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Originally Posted by infrequentflyer789
The BEA text, and the "3D view" graphic, seems to me to indicate that stall warning was before the second nose-up input and ascent.
Incidentally, you must have unbelievably sharp eyes if you can discern s/w in "3D view". At M.68/215kCAS, FL375, AoA=4 degrees, the load factor is 0.8. It must be greater than one to increase vertical speed. |
Originally Posted by Machinbird
Those that wish to add a large turbulence/updraft element to this loss of control seem to be putting unnecesary sauce on the stew. Occam's Razor applies.
The potential/kinetic energy transfert calculation shows that at 37500 ft TAS should be 413 kt @ Std + 10 assuming constant thrust and drag. The BEA reports CAS 215 kt (M 0.68) at this altitude which gives 399 kt TAS @Std + 10. Factoring decreasing thrust with increasing altitude and a bit of extra drag due to manoeuvring should easily account for the 14 kt discrepancy. In no way the a/c gained energy as would have been the case in an updraft. |
Originally Posted by HazelNuts39
(Post 6523690)
The occurrence of stall warning indicates that AoA was increasing through the threshold. The BEA text says it was six degree at threshold, and "continued to increase". What caused that increase, if not a nose-up input? BEA again: "About 15 seconds later, (...) the PF continued to make nose-up inputs".
Incidentally, you must have unbelievably sharp eyes if you can discern s/w in "3D view". I should have been clearer that my post was merely conjecture, and the info we have at this point form BEA doesn't give sufficient detail or clarity to confirm it. |
Originally Posted by infrequentflyer789
Was going by the "5" marker which the text states as s/w point.
Otherwise, I don't see how the airplane arrives 15 seconds later at FL380 with zero v/s. |
Originally Posted by DozyWannabe
That image looks a little... how should I say... "dramatic" for an accident report. It looks more like a sensationalistic press cutting to me - how are the BEA responsible for that (any more so than the investigators in other countries responsible for their press getting the wrong end of the stick)?
Let me know what you think of the stuff I PM'ed you! You could be surprised I don’t actually disagree on everything you write …
Originally Posted by HN39
NAV ADR DISAGREE
That message, time stamped 2:12, was received at 2:12:51. At that point in time the airplane was already in a full stall, with all airspeeds probably misreading due to pressure errors at the pitots and at the static sources due to the high AoA. I wonder if that could tell us anything about the speed displayed on PFD2 prior to stall, but can't figure it out. Anyone? PFD2 and ISIS speeds may have agree for a while … BEA : How long is it "then a few moments later" ? 275kt at FL350 is not slow either – How far is it from Vmax ? What was the reason for AP disconnect then ? ALT LAW maybe came 'then a few moments later' … until then protections were still avail. Also, if 2 speeds sharp fall to 60kt one after the other … don’t they agree again ? Svarin, what’s your take on this ? Full FDR data … anyone ?
Originally Posted by 'BEA note 2011 05 27
The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).
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Rudderrat & Retired F-4 From the BEA Note: At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the
engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again. This tells me that the crew performed an "experiment" that indicates they could have reduced angle of attack using the elevators. Even if there was a notch in the wing pitching moment, it is likely that this aircraft could have developed enough nose down momentum to proceed past the notch. Particularly if, as the aircraft began to pitch down, they then began to roll nose down trim in using the manual trim. In effect, as the aircraft began to pitch nose down, they began to match (approximately) the rotation rate of the aircraft nose down with the THS rotation. Success would have been signaled by getting light in their seats and return of rapidly accelerating airspeed at approximately 45 degrees nose down attitude. If you will think back to Gum's Viper deep stall recovery, the recovery technique was to pitch the aircraft up and then develop sufficient pitch momentum nose down to pass through the sticking spot. In effect (with all that NU THS), AF447 was starting from the stick back position already and just needed to start the ball rolling forward. I am wondering whether as the aircraft began to rotate nose down, the crew began to get light in the seat as the aircraft began to fall faster. That also could have been a discouraging factor to continued nose down input. Of course in my F-4, best acceleration occurred at zero g, but the AF447 crew was undoubtedly not accustomed to the concept. |
I am wondering whether as the aircraft began to rotate nose down, the crew began to get light in the seat as the aircraft began to fall faster. That also could have been a discouraging factor to continued nose down input. |
Originally Posted by CONF iture
(Post 6524193)
