Ground Proximity Warning System
In one with a ground proximity warning system (dt .: ground proximity warning system equipped) aircraft are in low altitude below 762 m radio altitude (2,500 ft ) from various data criteria derived in below which an alarm in the cockpit is triggered.
history
The system was developed at Honeywell International in the late 1960s under the direction of C. Donald Bateman , introduced in 1975 and was a response to so-called CFIT accidents in which an otherwise fully functional aircraft was flown "into the ground". The GPWS works in an operating range from 9 m to 747 m above ground (radar height). Five different conditions ( modes , operating modes) lead to warnings when different limits are exceeded.
GPWS modes
In all modes, with the exception of mode 6 , warnings are issued both audibly and visually:
- Mode 1 , Dangerous descent rate - English excessive rate of descent
- Warning message: "SINK RATE" "PULL UP"
- Radar height and barometrically measured rate of descent are evaluated. The lower the radar height, the smaller the tolerance of the maximum permitted rate of descent.
- Mode 2 , Dangerous Ground proximity Rate - English excessive terrain closure rate
- Warning message: "TERRAIN" "PULL UP"
- Warning of rapidly rising terrain. The altitude and altitude change rate derived from the radar altimeter are taken into account . The lower the altitude, the smaller the tolerance of the maximum permitted altitude change rate. If the flaps are in the landing configuration, the warning below 60 m is switched off.
- Mode 3 , altitude loss after takeoff or go-around - English altitude loss after take-off or go-around
- Warning message: "DON'T SINK"
- The radar altitude and the barometric altitude loss are evaluated after activation of the TOGA mode. The lower the radar altitude, the smaller the tolerance of the maximum permitted altitude loss.
- Mode 4 , Unsafe ground clearance and no landing configuration - English unsafe terrain clearance and not in landing configuration
- Warning message: "TOO LOW - TERRAIN" "TOO LOW - GEAR" "TOO LOW - FLAPS"
- The warning criterion is derived from the radar altitude, airspeed and the position of the landing gear and the flaps.
- Mode 5 , deviation approach ILS glide path under the - English deviation below glideslope
- Warning message: "GLIDESLOPE"
- The warning criterion is formed from the radar height and the deviation below the glide path . The lower the radar height, the smaller the tolerance of the maximum permitted glide path deviation.
- Mode 6 , Notes - English advisories
- Depending on how the GPWS is programmed, radar altitude announcements will sound, for example “fifty”, “thirty”; as well as "minimums" when reaching the decision height. Optional is also the announcement "bank angle" she sounds when the bank angle exceeds 35 degrees.
- Mode 7 , wind shear - English windshear
- Warning message: "WINDSHEAR"
- Trend comparison between the IAS from the Air Data Computer and the GS from the IRS : Fast IAS change versus slow GS change indicates wind shear. A rapid IAS decrease indicates a negative wind shear (tail wind gust), a rapid IAS increase indicates a positive wind shear, which the GPWS - if programmed - also recognizes. The GPWS also detects excessive vertical accelerations in the IRS (down wind, microburst).
Flow of information GPWS
The GPWS processes signals from the radio altimeter (altitude above ground), from the ADIRS (Air Data and Inertial Reference System: pressure measurements and inertial navigation, from this the barometric altitude , the vertical speed and the speed), from the instrument landing system (ILS, from which the storage of the glide path), the management computer Flight and Guidance computer , from the chassis (extended or not) of the flap (position).
An additional "Stable" signal from the Flight Warning Computer stops all GPWS spending because the response to a stall has priority. In addition, individual modes can be suppressed using an "Inhibit" switch.
Man-machine interface
GPWS alarms are output as an auditory display (tones and speech), and also as a visual display (text message and indicator light) in the field of vision of each pilot. No exact measured values (the altitude or the rate of descent) are given, the alarms attract attention and increase awareness of the situation . It is operated with buttons in the overhead panel.
Further development
Using a terrain database and positioning with satellites , the system was expanded to become the Enhanced Ground Proximity Warning System .