May 1, 2006
Steven W. Ells
The hurricane season of 2005 hammered the U.S. Gulf Coast with unprecedented fury, leaving more than 1,300 dead and thousands homeless. In addition to the cost in human suffering, the storms also tore through the Gulf Coast petroleum industry — the offshore wells, the transport infrastructure, and the refineries — and sent automobile gasoline prices soaring to new levels. Rumors flew across the country of $5- and $6-a-gallon gasoline, especially in the storm-ravaged South.
Today, the Gulf Coast petroleum industry, which supplies 28 percent of the nation's crude oil production and 47 percent of the country's refining capacity, is back up and running, and auto fuel prices have almost returned to pre-Hurricane Katrina levels. Avgas prices paralleled auto fuel increases, making $4-a-gallon avgas commonplace.
The rapid increase in avgas prices set the rumor mill in motion — will avgas supplies be affected?
To answer this question, we must first consider the overall avgas picture. We looked at the future of avgas four years ago. " Lead Is Still King," published in the May 2002 issue of AOPA Pilot, reported that nothing worked as well as tetraethyl lead (TEL) to control the detonation that's capable of causing engine damage in high-powered air-cooled airplane engines.
The American Society for Testing and Materials (ASTM) has established a standard for an alternative 91/98-octane unleaded avgas, and the FAA has approved 82UL — an 82-octane unleaded fuel. It is estimated that these fuels will work in 70 percent or more of the general aviation fleet. In response to the approval of 91/96 unleaded avgas in Europe, Lycoming Service Instruction 1070L was amended to add this fuel to the list of approved alternative fuels for its 80- and 91-octane engines.
Engines that must burn 100-octane avgas depend entirely on the additive TEL — a toxic product that is produced in declining quantities by one factory in the United Kingdom. An Environmental Protection Agency (EPA) ban on TEL in all other fuels and the fines associated with violating the ban prevent oil companies from using pipelines to move avgas around the country. Since dedicated barges, trucks, and railcars are required to distribute what amounts to small quantities of avgas to hundreds of airports spread out over a very wide geographical area, it's estimated that avgas transport alone costs $3 per mile.
Avgas prices, as a percentage of ownership costs, average approximately 13 to 15 percent for a Cessna 172 flown 50 hours a year. This slice of the cost of the aircraft ownership pie is no more immune to increases than increases in the cost of insurance or hangar rental. Oil prices increased 50 percent, from $40 to $60 a barrel, during the year preceding August 2005. Avgas and auto gas prices increase in lockstep with crude oil prices. In December 2005 the average price of a gallon of 100LL across the nation was $3.78. In 1970 the price of 100-octane fuel was 38 cents a gallon. If the increase in the consumer price index from 1970 to 2005 was applied to the price of a gallon of avgas, it should now cost about $1.94 a gallon. But even with the additional costs related to the transportation of leaded avgas and TEL, experts believe that alternative aviation fuels under consideration will be more expensive than today's 100LL.
In addition to the transportation obstacles, there are several other clouds on the 100LL avgas horizon. The quantity produced each year is smaller than tiny. Avgas amounts to 0.5 percent of the yearly U.S. gasoline production. Usage of 100LL peaked in 1959 at 3.3 billion gallons a year — last year that figure hovered around 550 million gallons. Since refineries can produce a three- to six-month supply of avgas during a one- or two-day production run, stabilizing agents and storage also add to the cost.
TEL clearly is the magic bullet for 100LL avgas today. In spite of a two-decade-long search for a replacement, nothing has yet been found to take its place. But there is the possibility that the EPA will change its mind and revoke the exemption to the 1990 Clean Air Act that permits TEL use for avgas.
Ben Visser is an aviation fuels expert who spends his retirement on his South Dakota farm. During the long cold winters, he tinkers with tractors — he has 12 — so he can enter them in tractor pulls during the long days of summer. A few years ago Visser retired from Shell Aviation Products, but he still keeps up with the industry. "This is all about money and politics, and right now there's no interest in Washington in getting rid of the lead," said Visser. That's good news.
