Why Do Airplanes Dump Jet Fuel

When boarding an aircraft, the last thing you expect is for fuel to be dumped overboard shortly into the flight. However, for a small number of flights each year, this is exactly what happens. Just a few weeks ago, Delta Airlines Flight 89 was scheduled to travel from Los Angeles to Shanghai, and as a result of a mechanical failure, the plane needed to land and having too much fuel became an immediate problem. So much so that pilots ended up dumping 15,000 gallons of jet fuel over the city of Los Angeles, hitting residents, school children, and causing outrage as questions as to why exactly this happened began to be asked. Fuel dumping is a standard procedure amongst aircraft that are in certain emergency situations that require the aircraft to land short of the intended destination. Whether it be a mechanical failure or a medical emergency, it is important that the weight of the aircraft be reduced in order for the plane to land safely. All aircraft can be considered to have two major types of weight limits, the first being the maximum takeoff weight or the MTOW, and the second being the maximum landing weight or the MLW. The maximum takeoff weight is the maximum weight at which the pilot is allowed to attempt to take off and which the plane will generate lift. For an extremely large aircraft like the Airbus A380, this could be as much as 575,000 kilograms, while smaller aircraft like the Boeing 737 can range anywhere from 60,000 to 85,000 kilograms depending on the variant of the aircraft. This maximum takeoff weight is composed of several different pieces. The first component of the MTOW is made up of the operating MT weight. This is the weight of the aircraft without any fuel, baggage, or passengers on board. The next component is the passengers and baggage that are on the aircraft as well as any additional cargo being loaded onto the plane that needs to be transported. And the final component is the fuel required for the aircraft. This is composed of the fuel needed for all aspects of the flight including taxiing fuel, the actual flight fuel, and a bit of reserve fuel for any unexpected circumstances that may arise. During a typical flight like the one from Los Angeles to Shanghai, most of the fuel is burned during the course of the flight and when it comes time to land, the plane is under the necessary weight limits and the weight of the aircraft will be less than the maximum landing weight. However, when a plane is required to land much sooner than anticipated, like in the case of this flight, it can present a real problem. If the plane is too heavy during landing, a number of issues can arise. Structural damage can occur to the plane if the landing impact force is too great which can cause landing gear damage, increase stress on the brakes, and could potentially even cause the tires themselves to explode under too much heat and pressure. Additionally, if the plane is too heavy, the length of the runway available to bring the aircraft to a full stop may not be enough. A typical aircraft based upon its weight has what is known as a calculated landing distance. This is the expected amount of runway required for the aircraft to land based upon the weight of the aircraft, the available flap settings, the wind speed, and the runway surface composition. This combined with a safety factor of between 5 and 15 percent determines the required landing distance of an aircraft. The required landing distance must be less than the landing distance available, or you know, you slide off the end of the runway and nobody wants that. The problem with heavier aircraft is that they require a greater speed to generate lift. This higher approach speed in turn requires a longer runway to stop, potentially longer than you have, and thus you must get rid of some of the weight if there is an emergency landing required. I suppose you could begin launching passenger bags or cargo out the back of the plane to shed excess weight, or heck, even throw people out to parachute safely to the ground, but reasonably, fuel is the easiest and quickest item to shed in order to get down below the maximum landing weight. Typically, before takeoff and during the pilot brief where important points about the flight are discussed, consideration will be given as to what should happen if an emergency landing were to take place and where the fuel should be dumped. To initiate the fuel dumping process, a decision will first need to be made that fuel does indeed need to be dumped by the pilots in coordination with air traffic control. Each country has their own set of rules on dumping fuel, and as a result, an aircraft may need to be moved to a certain altitude or certain area before releasing any fuel. In the United States, the Federal Aviation Administration, or FAA, does not have any hard rules but does state some guidance as to what procedures should be The FAA instructs air traffic controllers to assign planes dumping fuel to be at an altitude of at least 2,000 feet and to dump fuel over unpopulated areas. Further, aircraft manufacturers like Boeing and Airbus recommend fuel be dumped at an altitude of at least 5,000 feet so that the kerosene jet fuel will vaporize and disappear into the sky without raining down upon anyone below. Once approval has been given by the air traffic controllers and the pilot and copilot both agree to dump fuel, the fuel jettison nozzle switches are flipped and fuel begins to drain from the aircraft. This will typically open up a nozzle on the rear of each wing that allows fuel to begin to flow from the left and right wing tanks as well as the center tank if required. Most aircraft will drain fuel at a rate of about 1 to 2 tons per minute and will continue to do so until the In the case of flight 89 from Los Angeles to Shanghai, it is unclear why they released the fuel when they did. Initially, radio calls to air traffic control indicated that releasing of jet fuel was not required however it happened anyway. Unfortunately, many schools and children were hit with the jet fuel causing over 60 people to be injured with complications such as skin irritation and breathing problems. Although the pilots may have needed to release fuel in order to conduct an emergency landing, it certainly could have been done over a more appropriate area such as over the ocean or outside of the city. However, it is hard to say exactly what the pilots were dealing with and how quickly the plane needed to reach the ground. In any event, hopefully the airlines, the FAA, and pilots in general can learn from the situation so that no more jet fuel rains down from the sky and into a city in the future. Let me know in the comments below what you think about this issue and whether you believe the pilots made the right decision. If you enjoyed this video, be sure to hit the like button below and consider subscribing to this channel. And as always, thank you so much for watching this video.