From Tar Barrels to Computer Control.
Man/woman is a two-dimensional being: visual cues and a sense of balance provide him/her with stability on the ground. When this two-dimensional being is flying, a third -- unfamiliar -- dimension is added. In darkness or bad weather, depth perception is reduced and balance affected. Without visual (photometric) cues and instruments, orientation is lost and a pilot can actually be flying upside down believing he or she is flying normally. Airfield lighting provides part of the adjustment needed to fly at night or in bad weather. How did we get to today's modern version of airfield lighting and how did it begin? Driven by the need to provide air mail in the early days of aviation, the first lighting was in the form of lighted beacons provided by burning tar barrels or hay bales spaced about 10 miles apart, which made a path for the pilot to follow. In the 1930s and 1940s, oil lamps were the next step, these being placed in a line determining the landing strip. In addition, the smoke from these lamps provided a second aid to navigation -- wind direction. World War Two saw the development of radio and en-route radio beacons and automatic direction finders, eliminating the need for lighted beacons.
After the war, the advent of civil aviation and heavier and faster aircraft saw runways lighted with edge lights, end lights and lighted wind tees. With the introduction of wider runways and jet aircraft, runway centreline lighting and approach lighting were added, and touchdown zone lighting, glide slope indicators, taxiway lighting, lighted signing and other lighting followed shortly thereafter. Airfield lighting has changed little since that time, though more efficient and smaller longer-life lamps have reduced the power consumption and size of airfield lighting fixtures.
The International Civil Aviation Organisation (ICAO) defines airfield lighting as "Any light specially provided as an aid to air navigation other than a light displayed on an aircraft". Combined, all elements of airfield lighting comprise a visual aid providing visual (photometric) cues and lighting configurations of different colours and recognisable patterns which help pilots to manoeuvre on the ground, to take off, navigate, and to land their aircraft in a safe manner.
As a pilot, simply stated, I am looking for visual cues (photometrics) provided by `the five Cs of modern-day airfield lighting' in order to operate my aircraft safely. These five Cs are:
Configuration, Colour, Candelas, Coverage, Consistency
Configuration of an airfield lighting component is lights being evenly spaced in a line and more closely spaced on a curve along a desired path of an aircraft or perpendicular to that path. ICAO, the FAA or other governing body sets configuration.
Colour of airfield lighting is one of the five standard colours to aid a pilot's understanding of location or what he is required to do. Red lights meaning `hazard' or `stop'. Yellow lights mean `caution' or a holding point. White lights define the runway approach, runway edge, runway centreline or one colour of the airport beacon. Green lights are for the beginning of a runway usable surface, taxiway centreline or one colour of the airport beacon. Lastly, blue designates the edge of usable taxiways. ICAO, the FAA or other governing body sets specific colour criteria. Note that colour is never added to white light, but instead is always the unwanted portion of the light spectrum being filtered out of white light to achieve a desired colour -- thus the intensity of any coloured light will always be less than that of white light using the same wattage lamp.
Candela is a technical term for the quantity of light output or brightness of a particular airfield lighting fixture. ICAO, the FAA or other governing body sets the specific value for this light output. Please note this candela value is initial and all airfield lighting systems will start deteriorating immediately.
Coverage is another technical term applied to airfield lighting, meaning the light beam width and depth as well as the angle in which it is emitted both vertically and horizontally from the fixture. This coverage will be different for each airfield lighting fixture. Coverage of the light beam from the fixture's main axis is accomplished through the use of any number of optical devices, such as reflectors, prisms, and lenses. Again, ICAO, the FAA or other governing body sets values for each fixture's beam height, width and direction.
Consistency in design and use of the other four Cs is critical in order that a pilot receives identical information when operating his or her aircraft at any airport in the world. It is the prime purpose of ICAO, to which most countries of the world are voluntary signatories. Consistency of use, particularly in construction areas, seems to be a problem which may have contributed to recent accidents and near-accidents in different parts of the world.
Although items may vary in different countries, very simply stated, the following airfield lighting components are generally required for different categories of operation of an aircraft in and out of an airport.
1. Daytime VFR (Visual Flight Rules). No airfield lighting required, windsock.
2 Nighttime VFR Airport beacon, runway edge lights, threshold lights, wind cone (preferably lighted). Additional preferred items: lighted signing, taxiway edge lights and glide slope indicator.
3 Non-Precision Approach Basic instrument landing system, basic approach lighting system, glide slope indicator, airport beacon, runway edge lights, threshold lights, runway end identifier lights, wind cone (preferably lighted), lighted signing, lighted taxiway edge lights.
4 Precision Approaches. Generally defined by the following table:
Category Decision Runway visual Height (feet) range (meters) I 200 550 II 100 300 III A Below 100 200 III B Below 50 Less than 200 III C Zero Visibility Zero Visibility
4A Category I
Instrument landing system, approach lighting system, glide slope indicator, high intensity airport beacon, high intensity runway edge lights, high intensity threshold and end lights, runway end identifier lights, wind cone (preferably lighted), lighted signing, lighted distance remaining signing, and taxiway edge lights.
