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A320:Unreliable Airspeed

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A320:Unreliable Airspeed

Old 8th Jan 2021, 13:29
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A320:Unreliable Airspeed

In unreliable airspeed the FCTM states:ONE ADR OUTPUT IS ERRONEOUS AND THE TWO REMAINING ARE CORRECT :The ELACs and the FAC and/or FMGC eliminate the erroneous ADR.There is no cockpit effect (no caution, normal operation is continued), except that one display is wrong and the autoland capability is downgraded to CAT 3 SINGLE.

Suppose ADR 1 is erroneous.My PFD will show me the wrong airspeed.Will I not get any indication of the IAS discrepancy ?
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Old 8th Jan 2021, 14:41
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The NAV ADR 1 FAULT should trigger and will ask you to:
AIR DATA SWTG........................................................ ......................................................CAPT 3
ADR 1 P/B........................................................... ............................................................ .......OFF

If not, use the QRH ADR CHECK PROC which refers to UNRELIABLE SPEED INDICATION and subsequent AFFECTED ADR IDENTIFICATION.
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Old 8th Jan 2021, 14:47
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Suppose ADR 1 is erroneous.My PFD will show me the wrong airspeed.Will I not get any indication of the IAS discrepancy ?


Speaking from memory here but if the faulty ADR is detected by the aircraft it's more likely the speed tape will be removed from your PFD entirely and replaced with a red SPD flag.
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Old 8th Jan 2021, 14:53
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The FCTM states that :There is no cockpit effect (no caution, normal operation is continued), except that one display is wrong and the autoland capability is downgraded to CAT 3 SINGLE.
And also it says:However, there may be cases where an airspeed and/or altitude output is erroneous, while the ADRs do not detect it as erroneous.

Therefore the confusion 😕
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Old 8th Jan 2021, 15:19
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If two ADRs are erroneous but giving the same indication, there won't be any caution for except for the faulty and also correct ADR. That's the scenario you weren't thinking about. Hope it helps!
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Old 8th Jan 2021, 16:45
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As this topic has come up.....would like to query as to what you would do in the following;

Just after becoming airborne (after T/O), CM1 position as PF.....CM1 loses PFD indications (air data, not ATT). Transfers control to CM2 as PF (below thrust reduction altitude), PFD 2 indications appear normal. What would you do, bearing in mind of course "If the safe conduct of the flight is impacted", or not perhaps?.

I'm deliberately not stating what I would do, so as not to cloud any responses - hopefully makes sense? this is just mere curiosity and obviously I adhere to my company's training and procedures.

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Old 8th Jan 2021, 17:40
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As CM1 PF when you loose speed indication you are not sure of PM's situation, so just handing over may complicate matters. So just announce loss of speed and go for memory item TOGA, 15 pitch. That's all is there. Then check speed with standby ASI and PM. If OK hand over and use transfer switch and recover. If PM also problem with speed then level off at MSA and apply UAS procedure.
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Old 8th Jan 2021, 17:57
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Thanks for the reply Vilas, makes absolute sense as you describe it - quick question if I may? assuming that the CM2 position has control after the scenario as described (even though not as you would do, obviously) - what would you expect the CM2 position to do ideally? if indications look normal on PFD2, just fly the aircraft (No AP, FD or A/THR, ALT Law) - or would you prefer application of the "Unreliable Airspeed" procedure? I appreciate there is a lot more to consider, this is just in general.
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Old 8th Jan 2021, 21:31
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A little assesment is prudent, and prescribed before any action. Especially non-recoverable items, worse yet if from memory.

If you lose the air data, there is no neeed to change the pitch or thrust. Hitting a bird or a stupid insect at liftoff, - as long that you know that the speed is good but not what exactly - do nothing and survive. Hitting toga and going 15 will make the suituation three times more complex.

You need to do what needs to be done, and no more. In the correct sequence, at measured pace. Preferrably watching out one for another. You will find that spirit more developed in the FCTM. What it reads on unreliable airspeed also provides guidance to your questoin.

