Acceptance of LED lights and new airfield lighting control system standards signal a change for the better.
Over the past decade, a few airports have cautiously run trials on Light Emitting Diode (LED) lights before installing them on taxiways. But now, says Ed Runyon, advanced technology manager, Siemens Airfield Systems (SAS): "No-one is asking for proof. They are just writing them into the specs. They are becoming standard".
Last year, Cincinnati/ Northern Kentucky International Airport (CVG) installed 101 LED elevated edge lights on Taxiway Kilo. By February this year, CVG had installed half of 290 new high-speed turn-off LED lights for the centrelines of four Runway 18L turn-offs; the remaining half are in the process of being installed. Also on this summer's work order are LED centreline lights for taxiways A and B.
"We had been using LED exit signs and we said, 'This is what we need for the airside'," says Chris Allgeyer, electrical supervisor for CVG. The cost/benefit numbers for using LEDs looked attractive enough for CVG to order them for a light replacement programme on Kilo as part of a taxiway reconfiguration, extension and repaving associated with a 2,000ft extension of Runway 9/27.
Although a LED light costs US$277, compared to just $70 for a quartz light with an incandescent bulb, an 11-watt LED burns just $1.77 worth of electricity a year as against $4.14 for a 3o-watt incandescent bulb.
However, stresses Allgeyer, "You have to factor how you value labour in the life-cycle cost of the LEDs. It is the labour savings you are banking on." In its cost/benefit analysis, CVG assumed that incandescent bulbs would need replacing twice a year, although three times a year is not uncommon. LED bulbs, on the other hand, are expected to last at least ten years.
Then there is the risk of a runway incursion when a truck is on an active airfield. "If you have a truck running around changing bulbs, then there is more risk of this," says Allgeyer.
Four years of testing four elevated 3in (7.62cm) -diameter Siemens lights at CVG yielded interesting results, says Allgeyer. "We told Siemens that snow was collecting on them and they wouldn't work. Siemens developed heaters to keep the insides of the globes at about 4o°F `4°C`. We tested one in the winter of 2003/2004 and it worked fine." These 'Arctic Kits' consume 11.5 watts and are set on a thermostat. They come on when the temperature level drops below a certain point."
The in-pavement LED lights with 12in (30.48cm) cans that CVG tested in the winter of 2003/2004 developed enough heat to melt a ring of snow around them at 17°F (-8°C). An unexpected bonus, says Allgeyer, was the elimination of an annoying maintenance issue with the old in-pavement lights. "The window recess is really shallow, which is great because they don't hold sand. The old lights collected so much sand that it looked like there was no light there. We had to blow the sand out with air compressors."
Substituting energy-efficient LEDs may permit expensive electrical upgrades to be deferred, even as the number of lights drawing off the airfield lighting system are increased. "A lot of times people are looking at extending a taxiway or installing signs. They could avoid an overload and possibly use the same regulator (which sends electricity out to the circuits, and can cost US$15,000 to replace) and breaker in the electrical vault," explains Allgeyer.
CVG's taxiways work on three light levels, with a threestep regulator. Allgeyer reports, "We have a system that monitors on a circuit and tells us how many bulbs are burned out. We can detect a burned-out LED `but not which one`. It works fine."
Allgeyer also observes: "The 3in (7.62cm) LEDs are so bright blue that the lights in the rest of the field look washed out. You wouldn't want to intersperse them in a 'hit-and-miss' manner, as they are a rich blue - deeper and more intense than the incandescent lights."
The low current draw of LEDs has also enabled solar-powered airfield lights to be developed independent of any wiring system or power grid. Carmanah Technologies has sold tens of thousands of its solar-powered LED units for military applications, but the Canadian company is also making in-roads at commercial and general aviation (GA) airports. Carmanah's Model 601 blue light conforms with the applicable requirements of ICAO Annex 14, Volume 1, third edition, dated July i9, 1999, sections 22.214.171.124 and Appendix 1, 2.1.1.
Solar panels in each unit generate electricity to charge a battery that powers the light all night. They have found acceptance as temporary lighting - for instance, as taxiway edge lighting during construction work at Auckland International Airport in New Zealand, where the alternative would have been diesel generator-powered or regular battery-powered lights.
Chicago 0'Hare International Airport (ORD) has been using 60 Carmanah lights since January 2003 for a rolling security barricade. Until it bought the Carmanah lights, ORD was spending $900 on light batteries every three months, according to Allister Wilmott, Carmanah's Aviation Division Manager.
At Nova Scotia's Halifax International Airport, Carmanah lights do winter duty replacing regular taxiway edge lights torn out by snowploughs. "Sometimes in the winter when a plough breaks off a light, it breaks off the cable that feeds power to that light. It is really difficult to repair that in the winter, so we use the Carmanah lights," says David Lajoie, the airport's electrical maintenance supervisor.
