Some text was adapted from the 3rd edition Encyclopaedia article “Aviation - ground personnel” authored by E. Evrard.
Commercial air transport involves the interaction of several groups including governments, airport operators, aircraft operators and aircraft manufacturers. Governments are generally involved in overall air transport regulation, oversight of aircraft operators (including maintenance and operations), manufacturing certification and oversight, air traffic control, airport facilities and security. Airport operators can either be local governments or commercial entities. They are usually responsible for the general operation of the airport. Types of aircraft operators include general airlines and commercial transport (either privately or publicly owned), cargo carriers, corporations and individual aircraft owners. Aircraft operators in general are responsible for operation and maintenance of the aircraft, training of personnel and operation of ticketing and boarding operations. Responsibility for security can vary; in some countries the aircraft operators are responsible, and in others the government or airport operators are responsible. Manufacturers are responsible for design, manufacturing and testing, and for aircraft support and improvement. There are also international agreements con- cerning international flights.
This article deals with the personnel involved with all aspects of flight control (i.e., those who control commercial aircraft from takeoff to landing and who maintain the radar towers and other facilities used for flight control) and with those airport personnel who perform maintenance on and load aircraft, handle baggage and air freight and provide passenger services. Such personnel are divided into the following categories:
- air traffic controllers
- airways facilities and radar towers maintenance personnel
- ground crews
- baggage handlers
- passenger service agents.
Flight Control Operations
Government aviation authorities such as the Federal Aviation Administration (FAA) in the United States maintain flight control over commercial aircraft from takeoff to landing. Their primary mission involves the handling of airplanes using radar and other surveillance equipment to keep aircraft separated and on course. Flight control personnel work at airports, terminal radar approach control facilities (Tracons) and regional long-distance centres, and consist of air traffic controllers and airways facilities maintenance personnel. Airways facilities maintenance personnel maintain the airport control towers, air traffic Tracons and regional centres, radio beacons, radar towers and radar equipment, and consist of electronics technicians, engineers, electricians and facilities maintenance workers. The guidance of planes using instruments is accomplished following instrument flight rules (IFR). Planes are tracked using the General National Air Space System (GNAS) by air traffic controllers working at airport control towers, Tracons and regional centres. Air traffic controllers keep planes separated and on course. As a plane moves from one jurisdiction to another, responsibility for the plane is handed from one type of controller to another.
Regional centres, terminal radar approach control and airport control towers
Regional centres direct planes after they have reached high altitudes. A centre is the largest of the aviation authority’s facilities. Regional centre controllers hand off and receive planes to and from Tracons or other regional control centres and use radio and radar to maintain communication with aircraft. A plane flying across a country will always be under surveillance by a regional centre and passed along from one regional centre to the next.
The regional centres all overlap each other in the surveillance range and receive radar information from long-range radar facilities. Radar information is sent to these facilities via microwave links and telephone lines, thus providing a redundancy of information so that if one form of communication is lost, the other is available. Oceanic air traffic, which cannot be seen by radar, is handled by the regional centres via radio. Technicians and engineers maintain the electronic surveillance equipment and the uninterrupted power systems, which includes emergency generators and large banks of back-up batteries.
Air traffic controllers at Tracons handle planes flying at low altitudes and within 80 km of airports, using radio and radar to maintain communication with aircraft. Tracons receive radar tracking information from the airport surveillance radar (ASR). The radar tracking system identifies the plane moving in space but also queries the plane beacon and identifies the plane and its flight information. Personnel and work tasks at Tracons are similar to those at the regional centres.
Regional and approach control systems exist in two variants: non-automated or manual systems and automated systems.
With manual air traffic control systems, radio communications between controller and pilot are supplemented by information from primary or secondary radar equipment. The trace of the aeroplane can be followed as a mobile echo on display screens formed by cathode-ray tubes (see figure 1). Manual systems have been replaced by automated systems in most countries.
Figure 1. Air traffic controller at a manual local control centre radar screen.
