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-   -   A320:Unreliable Airspeed (https://www.pprune.org/tech-log/637929-a320-unreliable-airspeed.html)

sonicbum 25th Jan 2022 07:22


Originally Posted by Lantirn (Post 11174600)
Have a question and since the subject is relevant, will post it here to not open new thread.

When in takeoff, in a speed discrepancy between PFD1 and PFD2 you apply memo items. When in cruise you dont have to, since the safety of the flight is not impacted. 2,5 and 78 and off you go for the 320.

What is not clear to me is how you handle that when climbing and passing lets say 10.000

Do you still apply memos and then go through QRH? Or do you disconnect FDs/AP and level off with known values that we know from memory (3 and 60 works fine) and then go through QRH?

Have done both in the sim, however I am not sure which is the correct one, but the second seems incorrect to me. Instructor didnt tell me anything about that.

Its a stupid habit I have to avoid overspeed warnings when climbing with blocked pitot tube. I complete the procedure and then climb to avoid all that noise in the sim. But dont think thats correct way

You apply the memory items when the safe conduct of the flight is impacted as you correctly said. In the scenario you describe you have to mainly assess the MORA, wx conditions (IMC in icing conditions?) and the energy state of the aircraft prior to your acknowledgment of the failure (where you climbing at green dot to make an ATC restriction? Where You at the standard 250/10000ft/econ climb ?). In other words, am I happy with current pitch/thrust with respect to the environment? If the answer is yes, than keep your present parameters and ask for the unreliable speed checklist to level off for trouble shooting and don’t forget to communicate with ATC your situation. You still must disconnect AP/FD/ATHR anyway as you don’t want the automation to start chasing erroneous parameters. Besides that, any harm in having 5 degrees ANU and CL thrust passing 10’000ft (memory items value) ? Your normal climb parameters will be the same in terms of thrust and almost the same in terms of pitch. One thing: don’t level off by memory. It’s a big no-no. If Airbus wanted us to know 6/60 or whatever they would have put it as a memory item as well. Levelling of by memory because you’ve read it works on pprune doesn’t look nice at all. Always use known and official parameters. If the aircraft climbs, then keep climbing, no one has ever hit the sky and the t-cas is there for this reason. Once you have figured out the level-off parameters then apply them.


pineteam 25th Jan 2022 07:53

Just to be clear: On my previous post I never intend these numbers to be used in an emergency. I did not see the question about unreliable airspeed above FL100 until now. I just wanted to share some fun facts observed while flying. Unreliable Airspeed is a memory items and shall be applied as Sonicbum explained very well. I will edit my last post just in case. xD

Lantirn 25th Jan 2022 10:44

Nice that the subject got hot.

About the "passing 10000ft unrel speed" case:

Sonicbum and vilas, your posts imply applying the memo items before going to QRH and then ECAM to do the switching or whatever the ECAM is.

What I can understand is, that when on cruise you dont apply if the safety is not affected. When on takeoff its affected, so you apply memo.

In the 10000ft scenario just using a pitch obtained from memo items, without completing the memos seems like an improvisation. And an improvisation can have some of the memos, added actions like "leveling off", switching controls (which is really big no no again if you are not sure from QRH which side is correct) , other personal techniques and then where is that red line? You can have endless personal opinions. From these posts Sonicbum implies AP/FD/ATHR off, while vilas talks about CLB 5. Respect both. Of course its a forum and I know that maybe you didnt explain by detail exactly the steps, but you got my message. Techniques can be endless but airbus procedures are specific. And the airbus procedures werent clear for me for that phase.Thats why I made the question in the beginning.

I have done a level off it in the sim by memory, but in the end I was thinking that that maybe was a bull****. Unluckily my instructor didnt tell me anything.
The reason that I adopted this subconsciously was to avoid the overspeed warning from the erratic block pitot tube during further climb, which gave me the sense of a correct completion of the exercise because the overspeed warning never occured.

Now about the subject of personal pitch and power settings memorization that pilots do, I find it perfectly normal because this is what saves your day in the end. Also your colleague might also give you wrong values from the QRH, which has happened especially with new F/Os. How to use it and when to use it is what we discuss here. I think its a good habit to know soma basic values.

Goldenrivett 25th Jan 2022 11:19


Originally Posted by Lantirn (Post 11174979)
Nice that the subject got hot.

