Thursday, 31 March 2011 17:32

Aircraft Maintenance Operations

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Aircraft maintenance operations are broadly distributed within and across nations and are performed by both military and civilian mechanics. Mechanics work at airports, maintenance bases, private fields, military installations and aboard aircraft carriers. Mechanics are employed by passenger and freight carriers, by maintenance contractors, by operators of private fields, by agricultural operations and by public and private fleet owners. Small airports may provide employment for a few mechanics, while major hub airports and maintenance bases may employ thousands. Maintenance work is divided between that which is necessary to maintain ongoing daily operations (line maintenance) and those procedures that periodically check, maintain and refurbish the aircraft (base maintenance). Line maintenance comprises en route (between landing and takeoff) and overnight maintenance. En route maintenance consists of operational checks and flight-essential repairs to address discrepancies noted during flight. These repairs are typically minor, such as replacing warning lights, tyres and avionic components, but may be as extensive as replacing an engine. Overnight maintenance is more extensive and includes making any repairs deferred during the day’s flights.

The timing, distribution and nature of aircraft maintenance is controlled by each airline company and is documented in its maintenance manual, which in most jurisdictions must be submitted for approval to the appropriate aviation authority. Maintenance is performed during regular checks, designated as A through D checks, specified by the maintenance manual. These scheduled maintenance activities ensure that the entire aircraft has been inspected, maintained and refurbished at appropriate intervals. Lower level maintenance checks may be incorporated into line maintenance work, but more extensive work is performed at a maintenance base. Aircraft damage and component failures are repaired as required.

Line Maintenance Operations and Hazards

En route maintenance is typically performed under a great time constraint at active and crowded flight lines. Mechanics are exposed to prevailing conditions of noise, weather and vehicular and aircraft traffic, each of which may amplify the hazards intrinsic to maintenance work. Climatic conditions may include extremes of cold and heat, high winds, rain, snow and ice. Lightning is a significant hazard in some areas.

Although the current generation of commercial aircraft engines are significantly quieter than previous models, they can still produce sound levels well above those set by regulatory authorities, particularly if the aircraft are required to use engine power in order to exit gate positions. Older jet and turboprop engines can produce sound level exposures in excess of 115 dBA. Aircraft auxiliary-power units (APUs), ground-based power and air-conditioning equipment, tugs, fuel trucks and cargo-handling equipment add to the background noise. Noise levels in the ramp or aircraft parking area are seldom below 80 dBA, thus necessitating the careful selection and routine use of hearing protectors. Protectors must be selected that provide excellent noise attenuation while being reasonably comfortable and permitting essential communication. Dual systems (ear plugs plus ear muffs) provide enhanced protection and allow accom-modation for higher and lower noise levels.

Mobile equipment, in addition to aircraft, may include baggage carts, personnel buses, catering vehicles, ground support equipment and jetways. To maintain departure schedules and customer satisfaction, this equipment must move quickly within often congested ramp areas, even under adverse ambient conditions. Aircraft engines pose the danger of ramp personel being ingested into jet engines or being struck by a propeller or exhaust blasts. Reduced visibility during night and inclement weather increase the risk that mechanics and other ramp personnel might be struck by mobile equipment. Reflective materials on work clothing help to improve visibility, but it is essential that all ramp personnel be well trained in ramp traffic rules, which must be rigorously enforced. Falls, the most frequent cause of serious injuries among mechanics, are discussed elsewhere in this Encyclopaedia.

Chemical exposures in the ramp area include de-icing fluids (usually containing ethylene or propylene glycol), oils and lubricants. Kerosene is the standard commercial jet fuel (Jet A). Hydraulic fluids containing tributyl phosphate cause severe but transient eye irritation. Fuel tank entry, while relatively rare on the ramp, must be included in a comprehensive confined- space-entry programme. Exposure to resin systems used for patching composite areas such as cargo hold panelling may also occur.

Overnight maintenance is typically performed under more controlled circumstances, either in line-service hangers or on inactive flight lines. Lighting, work stands and traction are far better than on the flight line but are likely to be inferior to those found in maintenance bases. Several mechanics may be working on an aircraft simultaneously, necessitating careful planning and coordination to control personnel movement, aircraft component activation (drives, flight control surfaces and so on) and chemical usage. Good housekeeping is essential to prevent clutter from air lines, parts and tools, and to clean spills and drips. These requirements are of even greater importance during base maintenance.

