Why Aircrafts Dump Jet Fuel for Emergency Landing?

In the event of an emergency requiring a return to the departure airport, the aircraft circles nearby in order to consume fuel to get down to within the maximum structural landing weight limit, or, if the situation demands, simply lands overweight without delay. When aircraft dump fuel they release thousands of gallons of aircraft fuel, or kerosene, into the atmosphere. Usually, the fuel evaporates before it reaches the ground. However, this is only the case if the aircraft is flying high enough.

Some airplanes, usually the 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. As a rule of thumb for the Boeing 747, pilots quote dump rates ranging from a ton per minute, to two tons per minute, to a thumb formula of dump time = (dump weight / 2) + 5 in minutes. In 2009, an Airbus A340-300 returning to its airport of departure shortly after takeoff dumped 53 tons of fuel in 11 minutes.

Fuel Dumping is the term generally given to when an aircraft disposes fuel mid-air prior to landing. ... It involves intentionally pairing two separate flights on the same airfare ticket in the hope that the fuel surcharge component of the main, more-expensive flight is either partially or fully dumped/eliminated. Dumped jet fuel is supposed to evaporate before it hits the earth, but even Boeing has said that "Even though fuel is vaporized, "it is still suspended in the atmosphere. When an airplane takes off, the forces acting on the plane are: The weight of the airplane itself. The normal force keeping the airplane on the ground.