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Radar Height Finder and Altimeter
Published in Habibur Rahman, Fundamental Principles of Radar, 2019
In 1924, American engineer Lloyd Espenschied invented the radio altimeter. In 1938, Bell Labs put Espenschied's device in a form that was adaptable for aircraft use. In 1938 in cooperation with Bell Labs, United Airlines fitted a radar-type device to some of its airliners as a terrain avoidance device. A significant development in radar altimetry makes it useful in commercial and military applications. Currently, radar altimeters are frequently used by commercial aircraft for approach and landing, especially in low-visibility conditions and automatic landings, allowing the autopilot to know when to begin the flare maneuver. Radar altimeters are also used in ground proximity warning systems (GPWS), warning the pilot if the aircraft is flying too low or descending too quickly. However, radar altimeters cannot see terrain directly ahead of the aircraft. Radar altimeters are also used in military aircraft to fly quite low over the land and the sea to avoid radar detection and targeting by anti-aircraft guns or surface-to-air missiles. A related use of radar altimeter technology is terrain-following radar, which allows fighter bombers to fly at very low altitudes.
Aviation Displays
Published in Pamela S. Tsang, Michael A. Vidulich, Principles and Practice of Aviation Psychology, 2002
The GPWS is a system for alerting the pilot when the aircraft is dangerously close to the ground and is flying toward(rather than parallel) to it in a nonlanding configuration. Although it had been proposed for several years, the active mandate to require the GPWS in all commercial aviation cockpits only followed a tragic crash that a GPWS would very likely have prevented. The disaster was the 1975 crash of a commercial aircraft into the mountains west of Dulles Airport in Virginia, as the pilot heeded an ATC instruction for a direct vector to the airport. The pilot was apparently unaware that the mountain ridge intervened between the aircraft and the airport at a higher altitude than the vectored approach path (Wiener, 1977).
Current Safety Problems
Published in Harry W. Orlady, Linda M. Orlady, John K. Lauber, Human Factors in Multi-Crew Flight Operations, 2017
Harry W. Orlady, Linda M. Orlady, John K. Lauber
A basic limitation with the original GPWS and its modifications was that it provided warnings only for terrain obstructions that were directly below the airplane with information provided by the already installed radar altimeter. Its warning gave little time for action by the pilots. It did not provide sufficient warning for steeply rising terrain that was directly ahead. American Airline’s accident at Cali, Columbia made it clear that this was a meaningful deficiency.
Leverage points: insights from a field study in the air traffic control system
Published in Theoretical Issues in Ergonomics Science, 2020
Stathis Malakis, Tom Kontogiannis
In order to examine unsuccessful CoAs, we complied the following list of unwanted outcomes on the basis of regulations, operation manuals and interviews with the controllers:ACAS RA (airborne collision avoidance system, resolution advisory).Activation of genuine ground collision system such as GPWS (ground proximity warning system)/TAWS (terrain awareness and warning system) ‘warning’.Separation minima infringements.Aircraft deviation from ATC clearance;Approach continued against air operator stabilised approach criteria (i.e. unstable approach).Level bust.Lightning strike.Thunderstorm encounter.Turbulence encounterMissed approaches.Significant increase of controller ‘s workload.Poor approach sequencing.Strong verbal and written complaints from the flight crews for unfair treatment.Lengthy vectoring.Tightly coupled vectoring plan that allows little room for error and mistimed instructions.