AlliedSignal's EGPWS Explored



Farnborough, September 5 -- AlliedSignal showed off its Enhanced Ground Proximity Warning System today after an announcement earlier this week about American Airlines $20 million order to retrofit their entire fleet.

The AlliedSignal EGPWS contains a worldwide terrain database. The system reads information supplied by other systems on board the aircraft, such as GPS or FMS, and displays surrounding terrain below, at or above the aircraft's altitude. The system will also sound an audible warning if the aircraft's projected flight path will take it too close to terrain.

Traditional GPWS systems track trend information from a radio altimeter. These systems will sound a warning up to 30 seconds away from terrain. The implementation of GPWS systems has reduced accidents attributed to controlled flight into terrain (CFIT), but only provide audible warnings. Pilots have no visual display to confirm terrain details and are limited to information provided by other instruments. CFIT accidents have usually happened during poor visibility conditions. The enhanced system displays the surrounding terrain up to 320 miles away, from its database memory, and will provide audible warning up to 60 seconds from potential impact.

The visual display presents terrain details on the aircraft's weather radar display or electronic flight instrument system in one of three colors, depending on proximity. Green terrain is below the aircraft, yellow is above, and red is well above. Pixel resolution also gets denser as the height of the terrain increases. If the system issues an alert, the terrain that poses a threat is shown as a solid block of yellow or red.

An AlliedSignal spokesman suggested the EGPWS could have made a difference in both the crash in Cali and the plane of Secretary of Commerce Ron Brown. In the former incident, the pilot would have seen the walls of the valley on either side, rather than after banking the aircraft. This visual confirm- ation of terrain likely would have prevented him from taking the action which put the aircraft on a collision course. The EGPWS could have provided twice, three times or even four times the warning time for both pilots.

See related story in Wednesday's Farnborough Edition.


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