A320 OEB Blocked AOA probes
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CONF iture
I will try to answer your points but this is not slugfest between you and me nor I am promoting A or B.
Perpignan, AF447 or 757 what ever I said were not my opinions but inquiry reports. Perpignan wrong maintenance procedure, unplanned last minute execution at a dangerously low altitude without sufficient preparation, too many holes in Swiss cheese too easy to line up.
757 case if you Google it you will be able to find it was concluded that it was possible not to notice the masking tape and they had to make some changes, I didn't demand it and it didn't help that it was not FBW.
AF 447 was crew action absolved by the inquiry? Again not my opinion.
I am not saying two wrongs make one right. EASA AD or Airbus does not find it necessary to switch to direct law but alternate law which allows the pilot to override protections. As an Airbus pilot I tend to agree with it. If you think that in the 757 case same actions as were taken in 447 would have saved the situation I have nothing more to say.
I will try to answer your points but this is not slugfest between you and me nor I am promoting A or B.
Perpignan, AF447 or 757 what ever I said were not my opinions but inquiry reports. Perpignan wrong maintenance procedure, unplanned last minute execution at a dangerously low altitude without sufficient preparation, too many holes in Swiss cheese too easy to line up.
757 case if you Google it you will be able to find it was concluded that it was possible not to notice the masking tape and they had to make some changes, I didn't demand it and it didn't help that it was not FBW.
AF 447 was crew action absolved by the inquiry? Again not my opinion.
I am not saying two wrongs make one right. EASA AD or Airbus does not find it necessary to switch to direct law but alternate law which allows the pilot to override protections. As an Airbus pilot I tend to agree with it. If you think that in the 757 case same actions as were taken in 447 would have saved the situation I have nothing more to say.
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Posted from Wiki Aeroperu Flight603
In November 1996, Mike Eidson, a Miami attorney from Colson Hicks Eidson, said in an interview that many of the passengers survived the initial impact and drowned afterwards. Eidson represented 41 passengers and crew in a lawsuit contending that the aircraft's manufacturer, Boeing, bore responsibility for the disaster, as the company ought to have foreseen the misuse of its products.[1][11] The suit was filed against Boeing in federal court in Miami in May 1997. According to the complaint, the control panel errors were caused by careless maintenance by Aeroperú and negligence and defective design by Boeing. Boeing argued that it was not at fault, and that responsibility for the accident lay with the employee who did not take the tape off the static ports, and the aircraft's pilot for not finding the tape. Richard Rodriguez of the NTSB said that it was understandable that Schreiber did not find the tape because the maintenance worker used duct tape instead of the brightly colored tape that he was supposed to use. In addition, Rodriguez said that the pitot-static ports were high above the ground. Therefore Schreiber did not see the tape against the fuselage.[1] After extensive litigation, the parties agreed to transfer the case against Boeing and Aeroperú to an international arbitration in Santiago, Chile, for a determination of the damages. The defendants agreed not to contest liability in Chile.[11]
On December 13, 1999, family members of the flight's passengers received one of the largest cash awards stemming from an aviation accident outside the United States aboard a non-U.S carrier, averaging nearly $1 million per victim.[citation needed] The episode "Flying Blind" from Mayday (Air Crash Investigation, Air Emergency) stated that the manner of the crash resulting in the passengers' drowning was responsible for the large settlements.[citation needed]
Posted from Wiki Aeroperu Flight603
In November 1996, Mike Eidson, a Miami attorney from Colson Hicks Eidson, said in an interview that many of the passengers survived the initial impact and drowned afterwards. Eidson represented 41 passengers and crew in a lawsuit contending that the aircraft's manufacturer, Boeing, bore responsibility for the disaster, as the company ought to have foreseen the misuse of its products.[1][11] The suit was filed against Boeing in federal court in Miami in May 1997. According to the complaint, the control panel errors were caused by careless maintenance by Aeroperú and negligence and defective design by Boeing. Boeing argued that it was not at fault, and that responsibility for the accident lay with the employee who did not take the tape off the static ports, and the aircraft's pilot for not finding the tape. Richard Rodriguez of the NTSB said that it was understandable that Schreiber did not find the tape because the maintenance worker used duct tape instead of the brightly colored tape that he was supposed to use. In addition, Rodriguez said that the pitot-static ports were high above the ground. Therefore Schreiber did not see the tape against the fuselage.[1] After extensive litigation, the parties agreed to transfer the case against Boeing and Aeroperú to an international arbitration in Santiago, Chile, for a determination of the damages. The defendants agreed not to contest liability in Chile.[11]
On December 13, 1999, family members of the flight's passengers received one of the largest cash awards stemming from an aviation accident outside the United States aboard a non-U.S carrier, averaging nearly $1 million per victim.[citation needed] The episode "Flying Blind" from Mayday (Air Crash Investigation, Air Emergency) stated that the manner of the crash resulting in the passengers' drowning was responsible for the large settlements.[citation needed]
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Originally Posted by vilas
EASA AD or Airbus does not find it necessary to switch to direct law but alternate law which allows the pilot to override protections.
