Commercial Aircraft
The system monitors an aircraft's height above ground as determined by a radio altimeter. A computer then keeps track of these readings, calculates trends, and will warn the captain with visual and audio messages if the aircraft is in certain defined flying configurations ("modes").
The modes are:
- Excessive descent rate ("SINK RATE" "PULL UP")
- Excessive terrain closure rate ("TERRAIN" "PULL UP")
- Altitude loss after take off or with a high power setting ("DON'T SINK")
- Unsafe terrain clearance ("TOO LOW – TERRAIN" "TOO LOW – GEAR" "TOO LOW – FLAPS")
- Excessive deviation below glideslope ("GLIDESLOPE")
- Excessively steep bank angle ("BANK ANGLE")
- Windshear protection ("WINDSHEAR")
Traditional GPWS does have a blind spot. Since it can only gather data from directly below the aircraft, it must predict future terrain features. If there is a dramatic change in terrain, such as a steep slope, GPWS will not detect the aircraft closure rate until it is too late for evasive action.
In the late 1990s improvements were made and the system was renamed "Enhanced Ground Proximity Warning System" (EGPWS/TAWS). The system was now combined with a worldwide digital terrain database and relies on Global Positioning System (GPS) technology. On-board computers compared its current location with a database of the Earth's terrain. The Terrain Display now gave pilots a visual orientation to high and low points nearby the aircraft.
EGPWS software improvements were focused on solving two common problems; no warning at all, and late or improper response.
Read more about this topic: Ground Proximity Warning System
Famous quotes containing the word commercial:
“The home is a woman’s natural background.... From the beginning I tried to have the policy of the store reflect as nearly as it was possible in the commercial world, those standards of comfort and grace which are apparent in a lovely home.”
—Hortense Odlum (1892–?)