Kerosene

Why can it become necessary to jettison kerosene?

Only few long-haul aircraft types are equipped with fuel dump systems such as Airbus A340 and A380 as well as Boeing B747, B767 and B777 for instance. The maximum takoff weight (MTOW) of these aircraft is well above the maximum landing weight (MLW) in order to carry along the required amount of fuel for the distance flying. On regular long-haul flights, aircraft will reach their destination below MLW as fuel is burnt along the way. However, in the event of a declared emergency requiring immediate landing, the pilot has the option to attain MLW by jettisoning fuel. This is an absolute exceptional situation in which only the safety of the passengers, the crew and the aircraft has priority.
 

Fuel jettison procedure

The decision to jettison fuel and the amount of kerosene to be jettisoned is made by and the sole responsibility of the cockpit crew and ultimately the responsible pilot. The German Air Traffic Control is informed about the necessity to jettison fuel. Air Traffic Control then assigns a suitable airspace with as low as possible air traffic over an unpopulated or sparsely populated area. Fuel jettisoning usually takes place at an altitude between 4,000 and 8,000 meters above sea level, but at least above 1,800 meters. The flight speed is at least 500 km/h. The surrounding airspace must be kept clear of passing air traffic during the jettisoning process as well as for a certain time thereafter.
 

Fate of jettisoned fuel

Kerosene is released through nozzles by gravity and disperses into a spray of very fine droplets. This mist only descends very slowly and remains in the atmosphere, ultimately being converted to water and carbon dioxide by the radiant energy of the sun. Fuel jettison is a standardised procedure that limits negative impacts on the ground to an absolute minimum. Analytical measurements show no detectable pollution.
 

Obligation to report

Fuel jettison events must be reported and are registered to a national database. The corresponding airline reports the event to its relevant supervisory authority; for German airlines this is the Federal Aviation Office (Luftfahrt-Bundesamt, LBA). A report is also given by the German Air Traffic Control to the Federal Air Traffic Control Authority (Bundesaufsichtsamt für Flugsicherung, BAF). This in turn reports back to the LBA, so that registration of all fuel jettison events in German airspace is guaranteed. In the period from 2010 to 2017, an average of 21 cases per year were reported for German airspace.

Information on reported events regarding the current year can be found on the LBA website. Further information on the subject can also be found in an information sheet published by the Federal Association of the German Aviation Industry (Bundesverband der Deutschen Luftverkehrswirtschaft, BDL) and in a position paper published by the Federal Environment Agency (Umweltbundesamt, UBA).