In aviation, the runway visual range (RVR) is the distance over which a pilot of an aircraft on the centreline of the runway can see the runway surface markings delineating the runway or identifying its centre line. RVR is normally expressed in meters or feet. RVR is used to determine the landing and takeoff conditions for aircraft pilots, as well as the type of operational visual aids used at the airport. [1]
Originally RVR was measured by a person, either by viewing the runway lights from the top of a vehicle parked on the runway threshold, or by viewing special angled runway lights from a tower at one side of the runway. The number of lights visible could then be converted to a distance to give the RVR. This is known as the human observer method and can still be used as a fall-back.
Today most airports use instrumented runway visual range (IRVR), which is measured by devices called scatterometers which provide simplified installation as they are integrated units and can be installed as a single unit(s) at a critical location along the runway or transmissometers which are installed at one side of a runway close to its edge. Normally three transmissometers are provided, one at each end of the runway and one at the midpoint. In the US, Forward Scatter RVRs are replacing transmissometers at most airports. According to the US Federal Aviation Administration: "There are approximately 279 RVR systems in the NAS, of which 242 are forward scatter NG RVR Systems and 34 are older Transmissometer Systems."
Because IRVR data are localized information, the values obtained are not necessarily a reliable guide to what a pilot can actually expect to see. This can easily be demonstrated when obscuration such as fog is variable, different values can apply simultaneously at the same physical point.
For example, a 2000 m runway could have reported touchdown, midpoint and rollout IRVR values of 700m, 400m and 900 m. If the actual RVR at the touchdown point (300 m from the threshold) is 700 m as reported, then a pilot could expect to see the light 700 m away, at the runway midpoint. If the pilot taxies to the midpoint and looks back through the same air mass, he or she must also be able to see the light at the touchdown point, but since the midpoint RVR is reported as 400 m, a light 700 m away must be invisible. Similarly, looking forward he or she cannot see the light in the rollout area, but according to the rollout RVR of 900m, the light there is visible and has already been so for the last 200 m.
RVR is used as one of the main criteria for minima on instrument approaches, as in most cases a pilot must obtain visual reference of the runway to land an aircraft. The maximum RVR range is 2,000 metres or 6,000 feet, above which it is not significant and thus does not need to be reported. RVRs are provided in METARs and are transmitted by air traffic controllers to aircraft making approaches to allow pilots to assess whether it is prudent and legal to make an approach.
RVR is also the main criterion used to determine the category of visual aids that are installed at an airport. The International Civil Aviation Organization ICAO stipulates in its Annex 14 that for RVR values above 550 m, CAT I lighting shall be installed, if RVR is between 300 m and 549 m then CAT II lighting is required. CAT IIIa is installed for RVR values between 175 m and 300 m. CAT IIIb is required for RVR values between 50 m and 175 m while there is no RVR limitation for CAT IIIc visual aids.
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". Runways may be a human-made surface or a natural surface. Runways, taxiways and ramps, are sometimes referred to as "tarmac", though very few runways are built using tarmac. Takeoff and landing areas defined on the surface of water for seaplanes are generally referred to as waterways. Runway lengths are now commonly given in meters worldwide, except in North America where feet are commonly used.
In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to approach until it is 200 feet (61 m) over the ground, within a 1⁄2 mile (800 m) of the runway. At that point the runway should be visible to the pilot; if it is not, they perform a missed approach. Bringing the aircraft this close to the runway dramatically increases the range of weather conditions in which a safe landing can be made. Other versions of the system, or "categories", have further reduced the minimum altitudes, runway visual ranges (RVRs), and transmitter and monitoring configurations designed depending on the normal expected weather patterns and airport safety requirements.
An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator's control of the vehicle, allowing the operator to focus on broader aspects of operations.
A taxiway is a path for aircraft at an airport connecting runways with aprons, hangars, terminals and other facilities. They mostly have a hard surface such as asphalt or concrete, although smaller general aviation airports sometimes use gravel or grass.
The visual approach slope indicator (VASI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach. These lights may be visible from up to 8 kilometres (5.0 mi) during the day and up to 32 kilometres (20 mi) or more at night.
A precision approach path indicator (PAPI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach. It is generally located on the left-hand side of the runway approximately 300 meters beyond the landing threshold of the runway.
In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a landing, or to a point from which a landing may be made visually. These approaches are approved in the European Union by EASA and the respective country authorities and in the United States by the FAA or the United States Department of Defense for the military. The ICAO defines an instrument approach as, "a series of predetermined maneuvers by reference to flight instruments with specific protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if landing is not completed, to a position at which holding or en route obstacle clearance criteria apply."
