Fuel Jettison, more commonly referred to as Fuel Dumping, is the intentional, controlled, jettison of fuel from an aircraft whilst in flight. Not all aircraft designs incorporate a fuel dump capability and, even if dump capability is inherent to a particular aircraft type, a specific aircraft of that type may or may not be fitted with fuel jettison capability.
Fuel dump may be initiated by the pilot to lighten the aircraft when performance is compromised due to failure of one or more engines whilst in flight. It can also be used to reduce the aircraft weight to a value below maximum landing weight when compelled to land earlier than expected due to a turnback or an enroute diversion.
Useful to Know
Fuel dump could be initiated without any forewarning and at almost any altitude, as might be the case should an engine failure, in combination with another performance limiting malfunction, occur on takeoff. Whilst it is likely that the pilot would declare an emergency in this situation, it is equally unlikely that they would have the time immediately available to detail any specific actions (including dumping fuel) that they might be taking.
For a more benign circumstance such as a fuel dump due to diversion or turnback, it is likely that the pilot will pre-notify ATS and seek guidance/clearance for altitude and location prior to commencing the fuel dump.
What to Provide
Best practice embedded in the ASSIST principle could be followed (A - Acknowledge; S - Separate, S - Silence; I - Inform, S - Support, T - Time):
- A - acknowledge the emergency, ask for intentions and provide information regarding suitable fuel dumping areas and altitudes as well as suitable landing aerodromes as necessary;
- S - separate the aircraft from other traffic (see next section). If such an area exists, vector the aircraft to the designated fuel dumping area. Ensure that dumping occurs at an altitude that will allow evaporation/dissipation of the fuel before it reaches the ground - 5000 to 6000" AGL is usually sufficient.
- S - silence the non-urgent calls (as required) and use separate frequency where possible;
- I - inform the supervisor and other sectors/units concerned; inform the airport emergency fire rescue services and all concerned parties according to local procedures; inform other (uncontrolled) traffic in the vicinity using a general call, e.g. "All stations, [ATS unit], [TYPE] dumping fuel [level] [route or location]"
- S - support the flight by providing any information requested and necessary such as type of approach, runway length and any additional aerodrome details, etc.
- T - provide time for the crew to assess the situation, execute the dumping procedure and complete associated checklists - don’t press with non urgent matters.
ICAO Doc 4444 PANS-ATM specifies the following separation minima to be used in respect to other known traffic in case of fuel dumping:
- at least 10 NM horizontally, but not behind the aircraft dumping fuel
- vertical separation if behind the aircraft dumping fuel within 15 minutes flying time or a distance of 50 NM by:
- at least 1 000 ft if above the aircraft dumping fuel
- at least 3 000 ft if below the aircraft dumping fuel
The horizontal boundaries of the area within which other traffic requires appropriate vertical separation extend for 10 NM either side of the track flown by the aircraft which is dumping fuel, from 10 NM ahead, to 50 NM or 15 minutes along track behind it (including turns).
Area where increased separation is provided in respect to the aircraft dumping fuel
To mitigate the effect of fuel dumping, the following additional guidelines should be considered by ATCOs:
- Clear airspace in the immediate vicinity of the emergency aircraft - provide adequate horizontal and vertical separation between the aircraft dumping fuel and other traffic
- If practicable, make use of dedicated fuel dumping areas. These are normally published in the AIP.
- Try to vector the aircraft clear of populated areas during the fuel dump process
- Determine the amount of time needed for the fuel dump
- Consider the possibility of a blocked runway in the event that, after landing, the Pilot in Command elects to stop on the runway for an aircraft inspection