Fuel dumping
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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.
Aircraft fuel dump
Weight issues
Aircraft have two major types of weight limits: the maximum takeoff weight and the maximum structural landing weight, with the maximum structural landing weight almost always being the lower of the two. This allows an aircraft on a normal, routine flight to take off at a higher weight, consume fuel en route, and arrive at a lower weight.
It is an abnormal, non-routine flight where landing weight can be a problem. If a flight takes off at the maximum takeoff weight and then must land well before its destination, even returning immediately after takeoff to the departure airport (for example, because of mechanical problems or a passenger medical problem), it will contain more fuel than was intended for landing. If an aircraft lands at more than its maximum allowable weight, it might suffer structural damage or even break apart on landing.
History
As jets began flying in the US in the late 1950s and early 1960s, the FAA rule in effect at the time mandated that if the ratio between an aircraft's maximum structural takeoff weight and its maximum structural landing weight was greater than 1.05, the aircraft had to have a fuel-dump system installed. Aircraft such as the Boeing 707 and 727 and the Douglas DC-8 had fuel dump systems. 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, and then land.
During the 1960s,
- On 11 September 2001 a large-scale fuel dumping occurred, when U.S. airspace was closed due to the September 11 attacks. International flights en route to the U.S. were either turned back to their point of origin or diverted to land in Canada and other countries. Many of these flights were fuelled for travel well into the American interior; for those mid-flight aircraft unable to land due to excessive fuel weight, dumping was necessary.
- On 04 April 2018 a McDonnell Douglas KC-10 Extender operated by the United States Air Force dumped 43 tonnes of fuel over Rhineland-Palatinate at a height of 5,000 meters shortly after taking off from Ramstein Air Base.[1]
- On 14 March 2023 a
Types of aircraft
Since most twin jet airliners can meet these requirements, most aircraft of this type such as the
Long-range twin jets such as the
Area and flight level
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. Fuel leaves the aircraft through a specific point on each wing, usually closer to the wingtips and farther away from engines, and initially appears as more liquid than vapor. Specific areas have been designated where fuel dumping is allowed to avoid damage or harm where the fuel may drop; generally speaking, this is above seas or unpopulated areas above land. Delta Air Lines Flight 89 is an example of fuel dumping that violated established regulations: on 14 January 2020, it dumped more than 10,000 gallons of fuel at a low altitude over a populated area in Los Angeles, causing injuries to 56 people including school children below.[5]
Dump rates
It is difficult to quote specific dump rates even for specific types of aircraft since the dumped fuel is not pumped but delivered by gravity feed so as to be more independent of electrical systems, which might be unavailable in a fuel-dump scenario. This means the actual rate depends on the pressure exerted by the fuel head: the more fuel on board, the higher the rate at which it flows out. This also means that the dump rate is not constant, but decreases while dumping because the fuel head and its pressure decrease.
As a rule of thumb for the Boeing 747, pilots either quote dump rates ranging within 1–2 tons per minute or reference a thumb formula of dump time = (dump weight / 2) + 5 in minutes.[6] In 2009, an Airbus A340-300 returning to its airport of departure shortly after takeoff[7] dumped 53 tons of fuel in 11 minutes.[8]
Dumped fuel descent rate
The average rate of descent of the dumped fuel is approximately 500 feet per minute (2.5 m/s). Air traffic control, after receiving information from the pilots executing the dumping procedure, usually separates other traffic by 2,000 feet (610 m) vertically and 5 nautical miles (9.3 kilometres) laterally, since the dumped vapours if ingested by a jet engine might cause serious problems to the engine's normal operation.
Dump-and-burn
A dump-and-burn is a fuel dump in which the fuel is ignited, intentionally, using the plane's afterburner. A spectacular flame combined with high speed makes this a popular display for air shows or as a finale to fireworks. Dump-and-burns are also referred to as "torching" or "zippos".
The
See also
- Drop tank – external tank that can be jettisoned when empty or in an emergency
- Delta Air Lines Flight 89 - dumped fuel over a densely populated area, resulting in illness on people on ground
- Cessna 188 Pacific rescue – use of fuel dumping in an attempt to make the aircraft more visible
- Philippine Airlines Flight 434 – dumped fuel to reduce strain in landing
- Swissair Flight 111 – dumped fuel as per procedures, but was engulfed in flames before the landing weight was reached
- Samoan Clipper – in-flight explosion
References
- ^ Saarbrücker Zeitung, Wieder Kerosin nahe von US-Airbase Ramstein abgelassen 04.04.2018
- ^ Samuels, Brett (14 March 2023). "Russian jet forces downing of US drone over Black Sea". The Hill. Archived from the original on 14 March 2023. Retrieved 2023-03-14.
- ^ Olson, Emily; Chappell, Bill (16 March 2023). "The U.S. military releases footage of Black Sea drone crash with Russian jet". NPR. Archived from the original on 16 March 2023. Retrieved 16 March 2023.
- ^ Redmond Shannon (3 February 2020). "Air Canada flight forced to make emergency landing in Madrid". Global News. Archived from the original on 2021-12-21. Retrieved 15 October 2020.
- ^ Martinez, Peter (January 14, 2020). "Delta jet dumps fuel over Southern California, sickening dozens of schoolkids and adults". CBS News. CBS Interactive. Retrieved January 15, 2020.
- ^ "B747-400 fuel dump rate? - PPRuNe Forum". Pprune.org. 10 February 2017. Retrieved 4 July 2023.
- ^ "Incident: Swiss A343 near Vienna on Nov 26th 2009, engine shut down in flight". Avherald.com. 10 February 2017. Retrieved 4 July 2023.
- ^ "Airbus A340 EMERGENCY - Engine Failure". YouTube. 6 June 2012. Retrieved 10 February 2017.
- ^ Crandall, Richard; Rogoway, Tyler (2016-07-27). "Flying the Iconic Swing-Wing F-111 Aardvark at the Height of the Cold War". The Drive. Retrieved 2019-10-31.
- ^ "Defence News & Releases | News | | Department of Defence".