If you think that in the 757 case same actions as were taken in 447 would have saved the situation I have nothing more to say.
- Coupled flight control commands
- No auto trim under manual flight
- Therefore the continuity of the stall warning
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I am not against the idea of having a single switch which knocks out protections But the idea of no auto trim in manual flight goes against the concept of AB FBW. Flight without auto trim for substantial amount of time will require some tactile feed back in the side stick. It is almost changing airbus to Boeing FBW. I do not think it is going happen nor it required. Coming back to 447 what would have helped and has helped in some other such events is sensible piloting and following proper procedures. But some how that is not important to you. You sarcastically used the phrase pilot proof aircraft but you are actually demanding better pilot proof systems because you support pilot's lack of skill. FBW feels the same at 35000ft. or 10000ft. but a 747 or 707 doesn't. AF447 crew the way they handled A330 could flying manually very well stall a 747 at FL350 even with valid speed. Continuity of stall warning sure nothing against it, they ignored it 50 times may be 51st time they would have heard it but the problem was not the stall warning but not knowing what to do with it. Auto trim just trims what you asked. Should a pilot ask for upward trim in stalled condition?
Last edited by vilas; 14th Jan 2015 at 06:15.
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I am a little mystified about this "big red button", especially related to Perpignan?
The "big red button" was precisely what caused Perpignan! The AoA probes froze at a sensible cruise reading, and despite clear indications as such to the crew (illogical Angle of Attack displays on PFDs), they proceeded to test AoA protections.
Due to the frozen AoA probes, AoA protection did not occur. The crew just carried on slowing down (PPL indication of approaching stall: 1), with a very nose high attitude (PPL indication of approaching stall: 2), to well below the speed clearly written in the test schedule on the Flt Deck at which the test should be "knocked off".
In effect the frozen probes acted as "the big red button", and enabled, unfortunately, the crew to kill themselves It isn't a particularly good advert for the "big red button" concept to me?
The "big red button" was precisely what caused Perpignan! The AoA probes froze at a sensible cruise reading, and despite clear indications as such to the crew (illogical Angle of Attack displays on PFDs), they proceeded to test AoA protections.
Due to the frozen AoA probes, AoA protection did not occur. The crew just carried on slowing down (PPL indication of approaching stall: 1), with a very nose high attitude (PPL indication of approaching stall: 2), to well below the speed clearly written in the test schedule on the Flt Deck at which the test should be "knocked off".
In effect the frozen probes acted as "the big red button", and enabled, unfortunately, the crew to kill themselves It isn't a particularly good advert for the "big red button" concept to me?
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I am not against the idea of having a single switch which knocks out protections But the idea of no auto trim in manual flight goes against the concept of AB FBW.
Nigel makes actually an excellent point, although the big difference is that the perpignan crew was obviously unaware of the problem with their AoA vanes, whereas a crew disabling the protections should be aware of what they are doing.
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Originally Posted by NoD
The "big red button" was precisely what caused Perpignan! The AoA probes froze at a sensible cruise reading, and despite clear indications as such to the crew (illogical Angle of Attack displays on PFDs), they proceeded to test AoA protections.
Originally Posted by vilas
I am not against the idea of having a single switch which knocks out protections
But the idea of no auto trim in manual flight goes against the concept of AB FBW
Flight without auto trim for substantial amount of time will require some tactile feed back in the side stick.
It is almost changing airbus to Boeing FBW
Coming back to 447 what would have helped and has helped in some other such events is sensible piloting and following proper procedures. But some how that is not important to you.
You sarcastically used the phrase pilot proof aircraft
but you are actually demanding better pilot proof systems because you support pilot's lack of skill.
Continuity of stall warning sure nothing against it, they ignored it 50 times may be 51st time they would have heard it
Auto trim just trims what you asked.
Should a pilot ask for upward trim in stalled conditions?
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Coming back to 447 what would have helped and has helped in some other such events is sensible piloting and following proper procedures. But some how that is not important to you.
