Subpart E — Others

Section 1 – Terrain Awareness and Warning System (TAWS)

Installation requirements

CS ACNS.E.TAWS.070 Failure mode

ED Decision 2013/031/R

(a) A failure of the TAWS does not disable other protection functions (e.g. windshear or weather radar).

(b) The failure of the GPWS functions, except for power supply failure, input sensor failure, or other failures external to the TAWS functions, does not negatively alter the FLTA function, PDA function, or Terrain Display and vice versa.

(c) Where the terrain information is displayed on a multi-function display, failure of the TAWS does not prevent the normal functioning of other systems using that display.

CS ACNS.E.TAWS.075 Prioritisation scheme

ED Decision 2013/031/R

(See AMC1 ACNS.E.TAWS.075)

The prioritisation scheme for Class A TAWS alerts is compatible and consistent with other alerts including voice call outs from all alerting systems.

AMC1 ACNS.E.TAWS.075 Prioritisation schemes

ED Decision 2013/031/R

TAWS prioritisation schemes should be compliant with the content of Table 2:

Priority

Description

Alert Level

Comments

1

Reactive Windshear Warning

W

 

2

Sink Rate Pull-Up Warning

W

Continuous

3

Excessive Closure Pull-Up Warning

W

Continuous

4

RTC Terrain Warning

W

 

5

V1 Callout

A

 

6

Engine Fail Callout

W

 

7

FLTA Pull-Up Warning

W

Continuous

8

PWS Warning

W

 

9

RTC Terrain Caution

C

Continuous

10

Minimums

A

 

11

FLTA Caution

C

7 s period

12

Too Low Terrain

C

 

13

PDA ‘Too Low Terrain’ Caution

C

 

14

Altitude Callouts

A

 

15

Too Low Gear

C

 

16

Too Low Flaps

C

 

17

Sink Rate

C

 

18

Don’t Sink

C

 

19

Glideslope

C

3 s period

20

PWS Caution

C

 

21

Approaching Minimums

A

 

22

Bank Angle

C

 

23

Reactive Windshear Caution

C

 

Mode 6

TCAS RA (‘Climb’, ‘Descent’, etc)

W

continuous

Mode 6

TCAS TA (‘Traffic, Traffic’)

C

Continuous

Table 2: Alert Prioritization Scheme

Note 1: These alerts can occur simultaneously with TAWS voice callout alerts.

Note 2: W= Warning, C= Caution, A= Advisory.

TAWS internal priority alerting scheme should be compliant with the content of Table 3 below

Priority

Description

1

Sink Rate Pull-Up Warning

2

Terrain Awareness Pull-Up warning

3

Terrain Awareness Caution

4

PDA ‘Too Low Terrain’ Caution

5

Altitude Callouts ‘500’

6

Sink Rate

7

Don’t Sink (Mode 3)

TABLE 3: TAWS Internal Alert Prioritization Scheme

CS ACNS.E.TAWS.080 Pop-up mode

ED Decision 2013/031/R

(See AMC1 ACNS.E.TAWS.080)

(a) If implemented, the design of an automatic pop-up function ensures that:

(1) the terrain information is automatically displayed on all crew member terrain displays, when either a predictive terrain caution or a predictive terrain warning alert occurs;

(2) the TAWS pop-up function is consistent with pop-up weather and traffic alerts;

(3) it is evident that an automatic pop-up has occurred;

(4) the terrain display mode is annunciated on the display;

(5) manual switching back to the original display mode is simple.

AMC1 ACNS.E.TAWS.080 Pop-up mode

ED Decision 2013/031/R

For dual displays installations, when an automatic pop-up mode is provided, the pop-up function should be inhibited if terrain is already presented on at least one display.

If TAWS and the Predictive Windshear System share the same display and an automatic pop-up function is employed, the display priorities indicated in Table 4 are recommended:

Priority

Description

Highest

Terrain Awareness Warning

 

Predictive Windshear Warning

Terrain Awareness Caution

Predictive Windshear Caution

Normal Terrain Display

Lowest

Weather Radar Display

        TABLE 4: Alert display priorities

If the TAWS system provides alerting for obstacle threats, the priority for warning and cautions should be the same as those for terrain.