Ground proximity warning system

A ground proximity warning system (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground or an obstacle. The United States Federal Aviation Administration (FAA) defines GPWS as a type of terrain awareness warning system (TAWS). More advanced systems, introduced in 1996, are known as enhanced ground proximity warning systems (EGPWS), although sometimes called terrain awareness warning systems.

In the late 1960s, a series of controlled flight into terrain (CFIT) accidents took the lives of hundreds of people. A CFIT accident is one where a properly functioning airplane under the control of a fully qualified and certified crew is flown into terrain, water or obstacles with no apparent awareness on the part of the crew.

Beginning in the early 1970s, a number of studies examined the occurrence of CFIT accidents. Findings from these studies indicated that many such accidents could have been avoided if a warning device called a ground proximity warning system (GPWS) had been used. As a result of these studies and recommendations from the U.S. National Transportation Safety Board (NTSB), in 1974 the FAA required all large turbine and turbojet airplanes to install TSO-approved GPWS equipment.

The ICAO recommended the installation of GPWS in 1979.

C. Donald Bateman, a Canadian-born engineer, developed and is credited with the invention of GPWS.

In March 2000, the U.S. FAA amended operating rules to require that all U.S. registered turbine-powered airplanes with six or more passenger seats (exclusive of pilot and copilot seating) be equipped with an FAA-approved TAWS. The mandate affects aircraft manufactured after March 29, 2002.

Prior to the development of GPWS, large passenger aircraft were involved in 3.5 fatal CFIT accidents per year, falling to 2 per year in the mid-1970s. A 2006 report stated that from 1974, when the U.S. FAA made it a requirement for large aircraft to carry such equipment, until the time of the report, there had not been a single passenger fatality in a CFIT crash by a large jet in U.S. airspace.

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