Threshold Study Of Terrain Awareness And Warning System

Terrain Awareness and Warning System (TAWS) provides protectionagainst controlled flight into terrain (CFIT) as well as wind shear, whichplays an important role in the flight safety. Visual and aural warnings ofimpending windshear are provided via computer algorithms that can detectan increase in aircraft performance (a precursor to wind shear) and adecrease in aircraft performance (indicative of entry into wind shear).This paper focuses on three parts: functions and alerting algorithmintroduction of the classic TAWS products; modeling and simulating foreach mode to get alerting thresholds and curves; build test cases based onTSO-151B to verify if the curves can meet the design requirements.Honeywell’s Enhanced Ground Proximity Warning System (EGPWS)serves as an independent monitor of an aircraft’s position relative tosurrounding terrain. It uses aircraft inputs such as position, attitude, airspeed and glideslope, which along with internal terrain, obstacles, andairport databases predict a potential conflict between the aircraft’s flightpath and terrain or an obstacle. The ACSS TAWS+function is contained ina module called the ground collision avoidance module. The GCAMprovides fully predictive alerts and warnings to prevent controlled flightinto terrain accidents, as well as all the reactive GPWS capabilitiesrequired by TSO C151b.Based on the principle of TAWS six alerting modes, this paperestablishes the models of nominal trajectories and avoidance trajectories.Two statistical parameters of incident rate and un-alerting incident rate areaccumulated in a large number of flight events, to evaluate theperformance of the thresholds. A method based on SOC is presented to get the alert envelope. The simulation results are identical to the practicalenvelope, which show the correctness and effectiveness of our models.According to the test environment requirements of TSO-151b, thispaper sets the initial state of the aircraft with a digital simulating system togenerate highly really hazard-scenes. Then get the avoidance flighttrajectory to verify if the curves can meet the design requirements, whichshow the correctness and effectiveness of the models and curves.