Basic Fuel Management for Aircraft ~ 1988 Federal Aviation Administration Pilot Training Film

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A BACK TO BASICS Presentation

FAA Accident Prevention Prgram

Originally a public domain film, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.

The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/Avgas

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

Avgas (aviation gasoline, also known as aviation spirit in the UK) is an aviation fuel used in spark-ignited internal-combustion engines to propel aircraft. Avgas is distinguished from mogas (motor gasoline), which is the everyday gasoline used in motor vehicles and some light aircraft. Unlike mogas, which has been formulated since the 1970s to allow the use of platinum-content catalytic converters for pollution reduction, the most commonly used grades of avgas still contain tetraethyllead (TEL), a toxic substance used to prevent engine knocking (detonation), with ongoing experiments aimed at eventually reducing or eliminating the use of TEL in aviation gasoline.

Turbine engines are designed to use kerosene-based jet fuel. Kerosene is also used by most diesel piston engines developed for aviation use, such as those by SMA Engines, Austro Engine, Thielert...

Properties

The main petroleum component used in blending avgas is alkylate, which is essentially a mixture of various isooctanes. Some refineries also use reformate. All grades of avgas that meet CAN 2-3, 25-M82 have a density of 6.01 lb/U.S. gal at 15 °C, or 0.721 kg/l. (6 lb/U.S. gal is commonly used in America for weight and balance computation.)[1] Density increases to 6.41 lb/US gallon, or 0.769 kg/l, at -40 °C, and decreases by about 0.1% per 1 °C (1.8 °F) increase in temperature.[2] [3] Avgas has an emission coefficient (or factor) of 18.355 pounds CO2 per U.S. gallon (2.1994 kg/l) or about 3.05 units of weight CO2 produced per unit weight of fuel used. Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock.

The particular mixtures in use today are the same as when they were first developed in the 1940s... The high octane ratings were traditionally achieved by the addition of tetraethyllead, a highly toxic substance that was phased out of automotive use in most countries in the late 20th century.

Leaded avgas is currently available in several grades with differing maximum lead concentrations. (Unleaded avgas is also available.) Because tetraethyllead is an expensive and polluting ingredient, in leaded avgas the minimum amount needed to bring the fuel to the required octane rating is used... many post-WWII developed, low-powered 4- and 6-cylinder piston aircraft engines were designed to use leaded fuels; a suitable unleaded replacement fuel has not yet been developed and certified for most of these engines. Some certificated reciprocating-engine aircraft still require leaded fuels, but some do not, and some can burn unleaded gasoline if a special oil additive is used.

Lycoming provides a list of engines and fuels that are compatible with them. According to their August 2017 chart, a number of their engines are compatible with unleaded fuel...

Meanwhile, Teledyne Continental Motors indicates (in document X30548R3 most recently revised in 2008) that leaded avgas is required in their engines...

Jet fuel is similar to kerosene and is used in turbine engines; it is not avgas. 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 fuel-efficient diesel engines that 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 fuel and diesel fuel.

Consumption

The annual US usage of avgas was 186 million US gallons (700,000 m3) in 2008, and was approximately 0.14% of the motor gasoline consumption. From 1983 through 2008, US usage of avgas declined consistently by approximately 7.5 million US gallons (28,000 m3) each year...