Landing track
The runway or take-off runway is the surface of an airfield or an airport, as well as an aircraft carrier, over which aircraft they land and brake or in which the planes accelerate until they reach the speed that allows them to take off. In Spanish it is more common to speak of a landing strip than a takeoff runway. In English there is only one word for both terms, which is runway. The pilot and air traffic controller simply use the term "track" when communicating with each other.
Dimensions
Airfields
The landing and takeoff runway is sized based on the characteristic aircraft. This, in turn, is determined by previous studies on the traffic that the airport will support, ranges of the origins of this traffic and various other considerations that come together in determining which aircraft is the one that due to its capacity, autonomy and other technical characteristics turns out to be the ideal or characteristic. From this fundamental data, the "basic runway length" ideal data determined by the manufacturer and which is the ideal and safe length that the aircraft in question needs to operate at sea level and with an ambient temperature of 15 °C. It is with these data that the basic runway length is corrected based on the altitude of the runway in question and the average temperature of the place. The higher the altitude and/or the higher the temperature, the more the basic length must be increased, which will ultimately be the project length.
Large airports, where demand is very high, have several runways. Large, fully fueled and passenger aircraft such as the Boeing 747 or Airbus 340 require runways of at least 2.5 km to take off and land safely. On the contrary, small passenger planes need runways that do not exceed one kilometer. The same thing happens in the case of military air bases.
Aircraft Carrier
Exceptionally, in the case of aircraft carriers, the runway is different from the takeoff runway. The reason is that both tracks must be usable simultaneously. Its takeoff runway is very short, about 100 meters, so that the planes must be accelerated in a few seconds from 0 to 200 km/h using catapults in order to take off. The runway is somewhat longer, about 200 meters, a length that requires the use of braking cables so that the planes can land. However, it should be noted that in the case of an aircraft carrier, operations are carried out with the ship sailing at maximum speed against the wind, if any, for which the aircraft benefits from a virtual headwind that may be due to less than 25 knots, therefore runway length requirements are reduced. If there is a wind of twenty knots, this will add to the speed of the ship, that is, the plane, parked before being catapulted to take off, may already be enjoying 45 knots of headwind. If the simile is permitted, an aircraft carrier is an airport with a built-in headwind.
The landing and take-off runway can only have a few degrees of incline, since a greater slope would affect the speed of the planes when taking off and landing.
Runway design and location criteria
Airplanes require a certain speed to sustain themselves in the air. By having headwinds, planes require less relative speed to fly. On the other hand, aircraft have great difficulty taking off and landing in crosswinds (technically known as crosswinds). Based on this, airport runways are typically built in such a way that, during a year, crosswinds do not exceed 5% of the time the allowable values for the design aircraft. As the winds vary substantially from year to year, historical series of at least 10 years are required to establish whether the direction is adequate.
Pavement
At major airports, runways are usually made of asphalt or concrete pavement. The thickness of the runway base depends on the type and size of the aircraft that will use it and the composition of the demand. Thus, for example, runways intended for large aircraft require an extremely thick base (between 15 and 51 cm approximately) resistant to support the high weight of such devices. However, small-scale, small-town landing fields are often dirt, turf, gravel, grass, or gravel.
The structural package of a rigid pavement for airfield runways consists of a simple concrete base (or reinforced, at intersections with other runways and exits) that distributes the stresses to the compacted natural soil (or subgrade). If the design aircraft mass exceeds 100,000 pounds, an interlayer of stabilized material is included to evenly distribute the slab load and reduce freeze-thaw damage.
Semi-prepared tracks
For those small airports with short landing fields and located in small cities, farms or towns, these can be dirt, grass, gravel, grass, among others.
Aircrafts that have a high-resistance tricycle landing gear can land on these runways, such as:
- Cessna 208
- C-130 Hercules
- C-130J Super Hercules
- CASA CN-235
Name
Each track is named with two numbers, one for each of the two addresses and possibly a letter. This allows pilots to easily identify the runway and which side of it to use. The number means the direction in degrees (rounded to the nearest ten and trimmed in the last digit) with respect to magnetic north to which the runway is directed (in one headland) and respectively the opposite headland, will be denominated with the angle of complement (opposite direction, that is, 180° difference).
If, for example, a track has the name 04 in one direction, its identification in the opposite direction will be 22. These numbers are painted in very large characters, in white, on the runway surface at both ends, so that they can be recognized by pilots from the air at some distance. If an airport has two runways that run parallel, and that is why they are identified with the same number, an R (from English Right) is added after the number in the right track, and an L (for Left) on the left track. In such a case, the two tracks could have, for example, the identifiers 07R and 07L. If the airport even has a third runway parallel to the other two, the name of the center runway will in this example be 07C (for Center). The direction of the track is indicated in magnetic degrees, eliminating the last number. A runway whose direction is, for example, to the east, that is, 90 degrees, will therefore have the name 09, and a runway whose direction is to the southwest, that is, 225 degrees, will be identified like 22.