With automated air traffic control systems, information on the aeroplane is still based on the flight plan and primary and secondary radar, but computers make it possible to present in alphanumeric form on the display screen all data concerning each aeroplane and to follow its route. Computers are also used to anticipate conflict between two or more aircraft on identical or converging routes on the basis of the flight plans and standard separations. Automation relieves the controller of many of the activities he or she carries out in a manual system, leaving more time for taking decisions.
Conditions of work are different in manual and automated control centre systems. In the manual system the screen is horizontal or sloping, and the operator leans forward in an uncomfortable position with his or her face between 30 and 50 cm from it. The perception of mobile echoes in the form of spots depends on their brightness and their contrast with the illuminance of the screen. As some mobile echoes have a very low luminous intensity, the working environment must be very weakly illuminated to ensure the greatest possible visual sensitivity to contrast.
In the automated system the electronic data display screens are vertical or almost vertical, and the operator can work in a normal sitting position with a greater reading distance. The operator has horizontally arranged keyboards within reach to regulate the presentation of the characters and symbols conveying the various types of information and can alter the shape and brightness of the characters. The lighting of the room can approach the intensity of daylight, for contrast remains highly satisfactory at 160 lux. These features of the automated system place the operator in a much better position to increase efficiency and reduce visual and mental fatigue.
Work is carried out in a huge, artificially lighted room without windows, which is filled with display screens. This closed environment, often far from the airports, allows little social contact during the work, which calls for great concentration and powers of decision. The comparative isolation is mental as well as physical, and there is hardly any opportunity of diversion. All this has been held to produce stress.
Each airport has a control tower. Controllers at airport control towers direct planes in and out of the airport, using radar, radio and binoculars to maintain communication with aircraft both while taxiing and while taking off and landing. Airport tower controllers hand off to or receive planes from controllers at Tracons. Most of the radar and other surveillance systems are located at the airports. These systems are maintained by technicians and engineers.
The walls of the tower room are transparent, for there must be perfect visibility. The working environment is thus completely different from that of regional or approach control. The air traffic controllers have a direct view of aircraft movements and other activities. They meet some of the pilots and take part in the life of the airport. The atmosphere is no longer that of a closed environment, and it offers a greater variety of interest.
Airways facilities maintenance personnel
Airways facilities and radar towers maintenance personnel consist of radar technicians, navigational and communication technicians and environmental technicians.
Radar technicians maintain and operate the radar systems, including airport and long-range radar systems. The work involves electronic equipment maintenance, calibration and troubleshooting.
Navigational and communication technicians maintain and operate the radio communications equipment and other related navigational equipment used in controlling air traffic. The work involves electronic equipment maintenance, calibration and troubleshooting.
Environmental technicians maintain and operate the aviation authority buildings (regional centres, Tracons and airport facilities, including the control towers) and equipment. The work requires running heating, ventilation and air-conditioning equipment and maintaining emergency generators, airport lighting systems, large banks of batteries in uninterrupted power supply (UPS) equipment and related electrical power equipment.
The occupational hazards for all three jobs include: noise exposure; working on or near live electrical parts including exposure to high voltage, x-ray exposure from klystron and magnitron tubes, fall hazards while working on elevated radar towers or using climbing poles and ladders to access towers and radio antenna and possibly PCBs exposure when handling older capacitors and working on utility transformers. Workers may also be exposed to microwave and radio-frequency exposure. According to a study of a group of radar workers in Australia (Joyner and Bangay 1986), personnel are not generally exposed to levels of microwave radiation exceeding 10 W/m2 unless they are working on open waveguides (microwave cables) and components utilizing waveguide slots, or working within transmitter cabinets when high-voltage arcing is occurring. The environmental technicians also work with chemicals related to building maintenance, including boiler and other related water treatment chemicals, asbestos, paints, diesel fuel and battery acid. Many of the electrical and utility cables at airports are underground. Inspection and repair work on these systems often involves confined space entry and exposure to confined space hazards—noxious or asphyxiating atmospheres, falls, electrocution and engulfment.
