Chapter 10
Clearance of Debris
10.1
GENERAL
10.1.1
Me specifications of ECAR 139, call for the surface of aprons, taxiways and
runways to be kept clear of any loose stones or other objects that might cause
damage to aero planes or engines or impair the operation of aero plane systems.
Turbine engines are extremely susceptible to damage as a result of foreign
object ingestion. Other components of aero planes are vulnerable, and some
operators experience aero plane skin damage and incidents of nicked propellers
as a result of loose stones or other debris becoming dislodged by slipstream,
jet blast or tire action.
10.1.2
Although damage to aero planes is usually associated with engine ingestion,
substantial damage to tires is also a significant aspect of the overall
problem. Cuts or bursts resulting from
contact with sharp objects, untreated joints, or deteriorating pavement edges
are responsible for reduced tire life and account for a large proportion of aero
plane tires being scrapped prematurely. Of particular concern are tire failures
during the take-off run and the resulting risk of consequential failure of neighboring
tires from overloading, thereby causing an aborted take-off.
10.1.3
Debris constitutes a potential hazard to the safety of operations and has in
the past been directly responsible for aero planes abandoning take-offs or
executing emergency landings. Apart from the safety aspect, the unscheduled
replacement of damaged parts may involve
significant economic penalties.
10.1.4
The introduction of new aero plane types with their engines installed closer to
the ground has aggravated the problem. The cleanliness of the entire airport
surface should, therefore, be a matter of ongoing concern, requiring attention
by airport authorities.
10.1.5
Based on operational experience, the following are some of the aspects that
should not be overlooked in the development of a suitable programme intended to
achieve and maintain the required standard of cleanliness in the areas
concerned.
10.1.6
Experience with turbine engine aero planes indicates that one of the most
effective measures to minimize the problem of debris on the movement area is
frequent inspection and sweeping, including the use of ,equipment with magnetic
attachments. Where aero planes operate over an extensive route network, it is
sometimes difficult to pinpoint the precise location where damage has occurred, but airports at which
regular inspection and sweeping are known to be the practice are less likely to
encounter this problem.
10.1.7
Regular inspection by an airport official, together with a nominated
representative of the operators, is already a recognized procedure at many
airports and can form the basis for regular airport inspection reports
testifying to the effectiveness of the cleaning programme. Arrangements for
such joint inspections (which should permit access to all operational areas,
including runways and taxiways, as well as the immediate apron area) and the
development of a proper reporting form can be carried out in consultation with
a representative of the operators. In one State, this procedure has been used
to establish a sweeping priority/frequency programme, which includes of the
debris to determine its origin.
Thus,
areas where debris is most likely to occur can be isolated and cleaning operations in those areas
increased. Where the source of debris can be established, remedial measures can
also be taken with those responsible. In connection with this programme, a plan
of the paved area is divided into conveniently sized squares,
10.1.8
A potential source of debris, particularly on aprons, obviously stems from the
activities of the operators themselves in the handling and servicing of their aero
planes. Airline personnel receive training and recurrent reminders on the need
for apron cleanliness, but airport authorities can also assist by ensuring that
covered receptacles for litter and other debris are provided in sufficient number and are used. Such
receptacles should also be provided on all vehicles routinely used on the
movement area, regardless of ownership.
10.1.9
Other apron users, such as aero plane caterers fuel suppliers, forwarding
agents and handling agents, do not come under the direct supervision of the
operators. Airport authorities should
check that those engaged in the provision of such services have also taken
steps to instruct their staff properly regarding the prevention of litter and
the disposal of waste material.
Widespread use of polythene bags and sheets by the catering services and aero
plane maintenance personnel, and as temporary protection for freight or
components against weather, considerably increases the chance of engine
ingestion of this type of material. Engine failures have occurred as a direct
consequence. Sand used to clean fuel and oil spillage from aprons is a further
potential cause of turbine engine and propeller damage and should be
immediately and efficiently removed after use.
10.
1. 10 Cargo areas, by the very nature of the operations they support, are
particularly susceptible to contamination from strapping, nails, paper and
wood, which may become detached
from crates or other containers in the course of freight handling. Other
equipment which has been found in cargo areas includes loose buckles from cargo
tie down nets, loose turnbuckles and large sheets of polythene film. To the
extent that forwarding agents operate in these areas, the airport authority
should require that they assume their share of the responsibility for keeping
it in good condition. Where night activities are frequently involved, good
illumination is necessary so that the areas can be kept clean.