About the "passing 10000ft unrel speed" case:

I have done a level off it in the sim by memory, but in the end I was thinking that that maybe was a bull****. Unluckily my instructor didnt tell me anything.
The reason that I adopted this subconsciously was to avoid the overspeed warning from the erratic block pitot tube during further climb, which gave me the sense of a correct completion of the exercise because the overspeed warning never occurred.

Hi Lantirn, I believe the overspeed warning in the sim during climb with a totally blocked pitot (that's with both the pitot tube and the drain hole blocked by ice) has produced negative training value. Airbus frowns upon this sort of "training" as it is so unlikely to happen. See Adverse effects of Unrealistic simulator scenarios

In real life - you should have time to continue the climb with 5° pitch and the thrust set in CLB (as Vilas says) until you get figures from the QRH or you were already in level flight when the problem occurred (as in AF447) then all you had to do was maintain the cruise pitch and cruise power.

sonicbum 25th Jan 2022 11:41


Originally Posted by Lantirn (Post 11174979)
Nice that the subject got hot.

About the "passing 10000ft unrel speed" case:

Sonicbum and vilas, your posts imply applying the memo items before going to QRH and then ECAM to do the switching or whatever the ECAM is.

What I can understand is, that when on cruise you dont apply if the safety is not affected. When on takeoff its affected, so you apply memo.

In the 10000ft scenario just using a pitch obtained from memo items, without completing the memos seems like an improvisation. And an improvisation can have some of the memos, added actions like "leveling off", switching controls (which is really big no no again if you are not sure from QRH which side is correct) , other personal techniques and then where is that red line? You can have endless personal opinions. From these posts Sonicbum implies AP/FD/ATHR off, while vilas talks about CLB 5. Respect both. Of course its a forum and I know that maybe you didnt explain by detail exactly the steps, but you got my message. Techniques can be endless but airbus procedures are specific. And the airbus procedures werent clear for me for that phase.Thats why I made the question in the beginning.

I have done a level off it in the sim by memory, but in the end I was thinking that that maybe was a bull****. Unluckily my instructor didnt tell me anything.
The reason that I adopted this subconsciously was to avoid the overspeed warning from the erratic block pitot tube during further climb, which gave me the sense of a correct completion of the exercise because the overspeed warning never occured.

Now about the subject of personal pitch and power settings memorization that pilots do, I find it perfectly normal because this is what saves your day in the end. Also your colleague might also give you wrong values from the QRH, which has happened especially with new F/Os. How to use it and when to use it is what we discuss here. I think its a good habit to know soma basic values.

Lantirn,

seems like what you are looking for is a black and white answer on “I have unreliable speed at 10’000ft, what do I do?” And so on like “what about 11000, 12000, etc..”.

Airbus tells You very clearly: if the safe conduct of the flight is impacted then apply the memory items, otherwise applying the memory items is not required. You are a pilot hence you should be able to evaluate (also based on what I have described above) if the safe conduct of the flight is impacted or not, this is the reason we do still have human beings on board the airplanes. So let’s review again your scenario. In case of a partial or total blockage of a pitot tube your airspeed indicator will start over reading during a climb. How bad this is going to be depends upon how badly the pitot is blocked. It is absolutely normal to end up with several nuisances such as the overspeed warning but you don’t care as you know the airspeed is unreliable and all you care about having some parameters that will keep the acft within the envelope, such as the memo items parameters or the parameters you were flying prior to the failure if that is the case. You want to try an interesting failure to demonstrate how the system works? Next time you are in the sim ask the instructor to block the stby pitot and insert icing conditions in IMC. Keep climbing and you will get an ECAM overspeed warning out of nowhere when your PFD 1 and 2 will show normal climbing speeds, say 250 knots. In that case ADR 3 senses an overspeed due to the stby pitot blockage which will also be shown on the stby instruments. So the nuisances warnings are to be disregarded (except the stall warning) just rely on the pitch/thrust parameters. The biggest CRM training element in the unreliable speed scenario is Surprise and Startle especially when the failure doesn’t come as per textbook, and that is exactly what we must focus on as pilots.

Lantirn 27th Jan 2022 09:08

Yes I am getting your concept how to deal with this philosophy. I should just disregard the overspeed warning and Goldenrivett is right about unrealistic scenarios.

FlyA32F 31st May 2022 09:32

How do you manage your lateral navigation when encountering unreliable speed on take off?

FlyA32F 31st May 2022 13:26

Where do you navigate to in case of unreliable speed after take-off?


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