CHANNEL SELECTION
Channel selection determination.
Each ECU channel determines whether to be in the active state, or the standby state, based on a comparison of its health with that of the cross channel.
The channel with the better health status becomes the active channel. When both channels are of equal health, the channel selection state remains as the previous selection state.
A hierarchy is assigned to the list of possible faults that could lead to a channel switch.
When a single fault occurs, the channel with lower priority faults (if any) becomes active. If the same equal priority fault(s) exist on both channels, no switching occurs.
The internal logic of the ECU ensures that each channel achieves an active status on an alternating basis. An NVM flag is assigned to identify the channel that is presently active.
The last-active flag is only set when N2 becomes less than 35% speed.
The NVM last-active flag becomes the lowest priority status in channel health determination.
The occurrence of any higher priority faults overrides the last-active flag to ensure the healthiest channel is made the active channel.
EFFECTIVITY
ALL CFM56-5B ENGINES FOR A319-A320-A321
CFMI PROPRIETARY INFORMATION ARCHITECTURE
FAULT DETECTION
& ANNUNCIATION Page 10
Nov 02
CFM56-5B TRAINING MANUAL
NO. HEALTH STATUS DISCRETE DESCRIPTION
1 GROUP 1 FAULT (SERIOUS ECU INTERNAL FAULT)
2 FMV LOOP FAULT
3 VSV LOOP FAULT
4 VBV LOOP FAULT
5 LATCHED CHANNEL CCDL SERIAL FAULT
6 SAV WRAPAROUND FAULT
7 TRPV WRAPAROUND FAULT
8 TR INDETERMINATE STATE FAULT
9 TRDV WRAPAROUND FAULT
10 BSV WRAPAROUND FAULT
11 SPARE
12 FRV 1 / FRV 2 WRAPAROUND FAULT
13 HPTC WRAPAROUND FAULT
14 TBV WRAPAROUND FAULT
15 LPTC WRAPAROUND FAULT
16 NVM FAULT
17 ARINC OUTPUT WRAPAROUND FAULT
18 ALTERNATOR WINDING FAULT
19 LAST ACTIVE CHANNEL FLAG
CTC-231-005-00 FAULT HIERARCHY
EFFECTIVITY
ALL CFM56-5B ENGINES FOR A319-A320-A321
CFMI PROPRIETARY INFORMATION ARCHITECTURE
FAULT DETECTION
& ANNUNCIATION Page 11 Nov 02
CFM56-5B TRAINING MANUAL
CHANNEL SELECTION Output driver disconnect.
Once the active channel is determined, each channel executes the output driver disconnect logic to assign the respective active status for the disconnect relays.
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