OEB 45 - Operational recommendations for Blocked AOA probes
**** Hidden Message ***** Flight Operations Web Conference OEB 45 - Operational recommendations for Blocked AOA probes on aircraft equipped with conic AOA cover platesQuestions & Answers
The questions and answers of the three sessions held on December 20th, 2012 are gathered by themes below:
SAFETY
Question:
These new plates now seem to be an issue. Are the pre-mod plates a safer option?
Answer applicable to: A320 Family and A330/A340
Thanks to the hundred millions of flight hours accumulated with no issue on the flat cover plate design, Airbus considers the flat design as the preferred solution.
Question:
What risk exists of the same phenomena with the standard pre-conic AOA? we have had 2 probes freeze previously on one aircraft with limited effect. it was only discovered due to it being an airtest.....
Answer applicable to: A320 Family and A330/A340
Among the hundred millions of flight hours accumulated with the flat design of the AOA cover plates, we already have had very few events of transient AOA signal remaining at a constant value in ice crystal conditions, therefore only in cruise at high altitude. In those cases, as explained above, there is no risk of undue Alpha Prot activation since the Mach number is already high preventing the activation of the Alpha Protection.
Airbus has never been reported of any event at low/medium altitude with the flat design of the AOA cover plates. Should any airline encounters an in-flight event that lead to have two or three AOA signals remaining at a constant value in that range of altitude, we strongly encourage this airline to provide us with all the associated data (flight data, pilot report, maintenance report, etc...) so that we can provide a detailed analysis and associated recommendations.
OEB
Question:
When is the OEB going to be dispatched? Why the OEB 45 is not available on the Flt/ops library browser A320?
Answer applicable to: A330/A340 only
The OEB 45 for A330 and A340 along with the AFM A330-TR293 and A340-TR294 have been dispatched on December 3rd.
Answer applicable to: A320 Family only
The OEB 45 for A320 along with the AFM A320 TR286 have been dispatched on December 17th.
Answer applicable to: A320 Family and A330/A340
The availability of these documents on the Airbus World portal, in the different formats (OLB, XML, PDF), follows the dispatch with a delay of few days.
Question:
How does operator insert the OEB 45 to the OEB REMIND FUNCTION?
Answer applicable to: A320 Family and A330/A340
As mention in the OEB 45, there is no ECAM entry for this procedure. Therefore the OEB reminder function cannot be activated.
Question:
Can we use the GPS monitoring page on the MCDU to monitor the speed and altitude?
Answer applicable to: A320 Family and A330/A340
There is no need to use the GPS as a source of information for the speed and altitude, since the issue covered in the OEB45 does not affect the speed and altitude parameters. Whatever the two ADRs switched off, the speed and altitude information of the stand-by instruments and the remaining ADR are available.
Question:
Will the QRH Procedure be a temporary procedure until a modification is installed?
Answer applicable to: A320 Family and A330/A340
Yes, we confirm that the procedure provided through the OEB45 is a temporary procedure. The modifications that cancel the need for this OEB will be communicated as soon as available.
Question:
With the A320 family, why are you not selecting the FAC's off instead?
Answer applicable to: A320 Family only
For the A320 Family procedure, we have studied the option to select the FACs to OFF instead of selecting two ADRs to OFF. However we finally elected to ask to switch off the ADRs as for the A330/A340 aircraft for human factor reasons: we did not want the flight crew to waste time to find the FAC pushbuttons that are located in two different parts of the overhead panel and that the flight crew rarely uses. Also Airbus preferred to provide the airlines that operate both the A320 Family and the A330/A340 family with two consistent procedures.
Question:
So the objective of the OEB is to eliminate the high angle of attack protection, because the wrong information from the AOAs and to alternate in alternate law. is that right?
Answer applicable to: A320 Family and A330/A340
We confirm that reverting to the alternate law prevents the activation of the Alpha Protection.
TRAINING
Question:
Do we have to emphasize flight crew awareness with trainings?
Answer applicable to: A320 Family and A330/A340
We do not anticipate any specific training linked to the OEB procedure. As per Airbus Standard Operating Procedures, the flight crew should review the applicable OEBs before each flight in order to apply with no delay the relevant procedure if needed during flight. Moreover, the main idea of the OEB procedure is to revert to alternate law in case any of the symptoms is detected by the flight crew, and flying in alternate law does not require an additional specific training.
Question:
What training material will be available to support this OEB?
Answer applicable to: A320 Family and A330/A340
As mentioned in the previous answer, no specific training is required to support the OEB procedures; however, as a complement of information the Web Conference presentation as well as some short videos are available on Airbus World.
FLIGHT PHASES
Question:
Any instances or flight phase other than the example given in this presentation that this event may occur?
Answer applicable to: A320 Family and A330/A340
If the AOA signal remains at a constant value corresponding to cruise or descent values, the Alpha Prot should never activate since it will remain below the activation value. In cruise for example, the Mach number is already high and will not increase further, thus preventing the Alpha Protection from activating.
ADRs
General statement applicable to: A320 Family and A330/A340
If the flight crew switches off the ADR 1, the PFD on captain’s side does not display any longer the speed and altitude information.
If the flight crew switches off the ADR 2, the PFD on F/O’s side does not display any longer the speed and altitude information.
Switching off the ADR 3 has no effect in terms of display on the both PFDs.
Question:
In the OEB Airbus does not define which specific 2 ADRs to switch off. Any preference of order?
Answer applicable to: A320 Family and A330/A340
Airbus did not elect to direct the flight crew on which ADR to switch off.
The essential action is to switch two ADRs in order to revert to alternate law.
However, depending on: The status of the aircraft (aircraft dispatched with one ADR inoperative or not), Who is the pilot flying, Captain’s decision to take over control, Etc...
The flight crew may decide to switch the ADR 2 and 3 or the ADR 1 and 3 to OFF or the ADR 1 and 2 to OFF.
Question:
What happens if ADR 1 and 2 are NOT switched off with a blocked AOA signal on?
Answer applicable to: A320 Family and A330/A340
If the flight crew detects that the AOA signal remain at a constant value, if two ADRs are not switched to OFF the Alpha protection may activate with an increase in the Mach number.
What happens if ADR 1 and 2 are switched off?
Question:
All the PFD information will be lost related to speed and altitude?
Answer applicable to: A320 Family and A330/A340
Yes the speed and altitude information on both Captain’s side and F/O’s side are no longer available unless, ADR3 is already displayed on one PFD (ADR switching) as per MEL. Anyway the information on the standby instruments remains available and the speed and altitude information from ADR3 can be recovered on one PFD after ADR switching.
Question:
What would occur if the switching occur when the sidestick is in the full backward position?
Answer applicable to: A320 Family and A330/A340
When the two ADRs are switched to OFF along with the deflection of the sidestick in the full backward position, the flight control revert to the alternate law and the sidestick orders are immediately taken into account.
Question:
Will G limits be easily exceeded, and should back pressure be released prior to switching the ADR off?
Answer applicable to: A320 Family and A330/A340
Under Alternate law, the high load factor protection remains available. There is no risk of exceeding the maximum load factor if the switching of two ADRs to OFF is done with the sidestick in the full backward position. However, once the alternate law is activated, the flight crew should control the pitch attitude with appropriate sidestick orders.
Question:
Is there a risk of a undue stall warning?
Answer applicable to: A330/A340 only
As mentioned in the OEB procedure for A330/A340 aircraft, there is a risk of undue stall warning due to the fact that on this aircraft family the stall warning is a function of the AOA value and the Mach number. This is why the OEB procedure refers to the risk of undue stall warning as it is also mentioned by the ECAM when the flight control revert to the Alternate law.
Answer applicable to: A320 Family only
The situation is different on the A320 family since the stall warning is only function of the AOA value, there is no risk of undue stall warning.
Question:
Any risk of G Load Protection?
Answer applicable to: A320 Family and A330/A340
We confirm that in Alternate law, the load factor protection remains available.
Question:
Is the transition from Normal to Alt Law soft or hard? How fast the elevator travels up?
Answer applicable to: A320 Family and A330/A340
As soon as the two ADRs are switched to OFF, the Flight Controls revert to the alternate law with no delay. The sidestick orders are immediately taken into account, within the limits of the load factor protection. However the transition from normal law to alternate law is soft so that it does not generate an abrupt increase of the load factor if the sidestick is already in the full backward position.