Problem, in their animation, BEA also 'forgot' to represent those 2 flights which adventured 'in the middle of the storm' … Are BEA and mass media so different …
There is absolutely matter for constructive discussion on a dedicated thread to Habsheim. You could be surprised I don’t actually disagree on everything you write … |
ADR DISAGREE and others
CONF iture asked :
Svarin, what’s your take on this ? At the start of accident sequence, two apparently unrelated faults : PROBE PITOT 1X2/2X3/1X3 WRG:ADIRU1 BUS ADR1-2 TO FCPC2 PROBE FLR is very likely due to icing of probes by high altitude ice crystals. It triggers a specific 10 seconds ADR checking process by all three PRIMs. Starts 02:10:05. All three PRIMs work in Alternate 2 for 10 seconds. WRG FLR affects PRIM2 by cutting it from ADR1 data. My take is this happens right at the start of above mentioned 10 seconds ADR checking process. At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15. My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law. The sentence "the aircraft was in Alternate 2" makes no sense. The PRIMs compute flight laws, not "the aircraft". All three PRIMs are 99.9999% of the time in full agreement. Not this time. NAV ADR DISAGREE is CMC stamped 02:12 and ACARS ground-received at 02:12:51, which means it happened on board between 02:11:58 and 02:12:43. Aircraft was downwards fast at that time. Therefore, the ADR DISAGREE condition was not in effect to latch Alternate 2 for all three PRIMs at the start of pitch-up sequence at 02:10:16. At 02:10:16, the pitch-up sequence and "zoom-climb" happened with (according to my research and "flimsy theory") PRIM1 & PRIM3 in Alternate 2 and PRIM2 in Normal. |
Svarin - that is interesting. Excuse the non-AB brain here, but what are you are saying in terms of the Air Data presented to the crew at the outset? I'm afraid 'Prim 1 and 3 in Alt2 and 1 in normal' needs some translation for me. With 1 in 'normal' and the other two in 'Alt2' what would be the governing control law? Would the ASI's L and R now show a disagreement? Would they be 'invalidated'. Would the standby ASI be affected? What other baro/ADC sourced info is useable? IE Would the altimeters/VSI show the extreme climb?
Lastly, can you comment on what effect (if any) a low airspeed in the system might have on autotrim? Apologies for all the questions, but your post is vastly more important than tailplane camber! |
Where I'm not so sure if I understand it correctly is the thing with the Sine. I will give it a try based on how I understood your approach: I had experienced glorious moments . . and I now realize that it was all very beautiful. But I shall never again fly through a thunderstorm . ... unless the Fatherland should demand it. " Source : Manfred von Richthofen's letters to his family |
BOAC asked :
Air Data presented to the crew at the outset? [...] Would the ASI's L and R now show a disagreement? [...] Would the standby ASI be affected? ASIs were affected. But there is no way I could discern exactly how and when. Inside my own subset of research in this, however, ADR data (provided to Flight Controls Computers -> the PRIMs) was affected. In Normal law, PRIMs could effect ultimate authority on flight control surfaces. There are 3 of them. What happens when PRIMs are in disagreement ? Now that is a question... FDR might reveal some of these parameters. It is however unfortunate that ADR2 data and associated RHS airspeed was not recorded on FDR... |
Governing control law ?
BOAC asked :
With 1 in 'normal' and the other two in 'Alt2' what would be the governing control law? Occam's try on these hypotheses is the triggering of an undesired normal law (full authority) overspeed protection by PRIM2 only which uses erroneous airspeed data after having unexpectedly returned to Normal law. This protection reacts to speed only, and simply adds a nose-up order, with authority superior to that of pilot sidestick. Alarms and warning triggers to the crew are a big unknown in this situation... This situation I described is absolutely not what should happen on a FBW aircraft. Flight Controls Computers are not supposed to disagree at every turn. They are almost always in full agreement to the 0.0000001% precision. I have determined, however, that in this particular instance, they were likely not in agreement. After such an unprecedented problem, all bets are off. This is not fundamentally different from the unexpected rudder hardover in a 737, or the unexpected loss of all hydraulics on a DC-10 or 747, or whatever... These happen extemely rarely and are always specific to a certain design. No design is perfect, even this one. Designs always contain certain trade-offs, carry certain basic assumptions, and try to cater for the unexpected in the best way possible. The more complex they are, however, the more prone to human-like error they become. James Reason is always quoted for his Swiss-cheese model, but he could also be quoted for this : "intelligence and error are both sides of the same coin". |
Dozy, the BEA seems to have had extensive conversations with the crews of the other three flights (Lufthansa, Iberia, and AF459).
