Wulf-Diether Castell for airport lighting

Among the many important facilities that are essential for the operation of a modern airport, airport lighting is of particular importance. It is intended for the pilot who - despite excellent radio equipment - in the first phase of a flight after take-off and in the last phase before landing - both at night and [...]

Wulf-Diether Castell for airport lighting

Among the many important facilities that are essential for the operation of a modern airport, airport lighting is of particular importance. It is intended for the pilot, who - despite excellent radio equipment - is still dependent on optical observations in the first phase of a flight after take-off and in the last phase before landing - both at night and in poor visibility during the day, make it possible to recognize the location of the field, the take-off or landing direction, the taxiways and any obstacles present.

The airport lighting is used for navigation and thus the safety of passengers, crews and aircraft. In addition, it increases the operating value of the airport; because the better, the more effective the system, the longer it will be possible to fly to an airport. For these reasons - in particular for reasons of security - the airport pays particular attention to lighting. He will also usually be willing to invest considerable resources in the lighting. If an aircraft is approaching an airport and the pilot has to switch to optical observations in the last phase of the approach, he will first pay attention to the approach and guidance lights. It makes it easier for him to find his way around and to recognize the landing area and guides him to the runway in a straight flight. The lighting system consists of a series of lights on the approach baseline of the runway. Additional rows of fire are set up perpendicular to this as horizons. The horizon width decreases towards the threshold - the touchdown point on the runway. The total length of this system is 900 m, with the individual lights - mostly white or orange - having an elevation angle that roughly corresponds to the theoretical glide path. In addition, from a distance of 300 m from the threshold, the individual lights are directed outwards by 7 ° from the approach line. In addition to these fires, omnidirectional beacons are arranged for better orientation in traffic areas. Recently, flashing lights have also been installed in the central axis - in full length - which continuously send lightning from the start of the approach lights to the threshold with a transit time of half a second. The luminosity of these lightning bolts is amazing. The speed of the flash sequence avoids dazzling the pilot. This system enables the pilot to maintain the center line of the runway and a certain approach angle. The determination of the distance to the threshold is also possible - within permissible limits. The runway area delimits the areas on the sides and ends and thus ensures the movement of the aircraft on the runway. The lateral limitation is created by fire, which radiate in both directions and are 30 m apart. They are white and are colored orange at the ends of the runway to indicate the end of the runway to the pilot. The threshold lights, which indicate the beginning and end of a path, light up green and have an opening angle of 30 ° above the horizon. Often the runways are also equipped with white center line lights. These fires are built underground and their construction is kept in such a way that they can be overrun by aircraft. They radiate alternatively in both orbit directions at an increased angle and are an additional aid, not only for the aircraft's rolling movement on the runway but also for the approach. Towards the end of the runway, additional underfloor lamps are installed at a certain transverse distance to the center line, which are intended to draw the pilot's attention to the end of the runway. The AnilugwinkeHeuer is intended to make it easier for the pilot to land the aircraft in the area of the theoretical touchdown zone on the runway. It usually consists of 3 differently colored, sharply bundled light beams that shine towards the landing aircraft at the theoretical approach angle on both sides in the immediate vicinity of the runway. The aircraft should move on the central optical guide beam. The other two beams enable the pilot to correct the approach angle if the altitude is not yet correct. This fire - like the other systems - is operated from the control tower and switched to 5 different light intensities. It can be used both at night and during the day.

The stop surface lights illuminate the strips of land at the ends of the runway, which are specially secured and can be rolled over by the aircraft in an emergency.

The taxiway lighting is installed to mark the taxiways for aircraft to and from the runway. It is also arranged on the side and glows blue. The center line of the taxiways in the area of the runway is often specially marked by underfloor lights that emit green light. The apron is demarcated by the apron lighting, which is constructed similarly to the taxiway lighting and lights up blue.

The airport beacon is intended to facilitate the approach to an airport. A rotating spotlight with a range of up to 80 km is used. However, the importance of this fire has diminished in the course of continuously improving radio navigation. To secure the airspace in the area of the airport, all buildings and structures that represent an obstacle to aviation in the immediate vicinity of the runways or in the area of the approach and departure sectors are provided with obstacle lights. In addition, all buildings that are more than 100 m high will also receive such a fire. The obstruction light is a red omnidirectional light and switches itself on automatically when the daylight decreases. The basic arrangement of all lighting systems, which can be built according to different systems, is based on the recommendations of the ICAO (International Civil Air Organizations). In this way it is achieved or should be achieved that similar or identical lighting systems are built at all international airports. This is not only practical but absolutely necessary; as well as the further development and improvement of the existing equipment and systems in the interest of safety must be constantly worked.

Originally, around 35 years ago, the task of lighting an airfield was to give the pilot the necessary information about the size of the space and the direction of take-off or landing at night for both take-off and landing. Only when the bad weather landing was introduced did it become necessary to use the lights as a means of navigation even during the day. This made lighting an increasingly important factor, because until the point in time up to which automatic landing will be possible, navigation during final approach and navigation when taxiing is not possible under certain weather conditions without lighting systems. At a certain point in time, the pilot has to take up view of the earth and switch from his radio-electric to terrestrial navigation. It is therefore understandable when technology strives to develop better and better headlights and more effective lighting systems.