Base Maintenance Operations and Hazards

Maintenance hangars are very large structures capable of accommodating numerous aircraft. The largest hangars can simultaneously accommodate several wide-body aircraft, such as the Boeing 747. Separate work areas, or bays, are assigned to each aircraft undergoing maintenance. Specialized shops for the repair and refitting of components are associated with the hangars. Shop areas typically include sheet metal, interiors, hydraulics, plastics, wheels and brakes, electrical and avionics and emergency equipment. Separate welding areas, paint shops and non-destructive testing areas may be established. Parts-cleaning operations are likely to be found throughout the facility.

Paint hangars with high ventilation rates for workplace air contaminant controls and environmental pollution protection should be available if painting or paint stripping is to be performed. Paint strippers often contain methylene chloride and corrosives, including hydrofluoric acid. Aircraft primers typically contain a chromate component for corrosion protection. Top coats may be epoxy or polyurethane based. Toluene diisocyanate (TDI) is now seldom used in these paints, having been replaced with higher molecular weight isocyanates such as 4,4-diphenylmethane diisocyanate (MDI) or by prepolymers. These still present a risk of asthma if inhaled.

Engine maintenance may be performed within the maintenance base, at a specialized engine overhaul facility or by a sub-contractor. Engine overhaul requires the use of metalworking techniques including grinding, blasting, chemical cleaning, plating and plasma spray. Silica has in most cases been replaced with less hazardous materials in parts cleaners, but the base materials or coatings may create toxic dusts when blasted or ground. Numerous materials of worker health and environmental concern are used in metal cleaning and plating. These include corrosives, organic solvents and heavy metals. Cyanide is generally of the greatest immediate concern, requiring special emphasis in emergency preparedness planning. Plasma spray operations also merit particular attention. Finely divided metals are fed into a plasma stream generated using high-voltage electrical sources and plated onto parts with the concomitant generation of very high noise levels and light energies. Physical hazards include work at height, lifting and work in uncomfortable positions. Precautions include local exhaust ventilation, PPE, fall protection, training in proper lifting and use of mechanized lifting equipment when possible and ergonomic redesign. For example, repetitive motions involved in tasks such as wire tying may be reduced by use of specialized tools.

Military and Agricultural Applications

Military aircraft operations may present unique hazards. JP4, a more volatile jet fuel that Jet A, may be contaminated with n-hexane. Aviation gasoline, used in some propeller-driven aircraft, is highly flammable. Military aircraft engines, including those on transport aircraft, may use less noise abatement than those on commercial aircraft and may be augmented by afterburners. Aboard aircraft carriers the many hazards are significantly increased. Engine noise is augmented by steam catapults and afterburners, flight deck space is extremely limited, and the deck itself is in motion. Because of combat demands, asbestos insulation is present in some cockpits and around hot areas.

The need for lowered radar visibility (stealth) has resulted in the increased use of composite materials on fuselage, wings and flight control structures. These areas may be damaged in combat or from exposure to extremes of climate, requiring extensive repair. Repairs performed under field conditions may result in heavy exposures to resins and composite dusts. Beryllium is also common in military applications. Hydrazide may be present as part of auxiliary-power units, and anti-tank armament may include radioactive depleted uranium rounds. Precautions include appropriate PPE, including respiratory protection. Where possible, portable exhaust systems should be used.

Maintenance work on agricultural aircraft (crop dusters) may result in exposures to pesticides either as a single product or, more likely, as a mixture of products contaminating a single or multiple aircraft. Degradation products of some pesticides are more hazardous than the parent product. Dermal routes of exposure may be significant and may be enhanced by perspiration. Agricultural aircraft and external parts should be thoroughly cleaned before repair, and/or PPE, including skin and respiratory protection, should be used.



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Transport Industry and Warehousing References

American National Standards Institute (ANSI). 1967. Illumination. ANSI A11.1-1967. New York: ANSI.