The first interim report had this to say about AF459's use of radar. (AF459 was 35 minutes behind at 350) After flying through a turbulent zone in the head of a cumulus congestus formation at the level of NATAL, without having detected this zone on the radar, he selected gain in MAX mode. At about 2 h 00, he observed a first echo that differed significantly depending on whether the radar’s gain was in CAL or MAX mode. The TILT was set between -1° and 1.5° ....the screen, which was set to a scale of 160 NM. The echoes were yellow and red when the radar was set with gain on the MAX position and green and yellow when the gain was on the CAL position The crew reported that it flew at the upper limit of the cloud layer and then in the clouds in the region of ORARO. In this zone they saw green echoes on the radar on their path, which they avoided by changing their route These conditions were particularly severe 70 NM to 30 NM before the TASIL waypoint. They moved away from the route by about 30 NM to the east to avoid cumulonimbus formations with a significant vertical development, and then returned to the airway in clear skies close to the TASIL waypoint. Even in the absence of a full CVR, inferences can start to be drawn regarding the situational awareness of the AF447 flight crew, before and during. In its brief note, the BEA did not mention any crew conversation about the radar setting. If they had changed the mode and discussed it, would not the BEA have mentioned such? The BEA does note that the flight crew notified the cabin crew that they would be going through an area of turbulence, but no indication of any specific instructions to the cabin crew to be seated, stop service, etc. The BEA does not note any attempt by the crew to communicate with ATLANTICO or DAKAR about its circumstances, even though it had looped in its heading. (If IB6024 had not deviated, it would be only eight minutes behind at the climactic point.) My own feeling is that if there was exculpatory conversation on the CVR, the BEA would have referenced such in its brief note. |
ATSB's 1st Interim Report on the QF32 pitch-down accident describes the role division between the PRIMs:
Review of PRIM monitoring functions The aircraft’s flight control system included three flight control primary computers (FCPCs, commonly known as PRIMs) and two flight control secondary computers (FCSCs, commonly known as SECs). One PRIM functioned as the master while the other two PRIMs could take over as master if a fault in the current master was detected. The master PRIM processed and sent control surface deflection orders to other computers, which executed them using servo-controls. The two other PRIMs continuously computed control orders and monitored control surface deflections but those orders were not actioned. Each PRIM consisted of two independent parts, a Command (COM) part and a Monitor (MON) part. The MON part monitored the performance of the COM part and the position of the control surfaces. If there was a discrepancy between COM and MON, then the PRIM would ‘fault’ itself. The fault could be for only a part of the PRIM (for example, pitch channel) or for the whole PRIM. A PRIM could not generate a fault for the whole PRIM unless it was the master. The PRIM Fault parameter recorded by the FDR was active only for a fault of the whole PRIM and not for a partial fault (for example, a pitch channel fault). However, partial faults were recorded by the PFR. For elevator control, the active servo-controller in normal operation was PRIM 1. The servo-controller priority order was PRIM 1, PRIM 2, SEC 1 and SEC2. If PRIM 1 could not perform this function, then the servo-control function reverted to PRIM 2 and so on. Table 4 provides a sequence of events for the PRIMs and is based on a review of the FDR and PFR data by the aircraft manufacturer and investigation team. Table 4: PRIM sequence of events (table deleted, does not reproduce in PPRuNe - HN39) In summary, the PRIM PITCH FAULTs and PRIM 3 FAULTs that occurred during the flight were consistent with the system design. They were consequences of the pitch-down events and not the initiators of those events. |