Almost 30 years ago, when night flight operations began in air traffic, kerosene lamps - so-called stable lanterns - were set up to mark the length and direction of the runway. Despite the low light intensity, the light could be seen from a great distance and from all directions in good weather. The kerosene lamps had green glass bells at the touchdown point and red glass bells at the end of the track. Despite ingenious lighting technology - lenses, mirrors, special diffusers, projector lamps with point light sources - an American specialist, Professor Horonjeff, is now returning to a very simple lamp. His PAN-Cake light for installation z. B. as a center line lighting in existing concrete runways has a 3-45 watt lamp without optics. But another insight from the early days of night flying is being taken up again today. At the beginning of the 1930s, retractable landing lights - large spotlights - were set up on the edge of the airfields, which radiated the touchdown zone. This was an excellent landing aid for instrument landing in poor visibility conditions. Today's attempts to illuminate the first 600 or 900 m of a runway through illumination are based on the same idea.

In Sweden, the touchdown zone of a runway was illuminated over a length of 640 m with floodlights placed on the right and left. The landings that have been carried out for years, even in bad weather, have proven that the type of illumination removes the “black hole” zone and is of great help to the pilot. Old knowledge that has been neglected for years has come into play again, especially since jet aircraft landing at high speed were deployed. Even today, the turning pointer that was placed in the corner of the instrument panel in the true sense of the word, the most perfect instrument aircraft, seems to be coming back into focus. I am also convinced that another excellent instrument will soon be honored again, namely the radio-electric altimeter, which is used to display altitude above ground. Instrument flight with subsequent bad weather landing will not be possible in the future without these two instruments, even if they only serve as monitoring devices for a fully automatic all-weather landing. Pilots are generally willing to get by with the technical aids that are offered to them. They are used to adjusting to what is available. That may also be the reason that various systems could develop in lighting technology and have also been approved by the ICAO (International Civil Aviation Organization). Fortunately, the ICAO ensures that the "fundamental" standardization is guaranteed. The airports have built in high-power and low-power tax in their lighting system. The high-power lights are directed, ie only recognizable in the approach direction, while the low-power lights are omnidirectional and can therefore be seen from all directions. The low-power lights are sufficient for good-sighted weather, while in bad weather conditions with limited visibility and low-lying clouds, only high-power floodlights are suitable for penetrating the atmosphere. A remnant from the beginnings of night flying still turns today on the towers of the airfields - the airport turntable - sometimes in two colors. This fire is reminiscent of the earlier route security. At that time, these rotating spotlights stood every 30 or 50 km on the night routes and enabled night flights at a time when radio direction finding was not yet available. When visibility is poor, the approach lighting is an indispensable aid, especially for fast aircraft. Should the landing speed of the aircraft become even higher in the future, it would be desirable to extend the approach lights beyond the current 900 m. With the American ALPA-ATA system, which has a center line lighting with only one transverse bar, the extension can be carried out without difficulty. The concentration of several light sources in a short crossbar, as it is e.g. B. is achieved with the ALPA-ATA system by 5 adjacent lights, brings an astonishing improvement in their effect. Early and perfect visibility for the pilot is very important, especially when visibility is poor. The same goes for that too. Threshold lighting. By moving the lights together on the outer edge of the thresholds, a better effect could also be achieved here.

In order to improve the recognizability of the approach lights, the ICAO requires a lightning chain for the ALPA ATA system. Although this chain of lightning does not increase the detection distance, it is a perfect identifier and shows that it is an approach light and the direction in which to land.

The wish of the pilots to get their aircraft to touch down in a very specific section of the runway can be made considerably easier with two aids. According to the day marking, which according to ICAO consists of two large white or yellow areas, for the approach at night either cross bars (consisting of some high-performance headlights) can be created to the right and left of the runway or, as I mentioned at the beginning, through Brightening of the contact area by illuminating this area from the right and left with spotlights. In hazy weather, then u. U. the on-board headlights can be dispensed with.

Another possibility is the installation of an optical glide path indicator. It would be very nice if this optical glide path could also be used in weather conditions with greatly reduced visibility. Unfortunately, there are still no light sources that can penetrate the fog. The ICAO has chosen an optical glide path that is unlikely to meet the needs of all users. In Australia, detailed comparison flights were carried out with 3 different "visual glide path systems", surprisingly the least known system received the highest score in these tests. Probably this system and also the one in 2nd place in the scoring was not selected because the installation conditions caused difficulties and additional obstacles would have arisen.

Individual aviation countries are trying to improve the lighting systems, and the ICAO, in turn, is trying to bring the results from the practical tests to a common denominator. The adaptation of the various views in the field of the application of colored light in airport lighting systems seems particularly difficult. In Germany one has so far assumed the principle that red light "stop" resp. Danger and green light means "free" as an invitation to use, similar to the traffic lights, ie in the approach direction the runway threshold is lit with "green" and there are red lights where it is not allowed to continue rolling. The lighting of obstacles is always done with red lights. In accordance with this principle, we have left out red markings in the approach lights in Germany.

If it is possible to introduce a uniform lighting system with uniform application of colors and the same configuration all over the world, the approach to or departure from an airport would be made considerably easier for the pilot in poor visibility conditions. It is not important that a sophisticated system with complicated technical devices is used. Test flights in America with fast airplanes have shown that only certain features of the lights can be recognized by the pilot during a fast overflight. For the approach it needs a sufficiently long and bright center line and a flawless determination of the distance from the start of the runway, for landing a well-marked touchdown zone and other colors that mean the same everywhere in the world.

Source: Airport Director Wulf-Diether zu Castell in Air München 02/1962