10.
1. 11 On taxi ways, bypass areas and holding bays, and on runways themselves,
the presence of stones and other debris as a result of erosion of the adjacent
areas can constitute a problem, and guidance on preventive measures, including
the sealing of runway and taxiway shoulders, is already contained in Part 2 of
the Aerodrome Design Manual (Doc 9157). The need for adequate sealing has been
highlighted by the introduction of large jet aero planes with greater engine
overhang. Until runway and taxiway shoulders are adequately sealed, care is
needed to ensure that vegetation and grass cuttings do not present an ingestion
problem to overhanging engines. Moreover, the areas immediately adjacent to the
paved and sealed surfaces should
also receive regular inspection and attention tonsure that debris which could
subsequently find its way onto the more critical areas is not present.
10.1.12
Deterioration of the bearing surface itself, leaving loose sand, fragments of
concrete and bitumen, is another possibility, and concrete joints, if not
properly filled, are excellent traps for debris. Such joints should be filled
to permit effective sweeping. There is also an indication
that kerosene spillage on bitumen taxiways and runways, caused by the venting
of fuel tanks of aero planes in motion, can result in deterioration of the
surface and engine ingestion problems.
These
areas should be frequently inspected and prompt repair work carried out,
whenever necessary, so as to prevent further break-up of the pavement.
10.1.13
Sand and grit remaining on the runway, after serving to improve runway braking
action under icy conditions, form debris which should be removed as soon as possible after their requirement
ceases. Similarly, slush containing sand, grit and lumps of ice should be
removed from the pavement as soon as possible.
10.1.14
Where construction is in progress on an airport, the authorities should, if
possible, prohibit use of the
movement area by contractors' vehicles or at least minimize it by restricting
them to marked lanes, particularly when they are engaged in transporting the
type of loads from which spillage
frequently occurs, such as building waste, gravel and fill. Earth and stones
adhering to the wheels of such vehicles can also become dislodged and
subsequently create a hazard to aero planes using the same areas. Where
building construction is in close proximity to the movement area, it is
important that some form of screening be provided to prevent sand and small
stones from being blown onto the movement area by high winds or jet blast.
Following the completion of construction, the contractor must remove all debris
from the surrounding areas.
10.2
EQUIPMENT FOR THE REMOVAL OF DEBRIS
10.2.1
Different methods for providing clean airport
pavement have been developed by airport authorities throughout the world.
Removal of debris is generally accomplished by utilization of mechanical units,
such as power brooms and vacuums or compressed air sweepers, which are operated
on the pavements to be cleaned.
10.2.2
Magnetic beam trailer. This unit is a
two wheeled trailer designed for towing on runways to magnetically pick up
loose metallic objects from the surface. Permanent magnets are mounted across a
bar to which brush segments are attached. The bar is lowered to a sweeping
position and the magnet attracts the metallic objects, gathering them from the
pavement surface. However, it would appear that powered sweeping brooms are
more effective for removing these objects from the surface.
10.2.3 Mechanical sweepers should have
characteristics such that the maximum possible amount of debris is removed in
each pass of the unit at the required operating speed: for fine sand, thinly
spread on the surface of a pavement, pick-up of the order of 98 per cent in one
pass has been achieved at speeds in excess of
10.3
SWEEPER TESTS
10.3.1
Sweepers should be tested regularly by a performance test. A description of the
practice being used by one State for
performance testing is given below.
(a) Select a flat,
smooth, bituminous, concrete area and mark out a section
(b) Assemble a
(1) Medium/ fine gravel.
The gradation of this material is such that 100 percent shall pass a
(2) Coarse sand. The
gradation of this material is such that 100 per cent shall pass a
(3) Medium/ fine sand. The gradation of this material is such that
100 per cent shall pass a 0.6 min, screen size and no particles pass a
(c)
Obtain eight stones, spherical in shape,
(d)
Spread the mixture of medium-fine gravel, coarse sand and medium/fine sand
evenly over the test area. Along one diagonal of the test area, place the eight
stones at equal spacing, and along the other diagonal, place the nail,
ball-bearing, aluminum square and nut at equal spacing.
(e)
The sweeper shall be operating normally and, on passing over the prepared test
area at
10.3.2
In the event of a sweeper failing to comply with a performance test, action
should be taken to restore the sweeper to the acceptable operational standard
of performance. The frequency of sweeper tests will depend largely on the
utilization of the unit. It is common practice to undertake such tests on a
regular weekly basis.