4B Category II
Instrument landing system, full approach lighting system with red side barrettes, glide slope indicator, high intensity airport beacon, high intensity runway edge lights, runway centreline lights, high intensity full threshold and full end lights, runway end identifier lights, touchdown zone lights, wind cone (preferably lighted), lighted signing, lighted distance remaining signing, taxiway edge lights, and preferably taxiway centreline lighting.
4C Category IIIA and Category IIIB
Instrument landing system, full approach lighting system with red side barrettes, glide slope indicator, high 'intensity airport beacon, high intensity runway edge lights, runway centreline lights, high intensity full threshold and full end lights, runway end identifier lights, touchdown zone lights, wind cone (preferably lighted), lighted signing, lighted distance remaining signing, taxiway edge lights and, preferably, a complete low visibility system consisting of taxiway centreline lighting, stop bars, hold bar lights and sensors.
4D Category IIIC Zero Visibility
Instrument landing system and total ground system compatible with complete `hands-off' capability for aircraft electronics.
Modern edge lighting fixtures are generally medium or high intensity mounted on either stake or steel light bases and fed by either direct burial or conduit and wire with 5,000 volt, 6.6 amp series circuits. Low intensity stake-mounted fixtures do exist and are used mainly on private airstrips and fed by lower voltage direct burial multiple systems.
Current centreline, touchdown zone, stop bar and holding bar lights are in-pavement lights mounted on load-bearing steel light bases and are fed by underground 5,000 volt 6.6 amp cable and conduit.
Modern airfield signing gives a pilot information day and night as to location, guidance, holding points, and distance remaining. Location is displayed as black background with yellow letters and boarder. Guidance information is displayed as black letters on a yellow background. Holding points are displayed with white numbers on a red background. Distance remaining information is displayed as white numbers on a black background. Signs are in four basic sizes and are normally fed off series taxiway circuits, with the exception of distance remaining signs which are fed off series runway circuits.
Latest standard for a glide slope indicator is the PAPI (Precision Approach Path Indicator). This device, like its earlier cousin the VASI (Visual Approach Slope Indicator), provides the pilot with proper altitude information as he descends to land, ensuring proper clearance over any obstacles which could be in the approach path. Modern airfield lighting standards are contained in the following ICAO publications:
1 International Standards and Recommended Practices -- Aerodromes -- Annex 14 Volumes I & II. This publication spells out configuration, colour, candelas and coverage.
2 Aerodrome Design Manual -- Part 4 -- Visual Aids. (This publication spells out specific fixture requirements.)
3 Aerodrome Design Manual -- Part 5 -- Electrical Systems (This publication spells out design and installation of electrical components necessary to provide power to the airfield lights.)
4 Airport Services Manual -- Part 9 -- Airport Maintenance Practices
Orders for purchasing ICAO publications may be placed with the Document Sales Unit, International Civil Aviation Organisation, 999 University Street, Montreal, Quebec, Canada, H3C 5H7. Telephone: (514) 954-0822 Telex: 05-24513 Facsimile: (514) 954-6769 Sitatex YULCAYA Internet: email@example.com Please note: this is the only way these documents are available at this time -- they are not available for download from the Internet.
While the United States is signatory to ICAO, the FAA has its own requirements for airfield lighting. Much more complicated than ICAO, its publications are broken down into specific items. In general, most are contained in the Advisory Circular 150 Series.
1. AC 150/5340 Series covers design and installation of airfield lighting systems.
Individual Advisory Circulars cover Configuration and some Colour.
2. AC 150/5345 Series covers specifications for individual airfield lighting components.
Individual Advisory Circulars cover Colour, Candelas and Coverage. One notable exception to the above is:
Advisory Circular 120-57A Surface Movement Guidance and Control System. Spells out general guidelines for low visibility systems for computer-controlled airfield lighting.
Most advisory circulars from the Federal Aviation Administration of the United States are now available for view and downloading from the FAA Website www.faa.gov. Finding what you are looking for is not an easy task, but if you can click your way through to Advisory Circulars, then downloading will sometimes be slow to do the length and graphics involved in some of the publications. The download can only be accomplished using Adobe Acrobat[R], which can also be downloaded free of charge from the FAA Website. The International Association of Airport Lighting Specialists has made the searching part easier with direct links posted on its Fingertip[R] Technical Library Page. Its website address is www.airport-lighting.org/.
The future of airfield lighting will include more energy-efficient and smaller lamps with LEDs on the horizon as well as the possibility of Zeon sources. Look for increased computer control and monitoring of airfield lighting in order to help prevent runway and taxiway `incursions' and as a way of increasing the capacity of existing airports. Newer technology for instrument landing systems such as GPS and Microwave Landing Systems, and newer aircraft electronics could result in the reduction and reconfiguration of approach lighting systems as we know them today. This change would result in less real estate being needed for airports as well as a substantial reduction in the energy and maintenance costs required to run these systems.
