Avgas is a
high-octaneThe octane rating is a measure of the resistance of gasoline and other fuels to detonation in spark-ignition internal combustion engines. High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel...
aviation fuelAviation fuel is a specialized type of petroleum-based fuel used to power aircraft. It is generally of a higher quality than fuels used in less critical applications such as heating or road transport, and often contains additives to reduce the risk of icing or explosion due to high temperatures,...
used to power many
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
and racing cars.
Avgas is a portmanteau for
aviation gasoline, as distinguished from
mogas (motor gasoline), which is the everyday
gasolineGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines...
used in
carsAn automobile, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
. Some light aircraft also use automobile fuel instead of avgas.
Avgas is used in aircraft that have piston or
Wankel engineThe Wankel engine is a type of internal combustion engine which uses a rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that is...
s.
Gas turbineA gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. Energy is added to the gas stream in the combustor, where air is mixed with...
s can operate on avgas, but typically do not. Turbine and
diesel engineA diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression...
s are designed to use
keroseneKerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
-based
jet fuelJet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw colored. The most common fuels are Jet A and Jet A-1 which are produced to an internationally standardized set of specifications...
.
Avgas properties and varieties
The main
petroleumPetroleum or crude oil is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds.The term "petroleum" was first used in the treatise De Natura Fossilium, published in...
component used in blending avgas is alkylate, which is essentially a mixture of various
isooctanes2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an octane isomer which defines the 100 point on the octane rating scale . It is an important component of gasoline....
, and some refineries also use some reformate. Avgas has a
densityThe density of a material is defined as its mass per unit volume. The symbol of density is ρ .- Formula :Mathematically:where: is the density, is the mass, is the volume....
of 6.02 lb/US gallon at 15 °C, or 0.72 kg/l, and this density is commonly used for weight and balance computation. Density increases to 6.40 lb/US gallon at -40 °C, and decreases by about 0.5% per 5 °C increase in temperature. Avgas has an
emission coefficientAn emission intensity is the average emission rate of a given pollutant from a given source relative to the intensity of a specific activity; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to GDP...
(or factor) of 18.355 pounds
CO2Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
per US gallon, or about 3.05 units of weight CO
2 produced per unit weight of fuel used. Avgas has a lower and more uniform
vapor pressureVapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed container. All liquids and solids have a tendency to evaporate into a gaseous form, and all gases have a tendency to condense back to their liquid or solid...
than automotive gasoline, which keeps it in the liquid state at high-altitude, preventing vapor lock. The particular mixtures in use today are the same as when they were first developed in the 1950s and 1960s, and therefore the high-octane ratings are achieved by the addition of
tetra-ethyl leadTetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula 4Pb. Once a common antiknock additive in gasoline , TEL usage was largely discontinued because of the toxicity of lead and its deleterious effect on catalytic converters...
(TEL), a highly toxic substance that was phased out for car use in most countries in the late 20th century.
Avgas is currently available in several grades with differing maximum lead concentrations. Since TEL is a rather expensive additive, a minimum amount of it is typically added to the fuel to bring it up to the required octane rating so actual concentrations are often lower than the maximum.
Jet fuelJet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw colored. The most common fuels are Jet A and Jet A-1 which are produced to an internationally standardized set of specifications...
is not avgas. It is similar to
keroseneKerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
and is used in turbine engines. Confusion can be caused by the terms Avtur and AvJet being used for Jet Fuel. In Europe, environmental and cost considerations have led to increasing numbers of aircraft being fitted with highly fuel-efficient diesel engines; these too run on jet fuel. Civilian aircraft use Jet-A, Jet-A1 or in severely cold climates Jet-B. There are other classification systems for military turbine and diesel fuel. See
Jet fuelJet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw colored. The most common fuels are Jet A and Jet A-1 which are produced to an internationally standardized set of specifications...
.
Consumption
The annual U.S. usage of avgas was 186 million gallons (704 million liters) in 2008, and was approximately 0.14% of the motor gasoline consumption. From 1983 through 2008, U.S. usage of avgas declined consistently by approximately 7.5 million gallons each year.
