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A320 OEB Blocked AOA probes

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A320 OEB Blocked AOA probes

Old 6th Jan 2015, 19:27
  #41 (permalink)  
 
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Flagon

What is the aversion amongst Airbus lovers to actually having control of the aeroplane? I do not understand it.
Well, I am a Airbus lover just because is the type I'm flying now, and I always love the aircraft I'm flying (mandatory for me). And I can tell you that I always and actually have control of the aeroplane, so I cannot understand what you say.

As in any other aircraft you may have abnormal/emergency situations you have to manage. Nothing new.

my choice, if I were flying the machine, would be to DL and take the computers out of the circuit completely.
This is probably because you don't know the Airbus FBW aircrafts. If you do that you go to mechanical backup only, what isn't very wise. It's much better to go into alternate or direct law (through the computers). Maybe it sounds terrible for somebody who doesn't know about this situations, but I can tell you is quite simple.
ADR,s are controlled by pushbuttons. To push two buttons isn't difficult from my point of view.

I have flown B707 years ago (too many ) and now A320. I love both, but for sure the Airbus is much much easier to fly (and in this one we are only two crewmembers )

Trust me, it is just an aircraft. Of course you have to study as in any other, otherwise if you don't understand something you cannot complain. For sure there are things you don't like, again as in any other.
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Old 6th Jan 2015, 20:42
  #42 (permalink)  
 
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@Vilas:

they might modify the AoA sensor
I would suggest a change to (A380/A350) Multi Functional Probe.
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Old 6th Jan 2015, 21:14
  #43 (permalink)  
 
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As a PPL I have a headache from just reading all this.

It seems such an unnecessarily complicated set of procedures to follow in the very infrequent event that you will need to. It seems too complicated for a human brain to follow in a moment of heightened anxiety. Unnecessarily so. A computer could do it, but not a human. Too much room for error when it's not a task that is practiced repeatedly.

Bring back the cables and vacuum gauges, I say!
I'm stuck on the 320 Mr Nooly and the bloody thing has been a constant headache for the past 10 years.

The Frogs can't help themselves complicating simplicity and have never got their act together since day one. For example their non-normal landing performance section has been changed FOUR TIMES during my tenure and gets more ridiculously complex each time.

Also their operating manuals (called FCOMs) were changed and became an even messier dogs dinner than the original ones they replaced. Here's an example - the procedure for refuelling with one engine running. Logic would dictate it would be found in the Supplementary ops section of the FCOM. Wrong! Its in the Aircraft Loading section FFS!

I was waiting for this latest directive to dribble down to the 320 ever since that QF 330 did its dirty dive enroute SIN-PER a few years ago.

Last edited by mikedreamer787; 6th Jan 2015 at 21:24.
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Old 6th Jan 2015, 21:50
  #44 (permalink)  
 
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@ Gryphon

Good thots overall, but we have to face reality of the man-machine-interface of the aircraft.

As you know from reading my user background, I am very familiar with FBW and all it entails. And as you rightly point out, many folks do not understand. They think FBW is a glorified autopilot. It is not.


The curent architecture of the 'bus could easily allow for one or two backup modes, with last one being "direct" but with specified "gains and rate limits" based upon gear up or gear down and zero dependecne upon air data. If all the computers go tango uniform, all bets are off, but with just one and a clear indication it was the sole survivor, then a condition such as we had for the last 40 years would exist. No force feedback because most everything was a hydraulic pressure on an actuator. No auto throttle or VNAV, pure manual with the "standby gains and pitch rates". After all, no mechanical connections so you depend upon the electrons.

The current 'bus laws are confusing once outta "normal". Sheesh. Doze will jump in here and assert that the engineers programmed everything with pilot assent. But I question how many ever flew a FBW system with zero mechanical backup.

Seems that the engineers tried to preserve every "protection" they could as the overall system degraded. But there were a myriad of combinations and last thing I need is a multiple choice quiz when things go to hell in a handbasket.

So I think a reasonable reversion sequence would be:

- Loss of data, be it AoA or speed or altitude or attitude and maybe gee sensors. Autopilot disconnect and a clear indication of the reversion mode. Latch existing air/gee/AoA data as it existed for 10 or 20 seconds. Then go to the standby gains/rates and standby gee limits. No stall protection, overspeed protection, roll angle protection, no autothrottle, just a nice smooth flying jet with rate and deflection gains fixed upon gear up/down. You would think you were flying a neat design from the 70's or 80's.

What is wrong with that?