There are two critical publications which should be a part of every airfield lighting maintenance sections library. These publications should become the `Bible' of airfield maintenance:
1. ICAO Airport Services Manual -- Part 9 -- Airport Maintenance Practices
2. FAA Advisory Circular AC 150/5340-26 -- Maintenance of Airport Visual Aid Facilities.
These publications provide recommended preventative maintenance procedures for maintaining ongoing photometric compliance for airfield lighting systems. The FAA document is more detailed and is by far the better of the two.
I take my hat off to the United Kingdom for taking the lead in the maintenance of airfield lighting systems by now requiring regular ongoing in-field photometric testing. This is the only way to assure continued photometric compliance. I would also applaud the UK for its lead in requiring airfield lighting training for those who design, install and maintain these systems -- both should be required throughout the world.
Good maintenance actually starts with good design and then good installation. Maintenance without proper design and installation can best be described as "being behind the 8-ball from the get-go". Recent tests have shown that mis-alignment of a runway edge lighting fixture by a mere 2 [degrees] can reduce light output by 50%, thus placing it out of photometric compliance before the system is accepted.
Good airfield lighting design should not be cut-and-paste references to general regulations, but should be specific in reference to installation tolerances such as fixture aiming and levelling. The specific tolerances specified should be given `teeth' to insure installation is correct. A good set of `teeth' is a design requirement of in-field photometric testing before final acceptance of the system components.
Good airfield lighting installation should follow good design requirements to the letter -- then pass in-field photometric testing before acceptance. This procedure is an excellent `risk management tool', better protecting the installer from liability. It also ensures that components were manufactured in accordance with governing regulations.
Recent tests have shown that even a thin film of dirt and/or jet fuel can reduce the light output of a airport lighting fixture by 50%, thus placing it outside the required minimum photometric requirements. Rubber build-up on in-pavement airfield fixtures can be an even more serious problem.
Constant Current Regulator over current (amperage) by as little as _ amp out of tolerance can severely reduce lamp life and dramatically increase maintenance costs. Under current of a Regulator by the same amount can reduce photometric output of airfield fixtures enough to put them out of compliance.
Installation of a replacement lamp purchased at the local hardware store can have critical effects on the photometric output of a fixture. Due to different lamp filament locations and dimensions, photometric coverage (beam width, height and angle) can actually be different from original specified lamps. Always use replacement lamps supplied by the manufacturer of the airfield lighting fixture. Good design, installation, maintenance and operation of airfield lighting systems will assure a safer flying experience -- not only for myself as a pilot, but for all air crews and travellers.
The next Airport Lighting feature will look at Emerging Technologies.
RON E JONES
RON JONES IS A LICENSED PILOT AND HAS A 35-YEAR CAREER IN LIGHTING OF ALL TYPES, THE LAST 14 YEARS BEING SPENT IN DESIGN, INSTALLATION AND MAINTENANCE OF AIRFIELD LIGHTING. HE ATTENDED THE UNIVERSITY OF KANSAS SCHOOL OF ENGINEERING AND ARCHITECTURE, IS A GRADUATE OF MANY TECHNICAL COURSES IN LIGHTING, AND SPECIALISES IN PHOTOMETRICS. HE IS A FORMER LIGHTING SYSTEMS ENGINEER WITH GENERAL ELECTRIC, APPLICATIONS ENGINEER FOR COOPER INDUSTRIES, MANUFACTURER'S REPRESENTATIVE FOR ADB AIRPORT LIGHTING AND, MOST RECENTLY, INSTRUCTOR FOR AN AVIATION GROUND AND APPROACH LIGHTING COURSE AT A MAJOR SOUTHWESTERN UNIVERSITY. HE IS CO-AUTHOR OF THE FIRST `LIGHT POLLUTION ORDINANCE' REDUCING ULTRAVIOLET POLLUTION AFFECTING BOTH THE LOWELL AND US NAVAL OBSERVATORIES, AT THAT TIME PARTICIPATING IN MANNED MOON LANDINGS. IN ADDITION, HE IS A QUALIFIED EXPERT WITNESS FOR CASES INVOLVING LIGHTING.
MR JONES IS A GRADUATE OF ONE OF THE UNITED KINGDOM'S RECOGNISED AIRFIELD LIGHTING TRAINING COURSES, HAS PARTICIPATED IN THE DESIGN, INSTALLATION AND MAINTENANCE AT OVER 100 AIRPORTS BOTH IN THE UNITED STATES AND OVERSEAS, IS CURRENTLY A CONSULTANT FOR AIRFIELD LIGHTING WORLDWIDE, AND TEACHES AIRFIELD LIGHTING COURSES. HE IS A FOUNDER MEMBER OF THE INTERNATIONAL ASSOCIATION OF AIRPORT LIGHTING SPECIALISTS.