Grades
GasolineGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines...
used for aviation fuel is generally identified by two numbers associated with its
Motor Octane Number(MON). The first number indicates the octane rating of the fuel tested to "aviation lean" standards, which is similar to the anti-knock index or "pump rating" given to automotive gasoline in the U.S. The second number indicates the octane rating of the fuel tested to the "aviation rich" standard, which tries to simulate a supercharged condition with a rich mixture, elevated temperatures, and a high manifold pressure.
Fuel dyesFuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear"....
aid ground crew and pilots in identifying the proper fuel grade:
100LL
Dyed blue, 100LL, spoken as "100 low lead", contains
tetra-ethyl leadTetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula 4Pb. Once a common antiknock additive in gasoline , TEL usage was largely discontinued because of the toxicity of lead and its deleterious effect on catalytic converters...
(TEL), a lead based
anti-knockKnocking in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front...
compound, but less than the "highly-leaded" 100/130 avgas it effectively replaced. Most piston aircraft engines require 100LL and a suitable replacement fuel has not yet been developed for these engines. While there are similar engines that burn non-leaded fuels, aircraft are often purchased with engines that use 100LL because many airports only have 100LL. 100LL contains a maximum of 2
gramThe gram , ; symbol g, is a unit of mass.Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or...
s of TEL per US gallon, or maximum 0.56 grams/litre and is the most commonly available and used aviation gasoline.
82UL
82UL is the specification for an unleaded fuel similar to automobile gasoline but without additives. It could potentially be used in aircraft that have a
Supplemental Type CertificateThe Supplemental Type Certificate is the Federal Aviation Administration term for the approval that extends a type certificate for modifications made to an airframe, engine, or appliance.-External links:*...
for the use of automobile gasoline with an aviation lean
octane ratingThe octane rating is a measure of the resistance of gasoline and other fuels to detonation in spark-ignition internal combustion engines. High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel...
(MON) of 82 or less or an antiknock index of 87 or less. It could not be used in engines that require 100LL. The FAA highly recommends installing placards stating the use of 82UL is or is not approved on those airplanes that specify unleaded autogas (mogas) as an approved fuel. As of 2008, 82UL is not being produced and no refiner has announced plans to put it into production..
80/87
Dyed red, avgas 80/87 had the lowest lead content prior to its phase out in the late 20th century, with a maximum of 0.5
gramThe gram , ; symbol g, is a unit of mass.Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or...
s lead per U.S.
gallonA gallon is a measure of volume of approximately four litres. Historically it has had many different definitions, but there are three definitions in current use. These are the U.S. liquid gallon and the lesser used U.S...
, and was only used in low compression ratio engines.
100/130
Dyed green, avgas 100/130 had a higher octane grade aviation gasoline, containing a maximum of 4 grams of lead per US gallon, maximum 1.12 grams/
litreThe litre or liter is a unit of volume. There are two official symbols: the Latin letter L in lower and upper case . The lower case L is also often written as a cursive ℓ, though this symbol has no official approval by any international bureau...
. 100LL "low lead" has replaced avgas 100/130 in most places, but Avgas 100/130 is still sold in
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
and
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
as one of the two manufacturers in Australia is unable to make Avgas 100LL.
91/96 & 115/145
In the past other grades were also available, particularly for military use, such as avgas 115/145 (dyed purple) and 91/96.
Automotive gasoline
Automotive
gasolineGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines...
(known as Mogas or Autogas among aviators) that does not contain oxygenates may be used in
certifiedA Type Certificate, is awarded by aviation regulating bodies to aerospace manufacturers after it has been established that the particular design of a civil aircraft, engine, or propeller has fulfilled the regulating bodies' current prevailing airworthiness requirements for the safe conduct of...
aircraft that have a
Supplemental Type CertificateThe Supplemental Type Certificate is the Federal Aviation Administration term for the approval that extends a type certificate for modifications made to an airframe, engine, or appliance.-External links:*...
for automotive gasoline,
experimental aircraftIn generic use, an experimental aircraft is an aircraft that has not yet been fully proven in flight. Often, this implies that new aerospace technologies are being tested on the aircraft, though the label is more broad. Experimental aircraft is also a specific term referring to an aircraft flown...
