Aircraft Fuel Systems

Avgas

• Aviation fuel is a specialized type of petroleum-based fuel used to power aircraft.

• 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, amongst other properties.

Avgas

• Avgas (aviation gasoline) is an aviation fuel used to power piston-engine aircraft.

• It can be distinguished from mogas (motor gasoline), which is the everyday petroleum spirit used in cars.

• Avgas is formulated for stability, safety, and predictable performance under a wide range of environments.

• Avgas is typically used in aircraft that use reciprocating or wankel engines.

• Dyes for the fuel are required in some countries.

Avgas

• Aviation fuels consist of blends of over a thousand chemicals:– primarily Hydrocarbons (paraffins, olefins,

naphthenes, and aromatics) as well as additives such as antioxidants and metal deactivators, and impurities.

– Principal components include n-octane, isooctane.– Like other fuels, blends of Aviation fuel used in

piston engine aircraft are often described by their Octane rating.

100LL

• The most commonly used aviation fuel is dyed blue for easy visual identification.

• 100LL, spoken as "100 low lead", contains a small amount of tetra-ethyl lead (TEL), a lead compound that reduces gasoline's tendency to spontaneously explode (detonation or "knock") under high loads, high temperatures and high pressures.

• Sustained detonation causes catastrophic engine failure.

AvgasTable of Aviation Fuel Types

Country Fuel Lead content Status Dye

Worldwide 80/87 Low leadPhased out, difficult to obtain

red

Worldwide 82UL Unleaded Not produced since 2008 purple

Worldwide 100LL Low leadMost commonly used aviation fuel

blue

Worldwide 100/1304 grams of lead per US gallon (1.1 g/l)

In process of being replaced by 100LL

green

Worldwide 91/96Discontinued (sometimes produced for races)

brown

Worldwide 115/145Discontinued (mainly military use)

purple

Don’t Lie About Your Fuel State

• I’ve never overloaded my airplane• I have the traffic in sight• Yes, tower, I responded. You didn't hear me?• You're not picking up my squawk code? Here,

let me recycle the transponder• I have the check-list memorized• I broke out of the clouds right at minimums

Still????

• http://www.google.com/search?um=1&hl=en&safe=off&biw=1024&bih=707&q=the%20runway%20behind%20you&ie=UTF-8&sa=N&tab=iw#sclient=psy&hl=en&safe=off&biw=1024&bih=707&source=hp&q=aircraft+crash+ran+out+of+fuel&aq=f&aqi=&aql=&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=a316b5cdb3fe9040

Weight & Balance

• Avgas has a density of 6.02 lb/U.S. gal at 15 °C, or 0.721 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 (9 °F) increase in temperature.

• As you use fuel, your CG will move.

?Hybrid?

Very Important

What’s Going In?

• Be present when Fuel is pumped.– Quantity– Quality– Correctness– Damage to A/C

Cases

On March 2, 2008, a turbo-normalized Cirrus SR22 was destroyed when it crashed shortly after takeoff in Rio de Janeiro, Brazil, killing all four people aboard. Shortly after the aircraft departed from Runway 20, the airplane's engine lost power, and the aircraft hit a building and exploded. Further investigation revealed that the aircraft had been refueled with Jet A instead of 100LL.

Effects of Contamination

• Zero Octane• Instant destructive detonation• You will loose the engine

The Fuel System

• Tanks• Lines• Vents• Drains• Primer• Gauges• Fuel Pump & Gravity Feed

Fuel Pump System

• Usually found in Low Wing Aircraft• High Performance aircraft with Fuel Injected

engines• Usually will have a boost pump (Aux Pump)

Question

In all fuel injected aircraft, if the engine fuel pump fails you will still be able to run the engine

if the aux fuel pump is activated?

False

Fuel Pressure

Fuel Pressure Gauge• Cherokee Six

Fuel Pump• Lycoming

The Relationship

Low Wing Design

High Wing Gravity Feed

Gravity Feed

Question

In order to maximize range performance, on aircraft equipped with more than one fuel tank, it is common and safe to run a tank completely

dry before switching fuel tanks.

Vapor Lock

Question

Once vapor lock is induced, there are steps a pilot can take while flying to counter it.

False

Fuel Tank Venting/Overflow Drain

Fuel Gauges

The Digital Age

More Reasonable

Fuel Selector Valve

Fuel Cross Feed

Question

Using a fuel grade higher than specified can cause cylinder head and engine temperatures to

exceed normal operating limits.

False

Question

You arrive at your aircraft for a flight and realize you need fuel. The fuel should be drained and

checked immediately following the filling/adding of fuel to the fuel tanks.

False

Fuel Tips

• Infrequently used fuel tanks should have their sumps drained before filling

• Agitation action of fuel entering the tank may suspend or entrain liquid water or other contaminants.

• After fueling, wait at least 15 minutes per foot of depth of the tank before sumping

AC-20-125

• How much fuel says the FAA?– 10 ounces or more!!

• Cross feed and multiple tanks should be checked separately.

3 Useless Things in Aviation

The runway behind youThe sky above youThe Fuel in the truck