Airways facilities maintenance workers and other ground crews in the airport operating area are frequently exposed to jet exhaust. Several airport studies where sampling of jet engine exhaust has been conducted demonstrated similar results (Eisenhardt and Olmsted 1996; Miyamoto 1986; Decker 1994): the presence of aldehydes including butyraldehyde, acetaldehyde, acrolein, methacrolein, isobutyraldehyde, propionaldehyde, croton-aldehyde and formaldehyde. Formaldehyde was present at significantly higher concentrations then the other aldehydes, followed by acetaldehyde. The authors of these studies have concluded that the formaldehyde in the exhaust was probably the main causative factor in the eye and respiratory irritation reported by exposed persons. Depending on the study, nitrogen oxides either were not detected or were present in concentrations below 1 part per million (ppm) in the exhaust stream. They concluded that neither nitrogen oxides nor other oxides play a major role in the irritation. Jet exhaust was also found to contain 70 different hydrocarbon species with up to 13 consisting mostly of olefins (alkenes). Heavy-metal exposure from jet exhaust has been shown not to pose a health hazard for areas surrounding airports.
Radar towers should be equipped with standard railings around the stairs and platforms to prevent falls and with interlocks to prevent access to the radar dish while it is operating. Workers accessing towers and radio antennas should use approved devices for ladder climbing and personal fall protection.
Personnel work on both de-energized and energized electrical systems and equipment. Protection from electrical hazards should involve training in safe work practices, lockout/tagout procedures and the use of personal protective equipment (PPE).
The radar microwave is generated by high-voltage equipment using a klystron tube. The klystron tube generates x rays and can be a source of exposure when the panel is opened, allowing personnel to come in close proximity to it to work on it. The panel should always remain in place except when servicing the klystron tube, and work time should be kept to a minimum.
Personnel should wear the appropriate hearing protection (e.g., ear plugs and/or ear muffs) when working around noise sources such as jet planes and emergency generators.
Other controls involve training in materials handling, vehicle safety, emergency response equipment and evacuation procedures and confined space entry procedures equipment (including direct-reading air monitors, blowers and mechanical retrieval systems).
Air traffic controllers and flight services personnel
Air traffic controllers work in regional control centres, Tracons and airport control towers. This work generally involves working at a console tracking planes on radar scopes and communicating with pilots by radio. Flight services personnel provide weather information for pilots.
The hazards to air traffic controllers include possible visual problems, noise, stress and ergonomic problems. At one time there was concern about x-ray emissions from the radar screens. This, however, has not turned out to be a problem at the operating voltages used.
Standards of fitness for air traffic controllers have been recommended by the International Civil Aviation Organization (ICAO), and detailed standards are set out in national military and civil regulations, those relating to sight and hearing being particularly precise.
The broad, transparent surfaces of air traffic control towers at airports sometimes result in dazzling by the sun, and reflection from surrounding sand or concrete can increase the luminosity. This strain on the eyes may produce headaches, though often of a temporary nature. It may be prevented by surrounding the control tower with grass and avoiding concrete, asphalt or gravel and by giving a green tint to the transparent walls of the room. If the colour is not too strong, visual acuity and colour perception remain adequate while the excess radiation that causes dazzle is absorbed.
Until about 1960 there was a good deal of disagreement among authors on the frequency of eyestrain among controllers from viewing radar screens, but it does seem to have been high. Since then, attention given to visual refractive errors in the selection of radar controllers, their correction among serving controllers and the constant improvement of working conditions at the screen have helped to lower it considerably. Sometimes, however, eyestrain appears among controllers with excellent sight. This may be attributed to too low a level of lighting in the room, irregular illumination of the screen, the brightness of the echoes themselves and, in particular, flickering of the image. Progress in viewing conditions and insistence on higher technical specifications for new equipment are leading to a marked reduction in this source of eyestrain, or even its elimination. Strain in accommodation has also been considered until recently to be a possible cause of eyestrain among operators who have worked very close to the screen for an hour without interruption. Visual problems are becoming much less frequent and are likely to disappear or to occur only very occasionally in the automated radar system, for example, when there is a fault in a scope or where the rhythm of the images is badly adjusted.