What I see from the drivers is the VNAV and other otto features that might help a single seat pilot as I was, but I was not carrying a few hundred pax.
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Old 7th Jan 2015, 02:34
  #45 (permalink)  
 
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Originally Posted by vilas
Direct law is a short term configuration to give you conventional aircraft response during landing. There is no feel and it cannot be practiced in aircraft. So not a good idea to suddenly get into.
If flying direct law is like flying the 737 then what exactly is the problem ... ?
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Old 7th Jan 2015, 05:55
  #46 (permalink)  
 
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Love it or hate it Airbus FBW is a different philosophy. The aircraft is designed with almost complete automation and very little requirements of raw piloting skills in mind. Perhaps it came before its time. I have said it before that the protection were designed to prevent the pilot from going beyond the flight envelope and it does a damn good job of it. What was perhaps not taken into consideration was that in a dynamic medium such as the air the aircraft could be pushed beyond those boundaries without any pilot action and that is where the design is found wanting. All these protections are triggered from data derived from one sensor or the other but the present system of sifting the data to ensure it's genuineness is being proved inadequate and is the cause of all these incidents. The answer to this will come from better sensors, better system of confirmation of data or even quantum leap of technology in measurement of airspeed, AoA etc. but definitely not from cables and vacuum gauges. Surely few automobile accidents are not going to bring back horse buggies. Direct law is short term condition from gear down to landing. It may not be vastly different from 737 but since you cannot practice it on line it is not your day to day experience so you are better off in alternate law which is almost similar to every day normal law minus the offending protections.
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Old 7th Jan 2015, 09:07
  #47 (permalink)  
 
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Vilas wrote:

All these protections are triggered from data derived from one sensor or the other but the present system of sifting the data to ensure it's genuineness is being proved inadequate and is the cause of all these incidents.
Pretty bold statement there sport!
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Old 7th Jan 2015, 11:11
  #48 (permalink)  
 
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@ Gums

Sorry but I'm not prepared for designing a flight control system. I cannot help you in this task.

As I said there are things I would prefer in a different way (and I must say this is not the first of my wishes), as in any other aircraft I've flown.

My only intention was to fight against the legend, but you did it better:

They think FBW is a glorified autopilot. It is not.
Thanks.
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Old 7th Jan 2015, 15:20
  #49 (permalink)  
 
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Originally Posted by vilas
The answer to this will come from better sensors, better system of confirmation of data or even quantum leap of technology in measurement of airspeed, AoA etc. but definitely not from cables and vacuum gauges. Direct law is short term condition from gear down to landing. It may not be vastly different from 737 but since you cannot practice it on line it is not your day to day experience so you are better off in alternate law which is almost similar to every day normal law minus the offending protections.

Who's talking cables and vacuum gauges, what is needed is humility as our system, logic, sensors will never be 100% accurate and reliable so we provide a simple switch to get rid of any protection or automatism if required. Yes, you the pilot may have to protect the airplane from our protections ...
If a 320 pilot needs regular practice before flying simple direct law then something is obviously wrong, what happens the day the elevators quit ... ?

And AF447 would have been much better served with direct law than any other law ...
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Old 7th Jan 2015, 15:27
  #50 (permalink)  
 
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Derived AoA

I forgot to include one aspect of a good HUD that helps you when the AoA vanes are unreliable.

On both HUDs I flew, we had a fuselage reference symbol at the top of the display, An actual display of where the jet was "pointing", and it could have easily been just a piece of chewing gum or a grease pencil mark, heh heh. So in fairly wings-level flight the difference of the flight path vector from that fuselage reference line was your AoA.
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Old 7th Jan 2015, 16:32
  #51 (permalink)  
 
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You are misinterpreting what I am saying. I come from cable and vacuum gauges age but when I flew a320 I liked it as much as I liked the 747. I did not say Direct law is complicated but you are more familiar with alternate law so if possible why not keep to that. Elevators quitting cannot be easier than in A320. In direct law AF447 would have been better? I am sure you are joking but I am not laughing. AF447 would have been better served if all three pilots would have left the cockpit together. And I am not joking. A330 could not handle the pilots.

Last edited by vilas; 7th Jan 2015 at 16:44.
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Old 7th Jan 2015, 18:20
  #52 (permalink)  
 
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Originally Posted by vilas
I did not say Direct law is complicated but you are more familiar with alternate law so if possible why not keep to that. Elevators quitting cannot be easier than in A320
As flying on THS only is already so easy ... what's the deal about to have to trim for direct law ?