Lajoie has seen as many as 100 lights broken off by ploughs during a storm, and when underground cabling gets torn up, maintenance has traditionally had to use jackhammers to dig up the ground in order to replace it. A cable repair in the winter requires two operators, two electricians and half-a-day, at a minimum cost of about C$500, according to Lajoie. That can be more than the cost of a Carmanah Model 601 unit, which a last check on the Carmanah website shows retailing at US$349. Lajoie just sets out the portable solar-powered lights, sometimes as early as November, and leaves them till the spring thaw.
However, the area in which Carmanah's solar-powered lights are poised to make significant inroads for regular use are at airports where power is prohibitively expensive, or where funds for normal wired systems are difficult to obtain.
This spring, Carmanah and California's Department of Transportation Aeronautics Division (DOT) submitted a proposal to the State Energy Commission (CEC) to run trials of the solar-powered LED lights at three GA airports in the state.
If approved, these will be conducted under three different environmental conditions. The first, at a GA airport with dense valley fog just south of Sacramento, will test whether the lights can charge up enough in the foggy conditions for a full night's operation. The second will test safety and electrical savings at a less foggy airport north of Sacramento, while the third will be at an airport in northern California which is exposed to low temperatures and snow. The ultimate goal of these trials is to be able to recommend the installation of solar-powered LED airfield lighting systems to airports otherwise unable to afford wired-in systems.
The experience at California's Truckee Tahoe Airport illustrates the value of using such a system. It installed over 500 Carmanah lights on its taxiways last year for about one-tenth of the cost of a traditional system. And the icing on the cake is that the electricity bill is $15,000 a year less than that for a similar, non-LED system -- valuable numbers for a GA airport.
Another reason for wanting to be able to recommend the solar-powered LED units concerns the reliability of the State's energy supply, explains Aeronautics Division Chief Robert Wiswell. "My interest was inspired by the fact that California was coming out of its energy crisis. Most airports do not have back-up generators and if anything goes haywire with the electrical grid, the lights go out. I view this as a safety issue."
Wiswell has authority over more than 224 public-use GA airports in California. His responsibilities include issuing certificates for night operations and providing 90% funding aid for projects. He sees solar-powered LED lights as a capacity enhancer, without the attendant worries about bulbs or electrical grid failures or old systems with deteriorating direct-buried cables.
If Wiswell gets the go-ahead from the CEC, which will provide most of the funding, the trials will start this autumn and run for about ten months. "Hopefully, we will have established that the taxiway edge lights meet expectations. We would also like to be set up for validation by analogy for runway edge lighting," he says.
Far to the north of California, on the 62nd Parallel, is the Canadian city of Yellowknife. Yellowknife Airport (YZF) recently finished putting 20 Carmanah lights through two years of northern weather on its taxiway, apron and runway. Solar-powered LED lights would be a boon there, as installation costs are high and the cost of power ferociously expensive, having hit C$2.oo a kilowatt-hour in some places.
"The idea was to see if the lights will come on and stay on all night at -3o°C to -4o°C," says John Curry, who works in the airport's technical department. Although there are only four hours of daylight in December, Curry reports: "The battery capacity was OK and they worked on short days and low temperatures. For the most part, the fixtures would come on at 3pm and would still be on the following morning when it was still dark. There were issues with clearing snow and frost accumulation on the solar panels, giving the site guy a bit more maintenance to do."
Flight testing revealed that the runway-installed lights were not bright enough for use, but apart from this there were no negative comments from pilots. The air traffic controllers commented that they would like to be able to turn them on and off. Carmanah has been made aware of this request and the latest news is that the company is to release next-generation LED runway lights with a new optical design capable of intensities ten times brighter than previously.
"In the next few years," says Curry, "we will be doing more expansion at Yellowknife and if issues and concerns are dealt with, I would like to see the LED lights used."
Lighting Control Systems
An airfield lighting system -- with its thousands of approach, touchdown, runway, exit, taxiway, stop bar and other lights, hundreds of kilometres of wiring, regulators, generators, electronics and more -- requires maintenance and constant monitoring. From the air traffic control (ATC) tower, various sets of lights need to be turned on and off and their intensity raised and lowered to reflect current meteorological conditions and operational requirements. Controllers must also be made aware of lighting failures, as these can seriously impact operations.
This is all done via what the latest parlance terms an Airfield Lighting Control and Monitoring System (ALCMS). Last year the Federal Aviation Administration (FAA) addressed the lack of standardisation of airfield lighting control systems in the September 30, 2004, advisory circular 150/5345-56 which specifies minimum ALCMS requirements. It came into force six months after the advisory was issued.
Siemens Airfield Systems Ed Runyon again: "The reason the FAA put together this spec is that there were complaints that low bids would win, local contractors would then put a system together and it wouldn't perform to expectations. Many airports were dissatisfied with the quality and long-term support. One of the ideas behind the circular was to assure a minimum level of performance, reliability and quality when buying one of these systems".
