Login
Register
| Contents [show] |
Auto Flight Protections
This is a function of the FMGS.
Engine failure compensation
The FG part of the FMGC ensures automatic yaw compensation after an engine failure. SRS pitch mode automatically adjusts target speeds.
Low speed protection
A/THR SPEED mode
If the selected speed target is below VLS, the A/THR will not allow the speed to decrease below VLS.
LOW ENERGY warning
If speed drops below VLS, a 'SPEED SPEED SPEED' aural is generated. Armed between 100' and 2,000' RA and in configuration 2, 3, or FULL.
ALPHA FLOOR protection
If speed drops further and AOA increases above a threshold, the A/THR commands full thrust, ie. TOGA. This occurs somewhere between VαPROT and VαMAX. The A/THR (which is required) is turned on if it was previously off. Armed from lift off down to 100' RA at speeds above M.53. EPR mode is required. α FLOOR is disabled below 100' to allow for the flare.
See also: Alpha Floor
WINDSHEAR protection
If the FE detects windshear, WINDSHEAR is displayed on the PFD and an aural 'WINDSHEAR WINDSHEAR WINDSHEAR' occurs. This armed from lift off to 1,300' on takeoff, and from 1,300' to 50' during landing, with at least CONF 1 selected.
On takeoff and in a go around, the FG SRS mode commands a pitch ensuring a minimum positive rate of climb. In approach, the auto pilot attempts to maintain a constant ground speed by managing the speed target.
Mode reversions
FCU altitude changes
If the altitude is set below present level when on climb or above present level when on descent, the vertical mode reverts to V/S and ALT is not armed. If ALT* is active and the selected altitude is changed, the vertical mode reverts to V/S.
NAV mode loss
When in NAV mode, a heading is selected and HDG engaged. CLB reverts to OP CLB. DES reverts to V/S, and THR IDLE reverts to SPEED. Loss of NAV mode may also occur due to a discontinuity.
FD orders not followed
On a descent, if the FD pitch bar is ignored and the aircraft pitched up, the FD bars are removed, and THR IDLE reverts to SPEED at VLS. Similarly in a climb, if the aircraft is pitched down, the FD bars are removed and the A/THR reverts to SPEED at Vmax.