CONF iture asked :Svarin, what’s your take on this ? I will summarize very quickly here : At the start of accident sequence, two apparently unrelated faults PROBE PITOT 1X2/2X3/1X3 WRG:ADIRU1 BUS ADR1-2 TO FCPC2 PROBE FLR is very likely due to icing of probes by high altitude ice crystals. It triggers a specific 10 seconds ADR checking process by all three PRIMs.Starts 02:10:05. All three PRIMs work in Alternate 2 for 10 seconds. WRG FLR affects PRIM2 by cutting it from ADR1 data. My take is this happens right at the start of above mentioned 10 seconds ADR checking process. At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 [B]or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15. My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law. The sentence "the aircraft was in Alternate 2" makes no sense. The PRIMs compute flight laws, not "the aircraft". All three PRIMs are 99.9999% of the time in full agreement. Not this time. NAV ADR DISAGREE is CMC stamped 02:12 and ACARS ground-received at 02:12:51, which means it happened on board between 02:11:58 and 02:12:43. Aircraft was downwards fast at that time. Therefore, the ADR DISAGREE condition was not in effect to latch Alternate 2 for all three PRIMs at the start of pitch-up sequence at 02:10:16. At 02:10:16, the pitch-up sequence and "zoom-climb" happened with (according to my research and "flimsy theory") PRIM1 & PRIM3 in Alternate 2 and PRIM2 in Normal. There’s only 1 PRIM in control and that will be the one which can deliver the highest possible law and in the sequence PRIM 1, 2 & 3 If PRIM 2, in your view, is in control and able to deliver NORMAL LAW this means that PRIM 1 was not able to compute NORMAL LAW protections and doesn’t say anything about the ability of PRIM 3. If PRIM 2 is in control in ALTERNATE LAW this means PRIM 1 and PRIM 3 could not deliver NORMAL LAW and PRIM 1 was also unable to deliver ALTERNATE LAW. I’m sure if PRIM 2 was in (NORMAL or ALTERNATE) control this had already been mentioned in the BEA update. ALTERNATE 2 mode is latched, so once it is declared (at the time message F/CTL ALTERNATE LAW appeared on ECAM and PF called it out) there can only be a reset on ground with all hydraulic systems depressurized. In my view, at that time PRIM 1 was in control, PRIM 2 and 3 couldn’t compute NORMAL LAW either. Due to the PITOT problem they had all the same ADR information. PRIM 1 declared ALTERNATE 2 LAW and no PRIM can revert to a higher law anymore even if ADR becomes normal thereafter. |
savrin:
How do you fit your analysis with this from the BEA note? At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]". My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law. <snip> At 02:10:16, the pitch-up sequence and "zoom-climb" happened with (according to my research and "flimsy theory") PRIM1 & PRIM3 in Alternate 2 and PRIM2 in Normal. 20th Jun 2011 05:55 |
GY
As the system is supposed to work (based on what I understand of it) that seems to be the case, but what has Svarin concerned seems to be the system not working as advertised ... which would lead the cockpit crew into some confusion regarding "what instruments are right?" and "what is it doing now?" In that state of confusion, attention to flying can easily be diverted, and diverted attention is one of the few hypotneses available to explain an inadvertent 3000 foot climb. <-------- That makes little sense. (Pitch and power chorus in three, two, one ... ) ;) If there's a bug, how to you find it? How much time and effort, and what initial conditions are necessary, to replicate it? And, cui bono? (Small bit of tinfoil on me head for the following) What incentive does AB have to pursue a very low probability bug with only circumstantial, and possibly second or third order, evidence? From a practical point of view, how do you determing the initial conditions (internal to the system) to try and trigger it? With a certain amount of information missing ... it may not be doable. |
Originally Posted by Lonewolf_50
(Post 6525356)
With a certain amount of information missing ... it may not be doable.
Don't confuse what we are trying to deduce here, from just an initial 'text' description of the 'events' from the BEA note, with the work being done by the BEA, with (one expects) AB support. THEY have the traces, the full FDR and CVR records, and the full documentation of the FCS. I'm sure they're going through some of the same discussions, but with a far greater amount of information at hand. I've seen no mention of the QAR having been recovered. It might have provided even more info. |
Understood, ChristiaanJ, and I'm not trying to get too far ahead of the problem.
