Enhanced Ground Proximity Warning System
The Enhanced Ground Proximity Warning System (EGPWS) is a further development of the Ground Proximity Warning System . The Federal Aviation Administration recommends the use of the generic term Terrain Awareness and Warning System (TAWS) for such systems. TAWS and EGPWS are often used synonymously. EGPWS is also a product name.
Extended properties compared to GPWS
Terrain Awareness and Display Function (TAD)
This function enables potential conflicts with previous surveys to be identified and shown on a display. For aircraft equipped with EFIS , this is usually the navigation display.
Terrain Clearance Floor (TCF)
Alerts the pilots in the event of the earth's surface approaching dangerously close during the approach. TCF supplements the existing GPWS mode 4.
technology
Basics
EGPWS works with the help of aircraft position, which it receives from either a GPS or inertial navigation system.
The terrain data is stored in a database, the accuracy of the information being highest in the area of airfields, since here there is mainly the risk of a CFIT ( Controlled flight into terrain ). The terrain data was collected during the Shuttle Radar Topography Mission ; This data from the year 2000 depicts a large part of the earth's surface with a horizontal accuracy of 3 arc seconds (90 m on the earth's surface) and 16 meters (vertical). Due to the orbit, the earth could only be measured up to approx. 60 ° north or south. Most of the gaps in the SRTM data have since been filled using stereoscopic images from the Terra satellite.
EGPWS uses this to determine the distances to the earth's surface in four directions:
- Forward
- downward
- on both sides
Reference height
- if the sink rate is more than 1000 feet per minute, the altitude that will be reached in 30 seconds if the rate of descent remains constant
- in other flight conditions: altitude
The flight altitude and the altitude of the terrain are based on the same reference plane. This is not necessarily the sea level: in GPWS mode 4 this can also be the height of the touchdown point.
Danger areas
The area of ± 2000 feet above the reference altitude is divided into intervals, each interval represents a danger area. The area that extends over +2000 feet above the reference altitude is very dangerous.
display
As a rule, only potential dangers are shown on the display. A color / texture is assigned to each danger area (see Basics).
Total losses
So far (as of March 2019) at least four total losses due to CFIT in aircraft equipped with EGPWS have been recorded in civil aviation. In all accidents, the prescribed procedures were not followed by the crews.
- A Boeing 737-400 operated by the Indonesian airline Garuda was lost on landing in Yogyakarta in 2007 after the crew ignored 15 warnings from the system.
- The second accident is the crash of a Tupolev Tu-154 of the Polish Air Force near Smolensk in 2010.
- The third accident was a demonstration flight of a Sukhoi SuperJet 100 . The crew had, in the mistaken assumption that the warnings were false, switched off EGPWS. See Sukhoi Flight 36801 .
- Airblue Flight 202