April 2014- In 1990 amendments to the Clean Air Act were enacted. In 1995 the industry and the FAA started seriously searching for an unleaded 100 octane avgas. In the intervening time 245 fuels were tested by the FAA at its William J. Hughes Technical Center; the testing was overseen by the Coordinating Research Council (CRC). That testing yielded 45 blends that held promise.
The goal of this testing was to find an unleaded formulation that would shoehorn into the existing leaded 100 octane fuel specification. If such a formulation was found it would mean the new Avgas would be a “drop-in” replacement for 100LL. No engine or airframe modifications or upgrades would be needed, and the new unleaded fuel and the existing leaded fuel would mix.
None of the new fuels ever completely met all 44 specifications in American Society for Testing and Materials (ASTM) D910, the spec for today’s 100LL Avgas. New ASTM standards would have to be developed.
The General Aviation Gasoline Coalition was formed to “look into the state of the aviation marketplace.” It concluded that the problem was so complex from so many angles that a federal/private partnership was needed to study the problem. It petitioned the FAA to form such a partnership and in January 2011 the FAA administrator signed the charter.
The UAT ARC and PAFI
In 2012 the Unleaded Avgas Transition Aviation Rulemaking Committee (UAT ARC), which consisted of parties such as fuel producers and suppliers, engine manufacturers, airframe manufacturers, association leaders and the FAA, concluded that a new approach was needed.
The 2012 UAT ARC report reached the following conclusions:
• An unleaded replacement fuel that meets the needs of the entire fleet does not currently exist.
• No program exists that can coordinate and facilitate the fleet-wide evaluation, certification, deployment, and impact of a fleet-wide replacement Avgas.
• No market-driven reason exists to move to a replacement fuel due to the limited size of the Avgas market, diminishing demand, specialty nature of Avgas, safety, liability, and the investment expense involved in a comprehensive approval and deployment process.
• No FAA policy or test procedures exist to enable fleet-wide assessment and certification of a replacement unleaded fuel.
• There is no standardized method for communicating to the industry and end users the impacts posed by a newly proposed fuel.
These five points illustrate the complexity of the problem. Simply put, the UAT ARC concluded that there’s no coordination system, there’s no financial motive to invest in an unleaded fuel, there’s no method to certify the use of an unleaded 100 octane fuel in existing aircraft or engines, and there’s no fuel.
One of the UAT ARC recommendations was the establishment of “a collaborative industry-government initiative referred to as the Piston Aviation Fuels Initiative (PAFI) to implement the UAT ARC recommendations in this report designed to facilitate the development and deployment of an unleaded Avgas with the least impact on the existing piston-engine aircraft fleet.”
One of the first actions by PAFI was to open a window for all developers of unleaded fuels to submit their fuel formulations and the test data supporting these fuels to the FAA for testing in Phase I of the fuels program.
Due to federal guidelines all submitters are required to use the established bid process for submissions. In other words, they’re bidding for a contract the same way a building maintenance supplier or a runway resurfacing company bids on an open contract.
The window for submissions is open until July 1, 2014. By September 2014, the most promising of fuels selected for further testing will be trimmed to 10. Evaluations will consider the impact each fuel will have on production/distribution, environmental and toxicology impacts, and economic impacts on the entire fleet. Phase II testing will continue through 2018.
During Phase I the submitter may be asked, in accordance with the contract guidelines, to provide 100 gallons of fuel. Fuels that are selected for Phase II testing may be asked to provide 10,000 gallons of fuel.
In the federal budget passed in early 2014, $5.7 million of the $15.6 billion FAA budget for 2014 was earmarked for PAFI and for testing unleaded fuel candidates.
According to Rob Hackman, vice president of regulatory affairs at the Aircraft Owners and Pilots Association (AOPA), “The two most promising would potentially come out of the testing with a certification package that the sponsors could use to seek approval to actually operate the fuel in the fleet.”
In other words, the two fuels that are given certification packages can then apply for an ASTM specification.
General Aviation Modifications Inc. (GAMI)
General Aviation Modifications Inc. (GAMI) is a well-established company headquartered in Ada, Okla. Best known for its GAMIjectors, this small company is, in my opinion, the leader among small companies developing an unleaded 100 octane Avgas.
According to George Braly, who, along with Tim Roehl founded GAMI in 1994, G100UL—GAMI’s unleaded 100 octane fuel—can be produced in any refinery and will be cost-competitive with today’s 100LL. GAMI first introduced G100UL over four years ago.
G100UL requires a high quality aviation alkylate stream. According to Braly, the only place that’s available is from the existing Avgas refineries. Braly said there are eight refineries that are presently capable of manufacturing G100UL.
Braly and Roehl built the Carl Goulet Memorial Engine Test Facility in Ada. Carl Goulet spent his working life intimately involved with aircraft engine technology and worked with companies such as Teledyne Continental Motors and Superior Air Parts over a period spanning nearly 40 years. Goulet provided guidance to the GAMI team that buttressed its understanding of the internal processes in Avgas combustion and mixture distribution in air-cooled aviation engines.
The Goulet Test Facility is one of the most sophisticated engine test facilities in the world. See Resources at the end of this article for more information on this facility.
The Goulet facility has proven pivotal for GAMI in testing G100UL. Because of the sophistication of the test facility, GAMI has the capability to vary every parameter needed to comply with the existing ASTM D910 standard. Tests calling for worst-case scenarios such as extremely high inlet air temperatures, cylinder head temperatures and fuel temperatures are no problem in the GAMI test cell.
Although D910 will not be the final standard for the “New Avgas,” it provides a very detailed preview of the tests that fuels submitted to PAFI will undergo.
ASTM has also issued D7826-13, “Standard Guide for Evaluation of New Aviation Gasolines and New Aviation Gasoline Additives” that further outlines the expected fuels evaluation process.
