lecture 9: g round p roximity w arning s ystem ( gpws )
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Lecture 9: G round P roximity W arning S ystem ( GPWS ). G round P roximity W arning S ystem ( GPWS ). Since 1960s, a series of C ontrolled F light I nto T errain (CFIT) accidents killed hundreds of people. - PowerPoint PPT PresentationTRANSCRIPT
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Lecture 9:Ground Proximity
Warning System (GPWS)
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Ground Proximity Warning System (GPWS)
• Since 1960s, a series of Controlled Flight Into Terrain (CFIT) accidents killed hundreds of people.
• Thus, a device called a ground proximity warning system (GPWS) had been used to overcome CFIT problem.
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Controlled Flight Into Terrain
• CFIT describes about aircraft collision, under pilot control, inadvertently flies into terrain, an obstacle, or water.
• The pilots are generally unaware of the danger until it is too late.
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Korean Airlines Boeing 747: CFIT while attempting to land in heavy rain: 228 of 254
killed (Aug. 6, 1997)
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Ground Proximity Warning System (GPWS)
• A Ground Proximity Warning System (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground or an obstacle.
• GPWS has greatly reduced the number of CFIT incidents.
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HOW GPWS WORKS
• The heart of the GPWS is a computer processor which interprets data from a number of sources such as radar, gear and flap indicating system & roll attitude input sensor.
• The computer analyzes a number of parameters including aircraft configuration, speed, proximity to terrain, and descent rate in order to issue appropriate warnings.
• The pilots are alerted through aural & visual warnings by GPWS display inside cockpit.
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Aural & Visual Warning
• Aural & Visual Warnings are provided under any of the following conditions:
– Excessive rate of descend (“sink rate”)
– when closure rate with terrain is too high (“terrain-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”)
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AURAL WARNINGS
• Some typical GPWS warnings are:– “DESCENT,DESCENT”– “CLIMB, CLIMB”– “SINK RATE”– “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.
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MODE 1
• Warns of excessive descent rate..
• A GPWS warning light will illuminate and “sink rate, sink rate” will be heard.
• If the situation is not corrected “whoop, whoop, pull up, pull up” will be heard.
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MODE 2
• Warns crew when closure rate with terrain is too high.
• Designed to warn crew when rising terrain is a threat.
• “terrain, terrain”• “whoop, whoop, pull up, pull up”• There may be no change in barometric altitude
but the radar altitude is decreasing.
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MODE 3
• Warns of loss of altitude after take-off, or go-around.
• If the aircraft sinks 10 percent of its radar altitude “don’t sink” will be heard.
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MODE 4
• MODE 4a: if the aircraft is too low and slow, with landing gear retracted.
• “too low, gear”
• If the airspeed is higher the warning will be “too low, 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.
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MODE 5
• Warns the crew of glideslope deviations.
• When the aircraft receives a valid glideslope and sinks two dots below “glideslope” will be heard.
• The warning will continue with increasing intensity if the problem is not corrected.
• This warning may be canceled by the pilot.
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RECOVERY PROCEDURE
• Recovery procedure will vary depending on the type of aircraft, but the general response is:– Roll level and simultaneously set maximum power.
– Slowly pitch up and maintain Vx.
– Retract gear and flaps.
– Continue climb until clear of terrain.
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Enhanced Ground Proximity Warning System
• Enhanced Ground Proximity Warning System• A limitation of GPWS is the fact that with radar
altimeter information only the aircraft is only capable of seeing terrain directly below.
• In the case of rapidly rising terrain it may not react quick enough to issue a warning in time.
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Enhanced Ground Proximity Warning System
• EGPWS corrects this problem by integrating an aircraft navigational source into the system.
• GPS position in conjunction with a terrain database is used to help predict terrain conflict.
• 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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