and ultralights. Most of these applicable aircraft have
low-compressionThe compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber; from its largest capacity to its smallest capacity...
engines which were originally certified to run on 80/87 avgas and require only "regular" 87 anti-knock index automotive gasoline. Examples of this include the popular
Cessna 172The Cessna 172 Skyhawk is a four-seat, single-engine, high-wing fixed-wing aircraft. First flown in 1955 and still in production, more Cessna 172s have been built than any other aircraft.-Design and development:...
or
Piper CherokeeThe Piper PA-28 Cherokee is a family of light aircraft designed for flight training, air taxi and personal use, built by Piper Aircraft.All members of the PA-28 family are all-metal, unpressurized, four-seat, single-engine piston-powered airplanes with low-mounted wings and tricycle landing gear...
with the variant of the
Lycoming O-320The Lycoming O-320 is a large family of 92 different normally-aspirated, air-cooled, four-cylinder, direct-drive engines commonly used on light aircraft such as the Cessna 172 and Piper Cherokee. Different variants are rated for 150 or 160 horsepower...
. Some aircraft engines were originally certified using a 91/96 avgas and have STC's available to run "premium" 91 anti-knock index automotive gasoline. Examples of this include some Cherokee's with the
Lycoming O-320The Lycoming O-320 is a large family of 92 different normally-aspirated, air-cooled, four-cylinder, direct-drive engines commonly used on light aircraft such as the Cessna 172 and Piper Cherokee. Different variants are rated for 150 or 160 horsepower...
or
O-360The Lycoming O-360 is a family of four-cylinder, direct-drive, horizontally opposed, air-cooled, piston aircraft engines. Engines in the O-360 series produce between 145 and 225 horsepower .-Design and development:...
or the
Cessna 152The Cessna 152 is an American two-seat, fixed tricycle gear, general aviation airplane, used primarily for flight training and personal use.-Development:...
with the
O-235The Lycoming O-235 is a family of four-cylinder, air-cooled, horizontally opposed piston aircraft engines that produce , derived from the earlier O-233 engine....
. However, for most aircraft, automotive gasoline is not considered to be a viable replacement for avgas, primarily because automotive gasoline is not subject to the stringent quality-control standards necessary for an aviation fuel.
The requirement for a non-oxygenated fuel is a major problem with these STCs. In the name of reducing emissions, most autogas contains additives designed to boost the oxygen available to the fuel, such as alcohol. The FAA does not allow alcohol-containing gasoline to be used in aircraft.
Avgas compared to other fuels
Many
general aviationGeneral aviation is one of two categories of civil aviation. It refers to all flights other than military and scheduled airline flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
aircraft engineAn aircraft engine is a propulsion system for an aircraft. Aircraft engines are almost always either lightweight piston engines or gas turbines. This article is an overview of the basic types of aircraft engines and the design concepts employed in engine development for aircraft.- Engine design...
s were designed to run on 80/87 octane, roughly the standard for North American automobiles today. Direct conversions to run on automotive fuel are fairly common and applied via the
supplemental type certificateThe Supplemental Type Certificate is the Federal Aviation Administration term for the approval that extends a type certificate for modifications made to an airframe, engine, or appliance.-External links:*...
(STC) process. However, the alloys used in aviation engine construction are rather outdated, and engine wear in the valves is a potential problem on automotive gasoline conversions. Fortunately, significant history of mogas-converted engines has shown that very few engine problems are actually caused by automotive gasoline. A larger problem stems from the wider range of allowable vapor pressures found in automotive gasoline; this can pose some risk to aviation users if fuel system design considerations are not taken into account. Automotive gasoline can vaporize in fuel lines causing a vapor lock (a bubble in the line), starving the engine of fuel. This does not constitute an insurmountable obstacle, but merely requires examination of the fuel system, ensuring adequate shielding from high temperatures and maintaining sufficient pressure in the fuel lines. This is the main reason why both the specific engine model as well as the aircraft in which it is installed must be supplementally certified for the conversion. A good example of this is the
Piper CherokeeThe Piper PA-28 Cherokee is a family of light aircraft designed for flight training, air taxi and personal use, built by Piper Aircraft.All members of the PA-28 family are all-metal, unpressurized, four-seat, single-engine piston-powered airplanes with low-mounted wings and tricycle landing gear...
with high-compression or engines. Only later versions of the airframe with different engine cowling and exhaust arrangements are applicable for the automotive fuel STC, and even then require fuel system modifications.