A rational arrangement of the premises is mainly one that facilitates the adaptation of the scope readers to the intensity of the ambient lighting. In a non-automated radar station, adaptation to the semi-darkness of the scope room is achieved by spending 15 to 20 minutes in another dimly lighted room. The general lighting of the scope room, the luminous intensity of the scopes and the brightness of the spots must all be studied with care. In the automated system the signs and symbols are read under an ambient lighting of from 160 to 200 lux, and the disadvantages of the dark environment of the non-automated system are avoided. With regard to noise, despite modern sound-insulating techniques, the problem remains acute in control towers installed near the runways.
Readers of radar screens and electronic display screens are sensitive to changes in the ambient lighting. In the non-automated system the controllers must wear glasses absorbing 80% of the light for between 20 and 30 minutes before entering their workplace. In the automated system special glasses for adaptation are no longer essential, but persons particularly sensitive to the contrast between the lighting of the symbols on the display screen and that of the working environment find that glasses of medium absorptive power add to the comfort of their eyes. There is also a reduction in eyestrain. Runway controllers are well advised to wear glasses absorbing 80% of the light when they are exposed to strong sunlight.
The most serious occupational hazard for air traffic controllers is stress. The chief duty of the controller is to make decisions on the movements of aircraft in the sector he or she is responsible for: flight levels, routes, changes of course when there is conflict with the course of another aircraft or when congestion in one sector leads to delays, air traffic and so on. In non-automated systems the controller must also prepare, classify and organize the information his or her decision is based on. The data available are comparatively crude and must first be digested. In highly automated systems the instruments can help the controller in taking decisions, and he or she may then only have to analyse data produced by teamwork and presented in rational form by these instruments. Although the work may be greatly facilitated, the responsibility for approving the decision proposed to the controller remains the controller’s, and his or her activities still give rise to stress. The responsibilities of the job, pressure of work at certain hours of dense or complex traffic, increasingly crowded air space, sustained concentration, rotating shift work and awareness of the catastrophe that may result from an error all create a situation of continuous tension, which may lead to stress reactions. The fatigue of the controller may assume the three classic forms of acute fatigue, chronic fatigue or overstrain and nervous exhaustion. (See also the article “Case Studies of Air Traffic Controllers in the United States and Italy”.)
Air traffic control calls for an uninterrupted service 24 hours a day, all year long. The conditions of work of controllers thus include shift work, an irregular rhythm of work and rest and periods of work when most other people are enjoying holidays. Periods of concentration and of relaxation during working hours and days of rest during a week of work are indispensable to the avoidance of operational fatigue. Unfortunately, this principle cannot be embodied in general rules, for the arrangement of work in shifts is influenced by variables that may be legal (maximum number of consecutive hours of work authorized) or purely professional (workload depending on the hour of the day or the night), and by many other factors based on social or family considerations. With regard to the most suitable length for periods of sustained concentration during work, experiments show that there should be short breaks of at least a few minutes after periods of uninterrupted work of from half an hour to an hour-and-a-half, but that there is no need to be bound by rigid patterns to achieve the desired aim: the maintenance of the level of concentration and the prevention of operational fatigue. What is essential is to be able to interrupt the periods of work at the screen with periods of rest without interrupting the continuity of the shift work. Further study is necessary to establish the most suitable length of the periods of sustained concentration and of relaxation during work and the best rhythm for weekly and annual rest periods and holidays, with a view to drawing up more unified standards.
There are also ergonomic issues while working at the consoles similar to those of computer operators, and there may be indoor air quality problems. Air traffic controllers also experience tone incidents. Tone incidents are loud tones coming into the headsets. The tones are of short duration (a few seconds) and have sound levels up to 115 dBA.
