A320 OEB Blocked AOA probes
An Airbus aircraft encountered an all Angle Of Attack (AOA) probes
blockage during climb. With the Mach number increasing, the blockage
led to Autopilot (AP) disconnection and activation of the alpha
protection.
PROCEDURE:
CAUTION Monitor the Alpha Prot strip and the Alpha max strip when they are visible
At any time, if the aircraft goes to an unmanageable pitch down attitude despite
continuous deflection of the sidestick in the full backward position (in case the flight
crew missed the below symptoms or delayed the application of one of the below
procedures):
ONE ADR......................................................... .......................................................KEEP ON
TWO ADRs........................................................ ............................................................ ...OFF In stabilized flight path (out of maneuvers involving an increase in load factor such as
turns or pitch variations), if the Alpha Max strip (red) is visible and hides completely
the Alpha Prot strip (black and amber):
SPEED / MACH........................................................ ............................... DO NOT INCREASE
When at or above safety altitude:
LEVEL OFF......................................................... ..................................................INITIATE
Limit speed and altitude in order to limit the Mach number and to prevent the activation
of Alpha Prot, even if the Alpha Prot strip is not displayed on the PFD.
ONE ADR......................................................... ..........................................................KE EP ON
TWO ADRs........................................................ ............................................................ ..... OFF
The AP, FDs and ATHR are lost for the remainder of the flight.
Switch two ADRs to OFF for the remainder of the flight in order to revert to alternate law to
prevent undue Alpha Prot activation.
In case of dispatch with one ADR inoperative, switch only one ADR to OFF.
FPV USE......................................................... ........................................................CONS IDER
SPEED / MACH / ALTITUDE.................................................... ...............DO NOT INCREASE
With AP ON, and with speed brakes retracted if, during maneuvers involving an
increase in load factor such as turns or pitch variations, the Alpha Prot strip (black
and amber) moves rapidly by more than 30 kt :
SPEED / MACH........................................................ ............................... DO NOT INCREASE
When at or above safety altitude:
LEVEL OFF......................................................... ..................................................INITIATE
Limit speed and altitude in order to limit the Mach number and to prevent the activation
of Alpha Prot, even if the Alpha Prot strip is not displayed on the PFD.
ONE ADR......................................................... ..........................................................KE EP ON
TWO ADRs........................................................ ............................................................ ..... OFF
The AP, FDs and ATHR are lost for the remainder of the flight.
Switch two ADRs to OFF for the remainder of the flight in order to revert to alternate law to
prevent undue Alpha Prot activation.
In case of dispatch with one ADR inoperative, switch only one ADR to OFF.
FPV USE......................................................... ........................................................CONS IDER
SPEED / MACH / ALTITUDE.................................................... ...............DO NOT INCREASE
After setting the flaps lever to 0, if the ECAM displays "A LOCK" and "A LOCK"
remains displayed when the aircraft speed is at VFE CONF 1:
SPEED....................................................... ......................... MAINTAIN BELOW VFE CONF 1
Maintain the speed below VFE CONF 1 in order to prevent the OVERSPEED warning from
triggering at VFE CONF 1 + 4 kt.
The VFE CONF 1 strip is not displayed when the flap lever is set to 0.
FLAPS LEVER....................................................... .......................................................CONF 1
SPEED SEL......................................................... ...................................................... S SPEED
When at or above safety altitude:
LEVEL OFF......................................................... ..................................................INITIATE
Limit speed and altitude in order to limit the Mach number and to prevent the activation
of Alpha Prot, even if the Alpha Prot strip is not displayed on the PFD.
ONE ADR......................................................... ..........................................................KE EP ON
TWO ADRs........................................................ ............................................................ ..... OFF
The AP, FDs and ATHR are lost for the remainder of the flight.
Switch two ADRs to OFF for the remainder of the flight in order to revert to alternate law to
prevent undue Alpha Prot activation.
In case of dispatch with one ADR inoperative, switch only one ADR to OFF.
FPV USE......................................................... ........................................................CONS IDER
SPEED / MACH / ALTITUDE.................................................... ...............DO NOT INCREASE
i have a question, why we do this action one ADR on and the other two keep off,what is the meaning of doing this?