CHAPTER 5 CHAPTER 5
5.4 Operational Areas
• Dead or model birds
• Model aircraft and kites
• Light and sounds of a disturbing nature
• Trapping
• Falcons
• Narcotics and poisons
If the presence of birds is a serious problem that threatens to disrupt the safe operation of the airport, the operator has no choice but to initiate a control program that will reduce the hazard to an acceptable level.
However, effective action cannot always be taken by the airport operator alone.
Indeed, an effective control program must include all airside tenants and possibly property owners adjacent to the airport because these areas could be a source of bird or animal activity hazardous to air traffic. ICAO recommends that the larger community be organized to form a wildlife hazard committee that jointly considers and approves measures to reduce bird and other wildlife risk to an acceptable level.
blowing sand might present conditions where operation will continue with less than optimal pavement surface conditions during a continuous clearing process. Therefore, procedures are set up to measure runway surface friction and the precipitant drag effect so that the pilots can adjust their techniques to existing conditions. In summary, the occasions under which assessment of the runway surface condition might be required include
• The dry runway case—infrequent measurement to monitor texture and wear and tear through the normal life of the runway
• The wet runway case—taking care to note the dramatic interaction of wet conditions with rubber deposits, which can result in a serious deterioration of the friction coefficient
• The presence of a significant depth of water and the possibility of aquaplaning
• The slippery runway case owing to the presence of ice, dry snow, wet snow, compacted snow, or slush, which reduce the coefficient of surface friction
• A significant depth and extent of slush, wet snow, or dry snow that can produce a significant level of precipitant drag
Because of the potential for runway excursions in extreme weather, especially overruns, the FAA and ICAO have recently advocated the extension of runway end-safety areas (RESA)—graded, obstacle-free zones to safely stop aircraft that have exited the runway end. Where available land is insufficient, specially designed systems can be installed to “capture” exiting aircraft with minimal damage and no loss of life.
At a very busy airport that frequently experiences conditions where braking might be impaired by contaminants, an adequate level of runway cleaning equipment must be maintained. Equipment also must be available to check the results of cleaning by measuring friction and drag. Rubber accumulation is inevitable on all active runways.
Appendix 2 of Part 2 of the ICAO Airport Services Manual contains an inspection guide for the visual estimate of rubber deposits accumulated on the runway (ICAO 2002). The time interval between rubber buildup assessments depends on factors such as air traffic volumes (frequency and type of aircraft), climatic conditions, pavement type, and the pavement’s service and maintenance requirements. ICAO recommends that airports with more than 210 landings per week should conduct detailed inspections weekly. If rubber contamination is excessive, the rubber can be removed by a variety of methods. These include high-pressure water cleaning, chemical removal, and even sand blasting (with vacuum containment to prevent debris). Each method has advantages and disadvantages;
the best practice for each airport will depend on such factors as the condition of the pavement, the ability to control runoff (if water is used), and the environmental effects of the chemicals used.
At a less busy airport, where conditions of impaired braking are experienced only infrequently, but where operations must continue despite inadequate cleaning equipment, assessment of runway friction is essential, and equipment for measuring these effects must be available to enable pilots to adjust their operations to the existing conditions. At an even less important airport where operations can be suspended, it is essential to have equipment to assess runway friction to be able to make a decision on when conditions have reached the point where suspension of activities is necessary. It is important to
remember that even where the removal of snow and ice is given high priority, there is frequently a significant loss of friction on an apparently dry, cleared runway. At airports that regularly experience heavy snowfalls, for example, in northern Europe and North America, clearance might have to be discontinued for a short while during a storm to permit some operations to continue. Runways are unlikely, in such conditions, to be completely clean.
There are also likely to be local slippery patches. The airport authority will need to measure and assess surface conditions to inform pilots of the overall condition and to determine the areas requiring more cleaning treatment.
Various types of friction testing equipment are available. Several versions are small trailers with a measuring device (Mu Meter) that is attached behind a towing vehicle. Figure 5.4a shows a truck with a retractable fifth wheel that performs the friction test. An illuminated control panel by the driver gives readings at the same time as a record is made of the coefficient of friction with a corresponding estimated braking action. Figure 5.4b shows the format of the visual display of the record of the runway surface condition. For further descriptions of such equipment, the reader is referred to FAA (1991, 2008) and CAA (2010b).
