BDA Flight Training © 2009

Fuel Dumping ( Fuel Jettisoning )

The reason aeroplane are equipped to release fuel in flight (Fuel dumping or Fuel jettisoning) is for safety.  To allow an aeroplane to make an emergency landing shortly after takeoff.  Other reason would be landing at an airfield other then the intended destination aerodrome, with a shorter runway or lower load bearing surfaces.   Due to aeroplane design, landing gears and aeroplane structures will absorb the impact of landing up to a certain weight.  This is call the landing weight. An aeroplane can be too heavy to land safely without risking a landing gear collapse or other structural failure when fully loaded. Dumping fuel is a safe way to reduce the aeroplane all up weight if needed.  Fuel dumping system Fuel is selectively jettisoned or dumped, by way of a normally closed, solenoid-operated jettison valve, which is fed from the boost pump in the engine fuel system. The jettison valve is servo activated by the main fuel flow so that the engine must be running for the opening of the solenoid valve to occur.

These systems are controlled from the cockpit.  It ejects several thousand pounds of fuel per minute.  Usually a fuel-dumping operation takes about 10 minutes to complete. Fuel dumping in flight  A typical fuel dumping system uses a series of pumps and valves to eject fuel from the aeroplane wingtips. Other area where fuel dumping conduit could be located are in the aeroplane tail, rear fuselage or mid wing.  When activated from the cockpit, a fuel dump system releases thousands of pounds/kilos of fuel per minute.

Most systems release fuel at a fast enough rate that the aeroplane total weight is reduced from maximum takeoff weight to maximum certified landing weight  (MCLW) in fifteen minutes or less.

Once released the fuel trails behind the aircraft and creates a pattern that looks much like a contrail. Planes are fitted with emergency fuel dump systems that release enough fuel to lighten the aircraft until they can land safely.  

© BDA 2009

BDA Flight Training © 2009

Fuel Dumping Regulations Fuel dumping is also known as Fuel Jettisoning. Regulations that pertain to fuel dumping are established by Transport Canada regulations (CAR’s). The following uses the term in used at Transport Canada. Fuel Jettisoning System The fuel jettisoning system must be capable of jettisoning enough fuel within 15 minutes, to enable the aeroplane to meet the require climb performance.   Fuel Jettisoning safeguard (1) The fuel jettisoning system and its operation are free from fire hazard(2) The fuel discharges clear of any part of the aeroplane(3) Fuel or fumes do not enter any parts of the aeroplane, and(4) The jettisoning operation does not adversely affect the controllability of the  aeroplane. Turbine Powered Aeroplane For turbine engine powered aeroplane, means must be provided to prevent jettisoning the fuel in the tanks used for take-off and landing below the level allowing climb from sea level to 10,000 feet and thereafter allowing 45 minutes cruise at a speed for maximum range.  The fuel jettisoning system must be designed so that any reasonably probable single malfunction in the system will not result in a hazardous condition due to unsymmetrical jettisoning of, or inability to jettison, fuel.  The controls for any fuel jettisoning system shall be designed to allow flight personnel (minimum crew) to safely interrupt fuel jettisoning during any part of the jettisoning operation.  Fuel Dumping in flight procedure (1) Whenever it is necessary to jettison fuel, the pilot should immediately notify ATC and provide information such as the course to be flown, the period of time and weather conditions.  (2) To allow for adequate vaporization, fuel dumping should be carried out at least 2 000 feet above the highest obstacle within 5 NM of the track to be flown.  (3) ATC may suggest an alternate area where fuel should be dumped; aircraft will be encouraged to dump fuel on a constant heading over unpopulated areas and clear of heavy traffic.  When necessary information has been obtained, ATC will broadcast on appropriate frequencies a “fuel dumping” advisory.  Pilots should advise ATC immediately when fuel dumping has been completed.

© BDA 2009