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Update on Avgas from the USA

here

As part of a study to attain a better understanding of how emissions from GA aircraft contribute to air quality, the Environmental Protection Agency has posted preliminary airport monitoring results indicating that 15 of the airports monitored during a year-long study have lead emissions well below the current National Ambient Air Quality Standard (NAAQS) for lead. The monitoring demonstrated that only two airports have preliminary data exceeding the NAAQS. It should be noted that these monitors were placed directly behind the run-up areas and were effectively monitoring direct emissions from the aircraft. The readings from these monitors are not reflective of levels that are normally found as distance from the aircraft is increased. AOPA, with input from air quality experts have questioned both the placement and subsequent results of these monitors and the relevance of their findings with respect to ambient air. According to the EPA, the monitors at these two airports were situated at locations representative of the highest expected airborne lead concentrations immediately downwind of the primary runup and takeoff area. The EPA also noted that information from other airports that have been studied in greater detail indicates that air lead concentrations decrease sharply within short distances from the takeoff areas.

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Despite extensive efforts, no unleaded replacement has been found and approved that provides adequate and comparable safety and performance to 100LL. But work on this important issue continues and is accelerating, with ongoing efforts to study and develop alternative aviation fuels.

Most significant is the realization that a replacement fuel will not be “drop-in” thus requiring the recertification of the entire fleet of existing aircraft. In doing so, this program will assess the viability of candidate fuels in terms of impact upon the existing fleet, production and distribution infrastructure, environment and toxicology, and economic considerations.

[my emphasis]

Administrator
Shoreham EGKA, United Kingdom

I have watched this issue since it first coming to light in US EPA presentations at the ASTM meetings I used to attend back in the late '80's and early '90's. At that time we, the industry, explained to the EPA, and the FAA backed us up, that it would be a monumental task to even test and evaluate all the different types for a fuel which was not a drop in (pour in?) replacement. Let alone the possible need for changes to the aircraft, or even just Flight Manual Supplements for changed operation.

There was talk of "derating" some aircraft, and I said that a few types could stand that, perhaps with gross weight reductions, but generally it would not work. It certainly would not work with any of the twins which need every bit of power available for single engine operations.

Even with the rhythm of testing established, there would still be tens of thousands of dollars of work per aircraft type, and in some cases model, to document and approve an alternate fuel.

If a drop in replacement fuel is not found, there are going to be many orphaned aircraft types, as it will not be economical to do the approval work at all. Other than for very mainstream legacy types like the Cessna 206, there will be little incentive for an approval organization to make the investment in testing and approving this.

Home runway, in central Ontario, Canada, Canada

My MSc research highlighted European GA's main environmental impacts of aircraft emissions and noise. Aircraft emissions and aviation noise pollution are taken seriously in Europe (2009/29/EC) especially as the EU is responsible for about 13% of global emissions (Worldbank.org, 2011). More than 50% of European land is used for agricultural and forestry production and directly impacts on Green House Gases (GHG-Europe, 2010) producing 48% European emissions (EC, 2009).

However, General and Business aviation together contribute less than 2 per cent of civil aviation emissions with GA producing 0.016% of all GHG global emissions and GA's ozone production reduces global warming caused by its own emissions. (Ozone destroys atmospheric methane (CH4) which is a powerful greenhouse gas with an atmospheric lifetime of 14 years) All European GA fuels are subject to taxation (2003/96/EC) which benefits governments.

True, aviation fuels and oil combustion do produce small amounts of sulphur and soot. However, sulphur reflects solar radiation back into space and soot traps outgoing infra-red radiation and not all sectors of GA contribute to GHG impact to the same extent.

Gliders use atmospheric energy causing no emissions and launching, by winch or motorised aircraft, produce minimal emissions and ballooning only causes minimal emissions when using the burner to gain height.

EGBJ, EGBP, EGTW, EGVN, EGBS

Pilot DAR, Peter.

The following was taken from the Comanche Owners Forum.

...The various comments about a “drop in” replacement can get lost in a fog of definitions.

What the words “drop in replacement" mean to you and other pilots - - and what they mean to Doug Mcnair may be very different.

Some people in the FAA and ASTM world have defined “drop in” to mean a fuel that fully meets the existing ASTM D910 spec for 100LL and 100/130 grade avgas - - but just differs only in the fact that the “drop in” would have zero lead.

With that definition of “drop in” - - then Doug is probably correct. But there is another concept of a ‘drop in’ replacement.

That alternative definition - - which we call a “functional drop in replacement” - - defines a fuel that works in the aircraft and engine without any changes to the aircraft and engine and is a fuel for which there is no operational difference apparent to the pilot.

That means the detonation response is the same. The range is the same (or better), vapor pressure is the same, material compatibility is the same, etc.

What GAMI did was to appreciate that back in the 1930s when the ASTM D910 standard was adopted - - they essentially did not start out with a specification - - and find a fuel that met the specification. They started out with a fuel that was known to “work” and wrote a specification around the fuel that “worked”.

We did the same. We found a fuel that worked in the high performance aircraft engine and wrote a new specification around the fuel that worked. As it turns out - - the new specification is very very close to the existing ASTM D910 specification.

But the reality is that the G100UL avgas is a completely functional drop in replacement. Multiple independent people have flown the fuel in the high compression (8.7:1) turbocharged Cirrus and have observed that the pilot cannot tell the difference when the fuel selector is positioned for the RH tank with G100UL avgas or the left tank with 100LL. And that evaluation has always taken place is in the presence of the exquisite digital instrumentation in the Cirrus glass panel. Among those independent people who have flown the G100UL avgas, is an FAA test pilot, a Phd aerospace engineer from one of the country’s large flight schools, AVconsumer (P. Bertorelli), people from TCM and Lycoming, and numerous other people. Any number of people, including AOPA, Cessna, the FAA, Avconsumer, TCM, Lycoming, and others have spent several hours each in the GAMI engine test facility and have observed the detonation performance of the G100UL on a high compression (8.7:1) turbocharged engine - - compared to 100LL.

In September of 2012, GAMI completed all of the required FAA STC flight testing for the TN SR22 aircraft. That testing was witnessed by no less than four FAA engineers who spent three days in Ada, Oklahoma. Testing was done all the way to 25,000 feet. Hot fuel testing. Climb cooling. Engine shut downs/restarts, etc. That flight test data has now been approved by the FAA. That is a milestone because it is the first time, ever, that anyone has completed all of the required FAA flight testing required to approve an unleaded fuel in a high performance aircraft.

If you have any questions, please do not hesitate to ask. I will try to respond.

Regards, George Braly

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