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GPWS

FOR TRAINING ONLY. DO NOT USE FOR FLIGHT!


OVERVIEW

The purpose of the Ground Proximity Warning System (GPWS) is to warn the flight crew of potentially hazardous situations, such as a collision with terrain.

It detects terrain collision threats and triggers applicable aural and visual indications.

The GPWS includes:

Five basic modes active up to radio height of 2 500 ft.

  1. Excessive rate of descent (Mode 1)

  2. Excessive terrain closure rate (Mode 2)

  3. Altitude loss after takeoff or go-around (Mode 3)

  4. Terrain clearance not sufficient, if not in landing configuration (Mode 4)

  5. Excessive descent below the glide slope (Mode 5).

A predictive GPWS function, based on a GPWS database, to display terrain information.

It can be provided:

• By Honeywell through Enhanced GPWS (EGPWS)

• By ACSS as Ground Collision Avoidance System (GCAS ), through T2CAS or T3CAS.

The predictive GPWS is composed of:

• Mandatory functions such as the Forward Looking Terrain Alerting function

• Optional functions such as the obstacle database.

PRINCIPLE

The GPWS computes the geometric altitude of the aircraft by using:

  • Pressure altitude

  • Radio altitude

  • Temperature

  • Barometric references

  • GPS altitude for predictive GPWS

  • Data from the GPWS database for predictive GPWS

A320 MEMORY ITEMS – GPWS

EGPWS CAUTIONS

“TERRAIN TERRAIN” – “TOO LOW TERRAIN” – “TERRAIN AHEAD” – “OBSTACLE AHEAD”


  • During night or IMC: Simultaneously:

PF Announces…………………………………………..”PULL UP TOGA”

AP………………………………………………………………………OFF

PITCH…………………………………………………………………PULL UP

Pull to full back stick and maintain in that position.

THRUST LEVERS…………………………………………… TOGA

SPEED BRAKES lever…………………………….CHECK RETRACTED

BANK………………………………………… WINGS LEVEL or ADJUST

Aircraft achieve the best climb performance when the wings are as level as possible.


  • During daylight and VMC, with terrain and obstacles clearly in sight:


FLIGHT PATH………………………………………………………ADJUST

Adjust pitch, bank and thrust to silence the alert.

“SINK RATE”

Above 1 000 ft AAL in IMC or above 500 ft AAL in VMC:

FLIGHT PATH………………………………………………………ADJUST

Adjust pitch and thrust to silence the alert.

Below 1 000 ft AAL in IMC or below 500 ft AAL in VMC:


GO-AROUND……………………………………………………… CONSIDER

“DON’T SINK”

FLIGHT PATH………………………………………………………. ADJUST

Adjust pitch and thrust to silence the alert.

TOO LOW GEAR” – “TOO LOW FLAPS”

GO-AROUND………………………………………………………PERFORM

“GLIDESLOPE”

Above 1 000 ft AAL in IMC or above 500 ft AAL in VMC:

FLIGHT PATH………………………………………………………ADJUST

Adjust pitch and thrust to reduce the vertical deviation from the glideslope.

When conditions require a deliberate approach below glideslope:

G/S MODE…………………………………………………………….OFF

Below 1 000 ft AAL in IMC or below 500 ft AAL in VMC:

GO-AROUND……………………………………………………. CONSIDER

GPWS WARNINGS

PULL UP” – “TERRAIN AHEAD PULL UP” – “OBSTACLE AHEAD PULL UP” – “AVOID TERRAIN” – “AVOID OBSTACLE”


Simultaneously:

PF Announces…………………………………………”PULL UP TOGA”

AP………………………………………………………………………. OFF

PITCH……………………………………………………………….PULL UP

Pull to full backstick and maintain in that position.

THRUST LEVERS…………………………………………………TOGA

SPEED BRAKES lever………………………… CHECK RETRACTED

BANK……………………………………….WINGS LEVEL or ADJUST


Aircraft achieve the best climb performance when the wings are as level as possible.

If the “TERRAIN AHEAD PULL UP” or “OBSTACLE AHEAD PULL UP” aural alert triggers, a turning maneuver can be initiated if the flight crew concludes that turning is the safest action.

The PULL UP maneuver must be performed before the turn towards the safe direction, as climbing increases the terrain clearance.


The “TERRAIN AHEAD PULL UP” or “OBSTACLE AHEAD PULL UP” aural alert may be followed by the “AVOID TERRAIN” or “AVOID OBSTACLE” aural alert. In this case, the flight crew must adjust bank as necessary:

– If the alert generates when the wings are level, the aural alert indicates that the obstacles are probably ahead.

– If the alert occurs while the aircraft is turning, the aural alert indicates that the obstacles are probably within the turn trajectory.

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