Anton, DJ. 1988. Crash dynamics and restraint systems. In Aviation Medicine, 2nd edition, edited by J Ernsting and PF King. London: Butterworth.

Beiler, H and U Tränkle. 1993. Fahrerarbeit als Lebensarbeitsperpektive. In Europäische Forschungsansätze zur Gestaltung der Fahrtätigkeit im ÖPNV (S. 94-98) Bundesanstat für Arbeitsschutz. Bremerhaven: Wirtschaftsverlag NW.

Bureau of Labor Statistics (BLS). 1996. Safety and Health Statistics. Washington, DC: BLS.

Canadian Urban Transit Association. 1992. Ergonomic Study of the Driver’s Workstation in Urban Buses. Toronto: Canadian Urban Transit Association.

Decker, JA. 1994. Health Hazard Evaluation: Southwest Airlines, Houston Hobby Airport, Houston, Texas. HETA-93-0816-2371. Cincinnati, OH: NIOSH.

DeHart RL. 1992. Aerospace medicine. In Public Health and Preventive Medicine, 13th edition, edited by ML Last and RB Wallace. Norwalk, CT: Appleton and Lange.

DeHart, RL and KN Beers. 1985. Aircraft accidents, survival, and rescue. In Fundamentals of Aerospace Medicine, edited by RL DeHart. Philadelphia, PA: Lea and Febiger.

Eisenhardt, D and E Olmsted. 1996. Investigation of Jet Exhaust Infiltration into a Building Located on John F. Kennedy (JFK) Airport Taxiway. New York: US Department of Health and Human Services, Public Health Service, Division of Federal Occupational Health, New York Field Office.

Firth, R. 1995. Steps to successfully installing a warehouse management system. Industrial Engineering 27(2):34–36.

Friedberg, W, L Snyder, DN Faulkner, EB Darden, Jr., and K O’Brien. 1992. Radiation Exposure of Air Carrier Crewmembers II. DOT/FAA/AM-92-2.19. Oklahoma City, OK: Civil Aeromedical Institute; Washington, DC: Federal Aviation Administration.

Gentry, JJ, J Semeijn, and DB Vellenga. 1995. The future of road haulage in the new European Union—1995 and beyond. Logistics and Transportation Review 31(2):149.

Giesser-Weigt, M and G Schmidt. 1989. Verbesserung des Arbeitssituation von Fahrern im öffentlichen Personennahverkehr. Bremerhaven: Wirtschaftsverlag NW.

Glaister, DH. 1988a. The effects of long duration acceleration. In Aviation Medicine, 2nd edition, edited by J Ernsting and PF King. London: Butterworth.

—. 1988b. Protection against long duration acceleration. In Aviation Medicine, 2nd edition, edited by J Ernsting and PF King. London: Butterworth.

Haas, J, H Petry and W Schühlein. 1989. Untersuchung zurVerringerung berufsbedingter Gesundheitsrisien im Fahrdienst des öffentlichen Personennahverkehr. Bremerhaven; Wirtschaftsverlag NW.

International Chamber of Shipping. 1978. International Safety Guide for Oil Tankers and Terminals. London: Witherby.

International Labour Organization (ILO). 1992. Recent Developments in Inland Transportation. Report I, Sectoral Activities Programme, Twelfth Session. Geneva: ILO.

—. 1996. Accident Prevention on Board Ship at Sea and in Port. An ILO Code of Practice. 2nd edition. Geneva: ILO.

Joyner, KH and MJ Bangay. 1986. Exposure survey of civilian airport radar workers in Australia. Journal of Microwave Power and Electromagnetic Energy 21(4):209–219.

Landsbergis, PA, D Stein, D Iacopelli and J Fruscella. 1994. Work environment survey of air traffic controllers and development of an occupational safety and health training program. Presented at the American Public Health Association, 1 November, Washington, DC.

Leverett, SD and JE Whinnery. 1985. Biodynamics: Sustained acceleration. In Fundamentals of Aerospace Medicine, edited by RL DeHart. Philadelphia, PA: Lea and Febiger.

Magnier, M. 1996. Experts: Japan has the structure but not the will for intermodalism. Journal of Commerce and Commercial 407:15.