Vapor lock typically occurs in fuel systems where a mechanically-driven fuel pump mounted on the engine draws fuel from a tank mounted lower than the pump. The reduced pressure in the line can cause the more volatile components in automotive gasoline to flash into vapor, forming bubbles in the fuel line and interrupting fuel flow. If an electric boost pump is mounted in the fuel tank to push fuel toward the engine, as is common practice in fuel-injected automobiles, the fuel pressure in the lines is maintained above ambient pressure, preventing bubble formation. Likewise, if the fuel tank is mounted above the engine and fuel flows primarily due to gravity, as in a Cessna high-wing airplane, vapor lock cannot occur, using either aviation or automotive fuels.
In addition to vapor locking potential, automotive gasoline does not have the same quality tracking as aviation gasoline. To help solve this problem, the specification for an aviation fuel known as 82UL has recently been developed. This fuel would be essentially automotive gasoline that has additional quality tracking and restrictions on permissible additives. This fuel is not currently in production and no refiners have committed to producing it.
The main consumers of avgas at present (mid-2000s) are in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
,
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
, and
AfricaAfrica is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people in 61 territories, it accounts for about 14.8% of the...
(mainly
South AfricaThe Republic of South Africa is a country located at the southern tip of Africa, with a coastline on the Atlantic and Indian Oceans. To the north lie Namibia, Botswana and Zimbabwe, to the east are Mozambique and Swaziland, while Lesotho is an independent country surrounded by South Africa.Modern...
). Care must be taken by small airplane pilots to select airports with avgas on flight planning. For example, U.S. and Japanese recreational pilots ship and depot avgas before flying into
SiberiaSiberia , is the vast region constituting almost all of Northern Asia and for the most part currently serving as the massive central and eastern portion of the Russian Federation, having served in the same capacity previously for the USSR from its beginning, and the Russian Empire beginning in the...
. Shrinking availability of avgas drives usage of small airplane engines that can use jet fuel.
In
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
, avgas prices are so high that there have been a number of efforts to convert the industry to diesel instead, which is common, inexpensive and has a number of advantages for aviation use. However, avgas remains the most common fuel in Europe as well.
Environmental regulation
The
tetra-ethyl leadTetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula 4Pb. Once a common antiknock additive in gasoline , TEL usage was largely discontinued because of the toxicity of lead and its deleterious effect on catalytic converters...
found in leaded avgas and its combustion products are potent
neurotoxinA neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels.Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
s that have been shown in scientific research to interfere with brain development in children. The
United States Environmental Protection AgencyThe U.S. Environmental Protection Agency is an agency of the federal government of the United States charged to regulate chemicals and protect human health by safeguarding the natural environment: air, water, and land...
(EPA) has noted that exposure to even very low levels of lead contamination has been conclusively linked to loss of
IQAn intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. The term "IQ", from the German Intelligenz-Quotient, was coined by the German psychologist William Stern in 1912 as a proposed method of scoring early modern...
in children's brain function tests, thus providing a high degree of motivation to eliminate lead and its compounds from the environment.
On 16 November 2007, the
environmental groupEnvironmentalism is a broad philosophy and social movement regarding concerns for environmental conservation and improvement of the state of the environment...
Friends of the EarthFriends of the Earth International is an international network of environmental organizations in 77 countries.Friends of the Earth International are the world's largest grassroots environmental network and they campaign on today's most urgent environmental and social issues...
formally petitioned the EPA, asking them to regulate leaded avgas. The EPA responded with a notice of petition for rulemaking.
The notice of petition stated:
The public comment period on this petition closed on 17 March 2008.
