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The Death Of 100LL Avgas

by John M. White |  | 1 comment

Yes, it's true, 100LL (Low Lead) Avgas will be going away sooner rather than later. At a recent AOPA Aviation Summit a number of industry leaders commented that lead will removed from aviation fuels in the near future. Many in attendance fell into despair, fearing the demise of general aviation and the junking of all of our airplanes that rely on 100LL to operate. As a pilot you should know all fuels used in aircraft need to meet standards set by the ASTM (American Society for Testing Materials), which means wherever you purchase a gallon of Jet A or 100LL Avfuel it must meet the ASTM specification for that fuel.
With the Federal Government's obsession with the environment there is no question but that they intend to legislate lead out of 100LL Avgas and require an unleaded version. The problem is, most of today's piston aircraft engines have been certified to run on 100LL only.

Non-Turbo and Non-Super Charged Engines Have Nothing To Worry About

If your aircraft is non-turbocharged or super charged the proposed change to an unleaded avgas will not be a problem because your engines will run just fine. Those who are using engines which use 80/87 avgas, and Rotax 4 cycle engines, will be able to use the same fuel with no problems either.

Turbo Charged, Super Charged and Radial Engines Have A Problem

Here the problem is greater, because these engines will not run on unleaded avgas. This means someone will have to come up with a solution, re-certify the engines to run on the new avgas and accept the legal liability for those modifications. I was in the aviation insurance business for over 30 years and liability coverage for the manufacturers of these modifications will probably be available. However, if there are not enough of these engines around to warrant the cost of the liability coverage then some of them - and in particular rare museum model aircraft - may wind up as static displays rather than flying exhibitors. And that would truly be a shame.

Unleaded Avgas With A Lean Rating of 94

This is likely to be the solution to the unleaded issue. The industry is working on a specification for a 94 minimum lean rating fuel that will be similar to 100LL but without the lead. The new fuel will be available ??/??/???? - only our leaders in Washington can tell us, and they are clueless. In the meantime the ASTM is starting to define the fuel so that a reference fuel can be blended which will in turn allow engine manufacturers and modifiers to begin working on the systems and technology that will be required once leaded avgas is banned. While other fuels may be considered this is at least a starting point for our industry to begin designing systems to allow us to operate our aircraft safely. If you are interested in the issue I suggest that you follow posts in GA by Ben Visser who is an expert in this area. Until next time keep your wings straight and level Hersch! JetAviator7
Science has not yet mastered prophecy. We predict too much for the next year and yet far too little for the next ten.— Neil Armstrong, speech to joint session of Congress, 16 September 1969.

Comments (1)

  • Peter Wesselius on June 24, 2019

    It’s a shame that 100LL will be completely eliminated by this legislation, but only because of the many historic planes that need 100LL to run at all.

    For aircraft that are flown regularly, I think that it makes great sense to phase out 100LL fuel, due its danger as a potent neurotoxin, especially to young children.

    How dangerous? Take a Cessna Skyhawk with a 130mph cruising speed for example (assuming 7 gallons per hour).

    Since 100LL can still contain up to 2.12 grams of lead per gallon, that equates to 0.24 grams of lead emissions per minute (7gph / 60m) * 2.12, or nearly 15 grams of lead per hour.

    Lead has an LD50 in humans (median lethal concentration) of 100mg/kg or 0.1 grams for every 2.20 pounds of bodyweight. That means that an average 150-lb adult could die from about 6.8 grams of lead, or less than half of the lead emissions from a one-hour flight in a Skyhawk.

    I don’t believe 100LL kills anyone, but I do think that if 6.8 grams of lead can kill an adult, then a much smaller amount could have serious effects on young children and pregnant women. And I think that issue deserves to be taken seriously.

    It would amaze me if anyone truly believed that having cheaper fuel for their private aircraft was more important than the health of the general public.

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