Martin, RL. 1987. AS/RS: From the warehouse to the factory floor. Manufacturing Engineering 99:49–56.

Meifort, J, H Reiners, and J Schuh. 1983. Arbeitshedingungen von Linienbus- und Strassenbahnfahrern des Dortmunder Staatwerke Aktiengesellschaft. Bremen- haven: Wirtschaftsverlag.

Miyamoto, Y. 1986. Eye and respiratory irritants in jet engine exhaust. Aviation, Space and Environmental Medicine 57(11):1104–1108.

National Fire Protection Association (NFPA). 1976. Fire Protection Handbook, 14th edition. Quincy, MA: NFPA.

National Institute for Occupational Safety and Health (NIOSH). 1976. Documented Personnel Exposures from Airport Baggage Inspection Systems. DHHS (NIOSH) Publication 77-105. Cincinnati, OH: NIOSH.

—. 1993a. Health Hazard Evaluation: Big Bear Grocery Warehouse. HETA 91-405-2340. Cincinnati, OH: NIOSH.

—. 1993b. Alert: Preventing Homicide in the Workplace. DHHS (NIOSH) Publication 93-108. Cincinatti, OH: NIOSH.

—. 1995. Health Hazard Evaluation: Kroger Grocery Warehouse. HETA 93-0920-2548. Cincinnati, OH: NIOSH.

National Safety Council. 1988. Aviation Ground Operation Safety Handbook, 4th edition. Chicago, IL: National Safety Council.

Nicogossian, AE, CL Huntoon and SL Pool (eds.). 1994. Space Physiology and Medicine, 3rd edition. Philadelphia, PA: Lea and Febiger.

Peters, Gustavsson, Morén, Nilsson and Wenäll. 1992. Forarplats I Buss, Etapp 3; Kravspecifikation. Linköping, Sweden: Väg och Trafikinstitutet.

Poitrast, BJ and deTreville. 1994. Occupational medical considerations in the aviation industry. In Occupational Medicine, 3rd edition, edited by C Zenz, OB Dickerson, and EP Hovarth. St. Louis, MO: Mosby.

Register, O. 1994. Make Auto-ID work in your world. Transportation and Distribution 35(10):102–112.

Reimann, J. 1981. Beanspruchung von Linienbusfahrern. Untersuchungen zur Beanspruchung von Linienbusfahrern im innerstädtischen Verkehr. Bremerhaven: Wirtschafts-verlag NW.

Rogers, JW. 1980. Results of FAA Cabin Ozone Monitoring Program in Commercial Aircraft in 1978 and 1979. FAA-EE-80-10. Washington, DC: Federal Aviation Administration, Office of Environment and Energy.

Rose, RM, CD Jenkins, and MW Hurst. 1978. Air Traffic Controller Health Change Study. Boston, MA: Boston University School of Medicine.

Sampson, RJ, MT Farris, and DL Shrock. 1990. Domestic Transportation: Practice, Theory, and Policy, 6th edition. Boston, MA: Houghton Mifflin Company.

Streekvervoer Nederland. 1991. Chaufferscabine [Driver’s cabin]. Amsterdam, Netherlands: Streekvervoer Nederland.

US Senate. 1970. Air Traffic Controllers (Corson Report). Senate Report 91-1012. 91st Congress, 2nd Session, 9 July. Washington, DC: GPO.

US Department of Transportation (DOT). 1995. Senate Report 103–310, June 1995. Washington, DC: GPO.

Verband Deutscher Verkehrsunternehmen. 1996. Fahrerarbeitsplatz im Linienbus [Driver’s workstation in buses]. VDV Schrift 234 (Entwurf). Cologne, Germany: Verband Deutscher Verkehrsunternehmen.

Violland, M. 1996. Whither railways? OECD Observer No. 198, 33.

Wallentowitz H, M Marx, F Luczak, J Scherff. 1996. Forschungsprojekt. Fahrerarbeitsplatz im Linienbus— Abschlußbericht [Research project. Driver’s workstation in buses—Final report]. Aachen, Germany: RWTH.

Wu, YX, XL Liu, BG Wang, and XY Wang. 1989. Aircraft noise-induced temporary threshold shift. Aviation Space and Medicine 60(3):268–270.