The problem with electrical ghost faults is the damnable time one has in replicating them. I've had gripes and write-ups that repeatedly got signed off as "could not replicate on deck" which sometimes, because they could not be replicated, were very difficult to trouble shoot. That is also true for spurious signals and strange behavior in computer driven equipment in aircraft. Sometimes, the only maintenance action was to reboot the damned thing. If the QAR is available, that raises the odds for successful analysis, but it is no guarantee. |
Lonewolf_50 writes :
the system not working as advertised Lonewolf_50 again : electrical ghost faults One would need to mount the whole identical system (all computers, soft versions, P/N, etc...) on a simulator and introduce the specific 10 seconds monitoring process, and see what happens. This 10 seconds process being likely the only case for which communication breakdown would occur between these two computers. GarageYears remarked : I seriously doubt the control law in effect was Normal during the "zoom-climb" event May I summon A33Zab great technical information for help ? There’s only 1 PRIM in control and that will be the one which can deliver the highest possible law and in the sequence PRIM 1, 2 & 3 This means Normal law is preferred over any inferior laws. This is the very core of this flight controls design. If PRIM 2, in your view, is in control and able to deliver NORMAL LAW this means that PRIM 1 was not able to compute NORMAL LAW protections In my view, at that time PRIM 1 was in control, PRIM 2 and 3 couldn’t compute NORMAL LAW either. Due to the PITOT problem they had all the same ADR information. WRG:ADIRU1 BUS ADR1-2 TO FCPC2 This means PRIM2 does not have the same ADR set available to it than the other two PRIMs have. |
Originally Posted by Svarin
(Post 6524918)
At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15.
From what is happening in the next two minutes I do not see much what resembles the expected reaction of Normal Law, given the AoA and speed. Could you point me to any single behaviour that you would logically expect in Normal Law ? Somehow, this theory strikes me as a bit strange. |
We have a whole bunch of disagreement on this from those who claim to know the system, and I wonder what chance two lads had in the middle of the night in the ITCZ?
Cold anyone venture a definitive answer to what they had left in baro terms with those ACARS warnings? |
the probable cause of this accident was preoccupation with an inflight malfunction and failure to monitor properly the airplane's flight instruments which resulted in losing control of the airplane. The flightcrew's statements about the ADIs failing were not substantiated by the facts. It is most likely that the flightcrew became spatially disoriented during the upset. They were unable to believe the information displayed on the ADIs, did not recognize the unusual attitude of the airplane, and were unable to take the correct action to recover the airplane until it began to emerge from the clouds. The increased automation has not necessarily reduced pilot workload, however, but has shifted it to monitoring tasks which the pilot formerly had to perform, and there is evidence, from both research and accident statistics, that people make poor monitors. Research also indicates that the excursion from a stabilized condition might be exaggerated even after a system anomaly is detected, because of the period required for a pilot to transition from system monitor mode to system controller. Time is needed to "ascertain the current status of the airplane and assess the situation," 13/ before the pilot can reenter the control loop and take corrective action. China Airlines B747SP Loss of Power and Inflight Upset Fortunatly they did break out of clouds in time to recover, although with some injuries and extensive damage. |
Originally Posted by Svarin
(Post 6524918)
My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law.
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MurphyWasRight;
Well said.:ok: It is time to stop trying to apportion blame to aircraft systems, and time to take a long hard look at the automation ~ human interface. It has often been said in these threads that the automation is 99.9^n% right, and now is the time to look at the human interface and the the well known fact that the same degree of reliability is and can not be expected of mere mortals. We have spent endless pages arguing over which pilot was seated where, and which of the two F/O's was PF. There is no need to go there in the meantime, but the outcome may help in determining who was where. I know this Aviation Weekly & Space Technology link has been posted by PJ2 previously, but it drew no response. I suggest that it is read and digested, compared with the China Airlines incident that MurphyWasRight has mentioned, and let the discussion start on training and how to keep the pilot in the automation loop. I suspect that the crux of this accident is not hardware or software, but a human condition, i.e. industry, management, training and CRM, that needs to be addressed. |
Originally Posted by svarin
At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15.
My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law. This message, transmitted by the FCDC2 (EFCS2), means that the FCPCs (or PRIMs) triggered one of the speed monitoring processes: they have detected a decrease of more than 30 kt in one second of the “polled” speed value. The three ADRs were considered valid by the EFCS2 at the time the monitoring was triggered, because the prior rejection of an ADR would have generated a class 2 fault message and there would therefore have been an asterisk in front of the source. In this case, the “polled” value is the median value. At the time this monitoring is triggered, the FCPCs open a window during which they operate with alternate 2 law (see following graphic). The rudder deflection limitation function is also frozen, but the associated alarm is inhibited. At the end of the window, if the difference between the values polled at each end of that window is less than 50 kt, the FCPCs return to normal law. Otherwise, they continue in alternate 2 law, the rudder deflection limitation function remains unavailable and the corresponding alarm is generated. Note: the alternate 2 control law is a load factor law for pitch and a direct law for roll. Only the load factor protection remains available. In certain cases, the high and low speed stabilities may also be lost. |
Basics
BEA put out their initial findings to quieten the press clamour, as predicted in thread 3, all is quiet as they complete their investigation, at which point speculation can stop, and discussion begin .. I say that with no disrespect to some very informed input from some people here .. others less so.
