Chapter 16
16.1 INTRODUCTION
16.1.1 The airport authority, the aircraft operator and the fuel
supplier each has responsibilities in respect of the safety measures to be
taken during fuelling operations. Some guidance on these safety measures is
given below. It is important to note that this material is not intended to
replace fuel supplier operator procedures which are usually developed to meet
requirements imposed by special equipment, national regulations, etc. The
material includes the following subjects:
(a)
general precautionary measures to be taken during fuelling operations;
(b)
additional precautionary measures to be taken when passengers remain on board
or embark/disembark during refuelling operations; and
(c) sources and dissipation of electrical energy
that may develop during aircraft fuelling operations.
16.1.2 The material relevant to c) was drawn up as a result of inquiries among States and aircraft operators regarding the practices followed
by them during aircraft refuelling operations.
16.2 GENERAL PRECAUTIONARY
MEASURES TO BE TAKEN DURING AIRCRAFT FUELLING
OPERATIONS
The following general precautionary measures should be taken during aircraft fuelling operations:
(a) aircraft fuelling operations should be done
outdoors;
(b) bonding and/or grounding, as appropriate,
should be done in accordance with 16.4;
(c) aircraft fuelling vehicles should be
positioned so that:
(1)
accessibility to aircraft by rescue and fire fighting vehicles is not
interrupted;
(2) a cleared path is
maintained to permit rapid removal of fuelling vehicles from an aircraft in an emergency;
(3) they do not obstruct
evacuation from occupied portions of the aircraft in the event of a fire; and
4) the vehicle engines are not under the wing;
(d) all vehicles performing aircraft servicing
functions other than fuel servicing (e.g. baggage trucks, etc.) should not be
driven or be parked under aircraft wings while fuelling is in progress;
(e) the
exhaust systems of all vehicles required to operate in the fuelling zone must
be subjected to the most
stringent and regular maintenance to eliminate defects which may result in the
emission of sparks or flames capable of igniting fuel or fuel vapour;
(f) aircraft-borne auxiliary power units which have an exhaust efflux
discharging into the zone should be started before filler caps are removed or
fuelling connexions made;
(g) if an auxiliary power unit is stopped for any reason during a fuelling
operation it should not be restarted until the flow of fuel has ceased and
there is no risk of igniting fuel vapours;
(h) aircraft should not be
fuelled within the immediate vicinity of radar equipment under test or in use
in aircraft or ground installations;
(i) aircraft batteries
should not be installed or removed nor should battery chargers be connected,
operated or disconnected;
(j) connecting of ground
power generators should not be done during this period;
(k) electric tools, drills
or similar tools likely to produce sparks or arcs should not be used;
·
Throughout this
chapter the term fuelling encompasses refuelling and defiling.
(1) photographic flash bulbs or electronic flash equipment should not be
used in the immediate vicinity of the fuelling equipment or of the fill or vent
points of the aircraft;
(m) open flames and lighted open flame devices
should be prohibited on the apron and in other locations within
(1)
lighted cigarettes, cigars, pipes; 2) exposed flame heaters;
(2)
welding or cutting torches, etc.; and
(3)
flare pots or other open flame lights;
(n) cigarette lighters or matches should not be
carried or used by anyone while engaged in aircraft fuelling operations;
(o) extreme caution should be used when fuelling
during lightning and electrical storms. The fuelling operations should be
suspended during severe lightning disturbances in the immediate vicinity of the
airport;
(p) when any part of an aircraft undercarriage is
abnormally heated, the airport rescue and fire fighting service should be
called and fuelling should not take place until the heat has dissipated; and
(q) portable fire extinguishing equipment
suitable for at least initial intervention in the event of a fuel fire and
personnel trained in its use shall be readily available and there shall be a
means of quickly summoning the rescue and fire-fighting service in the event of
a fire or major fuel spill. It should be ensured by regular inspection and
maintenance that this equipment is maintained in a fully serviceable condition.
16.3 ADDITIONAL PRECAUTIONARY MEASURES
TO BE TAKEN
WHEN PASSENGERS REMAIN ON BOARD OR
EMBARK/DISEMBARK
DURING REFUELLING OPERATIONS
16.3.1 Because of the importance of reducing transit times and
for security reasons, some States allow passengers to remain on board during
refuelling operations while others allow passengers to embark and disembark.
However, an aircraft shall not be refuelled when passengers are embarking, on
board or disembarking unless it is properly staffed by qualified personnel
ready to initiate and direct an evacuation of the aeroplane by the most
practical and expeditious means available.
16.3.2 The following additional precautions must be observed during
refuelling operations while passengers remain on board or embark/disembark.
(a) passengers should be
warned that refuelling will take place and that they must not smoke, operate
switches or otherwise produce sources of ignition;
(b) the illuminated--“-No
smoking”signs and exit lighting should be switched on;
(c) aircraft equipped with integral stairs should
have them deployed, or if aircraft stairways are used, these should be
positioned at each of the main doors normally used for passenger embarkation or
disembarkation which should be open or ajar and free from obstruction. Where it
is found desirable to close the main doors for climatic or any other particular
operational reason, these doors should never be locked, and a cabin attendant
should at all times be stationed at each door during any refuelling operation
with passengers on board. Where powered gangways (nose loaders or aerobridges)
are employed the deployment of integral stairs or off aircraft stairways is not
necessary. When only one powered gangway or stairway is available, the other
main door(s) should be unobstructed by ground equipment to permit the use of
the escape slide at that door. A cabin attendant should be available to operate
the slide in the event of an emergency. An adequate number of cabin attendants
or other staff suitably trained in emergency evacuation procedures for the
particular type aircraft and in communication with the flight crew should at
all times remain in the aircraft to direct an evacuation should the need arise;
(d) if, during refuelling,
the presence of fuel vapour is detected in the aircraft interior, or any other
hazard arises, refuelling and all cleaning activities using electrical
equipment within the aircraft should be stopped until conditions permit
resumption;
(e) ground servicing activities and the work within the aircraft
should be conducted in such a manner that they do not obstruct exits;
(f) where passengers are embarking or disembarking during refuelling
their route should avoid areas where fuel vapours are likely to be present and
this movement should be under the supervision of a responsible person;
(g) the "No smoking-
rule should be strictly enforced during such passenger movements;
(h) (two-way)
communications shall be maintained by
aeroplane intercommunications system or other suitable means between the
ground crew supervising the refuelling and the qualified personnel on board the
aeroplane; and
(i) ground equipment shall
be positioned so as to allow:
(1) the use of a sufficient
number of exits for expeditious evacuation; and
(2) a ready escape route
from each of the exits to be used in an emergency.
