Civil Aviation Flight University of China,,Ground Proximity Warning System,近地警告系统,Ground Proximity Warning System （GPWS）,,,,Civil Aviation Flight University of China,,,,Despite the significant advances in an aeronautical technology and operational standard of modern airlines, fatal accidents involving airline aircraft continue to occur throughout the world. With few exceptions, most fatalities in airline accidents result from controlled flight into terrain (CFIT). Ground proximity warning systems (GPWS) are used as a method of alerting pilots to abnormal closing rates with terrain that they may otherwise not detect. Bad weather, poor cockpit coordination, and dealing with abnormal situations can distract crews at a time when proximity to terrain presents the greater hazard.,Ground Proximity Warning System （GPWS）,Civil Aviation Flight University of China,,,,,Ground Proximity Warning System （GPWS）,A typical GPWS is a system that computes closure with terrain and then compares that result with acceptable values that have been pre-programmed. Inputs to the GPWS are typically: • Radio altitude; • Airspeed/mach; • Barometric altitude; • Landing gear position; • Flap position; and • Glideslope deviations.,Civil Aviation Flight University of China,,,,,Ground Proximity Warning System （GPWS）,Some modern GPWSs are equipped to provide windshear warning as well. For this function the GPWS must also have inputs of angle of attack from the stall warning computer and sensitive acceleration inputs from the inertial reference system(IRS). Typical warnings provided by a modern GPWS are in the form of aural alerts, where a synthesized voice makes the appropriate aural statement or a buzzer/horn is activated.,Civil Aviation Flight University of China,,,,,Ground Proximity Warning System （GPWS）,The various situations that can initiate a GPWS alert are normally called “modes”. Most modes provide two levels of alert as terrain is approached and safe margins are infringed. When initial limits are exceeded the first warning that is given is usually termed a soft warning (i.e. caution). If the aircraft then gets closer to terrain and exceeds the level set by the system, a hard warning is given. Hard warnings are usually sufficient to wake the dead.,GPWS Alert Modes,Civil Aviation Flight University of China,,,,,,Figure 8.1,Ground Proximity Warning System （GPWS）,MODE 1 Excessive Descent Rate Mode 1 is normally independent of aircraft configuration and provides an alert on the basic of excessive rates of descent at low altitude. In most installations this mode does not become active until below 2,500 ft radio altitude. This mode has inner and outer alert boundaries.,,Civil Aviation Flight University of China,,,,,,Ground Proximity Warning System （GPWS）,Penetration of the outer boundary activates the “PULL UP” warning lights and “SINKRATE, SINKRATE” alert enunciation.,Civil Aviation Flight University of China,,,,,,Ground Proximity Warning System （GPWS）,Penetration of the inner boundary changes the audio message to “WHOOP，WHOOP，PULL UP” which repeats continuously until the inner warning boundary is exited.,,,MODE 1 Excessive Descent Rate,Descent Rate,Radio Altitude,,,Radio Altitude,MODE 1 Excessive Descent Rate,Descent Rate,,,Radio Altitude,MODE 1 Excessive Descent Rate,Descent Rate,,,Radio Altitude,MODE 1 Excessive Descent Rate,Descent Rate,方式1,Civil Aviation Flight University of China,,,,,Ground Proximity Warning System （GPWS）,Figure 8.2,MODE 2 Excessive Terrain Closure Rate Mode 2 provides alerts to help protect the aircraft from impacting the ground when rapidly rising terrain with respect to the aircraft is detected. Mode 2 is based on Radio Altitude and on how rapidly Radio Altitude is decreasing (closure rate). Mode 2 exists in two forms, 2A and 2B.,,Civil Aviation Flight University of China,,,,Ground Proximity Warning System （GPWS）,• MODE 2A Mode 2A is active during climbout, cruise, and initial approach（flaps not in the landing configuration and the aircraft not on glideslope centerline）. If the aircraft penetrates the Mode 2A caution envelope, the aural message “TERRAIN，TERRAIN” is generated and the “PULL UP” warning lights will illuminate.,Civil Aviation Flight University of China,,,,Ground Proximity Warning System （GPWS）,• MODE 2A If the aircraft continues to penetrate the envelope, the aural warning message “Whoop, Whoop, PULL UP” is repeated continuously until the warning envelope is exited.,Civil Aviation Flight University of China,,,,Ground Proximity Warning System （GPWS）,• MODE 2A Upon exiting the warning envelope, if terrain clearance continues to decrease, the aural message “TERRAIN” will be given until the terrain clearance stops decreasing. In addition, the visual alert will remain on until the aircraft has gained 300 feet of barometric altitude, 45 seconds has elapsed, or landing flaps or the flap override switch is activated.,,,Radio Altitude,MODE 2 Excessive Terrain Closure Rate,Closure Rate,,,Radio 。