LEDs Light the Way

Monday, February 20, 2006

One of the most recent advances in airfield lighting technology has to be the widespread adoption of LED lights on runways and taxiways. LED technology is set to revolutionise airport lighting in the near future. LED technology's superior performance compared with older technology will increase safety levels, and it costs less to run and maintain.

LED lighting can replace existing lighting infrastructure in a hard-wired power network or it can be deployed as self-sustaining solar-powered systems at airports that do not possess the necessary powered infrastructure.

LED technology is also being used in airport guidance systems, such as infrared camera systems for airfield visibility, visual glide slope indicator systems and parallax aircraft docking systems. The advantages of LED lighting systems include:

  • Extended life of up to 100,000 hours, compared with 8000 hours for incandescent lamps, thus lowering maintenance costs
  • Higher light intensity
  • Lower power input for increased performance
  • Durability, since they have no filament
  • Availability in a range of colours for different airport applications
  • Instant operation (no warm-up)

Solar-powered LEDs

Carmanah Technologies, Inc. is a Canada company specialising in self-contained solar-powered LED airport lighting solutions. Allister Wilmott, aviation division manager at Carmanah, says that the company's latest LED light, a new aviation optic called the A704-5 runway threshold light, includes several new design features:

  • A parabolic mirror
  • Increased LED intensity through the use of 1W LEDs instead of 5mm LEDs
  • Expanded vertical divergence of 0-20° for the LED output, instead of the 0-7° of the previous product, providing a wider beam angle for approaching pilots
  • An interspersed design for the LED "puck" - both visible LEDs and infrared LEDs

These new design features provide higher performance, higher LED intensity and greater safety. Carmanah's lighting systems make use of low-powered LEDs, high-performance solar panels and power point tracking systems to make them some of the most efficient available. They have to be, as they must be able to charge during the day in whatever daylight is available so that they can remain on all night, from dusk to dawn. The systems use automatic light control that allows the lights to be dimmed to conserve charge in difficult solar conditions so that the lights can remain on through the night. Elmendorf air force base in Alaska has 300 LED units, which it runs at 5o per cent intensity during October, when there is little sun, to conserve power.

A new feature being introduced in April 2006 is wireless technology that will allow an airfield lighting system to be controlled via a handheld wireless computer or PDA-type system. This will mean that the lights can be powered down completely at certain times by the controller to conserve the charge in their lead-acid gel pack (charge storage device) and then pushed to high intensities when they are required for landing operations in snow or foggy weather. The controller will also be able to switch from visible to infrared, carry out battery-level checks and flash the lights to communicate with the tower. The lighting systems are fully modular, allowing easy expansion if runways are extended or modified.

Often solar-powered systems are only used when a well-established power infrastructure is unavailable. However, LED lighting systems have some advantages over conventionally powered systems. Nassau International Airport in the Bahamas has solar-powered emergency LED runway and taxiway edge lighting systems. On one occasion, airport workers were carrying out resurfacing work on the main runway when power was accidentally lost. Fortunately, the self-contained solar-powered systems were able to provide lighting for several months while repairs were made.

Solar-powered visual glide slope indicator systems, such as the precision approach path indicator (PAPI) system, can use LED technology. Wilmott says: "The Carmanah system (A-PAPI) will use two individual lamps which will give the pilot a signal using a fitter. The pilot receives a signal indicating whether the aircraft is too high or too low on approach to the runway using the colours red and white." The A-PAPI systems are very power hungry, so the Carmanah system uses only two lamps, one on each end of the runway on the left hand side. These can be attached to a modular autonomous photovoltaic power supply (MAPPS) to form a self-contained visual glide slope indicator that can be used at remote airports with little power infrastructure.

Infrared LEDs for low visibility Another LED technology gaining in popularity is infrared. Infrared LEDs are starting to be used to help commercial and defence aircraft land under conditions of low visibility. Gulf Stream recently released 200 of its high-performance business jets equipped with infrared and forward-looking infrared (FLI R) cameras. If these jets encounter low visibility, the pilots can switch on infrared cameras, and the heat signatures they pick up from infrared LED or even incandescent lighting on the airfield wilt allow the pilot to land the aircraft in these difficult conditions.

Mobile airfield light monitoring

The Mobile Airfield Light Monitoring System (MALMS) was designed and developed by TMS Photometrics as a rapid, easy-to-use test system to accurately measure the photometric performance of airfield ground lighting.

One of the biggest problems with airfield lighting systems is that they are very extensive and require a great deal of manpower to monitor and maintain. The MALMS is a mobile measuring unit that can be used while being towed at speeds in excess of 80km/h and can be set up and operated by a single user with minimal training. The MALMS unit is self-monitoring, using automatic data verification algorithms, and has a real-time system for driver/ operator guidance. A typical test run takes only four minutes, which is ideal for airfields with limited access time available. At the end of a run, the system produces a detailed report pinpointing failing lighting units according to International Civil Aviation Organisation (ICAO) standards. This information can then be used by airfield lighting maintenance personnel.

Parallax aircraft docking

The Parallax Aircraft Docking System (PADS) is a visual guidance docking system developed by ASM Group and is currently being tested at a major UK airport. The system uses parallax and LED technology to allow a pilot to manoeuvre an aircraft accurately onto its stand. David Sames, technical director for ASM Group, says: "PADS offers clear visibility of display to pilots in all weathers. If they can see it, then it works."

The PADS system starts with the stand marshal, who sets the system for the particular aircraft and stand. During docking, the pilot uses the system to manoeuvre onto the stand centre line using error demand "turn to" signals through the azimuth pointer. As the aircraft approaches the stand head, amber wing bars move up the display as green vertical bars reduce in length to indicate the rate of closure. The aircraft must stop when the wing bars coincide with the horizontal amber stopping indicator to form a symmetrical amber cross. The system will allow docking to be carried out more efficiently and rapidly, even in low visibility. The system requires very little maintenance and has been approved by ICAO.

The way forward

The deployment of LED lighting technology in airport lighting systems has many advantages. The use of LED technology can decrease energy costs, particularly if solar power is adopted, and it has lower running and maintenance costs. In inset lighting applications, LEDs will last for up to 100,000 hours of operation, cutting down on re-lamping and routine maintenance. Overall, the installation of LED lighting can save airport operators money, and it is better for the environment. In future, LEDs will be widely adopted for a range of airfield applications.