On a first iteration, I could well argue that handing over immediately is far better choice than actioning memory items . Argue with FCTM paragraps in one hand, A.N.C. in the other.

FCMT PR-AEP-NAV "P" - How to apply this procedure, and even more specifically the three ident Note just above it. As ever, the most importnant facts are in the notes box.

Punchlines for this case study:
  • Crew coordination is important. The PM should confirm any discrepancy:
  • If safety of flight path is not affected, the memory items are skipped and not to be done.


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Old 9th Jan 2021, 08:45
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For any problem first thing is to FLY i.e. keep control of the aircraft. What I suggested is no different than any takeoff except TOGA part. So just doing it by pitch rather than FD how will it create problems is not understood. Normally the PF will announce the problem shift the reference to ISIS and then check with PM if his side is OK then hand over. But UAS doesn't have standard format it comes in many forms. That's why any speed problem is UAS unless it is not. If you hand over to PM and his side is also affected and his speed is increasing he will intuitively raise the pitch and get in trouble. In simulator such situation pilots have stalled the aircraft. As a principle handing over should only happen after confirmation that his side is Ok. Another failure is IR disagree. You get CHECK ATT flag which is in faded pink that is hardly noticeable. The PF side may be OK and PM side may be faulty. If you hand over without checking he could cause an upset and may invert the aircraft. PF looses his speed at or after rotation he just flies the pitch(at takeoff it's value is known), announces, tells PM to check with ISIS. If OK hands over and uses transfer to recover his own speed. CRM, crew coordination everything covered. It can't get any simpler.
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Old 9th Jan 2021, 09:25
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Thanks for the replies to my question, all very helpful and food for thought. The scenario I have described was one which (admittedly I handled atrociously on the day) still causes me to question to this day the various entries in both FCTM and FCOM. I think it may be safe to assume that I am mis-interpreting/reading what is stated, as statements in (for example) the FCTM-PR-AEP-NAV-"UNRELIABLE SPEED INDICATION" QRH PROCEDURE suggests among other entries "When one indication differs from the others, the flight crew may be tempted to reject the outlier information. However, they should be aware that two or even all three ADRs can provide identical but erroneous data." I also perhaps was recalling an Airbus Safety First publication (05 - December 2007) that stated as a conclusion entry (6): "An unreliable speed situation may be difficult to identify, due to the multiple scenarios that can lead to it. Therefore, training is a key element: indeed the flight crew’s ability to rapidly detect the abnormal situation, and to correctly handle it, is crucial. In case of any doubt, the pilot should apply the pitch/thrust memory items, and then refer to the QRH to safely fly the aircraft, and to positively determine the faulty source(s) before eliminating it (them)." - and also (4.1); "If the safe conduct of the flight is affected, the flight crew applies the memory items: these allow “safe flight conditions” to be rapidly established in all flight phases (take-off, climb, cruise) and aircraft configurations (weight and slats/flaps). The memory items apply more particularly when a failure appears just after take-off." - for clarity, on the day I think its obvious to say that I had doubts, but even so it seems apparent I/we did the wrong thing.

On the day in question, as the CM2 position, I was handed control after take-off and (I think now obvious that this was a mistake) after a look across the cockpit (CM1 PFD, CM2 PFD, ISIS) and with crew co-ordination/agreement (albeit in hindsight probably nowhere near enough CRM!), I called "Unreliable Airspeed" and then went TOGA/15. I made an absolute mess of it! so that confirms that in absence of anything else, I did the wrong thing - overthinking at the time of what is written in the manuals? i.e. the bolded statement earlier on was in my minds eye - as also my thinking was that - "well, the CM1 PFD (air data) has failed/flagged" , "the ISIS airspeed looks a little odd" , "mine (CM2) does look okay". I then thought "what if mine looks okay, but is erroneous", and then "what is the safest option?". Below THR RED/ACC ALT, I did as previously stated. And yes, it was a much higher workload as a result!. There is of course the attendant CRM and crew-coordination that was happening, although maybe not clear in the narrative that I have stated, and either way my performance on the day was very poor.