Because I don't see a word from you about the procedure 447 crew followed.
Not in this case, the auto trim would have trimmed hands free from the stick.
If 2.5 degrees pitch and something like 80% N1 was set why would the aircraft trim full up? Airbus trims for the flight path if you point the nose up and keep the stick back sure it will do what you asked for. The aircraft was not left hands free at all. TOGA was selected which is not vastly different at 350 but never the less FBW resists the pitch up it only trimmed back because pilot pulled the stick back and kept it there. Perpignan and AF447 are what not to do examples and if you support these operating styles surely you are demanding pilot proof aircrafts.
Because I don't see a word from you about the procedure 447 crew followed.
Not in this case, the auto trim would have trimmed hands free from the stick.
If 2.5 degrees pitch and something like 80% N1 was set why would the aircraft trim full up? Airbus trims for the flight path if you point the nose up and keep the stick back sure it will do what you asked for. The aircraft was not left hands free at all. TOGA was selected which is not vastly different at 350 but never the less FBW resists the pitch up it only trimmed back because pilot pulled the stick back and kept it there. Perpignan and AF447 are what not to do examples and if you support these operating styles surely you are demanding pilot proof aircrafts.
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So what is the aim of the stall recovery ?
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OK465
I am not sure you know what you are saying. Can you quote some document to support your argument? Why was the dynamic pressure decreasing and how did the angle of attack reach 40 degrees with pilot doing nothing? High level handling in alternate law including stall and recovery is part of type rating now and I have done it many time it doesn't do anything of that sort.
I am not sure you know what you are saying. Can you quote some document to support your argument? Why was the dynamic pressure decreasing and how did the angle of attack reach 40 degrees with pilot doing nothing? High level handling in alternate law including stall and recovery is part of type rating now and I have done it many time it doesn't do anything of that sort.
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In ALT, from 265 or so KIAS, manually fly your A330 level D simulator to a 10 degree flight path angle at 35,000', at TOGA power if you like, and then take your hands off the SS. Watch the THS trim and sit back and enjoy () the ride, remain totally hands off at this point. (Monitor the FPV and SD Flight Control page for additional information.)
The THS will reach 13 ANU and AOA will reach 40+ hands-off. If you have the simulator Input Guidance capability selection at the instructor station, you can monitor AOA through-out on the VOR DME readout.
BTW, conversely, what do think the THS does in dive in ALT, without protections other than g limiting, with the SS full aft and airspeed (dynamic pressure) still increasing?
The THS will reach 13 ANU and AOA will reach 40+ hands-off. If you have the simulator Input Guidance capability selection at the instructor station, you can monitor AOA through-out on the VOR DME readout.
BTW, conversely, what do think the THS does in dive in ALT, without protections other than g limiting, with the SS full aft and airspeed (dynamic pressure) still increasing?
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OK465
In AF447 there was a failure of a component which has happened in non FBW aircraft also. The aircraft behaved the way it was designed to but the pilot not only did not handle the failure the way he should have but took the aircraft to the extremes of the flight envelope and kept it there without facing extremes of environment or incapacitation etc. In this situation the auto trim aspect of the aircraft which makes airbus such an easy aircraft to fly was found to have a negative role. Your suggestion is to redesign the aircraft for such a pilot. I am suggesting to put a better trained pilot in charge. After all we can passionately promote our views but the manufacturers and regulatory requirements and economics will govern the modifications and not what people like you and me demand. AB FBW is bęte noire for some people they are entitled to it but then the discussion becomes a merry go round and not professionally stimulating.
In AF447 there was a failure of a component which has happened in non FBW aircraft also. The aircraft behaved the way it was designed to but the pilot not only did not handle the failure the way he should have but took the aircraft to the extremes of the flight envelope and kept it there without facing extremes of environment or incapacitation etc. In this situation the auto trim aspect of the aircraft which makes airbus such an easy aircraft to fly was found to have a negative role. Your suggestion is to redesign the aircraft for such a pilot. I am suggesting to put a better trained pilot in charge. After all we can passionately promote our views but the manufacturers and regulatory requirements and economics will govern the modifications and not what people like you and me demand. AB FBW is bęte noire for some people they are entitled to it but then the discussion becomes a merry go round and not professionally stimulating.
I'm with vilas on this. FBW is an assistance tool, like the FADECs in the engines, and help prevent exceedences. (?spelling)
Problems with Airbus FBW are mostly down to pilot training, which companies are trying to reduce because it costs money - which reduces the profit they make because they refuse to charge the proper price for the tickets. That's not the pilot's fault.
(If I was an Airbus designer I would keep the system as it is but physically link the joysticks, so they both moved together, and have a disconnect function just like on the Dash 8, where the controls can be disconnected from each other in case of control problems).
Having said that, I think there needs to be some sort of review of how the voting system of three sensors is carried out. In the case of frozen AoA probes, I would think it would be relatively easy to add a few lines of software code to detect an AoA probe that had not moved at all (i.e. given out exactly the same measurement) for several minutes, while variables such as the THS, aircraft altitude, outside air temperature, IAS/Mach, and engine thrust settings had all changed. If this was found to be the case, then vote THAT probe out. If a second probe was also logged in this way as being 'frozen' or seized, then vote that one out as well and alert the pilots via ECAM and going to Alternate law.
Problems with Airbus FBW are mostly down to pilot training, which companies are trying to reduce because it costs money - which reduces the profit they make because they refuse to charge the proper price for the tickets. That's not the pilot's fault.
(If I was an Airbus designer I would keep the system as it is but physically link the joysticks, so they both moved together, and have a disconnect function just like on the Dash 8, where the controls can be disconnected from each other in case of control problems).
Having said that, I think there needs to be some sort of review of how the voting system of three sensors is carried out. In the case of frozen AoA probes, I would think it would be relatively easy to add a few lines of software code to detect an AoA probe that had not moved at all (i.e. given out exactly the same measurement) for several minutes, while variables such as the THS, aircraft altitude, outside air temperature, IAS/Mach, and engine thrust settings had all changed. If this was found to be the case, then vote THAT probe out. If a second probe was also logged in this way as being 'frozen' or seized, then vote that one out as well and alert the pilots via ECAM and going to Alternate law.
Last edited by Uplinker; 20th Jan 2015 at 10:53.
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Please expand...
Please could you also expand on this e.g. with an example or illustration of the point?
Quote:
Originally Posted by NoD
The "big red button" was precisely what caused Perpignan! The AoA probes froze at a sensible cruise reading, and despite clear indications as such to the crew (illogical Angle of Attack displays on PFDs), they proceeded to test AoA protections.
Time to read the report one more time Nigel ...
Originally Posted by NoD
The "big red button" was precisely what caused Perpignan! The AoA probes froze at a sensible cruise reading, and despite clear indications as such to the crew (illogical Angle of Attack displays on PFDs), they proceeded to test AoA protections.
Time to read the report one more time Nigel ...
It does not matter, the valid sensor was silently discarded and the other sensors were lying together with already the potential to wrongfully trigger a protection
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Originally Posted by NoD
Please expand...
There was none.
The system decided to silently discard the only reliable AOA data. When you realize the importance of the AOA data for the Airbus and its protection system to work properly, the logic would be for the system to at least advise the crew as soon as a significant difference between the AOA readings is identified.
Knowing that something was wrong with the AOA data, never the crew would have proceeded with an alpha protection system test ...
Please could you also expand on this e.g. with an example or illustration of the point?
Two AOA vanes blocked at 4 deg which is pretty close to the angle at which the alpha protection is ready to take over in altitude. The BEA did not publish the indicated alpha prot value at FL410 during that flight, it would be of interest.
What happened to Eva Air and Lufthansa could have happened already in Perpignan.
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CONF iture, Nigel On Draft
if you keep your prejudices out you will understand the accident better. I am correcting some of your assumptions.
1. Where did you see "clear indications" ?
There was none.
Yes there were. AOA sensors 1 and 2 were blocked at earlier values when they froze and got jammed. Same values are shown on PFD1 and PFD 2 as V alpha prot and V alpha Max after converting them to speed and that display was wrong. Below I quote BEA report.
"However, the blockage of angle of attack sensors 1 and 2 at identical values had inhibited the functioning of these protections and led to an erroneous display of the characteristic speeds of these protections."
2. The system decided to silently discard the only reliable AOA data. When you realize the importance of the AOA data for the Airbus and its protection system to work properly, the logic would be for the system to at least advise the crew as soon as a significant difference between the AOA readings is identified.