A few of the tests that all candidate fuels must be equivalent or better than 100LL include:
1. Resistance to detonation.
2. Materials compatibility—in hoses, seals, metal, composite and rubber bladder-type tanks. This also includes deposits. Roehl says that 100LL would never be approved today due to the existence of lead deposits that occur in fuel valves, lines and engine parts such as piston crowns and valves, and contamination of engine lubricating oils.
3. Economics—the fuel must be on par or better than 100LL; this includes the cost of manufacturing and transportation.
4. A new fuel must be completely fungible with 100LL to permit a gradual fleet-wide transition as the New Avgas is introduced.
5. The New Avgas must be transparent to all existing airframes and engines.
One of the biggest challenges facing the transition to the New Avgas is the granting of FAA approval for use of the new fuel. Historically certifications are obtained for both engines and airframes. A fleet-wide approval of a new fuel for use in both airframes and engines has never before been done in the United States.
GAMI milestones
In September 2012 GAMI completed the full series of required testing for airframe certification of a fuel in accordance with the latest (Part 23) FAA requirements. The company did the testing in a turbo normalized Cirrus SR22 airplane burning G100UL. The engine in that test airplane is a TNIO-550N; it’s an engine with a compression ratio of 8.6:1.
In December 2012 the FAA accepted the findings from that testing as approved data. In other words, if G100UL were an approved fuel, today it would pass the existing testing required for airframe certification. As far as I know this is the first time an unleaded 100 octane fuel has passed Part 23 airframe certification tests.
In April 2013, GAMI completed the materials capability rig testing of a large cross section of fuel system components including new, new old stock, and repaired bladder-type fuel cells and carburetor and fuel-injection system components. (For G100UL news, FAQs, photos and videos of the some of these tests, see Resources. —Ed.)
In August 2013 GAMI, with help from Embry-Riddle Aeronautical University, completed the required Part 23 hot day/hot fuel testing protocol in a Cessna 172. An Embry-Riddle flight test pilot and an FAA Designated Engineering Representative (DER) flew the tests in Ada.
This test protocol included hot day/hot fuel climb tests for vapor lock characteristics; a comparison of engine cooling characteristics between G100UL and 100LL; climb comparison characteristics between the two fuels; and hot day operability testing including in flight engine shutdowns and restarts and throttle slams/response as well as full mixture sweeps.
GAMI in partnership with Embry-Riddle is presently conducting a FAA approved flight test program using a C-172 in a 150-hour endurance and functionality/reliability test program.
The executive summary from Embry-Riddle on the first of three phases in the above-mentioned program says the difference felt and observed when switching from 100LL to G100UL “were small enough that the pilot could not feel them.” In addition, there was no spark plug lead fouling during the G100UL tests.
Dr. Richard “Pat” Anderson, an associate professor of aerospace engineering at Embry-Riddle, is overseeing the G100UL testing. In an interview with AvWeb, Anderson said, “I know some people are saying there’s no drop-in replacement for 100LL, but this looks a hell of a lot like a drop-in replacement to me.”
GAMI is already well into the testing and data gathering needed to buttress its goal of certifying G100UL using the Goulet test stand and through the testing described above. A TNIO-550N engine has been installed in the Goulet test cell in preparation for the required 150-hour endurance and reliability testing using G100UL. According to Tim Roehl of GAMI, other engines are in line for endurance testing.
The immediate goal in this testing is obtaining an STC for the use of G100UL. According to the FAA, an STC is a “document issued by the Federal Aviation Administration approving a product (aircraft, engine, or propeller) modification. The STC defines the product design change, states how the modification affects the existing type design, and lists serial number effectively.”
This official definition is somewhat limited since the wording doesn’t mention fuels, however, both EAA and Petersen Aviation have obtained STCs for the use of gas station pump auto fuel (mogas) in hundreds of aircraft engines and airframes.
GAMI has already completed a number of the required tests in the STC process.
Why is GAMI pursuing an STC for G100UL? And why is the extended testing being done in a Cessna 172 instead of one of the more highly stressed engines in the GA fleet?
The simple answer to that question is that an STC to use G100UL in a C-172 will provide the avenue to gather reams of data if, for instance, a fleet of 172s from a busy flight school such as Embry-Riddle burns G100UL for three months. Reliable, verifiable data is the foundation of every fuel certification process.
“At the present time doesn’t intend to enter the PAFI program,” said Roehl in a December 2013 interview. “We’re going to finish our program before because GAMI is already so far down the road that it would just slow us down.” Roehl went on to say that there’s already a commitment on the part of the FAA to support GAMI’s STC program.
The next step after the G100UL STC is approved is to submit a list to the FAA of other aircraft that GAMI’s data supports the use of G100UL. The list is called an Approved Model List (AML), and 90 percent of the STCs issued by the FAA are expanded to other aircraft through the AML process. Both EAA’s and Petersen Aviation’s autogas approvals use AMLs to expand their STCs.
Braly provided an indication of GAMI’s progress when he said, “We’re the only ones out there with a certification process that leads to a fleet-wide certification of its product.”
In the February 2013 issue of Piper Flyer, Dr. Tim Shea, when speaking about Shell’s unleaded 100 octane fuels, revealed that Shell is also concerned with the extended timeline in the PAFI program. As of late in December 2013, Shell hadn’t decided if it would submit its fuel to PAFI.
Next month I’ll report on Swift Fuels’ unleaded 100 octane fuel.
Steve Ells has been an A&P/IA for 39 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to editor@www.piperflyer.com.
Resources
Carl Goulet Memorial Engine Test Facility
G100UL
Further information, videos and photos
gami.com/g100ul
General Aviation Modifications Inc. (GAMI)
GAMI.com