FIGURE 5.4 (a) Instrumented pickup truck with retractable fifth wheel. (Dynatest.) (b) PC readout of Dynatest runway friction test. (Dynatest.)
Table 5.4 indicates the relationship between the coefficient of friction and the subjective estimate of braking efficiency. It is quite possible for a thin film of ice to reduce the coefficient of friction on an aircraft pavement from 0.50 to 0.15, reducing the braking efficiency to less than a third of that in the dry condition.
Source: FAA (2008).
TABLE 5.4 Relationship Between Coefficient of Friction and Braking Efficiency
Recognizing that an airport authority must be in a position to evaluate the level of runway friction, assessment of pavement condition should never take precedence over the clearance operations themselves. Within the operational areas, safety and efficiency require observing the following clearance priorities for the various areas involved:
• Runways
• Taxiways
• Aprons
• Holding bays
• Other areas
Snow clearance is frequently coordinated through the operation of the snow committee, consisting of members from the airline operators, meteorology, air traffic system (ATS) services, and airport administration. Clearance is laid down in a snow plan that ensures that agreed-on procedures exist for the provision and maintenance of equipment; for clearance according to stated priorities; for installation of runway markers, snow fencing, and obstruction marking; and for providing for maneuvering aircraft. For further details on snow clearance, the reader is referred to FAA (1991, 1992, 2008), which indicate the availability and uses of such specialized equipment as the snow blower shown in Figure 5.5. While snow conditions occur for only a limited period during the year, airports might turn to outside contractors to provide snow clearance services, having the equipment moved onto site only prior to the snow season.
FIGURE 5.5 Snow blower. (Oshkosh.)
Debris presents a separate and different problem at airports. Jet turbine engines are extremely susceptible to damage from ingestion of solid particles of debris picked up from the pavement surfaces. Tire life is also reduced by wear and cuts induced by sharp objects on the pavements, deteriorating pavement surfaces and edges, and poor, untreated pavement joints. Damage also can occur to the skin of aircraft from objects thrown up from the pavement. This is precisely what occurred on July 25, 2000, to Air France Flight 4590, the Concorde flight from Paris Charles de Gaulle International Airport to JFK International Airport in New York. During the takeoff run, the Concorde suffered a ruptured tire from a piece of debris that had fallen off an aircraft that had just departed from the same runway.
The tire debris struck the underside of the wing, eventually causing a rupture to a fuel tank, leading to a fire and a fatal crash.
Problems arising from debris can be reduced by regular inspections of the pavement surface condition of all operational areas and by establishing a sweeping and cleaning program that sets up priorities and frequencies. In order to help designate the particular location of debris, a plan of the paved areas should be divided into manageable paved segments of approximately 1,640 feet (500 m) (ICAO 1984). Descriptions of these pavement sections can be entered into a database that keeps a record of inspection results, current condition, and any operational restrictions in a pavement management system (PMS). A PMS also can perform cost-benefit analyses to recommend when and what kind of repairs/replacement should take place.
Runway inspections are almost always conducted in vehicles owing to their extensive area and evacuation considerations. These vehicles should travel at the lowest velocity possible in the opposite direction of takeoff or landing for air traffic safety. Increasingly, busy airports are using remote sensing to detect the presence of debris, wildlife, and defects on the operational airside pavements. The FAA has approved the use of certain
technologies, including radar-and video-based systems. An example of such a system is the Singapore Changi iFerret automated FOD detection system using a vision-based system linked to air traffic control (ATC) and ground operations control. In apron areas, the cleanliness of the airline operators and other users determines the amount of litter and debris that is present. Cargo areas are particularly susceptible to the presence of fragments of strapping, nails, and container and pallet debris. The problem can be reduced by careful adherence to a disciplined program of maintaining litter-free pavements.
Runways, taxiways, and holding bays are subject to debris eroded from the pavement shoulders. This kind of debris can be reduced by shoulder-sealing treatments, which might be necessary on highly trafficked facilities (FAA 2007). Removal of debris is achieved by powered mobile brooms, vacuum and compressed-air sweepers, and magnetic cleaners.
As a further incentive, some airports provide brightly painted litter bins adjacent to aircraft gates/parking bays in which any litter or debris found in the aircraft parking areas can be deposited. The airport operator must strive to instill a culture of safety in all personnel who have access to airside facilities.