The Flight Warning Computer (FWC) computes flight phases in the Airbus A320 family aircraft. These are numbered from 1 to 10. A flight phase refers to a specific period within a flight.
The Airbus A320 aircraft is equipped with two Flight Warning Computers (FWCs), which are key components of the Flight Warning System. They enable the crew to monitor the main aircraft equipment behavior and detect dangerous configurations through audio and visual devices, as well as two ECAM display units. The FWCs also provide the appropriate corrective actions.
Learn More: Complete Guide to Flight Phases
FWCs compute the flight phases from the configuration signals they acquire, and they control through DMC which aircraft synoptic diagrams are to be displayed in normal mode (according to the current flight phase). All the calculations and processing are controlled by a MONITOR part of FWC which manages the results of the calculations.
To improve its operational efficacy, the FWC inhibits some warnings and cautions for certain flight phases. It does so to avoid alerting the pilots unnecessarily at times when they have high workloads, such as during takeoff or landing. In these two phases, the DU displays magenta memos: “T.O. INHIBIT” (flight phases 3, 4, and 5), and “LDG INHIBIT” (flight phases 7 and 8).
As soon as the FWC detects a failure, and if there is no flight phase inhibition active, the EWD displays the title of the failure and actions that the flight crew must perform.
Note: These flight phases are different from and independent of the ones that the FMGC uses.
The 10 Flight Phases of A320
Here are the flight phase descriptions of the A320 Family aircraft:
Phase 1 • Phase 2 • Phase 3 • Phase 4 • Phase 5 • Phase 6 • Phase 7 • Phase 8 • Phase 9 • Phase 10
Flight phase 1
Flight phase 1: from Elec power ON to 1st engine start
- Aircraft on ground,
- Engine 1 and 2 not running,
- Aircraft not in flight phase 10.
Flight phase 2
Flight phase 2: from 1st engine start to 1st engine take-off power
- Aircraft on ground,
- Aircraft speed below 80kt,
- Engine 1 or 2 running,
- Engine 1 or 2 not at take-off power.
Flight phase 3
Flight phase 3: from 1st engine take-off power to speed increasing to 80kt
- Aircraft on ground,
- Aircraft speed below 80kt,
- Engine 1 or 2 at take-off power.
Flight phase 4
Flight phase 4: from speed up to 80kt to lift off
- Aircraft on ground,
- Engine 1 or 2 at take-off power,
- Aircraft speed greater than 80kt.
Flight phase 5
Flight phase 5: from lift off to 1500ft (climb)
- Aircraft in flight,
- Engine 1 or 2 at take-off power,
- Radio Altitude not failed,
- Radio Altitude < 1500ft.
Note that this flight phase is limited to 2 minutes, then the flight phase automatically becomes 6 if the aircraft is still on airborne.
Flight phase 6
Flight phase 6: from 1500ft to 800ft (cruise)
- Aircraft in flight,
- Aircraft not in flight phase 5 (see above conditions),
- Aircraft not in flight phase 7 (see below conditions),
Flight phase 7
Flight phase 7: from 800ft to touch down (descent)
- At least one RA is available (i.e. not invalid data),
- Engine 1 or 2 not at take-off power,
- RA altitude < 800 ft (with 1500 ft previously recorded during the flight),
Note 1: the flight phase 7 cannot last more than 3 minutes. After that, the flight phase automatically becomes 6 if the aircraft is still airborne.
Note 2: the flight phase 7 is computed as soon as RA altitude is below 800 ft. But the flight phase 7 remains active until aircraft is on ground, or until aircraft altitude is above 1500 ft again.
Flight phase 8
Flight phase 8: from touch down to speed reducing to 80kt
- Aircraft on ground,
- Aircraft speed up to 80kt,
- Engine 1 or 2 not at take-off power.
Flight phase 9
Flight phase 9: from speed = 80kt to 2nd engine shut down
- Aircraft on ground,
- Aircraft speed below 80kt,
- At least one engine running,
- Engine 1 or 2 not at take-off power,
- Flight phase 3 or 8 memorized.
Flight phase 10
Flight phase 10: from 2nd engine shut down to 5mn after
- Aircraft on ground,
- Engine 1 and 2 not running,
- Flight phase 9 previously memorized.
Note that after 5 minutes the flight phase automatically becomes 1.
In addition, I would like to highlight the fact that the mention “on ground” means that the aircraft landing gear is downlocked. This information is computed by the FWC when landing gear sensors are compressed and RAs value is below 5ft.
You can find details of the flight phases in FCOM DSC-31-15.
Under Flight phase 8, the second condition listed reads: “Aircraft speed up to 80kt,” I believe it should read, “Aircraft speed not below 80kts”.