In flight services work, there are hazards associated with lasers, which are used in ceilorometer equipment used to measure cloud ceiling height, as well as ergonomic and indoor air quality issues.
Other flight control services personnel
Other flight control services personnel include flight standards, security, airport facilities renovation and construction, administrative support and medical personnel.
Flight standards personnel are aviation inspectors who conduct airline maintenance and flight inspections. Flight standards personnel verify the airworthiness of the commercial airlines. They often inspect airplane maintenance hangers and other airport facilities, and they ride in the cockpits of commercial flights. They also investigate plane crashes, incidents or other aviation-related mishaps.
The hazards of the job include noise exposure from aircraft, jet fuel and jet exhaust while working in hangers and other airport areas, and potential exposure to hazardous materials and blood-borne pathogens while investigating aircraft crashes. Flight standards personnel face many of the same hazards as airport ground crews, and thus many of the same precautions apply.
Security personnel include sky marshals. Sky marshals provide internal security on airplanes and external security at airport ramps. They are essentially police and investigate criminal activities related to aircraft and airports.
Airport facilities renovation and construction personnel approve all plans for airport modifications or new construction. The personnel are usually engineers, and their work largely involves office work.
Administrative workers include personnel in accounting, management systems and logistics. Medical personnel in the flight surgeon’s office provide occupational medical services to aviation authority workers.
Air traffic controllers, flight services personnel and personnel who work in office environments should have ergonomic training on proper sitting postures and on emergency response equipment and evacuation procedures.
Airport ground crews conduct maintenance on and load aircraft. Baggage handlers handle passenger baggage and air freight, whereas passenger service agents register passengers and check passenger baggage.
All loading operations (passengers, baggage, freight, fuel, supplies and so on) are controlled and integrated by a supervisor who prepares the loading plan. This plan is given to the pilot prior to take-off. When all operations have been completed and any checks or inspections considered necessary by the pilot have been made, the airport controller gives authorization for take-off.
Aircraft maintenance and servicing
Every aircraft is serviced every time it lands. Ground crews performing routine turnaround maintenance; conduct visual inspections, including checking the oils; perform equipment checks, minor repairs and internal and external cleaning; and refuel and restock the aircraft. As soon as the aircraft lands and arrives in the unloading bays, a team of mechanics begins a series of maintenance checks and operations which vary with the type of aircraft. These mechanics refuel the aircraft, check a number of safety systems which must be inspected after each landing, investigate the logbook for any reports or defects the flight crew may have noticed during the flight and, where necessary, make repairs. (See also the article “Aircraft Maintenance Operations” in this chapter.) In cold weather, the mechanics may have to perform additional tasks, such as de-icing of wings, landing gear, flaps and so on. In hot climates special attention is paid to the condition of the aircraft’s tyres. Once this work has been completed, the mechanics can declare the aircraft flightworthy.
More thorough maintenance inspections and aircraft overhauls are performed at specific intervals of flying hours for each aircraft.
Fuelling aircraft is one of the most potentially hazardous servicing operations. The amount of fuel to be loaded is determined on the basis of such factors as flight duration, take-off weight, flight path, weather and possible diversions.
A cleaning team cleans and services the aircraft cabins, replacing dirty or damaged material (cushions, blankets and so on), empties the toilets and refills the water tanks. This team may also disinfect or disinfest the aircraft under the supervision of public health authorities.
Another team stocks the aircraft with food and drink, emergency equipment and supplies needed for passenger comfort. Meals are prepared under high standards of hygiene to eliminate the risk of food poisoning, particularly among the flight crew. Certain meals are deep frozen to –40ºC, stored at –29ºC and reheated in flight.
Ground service work includes the use of motorized and non-motorized equipment.
Baggage and air cargo loading
Baggage and cargo handlers move passenger baggage and air freight. Freight can range from fresh fruits and vegetables and live animals to radioisotopes and machinery. Because baggage and cargo handling requires physical effort and the use of mechanized equipment, workers may be more at risk for injuries and ergonomic problems.
