Fuel dumping - called fuel jettison - is a last-resort procedure by which an aircraft releases part of its fuel through dump nozzles that spray a fine mist into the air stream. It is initiated from the cockpit via dedicated pumps and valves when the airplane must return to the take-off airport while still above the maximum landing weight, and it is performed only over remote or unpopulated areas at a prescribed altitude. By reducing weight to the allowable landing limit, the maneuver prevents possible structural damage during an overweight touchdown. Because it is regulated by FAA standards and rare in occurrence, the procedure is deemed safe.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What does it mean when an airplane dumps fuel?
When an airplane dumps fuel, it performs an intentional controlled jettison of fuel, a step undertaken because the maximum allowable takeoff weight is in excess of the corresponding maximum landing weight. Fuel dumping reduces the aircraft's weight, and it is normally done at a certain altitude before emergency landing (when an aircraft has to land short of its intended destination or shortly after takeoff). Any of those aircraft needing to return to a takeoff airport above the maximum landing weight would jettison an amount of fuel sufficient to reduce the aircraft's weight below that maximum landing weight limit. Fuel dumping is a measure reserved for situations where no other options are available, but it remains a safe procedure designed to protect the airframe and its occupants. Wispy white trails that follow an aircraft during the process aren't contrails but are the visible clouds created as the atomised fuel meets the cold air.
Facilities must broadcast an advisory on appropriate radio frequencies at 3-minute intervals until the dumping stops, and they broadcast a terminating advisory when the fuel dumping operation is completed.
When an airplane dumps fuel, it is executing a deliberate safety process dictated by a rigid code of conduct. The team may be required to discard gas to get to a risk-free touchdown load, because the great departure load of an airliner is greater than its maximum landing weight. Gas dumping denotes a severe condition that typically comes after an exigency soon after departure. The option safeguards the frame's integrity and avoids a larger disaster like a structural breakdown during touchdown or a landing strip overrun. Pilots dump gas at upper altitudes, where gasoline can evaporate into a delicate fog, lessening its environmental influence before coming to the bottom.
Do airplanes dump fuel?
Yes, airplanes dump fuel but only a minority of commercial types can. Not all aircraft are equipped with fuel-dumping systems. Some planes like the 737, A320, and most regional jets do not have the fuel dump feature, while only larger, wide-body planes have fuel-dumping capability. Among them, the A380, 787, and similar models can release it from their wingtips. Historical jets like the Boeing 707, 727, and Douglas DC-8 had fuel dump systems, yet modern narrow-body jets like the B737 and A320 do not have fuel-dumping capability, so they never jettison fuel. Dumping is therefore confined to long-haul flights that take off heavy and need to lighten the aircraft before an early landing.
Airplanes chuck out gasoline only in crises, especially when an aircraft must go back to the airfield soon after ascent. The gas must be decreased to avoid structural and functional harm to the frame upon landing. The gas is released at an upper elevation where it disperses and vaporizes before touching the dirt, reducing environmental pollution before it reaches the lower layers. This procedure is only carried out in situations of emergencies.
How often do airplanes dump fuel?
The rate of fuel dumping was extremely low - 0.00000588% of flights per year. The U.S. airlines logged more than 25.5 million flights per year yet reported only fifteen deliberate dumps annually. Commercial airlines reported 485 instances of fuel jettison over a 5-year period, while the FAA knows of 47 American-airline events worldwide in the past three years, of which the military sector remains the outlier, as the U.S. Air Force jettisoned fuel nearly 1000 times per year. Requirements and equipment exist because most transport category aircraft have a maximum allowable takeoff weight that is in excess of the corresponding maximum landing weight, but the event itself remains rare.
Why does an airplane dump fuel?
An airplane dumps fuels to reduce weight for an emergency landing soon after takeoff. Most transport category aircraft have a maximum allowable takeoff weight that is in excess of the corresponding maximum landing weight. To prevent landing overweight during an abnormal operation, a procedure is used to reduce the aircraft's weight before a return to the airport shortly after takeoff. Overweight landing causes disastrous side effects, so reducing landing weight ensures safe landing.
Only larger, wide-body planes have this capability. The system consists of pumps and valves that divert fuel to nozzles located near the wingtips. In the event of an emergency requiring a return to the departure airport, the aircraft circles nearby to consume fuel to get down to within the maximum structural landing weight limit. If the situation demands an immediate landing, the aircraft lands overweight without delay, but fuel dumping is the last resort when no other options are available to reduce landing weight.
