Every vehicle moved by an engine needs fuel to power it. However, the fuel for air transport is not the same as that used for ground transport. The aviation fuel needs to have some special characteristics adapted to the environment in which it is to be consumed and is manufactured to ensure a safe flight operation.
People often wonder how airplane fuel is called. Well, airplanes use a hydrocarbon compound called kerosene, which is obtained by a fractional petroleum distillation as a fuel base. Kerosene is a yellowish oily liquid with a strong odor and low viscosity, an average density of 0.8 kg/l approximately, and a freezing point at 47 degrees Celsius below zero. In Russia, a different variant is used with a freezing point at 60 degrees below zero, necessary to fly under the low temperatures of Russian winter.
The commercial name of kerosene is Jet A1, Jet A, or Jet B, and beyond serving as fuel, it also can be used for aircraft maintenance such as hydraulic fluid or as an engine cooler. On the other hand, the gasoline for piston engine aircraft is marketed as AVGAS.
At present, there are the so-called SAF (Sustainable Aviation Fuels), different types of fuel used in jet aircraft with certain characteristics aimed at reducing the environmental impact of aviation. However, it is still difficult for aircraft fuel to be completely replaced by these alternative propellants.
There are two essential types:
Jet A1: This is a refined and colorless fuel based on kerosene. It is used by turbine-powered aircraft such as commercial airline planes. It is a highly efficient fuel that generates great power with a relatively low consumption and a freezing point at -47º centigrade. It also has multiple additive agents to dissipate static electricity. It is best suited for long-haul international flights and it is the most common aviation fuel over the world except in the United States.
Jet A: Also based on kerosene, it is the most common in the United States. Its freezing point is at -40º Celsius, which makes it less suitable than the Jet A1 for polar routes.
Jet-B or JP-54 is the most suitable aeronautical fuel for cold routes. It is based on naphtha (a type of refined oil) and kerosene. Its freezing point is very low: -60º Celsius, so it is undoubtedly the most appropriate for polar routes. This type of fuel is used especially in the United States and some military aircraft.
It is the fuel used for piston engine aircraft, so it is only used in small aircraft and private jets. It is also the most common in pilot schools and minor aviation. It is based on high-octane gasoline.
The Avgas is divided into two types:
Avgas 100: Aviation petrol with a high lead content, as it contains a significant proportion of lead tetraethyl additive to dampen and reduce the detonation noise of aeronautical engines. Its color is green.
Avgas 100LL: 100 octane gasoline, one of the highest octanes on the market. It has a low lead content and is blue-colored.
As we have already said, aeronautical fuel needs special characteristics necessary for a safe flight operation. Kerosene is made with these characteristics in order to ensure safety. Here are some of them:
Octane defines the anti-knock power of a propellant in relation to a mixture of hydrocarbons taken as the base unit. It is expressed as an octane number. Aviation gasoline, like that of automobiles, is classified by octane number or degrees. Each aircraft manufacturer specifies the fuel grade to use for each engine in question, the most common is the so-called 100LL (blue). If the recommended fuel cannot be supplied, upper octane fuel may occasionally be used, never lower.
To facilitate their identification, the fuels are dyed colors corresponding to red 80/87 octane (no longer used), blue 100/130, and purple 115/145 (only for large engines).
How much fuel a plane consumes is something that arouses a lot of curiosity. Well, although it will vary according to the model, number of passengers, kilos of cargo, route, etc., the consumption of an aircraft is around 3 liters per passenger every 100 kilometers, being 2 liters per passenger every 100 km in the most efficient models. However, although the fuel consumption of a commercial aircraft is very high, if we consider the number of people it transports, it is much more efficient than some cars on the market.
Many factors influence the fuel consumption. Let’s look at some of them:
The latest models from the manufacturer Airbus A350 and A320 Neo are designed to reduce fuel consumption. The A350, which is intended for long haul flights due to its larger size and fuel capacity that gives it greater autonomy, is between 30 and 35% more efficient in fuel consumption and consequently carbon dioxide emissions to the atmosphere. The state-of-the-art materials used for its manufacture contribute to this. On the other hand, the A320 Neo, intended for short-haul flights, is a technologically advanced model that reduces its CO2 emissions by up to 20%. In other words, it saves the atmosphere 5000 tons of this gas a year plus half of nitrogen oxide. Its Leap-1A type CFM engines make it, in addition to quieter, more sustainable.
As for the price of jet fuel, richest countries tend to have higher prices while the poorest and those producing and exporting oil have lower prices. This difference in prices is mainly due to the different taxes and subsidies on kerosene imposed by each nation. All countries buy energy raw materials on international markets at similar prices but apply different taxes. In general, airlines conclude multi-annual contracts with suppliers which guarantees a certain price in case of strong fluctuations.
The International Civil Aviation Organization (ICAO) has a protocol which states that an aircraft is required to have the necessary fuel to fly to an airport other than the one of destination in case of any eventuality.
Before the flight starts, pilots have to schedule the fuel for the route plus thirty minutes of possible waits and an extra amount needed to reach the established alternative airport. Flight forms must include which are those airports and documentation must specify the flight autonomy with the exact amount of fuel carried on board. The rules determine that this amount should never be exact for the route.
It is therefore very unlikely that an aircraft will run out of fuel. However, if it happens, the engines will stop and the cockpit screens will be turned off as there is no electrical power. In this situation, the aircraft is maintained by lift or by the airflow above the wings while continuing its descent at a speed that allows the plane to reach a greater distance.
So, when this occurs, the aircraft running out of fuel while making its route must immediately notify air traffic control and declare the fuel emergency. Once such an alert is declared, the control authority shall open the airspace clearing the route to the nearest aerodrome so that it can land as soon as possible.
Causes that may provoke this situation are, among others, taking off without the right fuel amount or using more than scheduled due to the use of the anti-ice system or bad weather. Also, it is important to perform a fuel drain test before flight to verify there is no presence of water or sediment in the ducts that transport it to the engine, which could cause an obstruction that prevents the correct flow of fuel and result in an engine failure.
However, as disastrous as it may seem, if an aircraft runs out of fuel, there are procedures to follow that provide many chances of landing successfully. At World Aviation Flight Academy, we teach our students all the necessary protocols to face any situation safely and professionally.
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