19ground proximity warning system.ppt
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GROUND PROXIMITY GROUND PROXIMITY WARNING SYSTEMWARNING SYSTEM
GPWSGPWS
Korean Airlines Boeing 747 CFIT while Korean Airlines Boeing 747 CFIT while attempting to land in heavy rain: 228 of attempting to land in heavy rain: 228 of
254 killed (Aug. 6, 1997) GPWS equipped254 killed (Aug. 6, 1997) GPWS equipped
Realvideo animation of Flight 801 descent
CFITCFIT
• Controlled flight into terrain.• Prior to the widespread implementation of
GPWS, CFIT was an all too common occurrence.
• CFIT accidents involve a normally operating aircraft which contacts the ground due to loss of situational awareness, or other pilot error.
• GPWS has greatly reduced the number of these incidents.
GPWSGPWS
• GPWS is a system developed to help prevent CFIT accidents.
• In the event of a loss of situational awareness by the crew GPWS is a last resort lifeline to warn of approaching terrain.
• The pilots are alerted through aural and visual warnings and in the case of EGPWS a visual display.
HOW IT WORKSHOW IT WORKS
• The heart of the GPWS is a computer processor which interprets data from a number of sources:– Radar altimeter– Air data computer– UHF Nav receiver– Gear and flap indicating system– Roll attitude input sensor
HOW IT WORKSHOW IT WORKS
• The computer analyzes a number of parameters including aircraft configuration, speed, proximity to terrain, and descent rate in order to issue appropriate warnings.
• If the aircraft is in landing configuration at approach speed and approaching the ground it is deemed a warning is unnecessary.
AURAL WARNINGSAURAL WARNINGS
• Some typical GPWS warnings are:– “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 annunciator.
• In the event of a “PULL UP” warning a recovery procedure must be initiated.
MODE 1MODE 1
• Warns of excessive descent rate.
• If the aircraft is less than 2500AGL, as determined by the radar altimeter, and is losing altitude too quickly.
• 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.
MODE 2MODE 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.
MODE 3MODE 3
• Warns of loss of altitude after take-off, or go-around.
• Within the first 1000 AGL if the aircraft starts to sink rather than climb.
• If the aircraft sinks 10 percent of its radar altitude “don’t sink” will be heard.
MODE 4MODE 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.
MODE 5MODE 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.
RECOVERY PROCEDURERECOVERY 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.
• NOTE: in VMC conditions terrain may be avoided visually.
ADVISORY CALLOUTSADVISORY CALLOUTS
• GPWS is capable of advisory callouts as an aid to normal operations:– “GLIDESLOPE” two dots below glideslope– “FIVE HUNDRED” 500 AGL on non-precision
approach– “MINIMUMS, MINIMUMS” upon reaching
radar altimeter selected decision height.
EGPWSEGPWS
• 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.
• 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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