As it turned out afterwards, this was a simulated bird strike and ADR 1+3 FAULT.

Last edited by First.officer; 9th Jan 2021 at 09:37.
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Old 9th Jan 2021, 10:14
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Hi First.officer

You got some very valid points from vilas and flightdetent. Now who is right ? The answer is : both !
As You can see to come up with their answers they have thought about their pilot core competencies, and how they would apply them in a real scenario. Remember that "modern" aviation training is getting away from the single solution scenario where we train pilots to react only in a specific way for each specific scenario as real life shows us that events happen in so many different forms and with so many different shapes. Every time You go flying or go to the sim, you bring your pilot's case, and this case is your toolbox, full of competencies that you have developed over time. In this scenario You might decide to pull-out some memory items (application of knowledge) and adapt them to the unclear situation that is developing (situation awareness) or you might decide to initially leave things as they are, the plane was flying perfectly till 1 second prior to the failure with current pitch and thrust, so chances are it will continue to do so for a little while. Now the reason I believe You ended up with a reduced safety margin (when You say that it's been a mess) is about HOW you applied the memory items. the UAS memory items and the subsequent procedure are designed to keep you safe in those kind of contexts, potentially even if there is no failure whatsoever but You have lost situation awareness. So bottom line is the answer to the question "what is the safest option" will be : it depends !
UAS procedure can very well be the answer if applied correctly. Don't touch anything and see what happens during the next few seconds (maybe we get a "ding" from the ECAM with ADR 1 or 3 fault ?) can also be the solution. There is no such thing as one size fits all in our racket and a very successful outcome can be achieved taking completely different paths.

Last edited by sonicbum; 9th Jan 2021 at 10:14. Reason: Typos !
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Old 9th Jan 2021, 10:28
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Originally Posted by First.officer View Post
the flight crew may be tempted to reject the outlier information. However, they should be aware that two or even all three ADRs can provide identical but erroneous data."T.
Not really. It's impossible in real life to have 2 or more ADR providing identical erroneous data. That's why Airbus does not recommend to train that scenario in simulator sessions.

The Adverse Effects of Unrealistic Simulator Scenarios | Safety First (airbus.com)
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Old 9th Jan 2021, 10:41
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Again, thanks for taking the time to answer the questions I have stated, much appreciated. I think this may well be my interpretations - a little too literally on occasion. It's borne from trying to remove what I perceive as ambiguity in any given scenario and the various training manual resources, and come up with a safe answer. It also begs the question to me personally as to whether really to perhaps re-assess my chosen career-path, as I get older and as the years drift by I'm most certainly becoming 'dumber'! and that's not a good thing on a flight deck....
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Old 9th Jan 2021, 11:44
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First Officer : Don’t beat yourself up. I certainly felt I was getting ‘dumber’ as I became older, however I believe the experience gained from age offset the ‘dumbness’ to a certain extent. When I self analysed myself I also came to the conclusion I was attempting to understand finer and finer nuances of the operation this effectively being a result of understanding more than I realised due to said experience. The mere fact you are asking these questions is a healthy indicator and I for one have enjoyed and learnt from this thread. Alas I have witnessed a minority of people in the career who do not think things through and when things get difficult are unable to see the wood for the trees.
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Old 9th Jan 2021, 11:46
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Originally Posted by Bus Driver Man View Post
The NAV ADR 1 FAULT should trigger and will ask you to:
AIR DATA SWTG........................................................ ......................................................CAPT 3
ADR 1 P/B........................................................... ............................................................ .......OFF

If not, use the QRH ADR CHECK PROC which refers to UNRELIABLE SPEED INDICATION and subsequent AFFECTED ADR IDENTIFICATION.
That should happen. However, ECAM procedures obviously do have some issues at times. Had an IR/ADR 2 fault during line flying once. ECAM only indicated an ADR 2 fault without the action line telling us to switch ADR 2 off. It just told us to switch air data to FO 3, nothing more. ECAM actions complete there was still no map indication, no ADI indication for the FO, just altitude and speed, although the altitude swung around by roughly 300ft at first and finally stayed roughly 100ft higher than the other two altimeters.
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Old 9th Jan 2021, 12:42
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@First Officer, don't be too hard on yourself. They don't let us take the aircraft home, so it is difficult to practise things such as memory drills in the actual cockpit. And memory drills need to be regularly physically practised to keep the neural pathways open in the brain. Musicians can practise their scales or the piece they are working on at home in their own time, but we have to do it in our armchair without the cockpit around us.

I asked if I could use the cardboard bomber that a previous company had to practise my drills in my own time after hours, but they refused me permission.

So we are limited to using a small cockpit poster, or doing touch drills in the cruise - neither of which are very satisfactory.

If it was up to me I would have pilots practising all the memory drills several times each at every SIM visit.
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Old 9th Jan 2021, 12:52
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Originally Posted by pineteam View Post
Not really. It's impossible in real life to have 2 or more ADR providing identical erroneous data. That's why Airbus does not recommend to train that scenario in simulator sessions.

The Adverse Effects of Unrealistic Simulator Scenarios | Safety First (airbus.com)
What first officer has stated is from FCTM. Unrealistic scenario in the simulator is a different aspect. FCTM cannot be ignored.
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Old 9th Jan 2021, 13:51
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Hi Vilas,
I saw that in FCTM. I think they just wrote that for us pilots to understand the consequences. That article from Airbus clearly states it can never happen in real life. I believe so far it has been the case.
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Old 9th Jan 2021, 14:33
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That article from Airbus clearly states it can never happen in real life
Sadly, I wish I could believe that and whilst I'm sure that it's highly remote in the extreme - it could happen and these things always find a way when all the "swiss cheese holes" align. And if it's possible to replicate in a simulator, then in theory there is obviously thinking that it's a valid training scenario and that has value however remote - or else it has no value and presence in a training programme I would suggest?.

I know from earlier training received elsewhere, it was always a case of "sitting on your hands" initially and paramount to not necessarily believe everything that is presented as true but perhaps only part of the whole picture....and later, use that thinking with your CRM as a crew to also look for reasons why what you believe has happened, maybe hasn't or is partially correct - does anyone else recall that?. It made sense to me at the time as that way you look for other extenuating factors to make sure you have identified the problem correctly and the action(s) taken are sensible and correct to effect a safe outcome as best can be obtained. Rightly, or wrongly (other than my dire performance) I felt that applying the unreliable airspeed memory items at that point could be no worse than just observing and applying ANC (as I had doubts about my PFD necessarily being correct) and validating that my PFD (ADR2) was indeed correct. It does make life damned hard, I will admit - an early level-off and the pitch-power couple etc., is extremely de-stabilising and increases workload hugely and could be considered an invalid response in the scenario as run. But in theory, it keeps within the FCTM and FCOM guidance if an element of doubt exists?. For me personally, if there is doubt then there is uncertainty, if there is uncertainty then the outcome is not assured and you have to make the best decision available to you at the time and that time allows. I felt that to be the TOGA/15 option - I/we was/were wrong.

Uplinker - yes, very good points - I keep thinking that maybe I should invest in some extra simulator sessions to attempt to address these issues, as a visit to the sim every 6-months (excluding pandemic induced delays) is in my case not leaving me feeling overly confident in my abilities (I also always stress prior to sims and adrenaline always makes it doubly hard). And that may be more to my thinking with regard to my future as an airline pilot as I get older. Overthinking it? quite likely - but we are who we are ;-). I also find the FCOM a terrible read, less so the FCTM - which doesn't help and I find at times lacks the details you need, or to find the answer requires hours spent hunting over various areas and keyword searches, to eventually illicit the answer your seeking - if your lucky. It's UI isn't the best and very easy to get caught out if you forget to set the "Layer" visibility as well - but I digress.
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