GPWS

Question 1

EGPWS

Answer 1

Newer version and is able to predict terrain ahead using a 3D database

Older versions could only see directly below using RA

Question 2

A/c requiring a class A TAWS

Answer 2

Req for turbine powered a/c with a TOM of more than 5,700kg and can carry more than 9 PAX

Question 3

A/c requiring a class B TAWS

Answer 3

Piston a/c with a TOM of more than 5700kg and carries more than 9 PAX

Question 4

Basic inputs to the TAWS

Answer 4

ADC
Radio altimeter
A/c configuration
ILS/MLS - g/s deviation

EGPWS - req a terrain database for looking ahead

Question 5

When is the TAWS system active

Answer 5

Between 50ft and 2450ft

Question 6

When can you use the self test on the TAWS

Answer 6

Can be tested in the ground or in the air above 1,000ft

Question 7

What can you inhibit manually from the TAWS

Answer 7

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

Question 8

Different warnings/ alerts

Answer 8

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

Question 9

What should you do with every GPWS warning

Answer 9

Report it to the aviation authority using a GPWS form

Question 10

Mode 1 - TAWS

Answer 10

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”

Question 11

Mode 2 - TAWS

Answer 11

Excessive terrain closure

Inputs - Rod, rad alt, airspeed

Alert = “terrain terrain” - initial penetration area

Warning = “pull up” - inner boundary

Question 12

Mode 2a - TAWS

Answer 12

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

Question 13

Mode 2b - TAWS

Answer 13

Flaps in the l/d config

Operates up to 789ft and if the rate of closure is 3000fpm or greater

Question 14

Mode 3 TAWS

Answer 14

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

Question 15

Mode 4 TAWS

Answer 15

Unsafe terrain clearance

Inputs - Baro, rad alt, a/c config, airspeed

Question 16

Mode 4a TAWS

Answer 16

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

Question 17

Mode 4b TAWS

Answer 17

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”

Question 18

TCF

Answer 18

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

Question 19

Mode 5 TAWS

Answer 19

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

Question 20

Mode 6 TAWS

Answer 20

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

Question 21

Mode 7 - TAWS

Answer 21

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

Question 22

40 - 60secs before impact GPWS

Answer 22

“Caution terrain” and sold amber terrain

Question 23

20-30 secs before impact

Answer 23

“Terrain, terrain. Pull up!” And pull up on PFD

Solid red on the ND

Question 24

RAAS

Answer 24

Prevents r/y incursions on r/y and taxiways

Provides an audible warning or approaching r/y and identifier

Question 25

TAWS colour coding

Answer 25

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