Thursday 16 April 2015

RUNWAY


RUNWAY
According to the International Civil Aviation Organization (ICAO) a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft".

NAMING THE RUNWAY
Runways are named by a number between 01 and 36, which is generally the magnetic azimuth of the runway’s heading in decadegrees: a runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°). When taking off from or landing on runway 09, a plane would be heading 90° (east).A runway can normally be used in both directions, and is named for each direction separately: e.g., "runway 33" in one direction is "runway 15" when used in the other. The two numbers always differ by 18 (= 180°).
      
        



RUNWAY DESIGNATION
Runway designations change over time because the magnetic poles slowly drift on the Earth's surface and the magnetic bearing will change. Depending on the airport location and how much drift takes place, it may be necessary over time to change the runway designation. As runways are designated with headings rounded to the nearest 10 degrees, this will affect some runways more than others. For example, if the magnetic heading of a runway is 233 degrees, it would be designated Runway 23. If the magnetic heading changed downwards by 5 degrees to 228, the Runway would still be Runway 23. If on the other hand the original magnetic heading was 226 (Runway 23), and the heading decreased by only 2 degrees to 224, the runway should become Runway 22.
  
RUNWAY LENGTH

  •         A runway of at least 6,000 ft. (1,829 m) in length is usually adequate for aircraft weights below approximately 200,000 lb. (90,718 kg).
  •     Larger aircraft including wide bodies will usually require at least 8,000 ft. (2,438 m) at sea level and somewhat more at higher altitude airports.
  •          International wide body flights, which carry substantial amount fuel are therefore heavier may also have landing requirement of 10,000 ft. (3,000 m).
  •     At sea level 10,000 ft (3,000 m) can be consider an adequate length to land virtually any aircraft.


RUNWAY MARKINGS

  • There are runway markings and signs on most large runways. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the thousands of feet remaining, so 7 will indicate 7,000 ft (2,134 m) remaining. The runway threshold is marked by a line of green lights.

  •    Runway surface marking are white color strips which h is in the center white broken strips which indicates the center on the runway and provides alignment guidance for aircraft.
  • Displaced thresholds may be used for taxiing, takeoff, and landing roll out, but not for touchdown. A displaced threshold often exists because obstacles just before the runway, runway strength, or noise restrictions may make the beginning section of runway unsuitable for landings. It is marked with white paint arrows that lead up to the beginning of the landing portion of the runway.
  • Blast pads, also known as overrun areas or stop ways, are often constructed just before the start of a runway where jet blast produced by large planes during the takeoff roll could otherwise erode the ground and eventually damage the runway. Overrun areas are also constructed at the end of runways as emergency space to slowly stop planes that overrun the runway on a landing gone wrong, or to slowly stop a plane on a rejected takeoff or a takeoff gone wrong. Blast pads are often not as strong as the main paved surface of the runway and are marked with yellow chevrons. Planes are not allowed to taxi, take off or land on blast pads, except in an emergency.

RUNWAY LIGHTNING
Runway lighting is used at airports that allow night landings. Seen from the air, runway lights form an outline of the runway. A particular runway may have some or all of the following:

  • Runway end identifier lights (REIL) – unidirectional (facing approach direction) or omni directional pair of synchronized flashing lights installed at the runway threshold, one on each side.
  • Runway end lights – a pair of four lights on each side of the runway on precision instrument runways, these lights extend along the full width of the runway. These lights show green when viewed by approaching aircraft and red when seen from the runway.
  • Runway edge lights – white elevated lights that run the length of the runway on either side. On precision instrument runways, the edge-lighting becomes yellow in the last 2,000 ft (610 m) of the runway, or last third of the runway, whichever is less. Taxiways are differentiated by being bordered by blue lights, or by having green center lights, depending on the width of the taxiway, and the complexity of the taxi pattern.
  • Runway center line lighting system (RCLS) – lights embedded into the surface of the runway at 50 ft (15 m) intervals along the runway center-line on some precision instrument runways. White except the last 900 m (3,000 ft): alternate white and red for next 600 m (1,969 ft) and red for last 300 m (984 ft).
  • Touchdown zone lights (TDZL) – rows of white light bars (with three in each row) at 30 or 60 m (98 or 197 ft) intervals on either side of the center line for 900 m (3,000 ft).
  • Taxiway center line lead-off lights – installed along lead-off markings, alternate green and yellow lights embedded into the runway pavement. It starts with green light at about the runway center line to the position of first center line light beyond the Hold-Short markings on the taxiway.
  • Taxiway center line lead-on lights – installed the same way as taxiway center line lead-off Lights, but directing airplane traffic in the opposite direction.
  • Land and hold short lights – a row of white pulsating lights installed across the runway to indicate hold short position on some runways that are facilitating land and hold short operations (LAHSO).
  • Approach lighting system (ALS) – a lighting system installed on the approach end of an airport runway and consists of a series of light-bars, strobe lights, or a combination of the two that extends outward from the runway end.

REFRENCES: