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Old 25th Dec 2012, 09:35   #1 (permalink)
 
Join Date: Feb 2011
Location: China
Age: 32
Posts: 10
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?
pacinolove is offline   Reply
Old 25th Dec 2012, 10:26   #2 (permalink)
 
Join Date: Jan 2001
Location: Around the world.
Age: 33
Posts: 560
It puts the jet into alternate law, therefore stopping the (erroneous) alpha protection.
tom775257 is offline   Reply
Old 25th Dec 2012, 11:37   #3 (permalink)
 
Join Date: Apr 2005
Location: Stockholm Sweden
Age: 64
Posts: 545
Quote:
Angle Of Attack (AOA) probes
blockage
Is this a modified probe of some sort?
All the A320/330 I have ever worked on have the airfoil type AOA probes which fly in the wind, not the type with holes in that can get blocked.

Airbus AOA probes can freeze, but cannot get blocked.
Swedish Steve is offline   Reply
Old 26th Dec 2012, 09:11   #4 (permalink)
 
Join Date: Oct 2007
Location: Iriomote
Posts: 172
The OEB notes make mention that the affected aircraft was a 330 yet some 320 family aircraft have the same probes.
TwoTone-7 is offline   Reply
Old 26th Dec 2012, 10:40   #5 (permalink)
 
Join Date: Oct 2009
Location: UK
Posts: 1,273
Hi TwoTone-7,

There are about 170 A330s fitted with these conic AOAs and over 500 A320s.

The A330 mentioned had the new "conic" plate AOAs fitted, but freezing problems have occurred previously with the old design. This example jammed at a cruise angle of attack. See:Sensor icing caught out A320 crew in Perpignan crash

Edit. with thanks to CONF iture.
If Pitots and AOAs simultaneously iced up then -
The pitch / power tables will resolve which is telling lies, but I don't think HAL can read those tables.

Last edited by rudderrudderrat; 27th Dec 2012 at 09:07. Reason: Missing conditional sentence
rudderrudderrat is offline   Reply
Old 26th Dec 2012, 11:25   #6 (permalink)
 
Join Date: Mar 2009
Location: pre-dep area
Posts: 162
Actually, the probes themselves were not changed, but were equipped with conic plates that protect the probes.

It is these conic plates that have the "probe holes" in them.
capt. solipsist is offline   Reply
Old 26th Dec 2012, 22:16   #7 (permalink)
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,780
Quote:
Originally Posted by rudderrudderrat
The pitch / power tables will resolve which is telling lies, but I don't think HAL can read those tables.
Actually, except from consulting the Aircraft Computer Maintenance System, it is not possible for the crew to compare the different AoA readings.
It is good to remind that all pitch displays are correct and also all IAS. Only the presented limit speeds are incorrect.

But the challenge is really on taking back the aircraft control that the duped protection thought necessary to grab.
CONF iture is offline   Reply
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