An airplane dumps fuel because the need to decrease load for a secure touch-down can arise after take-off. Nearly all aircraft are designed to take off at a weight far surpassing their certified landing weight, and a considerable part of that load is gas. Since gasoline is used up during the trip, a normal arrival would already be lighter. When a prompt return is required, the remaining weight can still exceed the safe landing limit. Discarding gasoline prevents possible structural harm to the landing equipment and airframe upon landing. The call to discard gas is an immediate reaction to a pivotal, time-sensitive trouble and a deliberate execution to turn a dangerous state of affairs into a tractable one.
How does airplane fuel dumping work?
Airplane fuel dumping starts with pilots flicking a switch in the cockpit to initiate fuel dumping. Pumps and valves are designed to let fuel jettison from nozzles on the wings. On a 747 the nozzles are located near the wingtips whereas on an A380 the nozzles are much closer to the fuselage. Fuel is released at an enormous pressure, and the fuel disperses at a high flow rate of more than 200 miles per hour (321.87 kilometers per hour). The fuel breaks down into small droplets very quickly. Enormous pressure projects fuel into the air stream, so fuel initially appears as more liquid than vapor. The fuel is already vaporized in the air before it reaches the ground, especially in warmer conditions.
Fuel dumping is normally done at a certain altitude, usually at least 6,000 feet AGL (1,828.8 meters) as it allows enough time for fuel to evaporate. Air traffic control assigns an altitude at least 2,000 feet (609.6 meters) above the highest obstacle within 5 miles (8.05 kilometers), and fuel dumping is performed over unpopulated areas. This procedure is regulated by ICAO, and typically only larger, wide-body planes have this capability, because transport category aircraft have maximum allowable takeoff weight in excess of maximum landing weight. Smaller narrow-body planes like the Boeing 737 or Airbus A320 are designed to land at weights close to maximum takeoff weight, so normally only larger wide-body jets need to dump fuel before landing. High altitude dispersion guarantees that fuel does not reach the ground and poses no risk to those onboard.
When an airplane dumps fuel, where does it go?
When an airplane dumps fuel, the fuel does not reach the ground. Pumps and valves divert it to nozzles near the wingtips, where it projects into the airstream as a stream that initially appears more liquid than vapor. At these heights, most of the fuel evaporates before it even hits the ground, especially when released at higher altitudes and in warmer conditions. The particles evaporate into a fine mist and disperse over a wide enough area, so fuel doesn't even reach the ground because it has already vaporized in the air.
When an aircraft must discard gas, it is released at an upper elevation. The fuel is sprinkled into the air as a delicate cloud. A substantial part of the gasoline evaporates into the air. The vaporization and diffusion happen far before reaching the ground. This avoids a focused spill on the land. The delicate droplets are brought by air flows and are subject to strong atmospheric pressures. The process is specifically intended to stop a dense dark flow of fluid gushing immediately onto the plain.
Is airplane fuel dumping bad for the environment?
Airplane fuel dumping contributes to atmospheric pollution through the vapours it releases because jet fuel is made up of hydrocarbons and contains toxic additives including benzene. These vapours add pollution to the air, and although FAA and EPA argue that vapor pollution from jettisoned fuel is negligible compared with cars, trucks, and industrial sources, fuel dumping contributes to air pollution by adding hydrocarbons that form ground-level ozone.
When fuel dumping occurs over land, it adds pollution to soil through contact with the ground. Jet fuel is highly volatile and evaporates quickly, yet the fraction that remains on land causes soil pollution and allows toxic hydrocarbons including benzene to seep into the ground. Fuel dumping over land causes odor and, by creating the potential for carcinogenic hydrocarbons exposure, makes it environmentally unfriendly.
Fuel dumping adds pollution to water when it is jettisoned over lakes, rivers, or coastal areas, leading to water contamination. Because fuel dumping damages aquatic environments by releasing biocides and other toxic substances, it is a serious threat to the environment. Fuel dumping does not increase atmospheric CO2 directly but still compromises water quality and marine ecosystems. Overall, fuel dumping negatively affects the environment in terms of water and soil pollution.
I understand that fuel dumping releases hydrocarbon-based gasoline into the atmosphere which significantly impacts the environment. It leads to contamination of land and water sites. Although the pollution from standalone events may not amount to much, accumulation overtime can prove disastrous. Aviation programs can contemplate solutions such as decreasing high arrival load needs as well as lighter touchdown equipment.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