Under a federal court order to set a new standard by 15 October 2008, the EPA cut the acceptable limits for atmospheric lead to 0.15 microgram/m
3 from the previous standard of 1.5 microgram/m
3. This was the first change to the standard since 1978 and represents an order of magnitude reduction over previous levels. The new standard requires the 16,000 remaining US sources of lead, which includes lead smelting, airplane fuels, military installations, mining and metal smelting, iron and steel manufacturing, industrial boilers and process heaters, hazardous waste incineration and production of batteries, to reduce their emissions by October 2011.
The EPA's own studies have shown that to prevent a measurable decrease in IQ for children deemed most vulnerable, the standard needs to be set much lower, to 0.02 microgram/m
3.
The EPA has previously named avgas as one of the most "significant sources of lead", but it was not clear how this current change in standards will affect aircraft burning 100LL fuel.
At an EPA public consultation held in June 2008 on the new standards, Andy Cebula, the
Aircraft Owners and Pilots AssociationThe Aircraft Owners and Pilots Association is a Frederick, Maryland-based non-profit political organization whose membership consists mainly of general aviation pilots in the United States...
's Executive Vice President of Government Affairs stated that
general aviationGeneral aviation is one of two categories of civil aviation. It refers to all flights other than military and scheduled airline flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
plays a valuable role in the US economy and any changes in lead standards that would change the current composition of avgas would have a "direct impact on the safety of flight and the very future of light aircraft in this country."
In December 2008 AOPA filed formal comments to the new EPA regulations. AOPA indicated that piston-powered aircraft produce "one-tenth of 1 percent" of national lead emissions and that they are 0.55% of all transportation emissions. AOPA has asked the EPA to account for the cost and the safety issues involved with removing lead from avgas. They cited that the aviation sector employs more than 1.3 million people in the USA and has an economic "direct and indirect effect that "exceeds $150 billion annually." AOPA interprets the new regulations as not affecting general aviation as they are currently written.
Phase-out of leaded aviation gasolines
The 100LL phase-out has been called "one of modern GA's most pressing problems", because 70% of 100LL aviation fuel is used by the 30% of the aircraft in the general aviation fleet that cannot use any of the existing alternatives.
In February 2008, Teledyne Continental's new president, Rhett Ross, announced that the company is very concerned about future availability of 100LL avgas, and as a result, they will develop a diesel engine in the range for certification in 2009 or 2010. This engine will be followed by lower power engines, as well. In a February 2008 interview, Ross indicated that Continental Motors believes that the aviation industry will be "forced out" of using 100LL avgas in the near future, leaving automotive fuel and jet fuel as the only alternatives.
In November 2008 National Air Transportation Association President Jim Coyne indicated that the environmental impact of aviation is expected to be a big issue over the next few years and will result in the phasing out 100LL, due to its lead content.
Swift fuel
John and Mary-Louise Rusek founded Swift Enterprises in 2001 to develop renewable fuels and hydrogen fuel cells. By 2006, they had submitted a sample of "Swift 142" to Oracle Airmotive Research & Development of
Delphi, IndianaDelphi is a city in and the county seat of Carroll County, Indiana, United States. Located fifteen minutes northeast of Lafayette, it is part of the Lafayette, Indiana Metropolitan Statistical Area...
, which found that the fuel gave a 10% longer runtime than an equal volume of 100LL fuel in the engine of a
Bakeng DeuceThe Bakeng Deuce is a parasol-wing monoplane designed in the United States in the early 1970s and marketed for homebuilding. Plans and parts are still available in 2007, although the rights have changed hands in the intervening years. A biplane derivative, the Double Duce was also available at...
aircraft. The following year, Swift Enterprises filed US and international patent applications for non-alcoholic Renewable Engine Fuels of a variety of octane ratings, to be blended from
"one or more low carbon number esters, one or more pentosan-derivable furans, one or more aromatic hydrocarbon, one or more C4-C10 straight chain alkanes derivable from polysaccharides, and one or more bio-oils...
[and, optionally,] triethanolamine", which could be derived from biomass fermentation. Swift Enterprises initiated "Carroll County Swift Development Inc.", to plan a pilot plant at the Delphi Municipal Airport in Indiana,, and submitted fuel to the FAA for testing.
