Current enhanced ground proximity warning computers are a natural outgrowth of the original system developed in the 1970s. One of the earliest GPWS computers was based on the Intel 8080 microprocessor, the first use of a microprocessor in a commercial avionics unit. It relied on the radio altimeter for its primary input and had distinct limitations as a result.
“Modern EGPWS units are attached to the aircraft GPS for position, altitude, course and speed,” stated Thay Humes, Co-founder of Humes McCoy Aviation. These units also receive a variety of discrete signals. They monitor flight modes during approach and departure and provide warnings if the aircraft is misconfigured, improperly lined up during an approach, or on a runway that is too short.
The main task for EGPWS is to provide pilot awareness and prevent controlled flight into terrain. The computer takes GPS information and compares it to a simplified terrain map. It displays the results with color-coded altitudes. The terrain below the aircraft altitude is green. Any terrain near the same altitude is yellow, and terrain that is higher than the aircraft is red. When a collision is possible, the EGPWS computer will override the weather radar display and provide an audible warning.
EGPWS also contains a database of antenna towers, high-tension lines, and other man-made obstacles. As new structures are built, the database must be updated regularly.
Terrain awareness systems save lives. Since 1992, the FAA has required EGPWS on all turbine-powered aircrafts capable of carrying 10 or more passengers. They continue to evolve, leading to greater precision and effectiveness.
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