.  
TAWS module is roughly equivalent to EGPWS,

.  
WXR/PWS module ensures the basic functions (detection of weather, wind shears, turbulence, ground mapping) and introduces a new feature (3D buffer).

WXR

AESS
Control Panel

For any module, each AESU records various parameters for any events that occur during the flight (e.g. TCAS parameters relative to an RA).

7.1.2.1. GROUPS OF FUNCTIONS
The integration highly simplifies the architecture. However, it introduces some new rules in terms of operations. The architecture with two AESUs duplicates each surveillance function.
AESU1  AESU2 
WXR  WXR 
TAWS  TAWS 
XPDR  XPDR 
TCAS  TCAS 
Figure 7-2: AESU groups of functions

Each AESU groups the functions as follows:
- WXR/TAWS,
- TCAS/XPDR.
7.1.2.2. AESS OPERATING MODES
AESS presents three different operating modes:
1.  
Normal mode: one AESU performs all functions. It is the Master AESU. The Master AESU is the AESU with the active WXR/TAWS group,

2.  
Mixed mode: one AESU performs the functions of one group, and the other AESU performs the functions of the other group, with or without failure (e.g. WXR/TAWS on AESU1 and TCAS/XPDR on AESU2),

3.  
Downgraded mode: a failure prevents the performance of all functions despite the redundancy of functions. Refer to examples below.

In the examples below, active functions are framed in green and failed functions are shaded in amber.
WXR TAWS XPDR TCAS AESU1  WXR TAWS XPDR TCAS AESU2 
Figure 7-3: Normal mode  Figure 7-4: Mixed mode

WXR TAWS XPDR TCAS AESU1  WXR TAWS XPDR TCAS AESU2 

WXR TAWS XPDR TCAS AESU1  WXR TAWS XPDR TCAS AESU2 
Figure 7-5: Downgraded mode – Loss Figure 7-6: Downgraded mode – TAWS of WXR alerts remain available via an interconnection with TAWS 2

WXR TAWS XPDR TCAS AESU1  WXR TAWS XPDR TCAS AESU2 

Note: In normal mode, when the aircraft is on ground, the master AESU is:
-
When an odd flight number is entered (e.g. AIB123), AESU1.

-
When an even flight number is entered (e.g. AIB234), AESU2.

7.1.2.3. AESS RECONFIGURATION PRINCIPLES
Two successive faults lead the AESS to operate in downgraded mode. A fault is a loss of a function (e.g. WXR1) or a loss of a group of functions (e.g. WXR/TAWS of AESU2).
Note 1: The TCAS automatically switches to STBY when the XPDR is in STBY or when the ALT RPTG is OFF. Indeed, the TCAS is not able to determine the vertical separation with the intruder. Therefore, the TCAS is not able to evaluate the threat. Refer to 3.1.4 – Collision Threat Evaluation.
Note 2: The TAWS function of one AESU is able to feed the other AESU for TAWS alert generation, when the TAWS function of the other AESU is faulty. Refer to Figure 7-9.
　
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