Ground crews and baggage and freight handlers are exposed to many of the same hazards. These hazards include working outdoors in all types of weather, exposure to potential airborne contaminants from jet fuel and jet engine exhaust and exposure to prop wash and jet blast. Prop wash and jet blast can slam doors shut, knock people or unsecured equipment over, cause turboprop propellers to rotate and blow debris into engines or onto people. Ground crews are also exposed to noise hazards. A study in China showed ground crews were exposed to noise at aircraft engine hatches that exceeds 115 dBA (Wu et al. 1989). Vehicle traffic on the airport ramps and apron is very heavy, and the risk of accidents and collision is high. Fuelling operations are very hazardous, and workers may be exposed to fuel spills, leaks, fires and explosions. Workers on lifting devices, aerial baskets, platforms or access stands are at risk of falling. Job hazards also include rotating shift work carried out under pressure of time.
Strict regulations must be implemented and enforced for vehicle movement and driver training. Driver training should emphasize complying with speed limits, obeying off-limit areas and ensuring that there is adequate room for planes to manoeuvre. There should be good maintenance of ramp surfaces and efficient control of ground traffic. All vehicles authorized to operate on the airfield should be conspicuously marked so they can be readily identified by air traffic controllers. All equipment used by the ground crews should be regularly inspected and maintained. Workers on lifting devices, aerial baskets, platforms or access stands must be protected from falls either through the use of guardrails or personal fall protection equipment. Hearing protection equipment (earplugs and earmuffs) must be used for protection against noise hazards. Other PPE includes suitable work clothing depending on the weather, non-slip reinforced-toe-cap foot protection and appropriate eye, face, glove and body protection when applying de-icing fluids. Rigorous fire prevention and protection measures including bonding and grounding and prevention of electric sparking, smoking, open flames and the presence of other vehicles within 15 m of aircraft, must be implemented for refuelling operations. Fire-fighting equipment should be maintained and located in the area. Training on procedures to follow in the event of a fuel spill or fire should be conducted regularly.
Baggage and freight handlers should store and stack cargo securely and should receive training on proper lifting techniques and back postures. Extreme care should be used when entering and leaving aircraft cargo areas from carts and tractors. Appropriate protective clothing should be worn, depending on the type of cargo or baggage (such as gloves when handling live animal cargo). Baggage and freight conveyors, carousels and dispensers should have emergency shut-offs and built-in guards.
Passenger service agents
Passenger service agents issue tickets, register and check in passengers and passenger baggage. These agents may also guide passengers when boarding. Passenger service agents who sell airline tickets and check in passengers may spend all day on their feet using a video display unit (VDU). Precautions against these ergonomic hazards include resilient floor mats and seats for relief from standing, work breaks and ergonomic and anti-glare measures for the VDUs. In addition, dealing with passengers can be a source of stress, particularly when there are delays in flights or problems with making flight connections and so on. Breakdowns in the computerized airline reservations systems can also be a major source of stress.
Baggage check-in and weigh-in facilities should minimize the need for employees and passengers to lift and handle bags, and baggage conveyors, carousels and dispensers should have emergency shut-offs and built-in guards. Agents should also receive training on proper lifting techniques and back postures.
Baggage inspection systems use fluoroscopic equipment to examine baggage and other carry-on items. Shielding protects workers and the public from x-ray emissions, and if the shielding is not properly positioned, interlocks prevent the system from operating. According to an early study by the US National Institute for Occupational Safety and Health (NIOSH) and the Air Transport Association at five US airports, maximum documented whole-body x-ray exposures were considerably lower than maximum levels set by the US Food and Drug Administration (FDA) and the Occupational Safety and Health Administration (OSHA) (NIOSH 1976). Workers should wear whole-body monitoring devices to measure radiation exposures. NIOSH recommended periodic maintenance programmes to check effectiveness of shielding.
Passenger service agents and other airport personnel must be thoroughly familiar with the airport emergency evacuation plan and procedures.