In aviation, autoland describes a system that fully automates the landing procedure of an aircraft's flight, with the flight crew supervising the process. Such systems enable airliners to land in weather conditions that would otherwise be dangerous or impossible to operate in.
The microwave landing system (MLS) is an all-weather, precision radio guidance system intended to be installed at large airports to assist aircraft in landing, including 'blind landings'. MLS enables an approaching aircraft to determine when it is aligned with the destination runway and on the correct glidepath for a safe landing. MLS was intended to replace or supplement the instrument landing systems (ILS). MLS has a number of operational advantages over ILS, including a wider selection of channels to avoid interference with nearby installations, excellent performance in all weather, a small "footprint" at the airports, and wide vertical and horizontal "capture" angles that allowed approaches from wider areas around the airport.
Runway edge lighting are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity they are capable of producing:
An approach lighting system (ALS) is a lighting system installed on the approach end of an airport runway and consisting of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end. ALS usually serves a runway that has an instrument approach procedure (IAP) associated with it and allows the pilot to visually identify the runway environment and align the aircraft with the runway upon arriving at a prescribed point on an approach.
Air Algérie Flight 702P, named Oasis and registered 7T-VEE, was a Boeing 737 owned by Air Algérie and leased by Phoenix Aviation. On 21 December, 1994, in low visibility conditions, it collided with power transmission cables and a pylon during its final approach to Coventry Airport in the United Kingdom. The aircraft was overturned and damaged several houses before crashing inverted into a wooded area beyond. All five people on board were killed.
Jammu Airport, officially known as Jammu Civil Enclave, is a domestic airport serving Jammu, the winter capital of Jammu and Kashmir, India. It is located 6.1 km (3.8 mi) south of the city centre and 14 km (8.7 mi) from the India–Pakistan border.
Linjeflyg Flight 267V was a controlled flight into terrain by a Convair 440-75 Metropolitan on 20 November 1964 at 21:14 in Ängelholm, Skåne, Sweden. The Linjeflyg pilots, misled by a non-conventional military runway light configuration, descended too early and on a faulty course during approach to Ängelholm–Helsingborg Airport. The crash killed 31 of 43 people on board, making it the deadliest aviation accident in Sweden.
Indian Airlines Flight 113 was a flight operating from Mumbai to Ahmedabad that crashed on its final approach to Ahmedabad Airport on 19 October 1988, killing 133 of the 135 people on board.
Mustique Airport is a private airfield owned by the Mustique Company for public use and is located on Mustique island, part of Saint Vincent and the Grenadines in the Caribbean Sea. It is used by civil aviation and national airlines using turboprop planes.
A visual approach is an approach to a runway at an airport conducted under instrument flight rules (IFR) but where the pilot proceeds by visual reference and clear of clouds to the airport. The pilot must at all times have either the airport or the preceding aircraft in sight. This approach must be authorized and under the control of the appropriate air traffic control (ATC) facility. The International Civil Aviation Organization (ICAO) definition adds that the visual approach can commence when "either part or all of an instrument approach is not completed", varying only slightly from the Federal Aviation Administration regulation and is essentially identical.
Inex-Adria Aviopromet Flight 450, JP 450, was an international charter flight from Tivat in the Socialist Federal Republic of Yugoslavia to Prague, Czechoslovakia which crashed in the Prague suburb of Suchdol on October 30, 1975, at 09:20 AM. The McDonnell Douglas DC-9-32 with 115 passengers and 5 crew on board descended, under Instrument Meteorological Conditions (IMC), below defined Minimum Descent Altitude (MDA) during the final approach to Prague Ruzyně Airport RWY 25, entered a gorge above Vltava river, and was unable to outclimb the rising terrain. 75 of the 120 occupants died during the crash itself while 4 others died in Hospital. The accident remains the worst aviation disaster on the Czech Republic soil.
An enhanced flight vision system is an airborne system which provides an image of the scene and displays it to the pilot, in order to provide an image in which the scene and objects in it can be better detected. In other words, an EFVS is a system which provides the pilot with an image which is better than unaided human vision. An EFVS includes imaging sensors such as a color camera, infrared camera or radar, and typically a display for the pilot, which can be a head-mounted display or head-up display. An EFVS may be combined with a synthetic vision system to create a combined vision system.
On 23 December 1983, Korean Air Lines Flight 084 (KAL084), a McDonnell Douglas DC-10-30 performing a cargo flight, collided during its takeoff roll with SouthCentral Air Flight 59 (SCA59), a Piper PA-31-350, on runway 06L/24R at Anchorage International Airport, as a result of the KAL084 flight crew becoming disoriented while taxiing in dense fog and attempting to take off on the wrong runway. Both aircraft were destroyed, but no fatalities resulted.