MEL
Question:
Are there any restrictions or effects in the MEL?
Answer applicable to: A320 Family and A330/A340
The temporary procedures do not modify the MMEL. The case of an aircraft dispatched with one ADR inoperative is addressed into the procedures to specify that only one more ADR should be switched to OFF.
Question:
Would you recommend to dispatch with three ADR's operational?
Answer applicable to: A320 Family and A330/A340
Airbus does not recommend specifically that the aircraft equipped with conic AOA cover plates are dispatched with the three ADRs operative. As mentioned the OEB procedure, in case the aircraft is dispatched with one ADR inoperative (thus with the associated ADR pushbutton set to OFF), the flight crew must switch off only one ADR to revert to the alternate law.
Question:
When dispatching with one ADR OFF, the OEB should ask to put OFF only one ADR?
Answer applicable to: A320 Family and A330/A340
We confirm that, in case the aircraft has been dispatched with one ADR inoperative (thus with the associated ADR pushbutton set to OFF), only one ADR should be switched to OFF. The FCOM-OEB reminds the flight crew with a dedicated note. As a general manner, the procedure highlight this by mentioning in any case that one ADR must be kept to ON.
MAINTENANCE/ENGINEERING
Question:
What is required to be done by maintenance on ground when crew reported such event or as preventive maintenance action prior to flight?
Answer applicable to: A320 Family and A330/A340
There is no specific check defined for the subject issue. The AMM already provides the necessary tasks to be performed prior the flight and the inspections to be done in case an issue with the AOA is reported.
Question:
Are operators required to contact Airbus prior to commencing any AMM inspections / checks?
Answer applicable to: A320 Family and A330/A340
There is no need to contact Airbus for tasks/inspections already published in the AMM.
Question:
What is the major impact on maintenance and engineering and on Aircraft Maintenance Schedule?
Answer applicable to: A320 Family and A330/A340
The subject issue does not affect the aircraft maintenance schedule.
Question:
Is there any restriction on replacing the Conic Cover Plate with the original Flat Cover Plate, thus cancelling the requirements of the OEB?
Answer applicable to: A320 Family and A330/A340
Should an airline has in-house spare parts of flat cover plates, the replacement of installed conic cover plates is possible, provided the airline contact the Airbus Engineering support to get a Technical Adaptation (TA).
Question:
Will Airbus be publishing documentation to demodify aircraft delivered with conic plates?
Answer applicable to: A320 Family and A330/A340
As mentioned in the OITs published along with the Operational documentation, an update of the technical information will be provided before end of January 2013.
Question:
Will you be releasing any 'official' maintenance information/documentation to be used as reference/maintenance material by Airline Maintenance Personnel?
Answer applicable to: A320 Family and A330/A340
The technical information related to the cover plates will be available before end of January 2013. All the associated details (reference to maintenance tasks/material) will be incorporated into this information.
Question:
Will Airbus provide FOC flat plates if the timescale for a fix becomes excessive?
Answer applicable to: A320 Family and A330/A340
The retrofit to come back to a flat cover plate design will be FOC for operators. Flat plates and protective covers will be supplied at no charge according to the planning defined based on the answer to the RIL that Airbus is about to issue (iaw subject OIT)
Question:
Does Airbus delivers these aircraft with the mod still installed or do they come with the flat plate again?
Answer applicable to: A320 Family and A330/A340
The new aircraft that Airbus delivers are all equipped with the flat design of the AOA cover plates.
Question:
When will be published the SB for the replacement of AOA conic plates by AOA flat plates? Will it be the only solution available?
Answer applicable to: A320 Family and A330/A340
As mentioned in the already published OITs for A320 family aircraft and A330/A340 aircraft, the next actions will be provided before end of January 2013.
Question:
OIT999.0086/12 Rev 01 states the corrective SB will be available end jan 13 with target fleet complete 4 months, do airbus think this can be improved due risk of operations through northern hemisphere winter?
Answer applicable to: A320 Family and A330/A340
Should the corrective SB be available before end of January 2013, Airbus will of course immediately provide it to the airlines.
Question:
You mention that Airbus will provide a TA to allow refitting of the original flat plates on the A330, will there also be a TA available for the A320 and A340 aircraft?