A special case such as that of the Dallas-Fort Worth International Airport, since of its seven runways for landing and takeoff (one of the airports with the most runways in the world), five are parallel, it needs to use a procedure a bit distinct. The two tracks located to the west are given the names 36L and 36R, and a number is subtracted from the remaining three, leaving them as 35L, 35C and 35R. It is not entirely correct, but it is the best way to determine them.
- Example: In Mexico City Airport (MMMX) the track 05L it is at 052°, but by denomination only the first 2 figures are taken, that is, the hundreds and the tens of degrees; therefore the other head, analogous to the sum of 180°, is called track 23R, located at 232°.
The letter refers to the position of the track with respect to the others that maintain the same direction. There are 3 letters: L (Left), R (Right), and C (middle). In the event that there are more than three parallel tracks, the W applies to the one to the left of the L. In the same way, if an airport does not have parallel runways, it is enough to put only the numbering, without adding letters.
Example: At the same airport as the previous example, there are two runways facing the same direction, and they are 05L (Left, 05 left), and 05R (Right , 05 right), similarly those on the other side are 23L (the other end of 05R) and 23R (the other end of 05L).
Signage
Landing and take-off runways have white signage painted on the runway surface, the purpose of which is to inform pilots when taking off, and especially when landing, about the various sections and distances of the runway, as well as on its central longitudinal axis, to facilitate maneuvering.
For takeoffs and landings at night and in conditions of reduced visibility, such as in the case of fog, the runways are illuminated by means of lights that mark their sides, the central longitudinal axis, the various sections of the runway, as well as its beginning and its end. For landings in such conditions, runways of a certain importance have landing beacons that are installed several hundred meters ahead of the runway, and which consist of spotlights mounted in a certain order.
Lighting
Visual Approach Slope Indicators (VASI)
An important visual aid to the final approach towards the head of the runway are the Visual Approach Slope Indicators, which provide greater certainty in the approach in conjunction with the visual and instrument approach aid systems. VASIs are typically installed in locations where one or more of the following conditions exist:
- The track is used by reactors (turbojet or turbofan).
- The pilot has difficulty judging the final approach by an inadequate visual reference on the water or by the characteristics of the terrain, by the deceptiveness of the surrounding elements or by the misleading inclinations of the track.
- Because there are serious risks in the approximation area that can jeopardize the aircraft if it is a little below the downward pattern in the approximation.
- Due to the high risk of the aircraft in the event of a sudden decline or an unexpected rise.
- Due to turbulence found or existing due to weather conditions or terrain conditions.
Runway End Indicator Lights (REIL)
Sometimes lights are located at the end of the runway to help quickly and effectively identify the approaching end of the runway. When in the second half of the track, the white center line and edge lights turn into a row of alternating white and red bulbs. In the last section of the track there are only red bulbs. In this way the pilot can properly identify the end of the runway without the possibility of confusion. A system consisting of two series of lights that synchronously flash (called strobe lights) is also usually incorporated, one on each side of the last stretch of the track. However, these are not usually installed, as the strobe light system is incorporated into the Approach Light System. The REIL system is used to distinguish the head of the runway in places characterized by numerous ground lights, such as neon signs or other lights that can distract the pilot's attention.
Approach Lighting Systems (ALS)
Approach Light Systems are used in the vicinity of the runway head as part of the electronic navigation aids for the final part of precise and non-precise approaches of an IFR flight; and also as a visual guide in VFR night flights. The approach lighting system provides the pilot with visual inputs regarding aircraft alignment, balance, horizon, width, and position relative to the runway head. Since airport lighting systems have replaced the necessarily quick mental actions on visual information that drive decisions, a visual system is ideal for guidance during the critical last few seconds of descending motion over the glide pattern. The approach lighting system was created based on glide pattern angle, visual range, cockpit cutoff angle of visibility, and landing speeds. This is essential so that pilots are likely to use and identify ALS and to interpret the system without confusion. Among the main ALS systems are:
- ALSF-1
- ALSF-2
- MALSR
- MALSF
- MALS
PAPI system
The PAPI system consists of a crossbar of four red or white lights, usually located on the left side of the runway. If the plane is going too high above the glideslope you will see all the white lights; if you go a little high you will see three white lights and one red; if you go too low, you will see them all red; if you just go a little low you'll see three reds and one white, and if you're going the right way, you'll see two whites and two reds.
Lighting of the central shoulder and the contact zone of the runway
These lighting systems make it easy to land, turn and take off. The touchdown zone lights are primarily used for landings, and the runway center lights assist after touchdown and provide primary guidance during the takeoff roll. Both systems are used as a complement to electronic approach aids and ALS under limited visibility conditions.
Center Runway Lights are attached nearly flush with the pavement and overlapped by a maximum of two feet to clear shoulder paint. Downtown lights are white except for the last 3,000 feet. From 3,000 to 1,000 feet from the runway, the lights alternate red and white.