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Ground Proximity Warning System _GPWS_

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					       Lecture 9:
Ground Proximity
  Warning System
         (GPWS)
            Ground Proximity Warning System
                                    (GPWS)
    Home
           • A Ground Proximity Warning System (GPWS) is
Previous     a type of equipment carried by aircraft to warn
             pilots if they are at a dangerously low altitude
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             and in danger of crashing.
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           • The main purpose of these systems is to
             prevent what is called a Controlled Flight Into
             Terrain (CFIT)
           • CFIT is an accident in which an aircraft crashes
             into the ground, the water, or an obstacle such
             as a mountain or building .
           CCFIT= Controlled Flight Into Terrain

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              Since 1960s, a series of Controlled Flight Into Terrain
                   (CFIT) accidents killed hundreds of people.
                                            CFIT and GPWS

    Home
           • CFIT can be the result of factors such as navigation
             errors, pilot fatigue or disorientation, or reduced
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             visibility owing to weather conditions.
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           • CFIT incidents have been reduced since GPWS entered
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             widespread use in the 1970s.
           • The use of a GPWS in large aircraft is required by law in
             many countries.
           • In the late 1990s improvements were made and the
             system was renamed "Enhanced Ground Proximity
             Warning System“ (EGPWS)
                 Ground Proximity Warning System (GPWS)

    Home   • A GPWS monitors the aircraft's altitude with a radar altimeter,
             which transmits radio waves downward from the plane to
Previous     determine how far away the ground is.
           • Most radar altimeters carried by commercial aircraft are short-
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             range devices with ranges of less than a mile (about 1.6 km).
 Help      • The information from the radar is monitored and analyzed by a
             computer that can identify hazardous situations and trends in the
             data, such as
               – a dangerously rapid rate of descent,
               – dangerously close ground during, or
               – unexpected loss of altitude.
           • If hazardous conditions are detected, the GPWS gives visual and
             audio warning signals to the pilot.
                                      Radar Altimeter

    Home
           • A radar altimeter or simply RA measures
Previous     altitude above the terrain presently beneath an
             aircraft .
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           • This type of altimeter provides the distance
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             between the plane and the ground directly
             below it, as opposed to a barometric altimeter
             which provides the distance above sea level.
                                   HOW GPWS WORKS

    Home   • The heart of the GPWS is a computer processor which
             interprets data from a number of sources such as:
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              – Radar & Navigation Antennas
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              – Gear and flap indicating system
 Help         – Roll attitude input sensor
           • The computer analyzes a number of parameters such
             as, speed, proximity to terrain, and descent rate in
             order to issue appropriate warnings.
           • The pilots are alerted through visual and audio
             warnings by GPWS display inside cockpit.
                              Audio & Visual Warning

    Home
           • Audio & Visual Warnings are provided under any of the
             following conditions:
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              – Excessive rate of descend (“sink rate”)
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              – when closure rate with terrain is too high (“terrain-
 Help           terrain”)
              – loss of altitude after take-off (don’t sink)
              – if the aircraft is too low and slow, with landing gear
                retracted (“too low, gear”)
                                   AURAL WARNINGS

    Home   • Some typical GPWS warnings are:
               – “DESCENT,DESCENT”
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               – “CLIMB, CLIMB”
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               – “SINK RATE”
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               – “TERRAIN, TERRAIN”
               – “DON’T SINK”
               – “TOO LOW, TERRAIN”
               – “TOO LOW GEAR”
               – “PULL UP”
           • These aural warnings will be accompanied by
             illumination of a GPWS display.
                                         GPWS Modes

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           • Mode 1: Excessive Descent Rate..
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           • Mode 2: Excessive Terrain Closure Rate
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           • Mode 3: Altitude Loss After Take-off
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           • Mode 4: Unsafe Terrain Clearance
             MODE 1: Excessive Descent Rate..

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           • Warns of excessive descent rate..
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           • A GPWS warning light will illuminate and “sink
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             rate, sink rate” will be heard.
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           • If the situation is not corrected “whoop,
             whoop, pull up, pull up” will be heard.
            MODE 2: Excessive Terrain Closure Rate

    Home
           • Warns crew when closure rate with terrain is
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             too high.
           • Designed to warn crew when rising terrain is a
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             threat.
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           • “terrain, terrain”
           • “whoop, whoop, pull up, pull up”
           • There may be no change in barometric altitude
             but the radar altitude is decreasing.
           MODE 3: Altitude Loss After Take-off

    Home
            • Warns of loss of altitude after take-off, or go-
Previous      around.
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            • If the aircraft sinks 10 percent of its radar
              altitude “don’t sink” will be heard.
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            MODE 4: Unsafe Terrain Clearance

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           • MODE 4a: if the aircraft is too low and slow, with
             landing gear retracted.
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           • “too low, gear”
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           • If the airspeed is higher the warning will be “too low,
 Help        terrain”
           • MODE 4b: When the gear is selected down, but the
             flaps are still retracted “too low, flaps”
           • This warning can be canceled by the pilot in the event
             of a flapless landing.
                             RECOVERY PROCEDURE

    Home
           • Recovery procedure will vary depending on the
Previous     type of aircraft, but the general response is:
              – Roll level and simultaneously set maximum power.
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              – Slowly pitch up and maintain Vx.
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              – Retract gear and flaps.
              – Continue climb until clear of terrain.
                     Enhanced Ground Proximity
                               Warning System
    Home
           • Enhanced Ground Proximity Warning System
Previous   • A limitation of GPWS is the fact that with radar
             altimeter information only the aircraft is only
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             capable of seeing terrain directly below.
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           • In the case of rapidly rising terrain it may not
             react quick enough to issue a warning in time.
        Enhanced Ground Proximity Warning System

    Home
            • EGPWS corrects this problem by integrating an aircraft
              navigational source into the system.
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            • GPS position in conjunction with a terrain database is
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              used to help predict terrain conflict.
 Help       • Any catalogued man made obstructions are included in
              the database.
            • This type of system can be used to display terrain
              profile to the pilot to improve situational awareness.
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    Home
           • Question 2: FAA defines GPWS as a type of
Previous     ________.
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           a) Terrain awareness and warning system
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           b) Aircraft flight control system
           c) Controlled flight into terrain
           d) Ground proximity warning system
    Home
           • Question 3: ________
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           a) American Airlines Flight 191
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           b) Antarctica1979
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           c) Garuda Fokker F28 crash
           d) Air New Zealand Flight 901
    Home
           • TACA Flight 390Santa Bárbara Airlines Flight
Previous     518Continental Airlines Flight 1404Hewa Bora
             Airways Flight 122
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 Help
    Home
           • In the late 1990s improvements were made and
Previous     the system was renamed "Enhanced Ground
             Proximity Warning System" (________/TAWS).
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           a) Global Positioning System
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           b) Local Area Augmentation System
           c) Ground proximity warning system
           d) Global navigation satellite system
    Home
           • Question 6: The system was now combined
Previous     with a worldwide digital terrain database and
             relies on Global Positioning System (________)
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             technology.
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           • Compass
           • Inertial navigation system
           • Global Positioning System
           • F-15 Eagle

				
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