In 2008, an article by technology writer and aviation enthusiast Robert X Cringely, stating that the fuel was renewable, cleaner-burning, and potentially cheaper than avgas or even mogas, attracted popular attention to the fuel. The company claims the fuel can be manufactured for
USDThe United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
$2 per gallon, although Swift Enterprises' cost per gallon for laboratory batches was USD$60. The Swift Enterprises website claims their product has 15% more volumetric energy for a 15-25% increase in range over 100LL. The FAA found SwiftFuel 702 to have a motor octane number of 104.4, 96.3% of the energy per pound and 113% of the energy per gallon as 100LL, and meets most of the ASTM D 910 standard for leaded aviation fuel. Following tests in two
LycomingLycoming Engines is an American aircraft engine company, known primarily for its general aviation engines. For most of its history Lycoming has been part of the AVCO group as AVCO Lycoming. In 1987 AVCO was purchased by Textron to become Textron Lycoming...
engines, the FAA concluded it performs better than 100LL in detonation testing and will provide a fuel savings of 8% per gallon, though it weighs 1 pound per gallon more than 100LL. GC–
FIDA flame ionization detector is a type of gas detector used in gas chromatography. The first flame ionization detector was developed in 1957 by scientists working for the CSIRO in Melbourne, Australia....
testing showed the fuel to be made primarily of two components -- one about 85% by weight and the other about 14% by weight.
Soon afterwards, AVweb reported that Teledyne Continental Motors had begun the process of certifying several of its engines to use the new fuel.
Swift fuel has been criticized by aviation analysts on a number of grounds, including that the forecast price is likely unattainable, that the USD$2 per gallon is a refinery price and not a retail price and that biomass yields are critical to the project and are unproven. As a replacement for 100LL avgas Paul Bertorelli of Aviation Consumer termed it "one that's still a long shot", but conceded "...if Swift Fuel's real manufacturing cost is $3 a gallon and that translates to $5 or a little more at retail, they've got a player. GA in the U.S. can and has adapted to $5 avgas. If Swift can deliver, this project could have legs".
94UL
In March 2009 Teledyne Continental Motors announced that it has been testing 94UL fuel. This fuel is essentially 100LL with the tetraethyl lead omitted during the production process. The company has indicated that this may be the best solution to the lead problems inherent with 100LL. The 94UL has been shown to meet the avgas specifications, including for vapor pressure, but has not been completely tested for detonation qualities in all Continental engines or under all conditions. Flight testing has been conducted on an IO-550-B powered
Beechcraft BonanzaThe Beechcraft Bonanza is an American general aviation aircraft introduced in 1947 by The Beech Aircraft Corporation of Wichita, Kansas. it is still being produced by Hawker Beechcraft and has been in continuous production longer than any other airplane in history...
and also ground testing on
Continental O-200The Continental C90 and O-200 are a family of air-cooled, horizontally opposed, four-cylinder, direct-drive aircraft engines of 201 in³ displacement, producing between 90 and 100 horsepower ....
,
240The Continental O-240 engine is a four cylinder, horizontally opposed, air-cooled aircraft engine that was developed in the late 1960s for use in light aircraft by Continental Motors. The first O-240 was certified on 7 July 1971.-Design and development:...
,
O-470The Continental O-470 engine is a family of carbureted six cylinder, horizontally opposed, air-cooled aircraft engines that was developed especially for use in light aircraft by Continental Motors. The family includes the E165, E185 and the E225 engines...
and
O-520The Continental O-520 is a six-cylinder, horizontally-opposed aircraft engine produced by Teledyne Continental Motors. First run in 1963 as a development of the O-346, it has been produced in versions incorporating fuel injection , turbo-charging , and gearing .-Design and development:The IO-520...
engines.
External links
- http://www.autofuelstc.com/autofuelstc/pa/PetersenAviation.html - information on STC to use mogas in aircraft, by Petersen Aviation, Inc., which sells such STC's
- http://www.age85.org, advocating for Aviation Grade Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
- http://www.ethanolmt.org/php/novdec05.php, ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
advocacy site telling story of "Shauck and his wife flew a single-engine airplane across the Atlantic Ocean in 1989, using 100% Ethanol"