making 300-500 horsepower engines — some even supercharged with commensurate higher compression ratios.

That’s where air racing legend Jimmy Doolittle stepped up to the plate. He was working for Shell Oil as their aviation go-to guy and understood aircraft performance better than most. Not only was he an ex-Army record-setting pilot and the winner of every major air racing trophy in existence, he had an MIT doctorate in aeronautical engineering. He knew car gas was not up to snuff for big engine air racers and military pursuit planes. He convinced Shell to get the lead in gas and boost the octane rating from a measly 75 to a solid 100.

That did the trick and probably did more than is commonly acknowledged to win World War II since, without it, planes like the Mustang and tanks like the Sherman would have had a rough go of it.

For more than 80 years 100-octane gasoline has been the fuel powering most of piston aviation. The downside of all of this is lead. It is a heavy metal and, like its cousin mercury, is a neurotoxin. Ingest enough of it and it will kill you. Of course, just handling a bar of lead won’t kill you, even if you lick it like a Popsicle. However, when it degrades to a corroded dust it may become airborne and therein lays the danger. You breathe in enough of it and it builds up in your system to a toxic level, eventually causing organ failure and a host of neurological disorders.

But let’s put things into perspective: From 1979 to 1998, roughly 200 people in the U.S. died from a documented case of lead poisoning. Over the same period roughly 1,007 people died from an allergic reaction to a bee sting.

The obvious danger in 100LL is exhaust. Rational people don’t drink it but will occasionally breathe in the fumes via evaporation of gas in its input state or in its output state — exhaust. In a confined area this would be deadly, but not because of lead. Don’t believe me: Ask any securities broker under indictment for fraud, with two alimonies and a million dollar home, sitting in a car in a closed garage. In fact, over a 20-year period, 200 times more people died of carbon monoxide poisoning than of lead.

Anthrax is a bacteria-based bio-weapon and lethal if you breathe in the spores. It’s one of the oldest recorded chemical killers out there. Over the past 20 years five people have died of Anthrax. Like other chemical and biological agents, such as Sarin gas, which is 500 times more deadly than cyanide, it has to be inhaled in large enough quantities, but readily disperses to non-lethal levels when exposed in open air. In fact, the atmosphere has a natural propensity to scrub itself of toxic elements.

I guess that’s my problem with the push to outlaw 100 octane avgas. It sounds like the right thing to do. It even sounds like the safe thing to do. But sounding like and “is” are two different things. Everything in the right dose will kill you, even corn flakes.

I tried to kick the lead habit and for a time used 87UL car gas in my Yak, and since the old bird has very low compression, ran fine on it. I still had to use a lead additive, though, to save the engine. The Feds banned the additive and then went and put ethanol in all of the car gas in order to subsidize farmers. I didn’t want to turn all of my engine seals to liquid rubber so there went my 100LL alternative.

Some say 94UL is the answer. Well it may be for them, but if the slop won’t run in my nine-cylinder 285-hp radial, it’s worth zip to me.

In fact, nothing I hear is giving me a warm and fuzzy feeling. Although I do hear a lot of claptrap about biofuel, but how many Mickey D’s will suffice to supply French fry grease for the entire GA fleet?

And I’m getting tired of everyone telling me how much of a hazard I am to the environment. I guess that is my core problem with this fuel scare agenda. I’m not an alarmist. I don’t know many pilots who are. Being an alarmist means you tend to react immediately, without much provocation, and usually to the detriment of rational thought. In flying, that kind of thinking will get you and others killed faster than Anthrax, Sarin or even lead poisoning.

Hanshew has worked in aviation for over 35 years in all types of jobs, to include flight operations, flight technical, and air traffic control. He currently works in the Flight Standards department of a Part 121 airline. His wife, Donna, is a CFII and a Professor of Aviation Technologies at a large community college in Dayton, Ohio. Together they have owned owned numerous aircraft. They currently own a Nanchang CJ-6A (The Green Dragon) based at their home strip of Donner Field. Yes, after 24 years they still seem to get along.