More good news is that ongoing studies and research on future fuels continue under the umbrella of the nonprofit Coordinating Research Council (CRC). Research agendas from CRC have yielded solid progress following concentrated testing efforts by the FAA at the William J. Hughes Technical Center in Atlantic City, New Jersey.
Beginning in 1992 a study group started working toward an alternative to leaded avgas. The group is named the Unleaded Avgas Development Group (UADG) and includes representatives from AOPA, the FAA, the petroleum industry, and aviation airframe and engine manufacturers from around the world. This group defined two tasks — determine exactly what octane was required for today's airplane engines and establish, through lab and field testing, fuels that would work as well as today's 100LL.
The group's stated goal was a transparent unleaded fuel, meaning it could replace 100LL from one day to the next with no difference in performance, cost, or engine reliability.
It's known now that the ASTM standard 91/98-octane unleaded avgas should provide detonation protection for 70 percent of the fleet. But for the other 30 percent of the fleet nothing has changed. UADG brainstormed a list of 212 additives that had potential as alternatives to TEL. Lab testing narrowed the list to 30 blends. In 2005 the FAA conducted test-cell-engine runs (using a Lycoming IO-540) with these formulations. A 314-page report titled "Full-Scale Engine Knock Tests of 30 Unleaded, High-Octane Blends" issued at the end of 2005 summarized the findings. Forty-two new blends were expected to be delivered to the tech center in February to start the next round of tests. According to David Atwood at the test center, "We're deep in the heart of the issue, and we're definitely making progress."
One obvious Achilles' heel of 100LL is the single source of TEL. But there's another cloud on the horizon that some experts think is a greater risk. At low combustion temperatures — when the engine is idling or at low taxiing speeds — TEL remains in solution in the fuel. Since fuel mixtures are typically very rich at these speeds, this results in lead deposits on spark plugs, valves, and cylinder head combustion chambers. A lead scavenging agent called ethylene dibromide — which combines with the lead at temperatures above 1,200 degrees Fahrenheit — is present in every gallon of 100LL. This additive is also on the EPA's hot list because of its potential to leach into groundwater.
Boosters of an ethanol-based avfuel solution are touting AGE (aviation-grade ethanol) as a future avgas. AGE consists of 85-percent ethanol and 15-percent light hydrocarbons and biodiesel.
According to Ted Aulich of the Energy & Environmental Research Center (EERC) at the University of North Dakota, the fuel used to be called AGE 85 and now goes by AGE — some people apparently thought the number 85 referred to the fuel's octane rating. Ethanol producers include agribusiness giants such as Archer Daniels Midland and Cargill. Even Bill Gates, founder of Microsoft, has bet on the future of ethanol by investing $84 million in the construction of five West Coast ethanol-producing plants.
According to Dennis Helder of South Dakota State University (SDSU), AGE provides better detonation protection than 100LL, with octane ratings as high as 106. Helder says there's only one drawback — it takes a lot more of it to produce those results.
Cesar Gonzalez and co-author Richard Jesik wrote a Cessna engineering report published in July 2002 titled "Evaluation of Ethanol-Based Aviation Spark-Ignition Engine Fuel." Gonzalez and Jesik concluded that although AGE does produce 10- to 15-percent-higher power outputs and cooler cylinder head and exhaust gas temperatures than 100LL, fuel flows that provided identical detonation margins — measured at identical power outputs — were higher by 43 to 47 percent.
One solution for this shortcoming is to increase the efficiency of the engines in the fleet. The easiest way to increase efficiency is to raise cylinder compression ratios, typically done by installing taller pistons in each cylinder. This alone makes it impractical to consider AGE as a transparent solution to 100LL because of cost and engine-recertification issues.
