Airplane Facts: What Happens to Fuel After It's Dumped from an Airplane

Fuel dumping (or a fuel jettison) is a procedure used by aircraft in certain emergency situations before a return to the airport shortly after takeoff, or before landing short of the intended destination (emergency landing) to reduce the aircraft’s weight. This is done to reduce the aircraft’s weight to a value below maximum landing weight when compelled to land earlier than expected due to a turnback or an enroute diversion.

Fuel-dumping operations are coordinated with air traffic control, and precautions are taken to keep other aircraft clear of such areas. Fuel dumping is usually accomplished at a high enough altitude (minimum 6,000 feet, AGL), where the fuel will dissipate before reaching the ground.

Why do pilots dump fuel during an emergency landing?

Pilots dump fuel during an emergency landing to reduce the aircraft’s weight. Normally, a plane achieves this safe weight by reducing its weight immediately before landing, but during an emergency, the plane may not have been in the air long enough to burn enough fuel. Dumping fuel is the quickest way to lose weight and achieve the safe weight needed to land the plane without suffering from structural damage.

Airplanes have a safe landing weight, the same way they have a safe takeoff weight. Landing above this weight may result in structural damage when landing, which would put everyone on the plane in danger. In fact, if an aircraft lands at more than its maximum allowable weight, it might suffer structural damage or even break apart on landing.

In an emergency situation, a captain has three choices when having to land quickly and overweight: Fly around long enough to burn the fuel down to the maximum landing weight, land with the plane still overweight or dump fuel. Depending on the situation, each option may be appropriate. For example, if the crew were fighting a fire onboard and struggling to do so, then landing quickly – even if overweight – would definitely be the best choice. On the other hand, a hydraulic problem would not necessarily require an immediate landing, giving the pilots time to burn or dump fuel.

Some airplanes – usually larger ones – have the capability to dump fuel to reduce the landing weight. Dumping fuel can reduce the weight quickly, dumping thousands of pounds in a few minutes. In rare instances where dumping fuel becomes necessary, there are procedures that are supposed to be followed. Air traffic controllers also advise the pilots of the closest appropriate fuel dumping area, where there are fewer people. And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.

How much fuel can be dumped at once?

The speed with which fuel can be dumped varies but as an indication it is worth bearing in mind that the Boeing 747 dump rate for fuel ranges from one to two tonnes per minute. In rare instances where dumping fuel becomes necessary, there are procedures that are supposed to be followed. Air traffic controllers also advise the pilots of the closest appropriate fuel dumping area, where there are fewer people. And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.

What happens when planes dump fuel?

When an aircraft dumps fuel at altitude, the fuel is pushed out of nozzles in the wings and disperses over a wide enough area that the particles evaporate into a fine mist. The fuel essentially evaporates into a gaseous form and then fades into the background gases of the atmosphere. Usually, the fuel evaporates before it reaches the ground, but this is only the case if the aircraft is flying high enough.

In rare instances where dumping fuel becomes necessary, there are procedures that are supposed to be followed. Air traffic controllers also advise the pilots of the closest appropriate fuel dumping area, where there are fewer people. And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.

What are the risks of fuel dumping?

Fuel dumping can cause environmental degradation, water pollution, and crop damage. Jet fuel contains different hydrocarbons, including benzene, which harms the environment and causes cancer. The uncontrolled dumping of pollutants in the ocean can cause contamination with high concentrations of harmful pollutants including heavy metals, inorganic nutrients, and chlorinated petrochemicals. This can cause severe depletion of oxygen levels in some ocean waters.

In rare instances where dumping fuel becomes necessary, there are procedures that are supposed to be followed. Air traffic controllers also advise the pilots of the closest appropriate fuel dumping area, where there are fewer people. And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.

How is fuel dumping regulated?

Fuel-dumping operations are coordinated with air traffic control, and precautions are taken to keep other aircraft clear of such areas. Fuel dumping is usually accomplished at a high enough altitude (minimum 6,000 feet, AGL), where the fuel will dissipate before reaching the ground.

In rare instances where dumping fuel becomes necessary, there are procedures that are supposed to be followed. Air traffic controllers also advise the pilots of the closest appropriate fuel dumping area, where there are fewer people. And pilots are trained to climb to a higher altitude, which allows the atomized fuel to evaporate before it reaches the ground.

On A Final Note...

Fuel dumping is the intentional, controlled jettison of fuel from an aircraft while in flight. It is a necessary safety procedure that helps to prevent accidents. Not all aircraft designs incorporate a fuel dump capability and even if dump capability is inherent to a particular aircraft type, a specific aircraft of that type may or may not be fitted with fuel jettison capability.

Fuel dump may be initiated by the pilot to lighten the aircraft when performance is compromised due to failure of one or more engines while in flight. It can also be used to reduce the aircraft weight to a value below maximum landing weight when compelled to land earlier than expected due to a turnback or an enroute diversion.

Fuel dumping can cause environmental degradation, water pollution, and crop damage. Jet fuel contains different hydrocarbons, including benzene, which harms the environment and causes cancer. The uncontrolled dumping of pollutants in the ocean can cause contamination with high concentrations of harmful pollutants including heavy metals, inorganic nutrients, and chlorinated petrochemicals. This can cause severe depletion of oxygen levels in some ocean waters.

However, if the liquid fuel reaches the ground, there is a potential for negative environmental consequences such as crop damage or water pollution. The Federal Aviation Administration argues that fuel dumping does not have major environmental implications.

Pilots must follow FAA regulations when dumping fuel to minimize the risks. If the need arises, aircraft are instructed by Air Traffic Control to dump fuel at high altitudes as far away from the airport or any populated areas as possible.