This year SAS is installing an ALCMS as part of the rehabilitation of Mexico's Toluca International Airport, an hour's drive west of Mexico City. To relieve traffic pressure on the overburdened Mexico City Airport, Toluca and other local regional airports, such as Puebla and Cuernavaca, are being improved and will handle new domestic and international traffic.
The ALCMS, a first for Mexico, is supporting a completely new airfield lighting system, including elevated LED taxiway edge lights and the country's first CAT IIIB Instrument Landing System. "We are going to use this ALCMS as a showcase for other airports in Mexico," says SAS international sales manager Elvis Jimenez.
The ALCMS will include the Siemens BRITE system, which has over 1,000 remotes that will monitor the health of individual lamps on nine of the 13 system circuits. The ALCMS will interface with all the lighting systems' devices which require control, monitoring and troubleshooting, right down to being able to detect a drop in load if someone accidentally shorts out two pieces of wire to lights during construction.
Central to the ALCMS control function specified in the FAA advisory circular is the requirement that it have a touch screen for the air traffic controller Human Machine Interface. Unlike touch screen 'pick and poke' operations, controllers in towers with the older mechanical systems -- which still far outnumber digital systems -- must toggle-operate sets of lights on and off. Any change in the airside lighting requires another box to be added to the tower console.
The Toluca ALCMS will have touch screens in the tower, the maintenance office and the vault (a building containing power supplies), from where the lighting system is serviced. The ALCMS is modular, with an open-architecture design, and can be easily expanded to accommodate any additions to the airfield lighting system, integrated with new airside ATC technologies. Technicians use drawing tools to modify the airfield graphic on the touch screen to reflect the new airfield configuration.
The controller's job has become much easier with touch screens and computers able to carry out certain lighting operations automatically; for instance, one-button operations that launch several lighting changes simultaneously. In fact, the toggle system is too cumbersome for certain operations, such as the tightly-orchestrated lighting, aircraft detection and timing sequences for lowvisibility departures.
SAS describes a lighting sequence its ALCMS is programmed to perform automatically which would probably be impractical with a toggle system. "When a red stop bar is switched ON, a number of green taxiway centreline lights beyond the stop bar are switched OFF. When the aircraft receives clearance, and when the red stop bar lights are extinguished by the air traffic controller, the green centreline lights are illuminated to indicate the aircraft is cleared to proceed. Incorporating a microwave sensor with the BRITE will allow automatic re-lighting of the stop bar and extinguishing of the green centreline lights in anticipation of the next aircraft."
The SAS ALCMS also has a distributed system which gives greater system reliability; for example, SAS systems have RAID 1 dual-mirrored hard drives. If one drive fails, a technician can replace it while the other one remains powered up. There are also redundant communication links: such as two communications relays to each system. To illustrate how an ALCMS can be incorporated into a larger suite of controller tools, the ALCMS in Montreal Trudeau International's control tower is an application on Nav Canada's Integrated Information Display System (IIDS) platform, which manages flight time data exchange. The ALCMS always appears as a background application on the farthest left LCD touch screen at each controller workstation, and displays a graphic of the airfield which controllers can refer to and manipulate.
Controllers can easily see the colour-coded status of all the airfield lighting systems on the graphic. When the runway edge lights are not on, they are not coloured. When they are on, they are yellow. If they have failed, they turn red. When they are under maintenance, they are black.
To make it easier to assist maintenance personnel during daily inspections, the ground controller uses six buttons to turn on the lights in the six inspection areas to the required intensity.
The tower receives aural warnings of condition alarms, such as a power supply regulator or field lighting segment failures, and controllers see their status on the screen. They pass on all faults to maintenance, but some require a controller to inform pilots on approach or, in the case of the loss of runway edge lights, to shut down the affected runway. If, say, the CAT II status indicator light turns red, the controller can call up the CAT II Operating Conditions window, which shows the status of all the components in the system that have failed and whether they are essential elements. They can drill down into the ALCMS for more detailed information.
The controllers can choose from various icons offering 'recipes' of operations that are performed automatically -- a big improvement over the 'steam-driven toggling' required before Nav Canada installed IIDS in the tower cab in 2003. "We analysed exactly the steps that are done, built a recipe around them and assigned an icon to that `task`," says Montreal tower supervisor Bill Smith.
By poking the day/night icon, the ALCMS automatically adjusts all the lights for night-time operations; turning on the taxiway lights, setting the runway lights to intensity two, reducing lights for the Precision Approach Path Indicator and turning on the approach lights at the same intensity as the runway lights. Intelligence programmed into the computer prevents the approach lights from ever being brighter than the runway edge lights. Poking another icon reconfigures the lighting when changing winds or traffic requires swapping runway ends for arrivals or departures. The computer will remember all the settings for, say, Runway 06L, including the lighting intensity, and switches them to the other runway end.