Answer applicable to: A320 Family and A330/A340
If an airline has some available spares, the Technical Adaptation (TA) to allow re-installing the flat design of the AOA cover plates can be requested to the Airbus Engineering Support for any of the A330/A340 and/or A320 Family aircraft.
Back-Up Speed Scale (BUSS):
Question:
What is the impact of the BUSS?
Answer applicable to: A320 Family and A330/A340
When the AOA signal remains at a constant value, the PFD displays a static BUSS corresponding to the AOA value. The use of the BUSS in the case of an issue with the AOA signal is therefore useless.
Question:
The OEB should mention the difference between BUSS and non BUSS aircraft?
Answer applicable to: A320 Family and A330/A340
There is no need to refer to the BUSS in the OEB45 procedure since the BUSS is activated only when all three ADRs are switched OFF whereas the OEB45 requests to keep one ADR ON. Indeed, the OEB45 addresses the case of an issue with the AOA signal, which does not affect the speed indication nor the altitude indication.
Question:
Was the incident aircraft equipped with BUSS?
Answer:
Yes the aircraft was equipped with the BUSS, however, as mentioned above, the BUSS is of no help if the AOA signal remains at a constant value.
Question:
Should it be mentioned in the QRH to 'not use' the BUSS in case of this problem arising?
Answer applicable to: A320 Family and A330/A340
The OEB clearly request to keep one ADR ON which prevent the crew from using the BUSS.
MISC
Question:
How was the new installation tested for icing as part of the mod cert process?
Answer applicable to: A320 Family and A330/A340
The conic cover plates were tested during the certification process in accordance with the applicable certification requirements.
Question:
Have there been similar occurrences on aircrafts from different manufacturers but with same AOA probes?
Answer:
We remind that the AOA probes themselves are not put into question. The issue is suspected to come from the conic cover plates.
Airbus is not aware of any other event.
Question:
Could you please explain again the behavior of the alpha prot strip in manual flight? Why does it only happen with AP is on?
Answer applicable to: A320 Family only
When the load factor equals 1g, the Alpha prot strip remains limited per design to VLS – 2kt. When the load factor is above 1g, the Alpha prot strip is free to increase above VLS - 2kt. In manual flight, depending on the sidestick inputs, the Alpha prot strip may vary by more than 30kt, even when the AOA signal is not affected by any issue.
However, when the autopilot is ON and when the load factor is above 1g, the Alpha prot strip does not vary by more than 30kt when the AOA signal is not affected. This comes from the gains of the autopilot that limit the maneuver orders (for turns and/or pitch variations).
When the AOA signal remains at a constant value, the variations of the Alpha prot strip may exceed 30kt, even with the autopilot ON.
This explains why the condition to enter into the procedure is limited to the cases of autopilot ON. As you understand, this is again to be sure that the flight crew is not tempted to enter into the procedure for (normal) situations that does not require applying the OEB.
Question:
What about having AOA information to the pilots view, now we are able by ACMS only?
Answer applicable to: A320 Family and A330/A340
It is not Airbus philosophy to ask the flight crew in the procedure to check systems information via the ACMS. The ACMS is dedicated to maintenance purposes.
Question:
Is it not allowed to increase the airspeed or the altitude even after the reversions to the alternate law?
Answer applicable to: A320 Family and A330/A340
The procedure recommend to not increase again the speed nor the altitude after two ADRs have been switched to OFF, especially on the A330/A340 aircraft for which it could unduly trigger the stall warning. Moreover in case the slats are in the extended position, the aircraft speed is “naturally” limited.
Question:
If A LOCK occurred, but the crew did not apply the OEB 45, but rather applied the slat jam check list, what would happen to the flight control if the crew continues the approach in normal law?
Answer applicable to: A320 Family and A330/A340
In any case, if the AOA signal remains at a constant value and the OEB45 procedure is not applied, the flight control remain in the normal law and the Alpha protection may activate with an increase in the Mach number (Altitude increase could be enough even if the speed is limited by VFE).
Question:
Were there any aggravating conditions to induce the icing in the reported incident? Severe icing, aircraft de-iced, heavy rain etc?
Answer:
From the data from the reported event, during which the AOA signal was recorded at a constant value, we know that the flight occurred in winter conditions, with little snow and negative temperatures. However the root cause of the blockage of the AOA is still under investigation.
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