A320 EGPWS

Question 1

What are the GPWS two categories of operation?

Answer 1

Basic and predictive

Question 2

How many modes of basic GPWS are there?

Answer 2

5

Question 3

Basic GPWS modes are active below what altitude?

Answer 3

2500’ RA

Question 4

What are the different modes of basic GPWS?

Answer 4

Mode 1: Excessive descent rate
Mode 2: Excessive terrain closure rate
Mode 3: Altitude loss after takeoff or go-around
Mode 4: Unsafe terrain clearance
Mode 5: Excessive deviation below glideslope

Question 5

True or false: Most GPWS failures effect either the basic modes or the predictive modes, but not both, as they’re nearly completely independent systems?

Answer 5

True

Question 6

If the TERR button on the GPWS overhead panel is pushed OFF, which modes are inhibited?

Answer 6

The predictive modes are inhibited, but not the basic modes

Question 7

If the SYS button on the GPWS overhead panel is pushed OFF, which modes are inhibited?

Answer 7

The basic modes are inhibited, but not the predictive modes

Question 8

Does the volume of the GPWS aural warnings depend on the position of the speaker volume knob?

Answer 8

No. It’s always played at max volume regardless of the knob position.

Question 9

When will the GPWS visual and aural alerts go away after they’ve been activated?

Answer 9

When the aircraft reaches a safe altitude the alerts automatically go away. They can also be manually cancelled by pressing the PULL UP GPWS push buttons above the ND brightness knobs on either the FO’s or Captains side.

Question 10

What happens if you push the PULL UP GPWS button while on the ground?

Answer 10

It tests the GPWS system. If the button is held down continuously, all of the aural warnings and indications are triggered. When it’s only pressed briefly, only some of the warnings and indications are triggered.

Question 11

What aural warnings are heard for a MODE 1: excessive descent rate warning?

Answer 11

“Sink rate”. If the descent rate continues you’ll hear “Pull up”

Question 12

What’s the difference between basic modes or 2A and 2B?

Answer 12

Mode 2A is active during climb, cruise, and initial approach, when the flaps are not in the landing position and the landing gear is extended

Mode 2B is active during approach and 60 seconds after takeoff

Question 13

What triggers Mode 2: Excessive terrain closure rate alerts?

Answer 13

Alerts are triggered based on a predetermined decreasing radio altimeter rate

Question 14

How many envelopes are there for Mode 2: Excessive terrain closure rate? What aural warnings are heard for penetrating them?

Answer 14

There are two envelopes.

When the first envelope (further from terrain) is penetrated you’ll get the “terrain, terrain” warning and the GPWS lights will illuminate.

When the second envelope (closer to terrain) is penetrated you’ll get the “pull up, pull up” warning and the PULL UP lights will illuminate

Question 15

When does Mode 3: altitude loss after takeoff trigger?

Answer 15

When the GPWS detects a sink rate after takeoff or go-around with the landing gear or flaps not in the landing configuration, a caution in generated. “don’t sink”

Question 16

How many forms of Mode 4: Unsafe terrain clearance are there? What are they?

Answer 16

3 forms. Form 4A, 4B, and 4C.

Question 17

When is Mode 4A active?

Answer 17

It’s active during cruise and approach if the landing gear is not extended

Question 18

What the purpose of Mode 4A: Unsafe terrain clearance (during cruise and approach with gear up), if we already have a different mode that measures unsafe terrain closure rates?

Answer 18

It’s intended to provide alerting for inadvertent flight into terrain where the terrain is not rising significantly or the aircraft is no descending significantly

Question 19

When is Mode 4B active?

Answer 19

It’s active during cruise and approach when the landing gear is down and the flaps are not in the landing configuration

Question 20

What warning will you hear if a Mode 4B alert is triggered?

Answer 20

“Too low, flaps”

Question 21

What aural warning will you hear if a Mode 4A alert is triggered?

Answer 21

First you’ll hear, “too low, terrain”. If you continue descending you’ll hear, “too low, gear”

Question 22

When is Mode 4C active?

Answer 22

It’s active during takeoff when the landing gear is up, or the flaps are not in the landing configuration

Question 23

If after takeoff the aircraft is climbing, but the terrain beneath the aircraft is also rising, what GPWS warning might you get?

Answer 23

Mode 4C, “too low, terrain”

Question 24

What aural warning would you get if Mode 5 is triggered?

Answer 24

“Glideslope”

Question 25

Under what general circumstances may you need to manually deactivate some of the GPWS modes?

Answer 25

Whenever an abnormal situation requires aircraft operation within the boundaries of the GPWS alerting envelope. E.g., gear up landing, landing in an abnormal flap configuration, etc.

Question 26

What is the general difference between the basic modes and predictive modes of GPWS?

Answer 26

Basic modes generally rely on aircraft configuration and radio altitude to trigger alerts. The basic modes do not know where in the world you actually are, only how high above terrain you are.

Predictive modes actually DO know where you are based on GPS. It knows where terrain is, not based on radio altitude, but by a terrain database that includes both natural terrain and manmade obstacles. Predictive modes are NOT dependent on aircraft configuration. Alerts will be generated regardless of whether the aircraft is in the landing configuration or not. Additionally, predictive modes will actually look ahead of your path even while turning. If high terrain and obstacles are outside of your turning area, they will not trigger an alert.

Question 27

Is the TERR ON ND push button part of the basic or predictive GPWS?

Answer 27

Predictive GPWS. Basic GPWS does not have a terrain database like the predictive GPWS does.

Question 28

What message will you get if you have the ND range set to either 160nm or 320nm and a terrain alert is triggered?

Answer 28

You’ll get a “TERR REDUCE RANGE” message on the ND in red (for a warning) or amber (for a caution)

Question 29

What message will you get if you’re in PLAN mode on the ND and you get a terrain alert?

Answer 29

You’ll get a “TERR CHANGE MODE” message on the ND in red (for a warning) or amber (for a caution).

Question 30

What should you do to avoid getting spurious terrain warning when your navigation accuracy is low?

Answer 30

Select the TERR push button to OFF on the GPWS panel. This inhibits the predictive modes only.

Question 31

When will the predictive GPWS give you a terrain caution?

Answer 31

When it determines that the aircraft is approximately 60 seconds away from hazardous terrain

Question 32

What does solid amber mean on the terrain display following a predictive GPWS terrain caution?

Answer 32

The solid amber areas on the terrain map are areas where the predictive GPWS has determined you’ll penetrate the caution area.

Question 33

When do predictive terrain cautions go away?

Answer 33

When the GPWS determines that the terrain no longer poses a threat

Question 34

When will the predictive GPWS give you a terrain warning?

Answer 34

When the predictive GPWS determines you’re within 30 seconds of hazardous terrain

Question 35

What aural warnings do you get for a predictive GPWS terrain caution, and terrain warning?

Answer 35

Terrain caution: “terrain ahead”
Terrain warning: “terrain ahead, pull up”

Question 36

What do the solid red terrain areas on the ND represent during a predictive GPWS terrain warning?

Answer 36

Areas where the predictive GPWS has determined the aircraft will penetrate the warning area

Question 37

What manmade obstacles are not included in the obstacle database?

Answer 37

Obstacles 100’ high or shorter.

Question 38

When will you get a predictive GPWS obstacle caution? Warning?

Answer 38

Caution: when you’re within 60 seconds of hazardous obstacles
Warning: when you’re within 30 seconds of hazardous obstacles