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Refuelling and Defuelling Risks

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Category: Ground Operations Ground Operations
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Content control: EUROCONTROL EUROCONTROL

Description

Aircraft refuelling and de-fuelling are accompanied by attendant hazards which must be managed sufficiently for their mitigation to acceptable levels. The issues are much the same whether the fuel source is a tanker/bowser or a fuel hydrant system. Pressure refuelling is normal for multi crew transport aircraft and business jets but gravity refuelling of these types may be available as a backup system. The kerosene fuel used by turbine engine aircraft has a higher flash/ignition point than the aviation gasoline used by piston engine aircraft but there are still potential hazards.

The primary risk is unintended ignition of fuel vapour, which can occur by a single spark. A sufficient quantity of fuel vapour to create a high risk of ignition may result from spillage arising from procedural errors, leaks, aircraft tank venting or failure of pressurized fuel lines or their couplings. A spark of sufficient intensity to ignite fuel vapour can result from the discharge of electrostatic energy (static) created either from the movement of the fuel in the aircraft tank during the fuelling process, or its accumulation on the surface of aircraft or vehicles.

Fuel movement during refuelling or defuelling may lead to the a static charge building up in the fuel. If the charge is of sufficiently high potential, it can cause sparking within the aircraft or the ‘origin’ storage tank. The charge density in the fuel and the possibility of sparks inside the tanks are not affected by bonding. However, the use of static dissipater additives in fuel can contribute materially to reducing the risk involved.

Accumulation of a surface static charge may occur on either an aircraft or its fuelling vehicle under certain conditions. Electrical bonding must be used to eliminate this hazard. Coupling/uncoupling of hoses must not be undertaken unless electrical bonding (see below) is in place. Re-fuelling should not take place during active electrical storms/thunderstorms in the immediate vicinity of the airport.

Electrical Bonding

There must be a cable to link to designated points or to clean unpainted metal surfaces on the chosen airframe. Bonding cables should connect the installation delivering the fuel with the aircraft or installation receiving the fuel. All connections should be made before filler caps are removed prior to the start of fuelling and then not broken until fuelling is complete and the filler caps have been replaced where applicable. On no account should either the fuelling vehicle (including hydrant dispenser) or the aircraft be bonded to a fuel hydrant pit. It should be noted that Fuel Hoses, including so-called “conductive” hoses, are not suitable substitutes for dedicated clips and bonding wires.

Static Dissipater Additive

If turbine fuels do not containing a static dissipater, or where wide-cut fuels are loaded, a substantial reduction in fuel flow rate is recommended to preclude ignition in the tank due to electrostatic discharge. Wide-cut fuel is considered to be 'involved' when it is being supplied or when it is already present in the aircraft tanks. It is recommended that when wide-cut fuel has been used, the next two uplifts of fuel should be treated as though they too were wide-cut. Mixtures of wide-cut and kerosene turbine fuels can result in the air-fuel mixture in the tank being in the combustible range at common ambient temperatures during fuelling.

PED Use during refuelling

There is a risk that a PED (personal electronic device) may create or induce a spark of sufficient intensity to ignite fuel vapour released during fuelling but it is extremely remote under normal circumstances. A particular concern is the proliferation of below-specification mobile telephone batteries that have the potential to fail dangerously. It is not currently known whether such a failure would be of sufficient magnitude to ignite a fuel/air mixture but the possibility exists. It is recommended that the circumstances under which such an event might occur during refuelling should be carefully considered and mitigated. It also appears that PEDs close to or on board modern aircraft can interfere with fuel gauges and some navigation equipment and may cause false fire warnings in cargo/baggage holds. Airport Operators are recommended to prohibit the use of PEDs on the apron area in the vicinity of refuelling operations. Passengers boarding or disembarking an aircraft other than via an airbridge should be discouraged from using PEDs.

Refuelling with Passengers On Board

Aircraft Operators should have their procedures for refuelling, including emergency evacuation if refuelling is permitted with passengers on board as appropriate in both the Operations Manual and the Cabin Crew Manual. Crew stations and duties should be clearly defined as should appropriate passenger communications. Procedures for Emergency Passenger Evacuation should take account of the availability or otherwise of airbridge access and in-position ground steps in the selection of exits to be used. Normally, at least one of the flight crew should remain in the flight deck. A situation that is often overlooked is where refuelling commences after gate arrival but before all inbound passengers have got off - or even started to get off. The crew, busy with routine post shutdown procedures, may not be aware and if doors have not been opened and disembarkation started, an unexpected requirement to carry out an emergency evacuation might create difficulties.

Defuelling

This is a special and infrequent operation; the personnel involved, including any flight crew, should be careful to refer to the necessary procedural documentation. Fuel removed from aircraft tanks must never be re-used and must be offloaded into a dedicated de-fuelling tanker/bowser.

Accidents and Incidents

  • B772, Denver CO USA, 2001 (GND FIRE HF): On 5 September 2001, a British Airways Boeing 777-200 on the ground at Denver USA, was substantially damaged, and a refuelling operative killed, when a fire broke out following the failure of a refuelling coupling under pressure because of improper attachment.

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