Inhibit that auto trim and AF447 reaches Paris.
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Old 7th Jan 2015, 18:42
  #53 (permalink)  
 
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I have no desire to restart AF447 all over again. AF447 wasn't going any where other than where it went. Put another two in front with same level of competence in a 747 and it will reach the same destination with another 150 Pax to give company. And sorry I meant stab jam and not elevator quitting

Last edited by vilas; 8th Jan 2015 at 18:48. Reason: correction
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Old 8th Jan 2015, 21:34
  #54 (permalink)  
 
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Nobody seems to have asked the question of WHY this is happening? Is it poor heating of the probes, or poor radars and poor manipulation and interpretation of the radar picture ? Could it be the weather becoming more extreme or is it because there are simply more aircraft in the air meaning there are more incidents?
I do not remember any aircraft of the previous generation reporting such problems.
The one thing that has surprised me is that the refined FBW laws and architecture of the A330 and later aircraft where it is very difficult to get the aircraft into Direct Law ,have not found their way back into the A320 family.
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Old 8th Jan 2015, 22:03
  #55 (permalink)  
 
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tubby, yes WHY … and yes, and yes, all of the above.
The difficulty is in identifying the dominant parameters; reduced heating, power consumption, etc, vs different airflow patterns around new designs.
I would start with the technical aspects, check the changes and the assumptions made about change … ‘there will be little or no effect’, then check why the designers thought that way, what assumptionswere made in the design and operation … why.

Previous types did not have/use AOA, its only now that we rely on it that the failures are noticed.
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Old 9th Jan 2015, 03:15
  #56 (permalink)  
 
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A small but important clarification I think
Originally Posted by safetypee View Post
Previous types did not have/use AOA
.. as an input to FBW control laws.

AOA sensors to drive various functions has been around for ages, and in some cases it's a safety-critical function, equally as much as for FBW. (I'm thinking any pusher-protected aircraft here, for example). So at least some aircraft have been "watching" the performance of AOA vanes for quite some time.

But it is odd that we seem to be getting more "issues" with novel forms of icing in the relatively recent past. At least some people are suggesting that the only logical explanation is that it's a change in the atmosphere of some kind - global warming? pollution? aircraft flying in different parts of the atmosphere more often (either vertically or geographically)

I think that you can safely assume that there are indeed people asking WHY - everyone building sensors, and everyone spec-ing them, is asking themselves what they have to do extra now that they didn't do before. There are already new regulations, and more on the way. but since we still dont understand all the physics behind this, it's a somewhat empirical reaction - better than nothing, and it should help, but how do we know it's enough?
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Old 9th Jan 2015, 08:32
  #57 (permalink)  
 
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MFS - safetypee has the answer, I think.

"Previous types did not have/use AOA, its only now that we rely on it that the failures are noticed."

I am convinced that the complexity of the current FBW systems leads to significant 'unexpected consequences' as designers add extra comparators and check logic to prevent malfunctions due to malfunctioning detectors, and each 'addition' adds its own failure complications such that driving to the root problem is extremely difficult. As has been said many times, having 'majority voting' was seen as the obvious and correct answer, but we appear now to be seeing 'majority errors' leading to isolation of the correctly functioning device with serious consequences.

Where then do we go? Do we add another sensor or 3 to the current group of 3 to give a 'casting vote'? Surely we unfortunately return to the need to have pilots who can

a) Easily wrest control from the malfunctioning system - DESIGN and
b) then fly the aeroplane as it should be flown until the wayward HAL can be sorted out - TRAINING.

The prevailing 'addiction' to the extremely clever FBW systems and an apparent undeniable belief in how 'wonderful' and 'infallible' it all is needs to change. We need to recognise that it is indeed 'wonderful' and 'infallible' when all works correctly, but when it doesn't, it can be a nightmare and push workload through the roof - and this does seem to be viewed as blasphemous by many.
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Old 9th Jan 2015, 12:57
  #58 (permalink)  
 
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Originally Posted by OK465
It's reasonably straight forward and simple to intentionally get a 330 or 340 into Direct Law
Which method is preferred in the sim ?
Is it to set it on both SEC only ?
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Old 9th Jan 2015, 14:47
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Originally Posted by Mad (Flt) Scientist View Post
But it is odd that we seem to be getting more "issues" with novel forms of icing in the relatively recent past. At least some people are suggesting that the only logical explanation is that it's a change in the atmosphere of some kind - global warming? pollution? aircraft flying in different parts of the atmosphere more often (either vertically or geographically)
It may also be that the operating norm has changed a bit: folks are more willing to risk / fly into such weather due to the much better kit that is currently available.
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Old 9th Jan 2015, 14:55
  #60 (permalink)  
 
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@Flagon

Sorry, that's not the answer in my opinion - my point is that aircraft with stick pushers have been monitoring AOA (and AOA deltas side to side) for a long time now. One would have expected that those types would have been seeing AOA anomalies.

Part of the story may be that FBW aircraft are more "exciting" and so get more "press" - witness the enthusiastic discussion on these forums of the details of FBW implementations, compared to people asking about gain changers and non-linear gearings and such! So the AOA anomalies on FBW aircraft are better known.

I do agree that the more complex systems are difficult to get "perfectly right". I will say that no-one designing and certifying these systems is in any illusion over this complexity and its implications for the design - bold statements about how great a system or aircraft is coming from the mouths of marketing/sales people don't always reflect the opinion of the engineers. Any engineer releasing something is of course confident he's done the best he can, but any good engineer also knows nothing is perfect.
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