16.3.3 It is important to note that an aircraft should not be defiled
when passengers remain on board or are embarking or disembarking. The normal
surge tanks and automatic shut-off features of the refuelling process are not
incorporated in the defiling systems on aircraft. This presents a greater
potential for an accident from the sources described in 16.4.
16.4 SOURCES AND DISSIPATION OF ELECTRICAL
ENERGY THAT MAY DEVELOP DURING AIRCRAFT FUELLING OPERATIONS
16.4.1 Distinct types of electrical potential difference, with the
accompanying hazard of spark discharge, are possible during aircraft fuelling
operations. A description of each type together with the practices used to
prevent its occurrence is given in the following paragraphs.
16.4.2 Electrostatic charge, which may be accumulated on the
surface of the aircraft or fuelling vehicle, when conditions are favourable.
The hazard of sparking can be eliminated by ensuring that the fuelling vehicle
is bonded to the aircraft so that a difference in electrical potential cannot
occur between the two. This appears to be a worldwide accepted practice.
Bonding between the aircraft and vehicle is made by connecting a conductor
between designated points on clean and unpainted metal surfaces of both the
aircraft and the fuelling vehicle. Electrically conductive fuel hoses normally
provide a back-up conductive path for discharge of any possible
electrostatic charge, but aircraft fuelling procedures recommend that
conductive hoses should not be regarded as adequate bonding between aircraft
and fuelling vehicle.
16.4.3 Where over wing refuelling is employed, the nozzle of the hose is
normally bonded to the aircraft before the filler cap is removed; however,
where underwing fuelling is employed, the automatic metal-to-metal contact
between the aircraft fitting and the coupling eliminates the need for separate
bonding connexion.
16.4.4 Drag chains on fuelling vehicles or conductive tires on fuelling
vehicles and aircraft are often used as additional safeguards but are not
considered effective by themselves. They are useful however, since in the event
that the aircraft/vehicle bonding is broken or faulty, the electrostatic charge
could be discharged from the aircraft or vehicle through their respective tires
or drag chains.
16.4.5 As an additional safety measure, some practices specify
individual electrical grounding of aircraft and vehicle. This measure would
prevent any possible hazard caused by a broken or faulty bonding. It appears,
however that this possibility is negligible if proper maintenance and testing
of the wire used for bonding purposes between aircraft and fuelling vehicle is
carried out.
16.4.6 In summary:
(a) where no electrical
grounding is specified, the normal
order of procedure to eliminate electrostatic
discharge during fuelling operations is as follows:
(1) bonding of aircraft and
fuelling vehicle to one another; and
(2) bonding of fuel nozzle
to aircraft for over wing fuelling arrangements; and
(b) where electrical
grounding is specified, the normal order of procedure is as follows:
(1) grounding of fuelling
vehicle;
(2) grounding of aircraft;
(3) bonding of aircraft and
fuelling vehicle to one another; and
(4) bonding of fuel nozzle
to aircraft for over wing fuelling arrangements.
On completion of fuelling
operations, the disconnexions should be made in reverse order.
16.4.7 Electrostatic charge, which may also build up in
the fuel during the fuelling operation. If of sufficient potential, it can
cause sparking within the aircraft tank. The charge density in the fuel and the
possibility of sparks inside the tanks are not affected by bonding or
grounding of the aircraft or the fuelling vehicle. Manufacturers and
fuel suppliers have studied this matter for a long time and have concluded that
the use of anti-static additives in fuel can contribute materially to reducing
the risk involved.
16.4.8 In summary, it may be concluded that hazards due to this
electrostatic charge are controlled by anti-static additives in the fuel.
16.4.9 Stray currents, which may occur because of short circuits
or other faults in the electrical power supply for the aircraft. Stray currents are dissipated by ensuring an effective
bonding between the fuelling vehicle and the aircraft.
16.4.10 When the aircraft is bonded to the fuelling vehicle and the
latter is grounded, large currents may flow through the bonding wire via the
vehicle to ground. When the ground is disconnected, severe sparking can occur
at the break point. To avoid this, it is normally recommended that grounding of
aircraft, if prescribed, should be direct and not through the bonding wire and
fuelling vehicle. When a hydrant system is used, the fuelling hydrant pit should not be used for the aircraft grounding because the sparks from
stray currents could be dangerous. Moreover, it is not advisable to
connect the grounding devices of the refuelling system, particularly where a
hydrant system is used, and the grounding devices of an electrical system used
for supplying electrical power to the aircraft since if a short circuit were to
occur in the electrical system, then damage could occur to the aircraft.
16.4.11 In summary, it maybe concluded that hazards due to stray
currents are eliminated by bonding of the aircraft to the fuelling vehicle.