Latest FAA fleet fuel report deeply flawed

In November, the FAA published its latest “Reciprocating Engine Aircraft Fleet Fuel Distribution Report” DOT/FAA/AR-TN11/22. As described in the report’s abstract, “The purpose of the data analysis was to establish a baseline of aviation fuels currently in use by all reciprocating engine-powered aircraft to quantitatively assess the effect of first reducing and, eventually, eliminating the tetraethyl lead content on the population of aircraft currently certificated by the FAA.”

Incredibly, the report states that “Only 0.4% of the aircraft are approved to use unleaded fuel.” On further study, the report reveals that its authors were allowed to report only on fuels specified in aircraft Type Certificates, completely ignoring the fact that some 60,000 Supplemental Type Certificates (STCs) have been issued for lead-free autogas since 1982.

Furthermore, the report misses over 2,200+ new S-LSA aircraft that are best operated on autogas. Since LSAs are issued a Special Airworthiness Certificate as opposed to a Type Certificate, they were not counted, although they qualify as reciprocating engine-powered aircraft.

None of the estimated 30,000+ homebuilt aircraft that have been registered in the E-AB category appear in this report, and it is known that many are operated regularly on lead-free autogas. The report also makes no mention of an array of new, autogas-burning aircraft engines that power these LSAs, as well as higher performance aircraft, including the latest generation of products from Continental and Lycoming.

At best, this report is deeply flawed; at worse it was intended to create a skewed baseline to justify continued use of 100LL/100VLL longer than is necessary, given that — in reality — between 70%-80% of all piston engine aircraft are capable of operating on 91 AKI lead-free, ethanol-free autogas, an FAA-approved aviation fuel since 1982.

We strongly recommend that the FAA revise this report to include all reciprocating engine-powered aircraft, including TC’d, STC’d, E-AB, ULs, LSAs, rotorcraft, motorgliders, etc. Otherwise it is essentially worthless in its current form.

The GAfuels Blog is written by two private pilots concerned about the future availability of fuels for piston-engine aircraft: Dean Billing, Sisters, Ore., an expert on autogas and ethanol, and Kent Misegades, Cary, N.C., an aerospace engineer, aviation sales rep for U-Fuel, and president of EAA1114.


  1. Shortimer831 says

    I think Pilotlance is assuming something about ethanol in aircraft fuel that is not true.  Ethanol is not legal for use in aircraft, but to say “one drop” will cause engine failure is clearly not true.  I ran a tank of 10% ethanol through my 150 hp Lycoming by mistake last year as a result of the pump not being labeled correctly.  Actually, the problem with ethanol, other than the lower BTU content, is the fact that ethanol will mix with water and later the water can seperate out of the fuel.  Not a good thing and can result in engine fuel starvation but likely would not cause engine destruction.  Also some materials in the fuel delivery system may be susceptable to damage from ethanol.  I suspect in many  airplanes the fuel system materials manufactured in the last 20 years are resistant to ethanol because the manufactures of the components we use come from the manufacturers that make auto parts.  

  2. Pilotlance says

    There is a fly in your ointment! One caveat of an autogas STC is YOU CANNOT USE ANY AUTOGAS WITH ETHANOL IN IT! This precludes use of anything but something called REC90 available in Florida and I am not sure what other states. Aside from the fact that there is no guarantee that the REC90 is 100 gasoline with NOT ONE DROP OF ETHANOL. The consequenses are dire. Engine failure is highly likely if there is any ethanol.

  3. SkylaneDriver says

    I have run a Cessna C182 on 87 unleaded autogas for more than 20 years and more than 3000 hours.  At the engine overhauls the overhaulers have remarked at how clean the engine is and how few problems I have had.  The biggest problem with autogas, particularly in states like Michigan who suddenly stopped labeling unleaded fuel as to alcohol content was alcohol was added to nearly everything, resulting in the fuel being largely unavailable or untrustworthy.  I tested fuel and found ETOH contents as high as 30%, a risk I am not willing to take on the road.

    Where suppliers are known and trustworthy, I use autogas exclusively and have not had any significant problems with the fuel in any way.

    In addition, there are many light twins, using the same engines as singles which would certainly be capable of running on autogas provided someone is willing to do the airframe testing to develop the STC.  There are certainly some twins and very high performance engines which will require 100LL but I suspect they are fewer than we think.

    The FAA not identifying STC’d aircraft is appalling to say the least and not further testing autogas is inexcusable.

  4. ZuluFlyer says

    I think that an inquiry would be worthwhile – if the person doing the report got it wrong, they should be held accountable and penalised.  If their superiors dictated that only a small subset be assessed then they should be held accountable and penalised.

    This is public money these people are playing with – they owe it to us to do things properly in a balanced way.  Enough of the agendas, put America first!

  5. Kent Misegades says

    Pilotman,  we have reviewed the FAA registry and other sources and indeed it is true that 70%-80% of all piston-engine aircraft can operate on 91+ AKI lead-free, ethanol-free autogas.  Since only 112 airports offer autogas, most of these are forced to use leaded avgas however.  Nearly all LSA aircraft are powered by engines that should be run on autogas.  If more airports offered autogas, we’d see both a reduction in the cost to fly, and we’d demonstrate to the environmentalists and the EPA that we are doing something to reduce lead emissions.   This is not to say however that Avgas should be banned, just that we need more choices.

  6. Nedavis49015 says

    Well, I suppose one can’t take for granted that the FAA does it’s job well. Too bad. Not impressed with the agency’s incompetance

  7. pilotman says

    It’s hard to believe that 70 to 80 % of piston aircraft are approved for autogas.What percent of piston fuel sold is autogas? It has to be very small.

    Many of the piston planes used for business purposes have high performance,fuel-injected engines not capable of using autogas. Eliminating 100LL and 100VLL would cause great economic damage to an already fragile general aviation economy .The percentage of lead in the air caused by avgas is a tiny fraction of one percent. 

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