GPWS Flashcards
EGPWS
Newer version and is able to predict terrain ahead using a 3D database
Older versions could only see directly below using RA
A/c requiring a class A TAWS
Req for turbine powered a/c with a TOM of more than 5,700kg and can carry more than 9 PAX
A/c requiring a class B TAWS
Piston a/c with a TOM of more than 5700kg and carries more than 9 PAX
Basic inputs to the TAWS
ADC
Radio altimeter
A/c configuration
ILS/MLS - g/s deviation
EGPWS - req a terrain database for looking ahead
When is the TAWS system active
Between 50ft and 2450ft
When can you use the self test on the TAWS
Can be tested in the ground or in the air above 1,000ft
What can you inhibit manually from the TAWS
Gear/flap inhibit - “too low flap/gear” when deliberately l/d in a non standard config
Terrain inhibit - inhibits the terrain look ahead function - for tricky approaches which require flying close to terrain
Different warnings/ alerts
Alert is a caution which is preceded by a warning which requires immediate crew response
Genuine - the GPWS provides a warning in accordance with the technical system
Nuisance - as above but pilot flying does no action as they accept a safe procedure
False - the system has malfunctioned and gives a false warning
What should you do with every GPWS warning
Report it to the aviation authority using a GPWS form
Mode 1 - TAWS
Excessive barometric descent rate
Take into account baro and Radio altimeter to measure rod
Alert = “sink rate, sink rate” - repeated every 1.5 secs Warning = “pull up”
Mode 2 - TAWS
Excessive terrain closure
Inputs - Rod, rad alt, airspeed
Alert = “terrain terrain” - initial penetration area
Warning = “pull up” - inner boundary
Mode 2a - TAWS
Flaps not in l/d config
Upper limit = speeds less than 220kts and 1650ft
When the a/c speed increases over 220kts - warning boundaries expand to 2450ft
Mode 2b - TAWS
Flaps in the l/d config
Operates up to 789ft and if the rate of closure is 3000fpm or greater
Mode 3 TAWS
Height loss after T/o or GA
Inputs - Baro, rad alt, a/c config
Armed between 30 - 700ft but wont arm until 200 ft on the aprch
Alert = “Don’t sink”
Warning = “Pull up” - when height loss = or exceeds 10% of the RA
Mode 4 TAWS
Unsafe terrain clearance
Inputs - Baro, rad alt, a/c config, airspeed
Mode 4a TAWS
Unsafe terrain clearance - gear retracted
Armed when passing 700ft
Alert = “Terrain, terrain”
Warning = “Too low gear” - below 500ft and a speed of less than 190kts - when the a/c is sped up to over 190kts - warning threshold increases to 1000ft
Mode 4b TAWS
Unsafe terrain clearance - gear extended
Below 159kts and 245ft = “Too low, flaps”
Above 159kts and between 245 to 1000ft = “Too low, terrain”
Warning = “Pull up”
TCF
EGPWS generates a Terrain clearance floor around the active r/y, longer than 3500ft using a terrain database
Function of the rad alt and position with respect to the r/y regardless of a/c config
Outer limit - up to 700ft
Mode 5 TAWS
Excessive descent below g/s
Armed when the g/s signal is received from the captains ILS receiver and the a.c is at or below 1000ft
Soft alert - below 1000ft + 1.3 dots deviation = “Glideslope, Glideslope”
Hard alert - below 300ft - 2 dots deviation = “GLIDESLOPE, GLIDESLOPE!” - louder call
Mode 6 TAWS
Advisory call outs - rad alts and excessive bank angle
Inputs - rad alt, height bug, IRS (for bank angle)
Bank angle - 35 to 40* above 150ft
10* within 30ft to prevent wing tip and engine pod damage
Mode 7 - TAWS
Windshear alerting
Armed from rotation/missed aprch to 1500ft ra
aprch - 1500ft to 10ft
Inputs - airspeed, GS, rod/roc, AoA, changes to h/wind and t/wind
Windshear only gives warnings, no alerts
40 - 60secs before impact GPWS
“Caution terrain” and sold amber terrain
20-30 secs before impact
“Terrain, terrain. Pull up!” And pull up on PFD
Solid red on the ND
RAAS
Prevents r/y incursions on r/y and taxiways
Provides an audible warning or approaching r/y and identifier
TAWS colour coding
Red = 2000ft or greater above the a/c elevation Yellow = between 500 to 2000ft above a/c elevation Green = 500 ft below the a/c elevation Black = 2000 ft below the a/c elevation