The Cessna paper also contained studies on the effects of AGE related to materials-compatibility issues with airframe parts including common aluminum alloys, soft parts such as fuel bladders, and rubber parts such as hoses and O-rings. The report also cited calibration problems with capacitance-type fuel indicating systems, incompatibility problems with fuel-fired combustion heaters because AGE is a low-volatility fuel — this prevents successful heater light offs at cold temperatures — and AGE instability during long-term storage conditions. This study also stressed the fact that water can't be sumped out of AGE-fueled airplanes.
In December 2004 the EERC issued a final report titled "Aviation-Grade Ethanol Materials Compatibility Evaluation." It was prepared by the EERC for Helder. This study — conducted in accordance with a variety of immersion test procedures specified by the ASTM and the Society of Automotive Engineers (SAE) — counters almost all of Gonzalez's conclusions. Helder also questioned Gonzalez's idea that water separation (in a fuel) is a desirable feature, citing FAA statistics noting that 88 fatalities between 1983 and 2001 were attributed to water- or ice-related fuel system problems. "Even if 5 percent of the liquid in a tank of AGE is water, the pilot will never know it's there," proclaimed Helder in a recent phone interview. Water dissolves in AGE. "Not only that, [but] AGE is an absolutely green fuel from an EPA point of view; in fact, people drink the stuff," joked Helder.
One reason for the increase in publicity about AGE is money. In November 2004, U.S. Sen. Tim Johnson (D-S.D.), former Sen. Tom Daschle (D-S.D.), and Rep. Stephanie Herseth (D-S.D.) announced that the SDSU aviation-grade ethanol research program was funded to the tune of $1 million a year for a three-year period as part of the omnibus spending bill.
The FAA testing center recently completed a 150-hour endurance test using AGE, but its study hasn't yet been published.
None of the experts interviewed for this article believes that any of the potential 100LL replacement fuels would be transparent. "They're going to cost more and deliver less performance," predicted Visser.
Leaving the political, legal, and financial problems aside for a moment, perhaps one of the biggest roadblocks to a 100LL replacement is the problem of FAA certification. There are many questions that have never before confronted an entire industry. Will the engine manufacturers issue a blanket unleaded-fuel approval for their existing GA engines? Or will each model have to be subjected to testing similar to the 150-hour endurance testing required for new engine certification? If airframe changes also are required, how will these be accomplished? Who is going to pay for these certifications? What about approvals for orphan airplanes and warbirds?
At this point the UADG steadily moves ahead. The group's goal is not the production of a new fuel. According to Ron Wilkinson, the acting head of the group, "There's no dedicated funding for petroleum-based avgas research so we haven't been able to move as fast as I hoped. [The funding referred to above is dedicated exclusively to AGE research.] We think we will be in pretty good shape to make some recommendations [to avgas producers] in a couple of years."
Tim Roehl of General Aviation Modifications Inc. (GAMI), of Ada, Oklahoma, provided an update on the company's pressure reactive intelligent spark management (PRISM) system. "We know PRISM is a solution because we have been able to produce rated power from a Lycoming TIO-540 engine under worst-case testing with 95-octane unleaded fuel," said Roehl. "This is a substantial electronic engine control system involving three certification issues." Certification includes the PRISM system, GAMI's Supplenator supplemental alternator system, and the system software. Roehl projected that airplane flight testing would begin later this year.
Teledyne Continental Motors/Aerosance also has stated that its full authority digital engine control (FADEC) system will enable its engines to run safely on 91/96 UL. The system is certified for retrofit on a few airplanes in the existing fleet, with prices hovering around $10,000.
AOPA has successfully lobbied for continued FAA research into technologies for modifications of existing general aviation piston engines to enable a transition to a more environmentally friendly and economically viable GA fuel.
There still is no transparent substitute for TEL-fortified avgas. But nor is there any reason to believe that a replacement will be needed in the near future. Of course, a shift in the political landscape could change this timetable, but rest assured that AOPA will be involved in this issue.
E-mail the author at email@example.com.
Links to additional information about avgas may be found on AOPA Online.
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