  1. says

    This article misses the most important point about 100 LL avgas, economics. TEL is made by one company in England in an old plant. The demand for TEL decreases every year. Not exactly the business of the future. The TEL used in the US and a few other major countries is delivered in two aging 30 year old ocean tankers. There is no future in the business.

    One other thing to keep in mind is that only about 300 million gallons of 100 LL are made a year and the demand is declining, especially considering 70-80% of the GA fleet could be using unleaded gasoline today. Meanwhile refineries make 135 billion gallons of unleaded gasoline, also declining because of the economy. That means that avgas is less than 1/4 of 1% of their output and all of it requires special handling and transport in order to avoid contamination of unleaded product. None of it can be transported in a pipeline, the cheapest, most efficient method of moving petrochemical products. I don’t even know why the refineries bother and less than 10 do. Actually they would like it if 100 LL went away, that’s why they aren’t squashing Swift Enterprises and Virent Energy Systems, because they are no economic threat whatsoever. If avgas disappeared tomorrow it wouldn’t show up on any oil companies bottom line.

  2. Larry D. Butler, Ph. D. says

    Having read the article above by Bill Henshew, I must agree with him. The “environmental alarmists”, who seem to be thick as flea’s on an old dog, seem to be running the country. In reality, there aren’t that many of them, they just make a lot of noise, as in the “global warming” controversy, which the world has now learned was completely contrived, just to make a few people rich while ripping-off the American people! The situation here is exactly the same! The effects of lead in aircraft fuel is infinitesimal compared to others sources a person could die from. The statement of Grainger above indicated to me he doesn’t have a clue! The brain damage, Grainger refers to, suffered by children, is from ingesting it as dust or chewing it, when found in the form of paint. I personally don’t know that there are that many children standing around at the airport with their little noses stuck up an exhaust stack. Mr. Henshew’s comparison of people documented to have died from lead poisoning and bee stings is accurate and in my view warrants the use of “common sense” before removing 100LL from use. Of course I did insist upon using “common sense” and that definitely lets out those now in control of our Congress, the Whitehouse and those of the frame of mind like Grainger.

  3. says

    Anthrax spores are the problem: When subjected to drying conditions, anthrax will coat itself in a protein which will embalm it until wet conditions are available, like in your lungs or your gut. Anthrax spores have been shown to be viable after 50 years of storage. A contaminated aircraft would need to be subjected to toxic fumigation – similar to the process used on the offices of Senator Leahy and Daschle. The real question is how the spores are prepared, to maintain dryness, and to create particles small enough to provide air suspension. Initially, it forms into sticky clumps of sporifying bacteria, which normally keeps it from going airborne. This makes anthrax spores ideal for transport in smuggled drugs – and that is why aviation crews must be aware that carrying contraband heroin from Pakistan and Afghanistan resulted in 7 deaths in Scotland and 1 death in England from anthrax contaminated heroin injections. In any case, air crews should carefully consider the decision to be inoculated with the human anthrax vaccine – which is a refined extract of one of three anthrax toxins: The human anthrax vaccine can result in severe chronic auto-immune disease and unleash cancers because it has the potential of eliciting an immune response that will antagonise and potentially shutdown the human immune system. If exposed to anthrax spores, the most important therapy is to seek out immediate treatment with doxycycline antibiotics. The problem is that inhalation anthrax symptoms initially resemble influenza or pneumonia, and emergency medicine staff may not treat a patient with congested breathing if they assume that the patient has a viral infection: This killed two misdiagnosed drummers in the UK who were infected from drumheads made with imported African skins contaminated with the artificially virulent Vollum variety of anthrax: Pounding the drums aerosolized the anthrax spores. In short, air crews should avoid drug contraband from Central Asia, untreated imported African animal skins, and live animal cargo showing charcoal-black anthrax sores on the skin of their legs. For more information, see Scott Miller’s documentary “A CALL TO ARMS 2009 EDITION” which reviews the entire sordid history of both the US and UK military’s human anthrax vaccine programs.

  4. Grainger says

    You need to read up on the many sub-clinical effects of lead. Even small amounts cause permanent brain damage in children, and that is only one of lead’s many impacts on the body and mind. Ask your doctor about lead in gasoline.

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