Nothing gets silently discarded. This is known as self detected failure and is intimated to the crew as ADR3 fail on ECAM . However in this case it discarded ADR3 in preference to the erroneous ADRs 1 and 2 in accordance with two versus one principle and since it treated it as a single failure normal law was maintained. Such a possibility is explained in FCTM. It defies logic that when there is evidence that some thing is fishy about the ADRs(speed display and rejection of the 3rd) from which the protection arise ,the crew proceeds with protection tests at a low altitude of 4000ft without any preparation. That deprived them of the crucial time they needed to analyse indication of USE MANUAL PITCH TRIM which indicates direct law and its implications.However this is not going to change your dis Confiture about the Airbus and you are habitually going to say "it doesn't matter". That is your privilege I am just presenting the facts.
if you keep your prejudices out you will understand the accident better. I am correcting some of your assumptions.
1. Where did you see "clear indications" ?
There was none.
Yes there were. AOA sensors 1 and 2 were blocked at earlier values when they froze and got jammed. Same values are shown on PFD1 and PFD 2 as V alpha prot and V alpha Max after converting them to speed and that display was wrong. Below I quote BEA report.
"However, the blockage of angle of attack sensors 1 and 2 at identical values had inhibited the functioning of these protections and led to an erroneous display of the characteristic speeds of these protections."
2. The system decided to silently discard the only reliable AOA data. When you realize the importance of the AOA data for the Airbus and its protection system to work properly, the logic would be for the system to at least advise the crew as soon as a significant difference between the AOA readings is identified.
Nothing gets silently discarded. This is known as self detected failure and is intimated to the crew as ADR3 fail on ECAM . However in this case it discarded ADR3 in preference to the erroneous ADRs 1 and 2 in accordance with two versus one principle and since it treated it as a single failure normal law was maintained. Such a possibility is explained in FCTM. It defies logic that when there is evidence that some thing is fishy about the ADRs(speed display and rejection of the 3rd) from which the protection arise ,the crew proceeds with protection tests at a low altitude of 4000ft without any preparation. That deprived them of the crucial time they needed to analyse indication of USE MANUAL PITCH TRIM which indicates direct law and its implications.However this is not going to change your dis Confiture about the Airbus and you are habitually going to say "it doesn't matter". That is your privilege I am just presenting the facts.
Last edited by vilas; 18th Jan 2015 at 08:49. Reason: correction
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vilas
Thank you for that response.
CONF iture:
I am not criticising in isolation the crew on the day. How and why they found themselves in that situation is discussed n the report. Management and Training and Supervision are clear factors. However, these are separate from the design characteristics.
Thank you for that response.
CONF iture:
Where did you see "clear indications" ?
- CHECK GW message is a clear indication there is an AoA "discrepency"
- Were conducting a briefed Test Flight
- The Test Schedule called for a Minimum FL100 (crew caried it out at 3000')
- Test Schedule indicated Absolute Min spped at their weight of 107K. The crew caried on until 99K, when the Stall Warning (from the correct AoA sounded) - the VLS indication was correct to the schedule
- The Alpha displays were clearly significantly different than they crew should have expected (pic above)
- The ISATM schedule called for the (Test) crew to record the 3 AoA values prior starting the test. This would have shown the AoA problem
- The Test was to check the functioning of the AoA protections. If you are to Test this, you must assume it will fail, and protect against it - betting your (and others') lives on it is a pretty high stakes gamble
I am not criticising in isolation the crew on the day. How and why they found themselves in that situation is discussed n the report. Management and Training and Supervision are clear factors. However, these are separate from the design characteristics.
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Originally Posted by vilas
Nothing gets silently discarded. This is known as self detected failure and is intimated to the crew as ADR3 fail on ECAM
The crew was not aware of the ADR 3 rejection.
During the 40 minutes period before the crash an unambiguous AOA DISCREPANCY ECAM MSG could have been presented to the crew.
Originally Posted by NoD
CHECK GW message is a clear indication there is an AoA "discrepency"
However, an unambiguous AOA DISCREPANCY ECAM MSG would be a clear indication.
The ISATM schedule called for the (Test) crew to record the 3 AoA values prior starting the test. This would have shown the AoA problem.
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The crew has rushed and was clearly poorly prepared, but how would you want them to check those 3 AOA values when only 2 are available and so only indirectly through the third MCDU ... ?
A CHECK GW MCDU MSG is certainly NOT a CLEAR indication of AOA DISCREPANCY
AOA DISCREPANCY ECAM MSG could have been presented to the crew
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Originally Posted by NoD
I have no idea, I am a mere Line Pilot who flies A320s. If I was undertaking a formal test schedule requiring these 3 values to be recorded, I am sure my preparatory material would inform me how.
It should be to a crew doing a test Flight about to bet their lives on the AoA protections.
I am not sure a Line Crew really needs this - all it could really say is "don't stall" which they really should not be doing anyway.