If we, as aviators, look back to brass tacks, not one of us would want to be in the situation whereby we are trying to figure out how an aircraft is trying to stop us from having an accident, whether that is through protections, stick shakers, buffet .. whatever, brass tacks is about making the decisions to avoid being in a position where those protections kick in, here I err towards the rational of those pointing out the deviations of previous aircraft, and the personally observed fallability of AWW. From first reading, there are issues that will become clear when the final report is issued, they will probably focus on training and awareness rather than discuss big red buttons to give the airplane back to the pilots. The wider point is surely, that loss of situational awareness took THIS aircraft into a regime that it could not make sense of, and took the crew and passengers with it, where as other aircraft did not encounter the same conditions, primarily by not being there in the first place. Whilst all the technical discussions as to what the aircraft, crew, and training culture subsequently did to neautralise a dynamic situation are appropriate to patching the responses in future, (even if the effect turns out to be that under stress all those protections cancelled one another out) it is surely the avoidance of the situation in the first place which closes the first hole in the Swiss cheese model. Lets wait for the report. |
Whilst all the technical discussions as to what the aircraft, crew, and training culture subsequently did to neautralise a dynamic situation are appropriate to patching the responses in future, (even if the effect turns out to be that under stress all those protections cancelled one another out) it is surely the avoidance of the situation in the first place which closes the first hole in the Swiss cheese model. I think about all the stuff that can go wrong every time I fly, but in the end I convince myself that even average pilots can save the day. |
but in the end I convince myself that even average pilots can save the day.
Indeed, most of us would be far more concerned about getting killed driving to and from the airport - although I sometimes shudder at some of the third world operators into whose tender care I have entrusted my life over the years. Risk principally is tied up with probability/seriousness of outcome/exposure period/frequency. It is human nature to accept mitigated risk. Caveat - young men, being programmed genetically to be less worried about risk than the rest of us, might tend to be less concerned about the mitigation bits and more about the adrenaline buzz. We just have to accept that, every now and again, the ducks all line up nicely to give Lady Luck a clean shot at the heart. It is this phenomenon which drives much in the way of regulated technological development. There are no guarantees, only probabilities. |
Originally Posted by john_tullamarine
(Post 6526215)
There are no guarantees, only probabilities.
If when something unusual happens (figures plucked out of the air for effect) the plane is 99.99999% reliable SOPS are 99.9% reliable A captain 98 % reliable A first officer 90% reliable You are going to get occasions when you lose the aircraft. Fortunately on the rare occasions that the plane gets it wrong one of the pilots has a clue, it should come as no surprise that sometimes both of them don't. |
john;
There are no guarantees, only probabilities. Lee Clark, Possibilistic Thinking |
Originally Posted by BOAC
(Post 6525797)
We have a whole bunch of disagreement on this from those who claim to know the system, and I wonder what chance two lads had in the middle of the night in the ITCZ?
Quite how this seemingly endless reservoir of venom towards Airbus and the BEA came about I'm not entirely sure... |
DW - that's accepted, but you need to open your horizons and consider the possible effect the whole 'automation' mentality is having on the industry - read mm43's post above and my somewhat extinct thread on 'Safety and CRM and Q&A'.
In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae of that knowledge to advance their agenda' and we can then disregard these other posts, since for those of us who are not 'experts' it is exceedingly difficult to know who is spouting rubbish.when statement after statement is challenged by someone else 'claiming' to be expert. With your expertise, could you also tell us (as I have asked) exactly what baro information would be available to which pilot with the given failures? I also have not had an answer (to Svarin) in post 207 "Lastly, can you comment on what effect (if any) a low (reported) airspeed in the system might have on autotrim?" - perhaps you could oblige? Is the autotrim function SOLELY based on elevator demand or is there a speed input? |
In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae Point and counterpoint will suffice for most of us. Often I have no expertise in the discussion but do admire a posters ability to rationalize arguments with facts rather than just analysis of minutae to furthur a suspicion. |
I know this Aviation Weekly & Space Technology link has been posted by PJ2 previously, but it drew no response. I suggest that it is read and digested, compared with the China Airlines incident that MurphyWasRight has mentioned, and let the discussion start on training and how to keep the pilot in the automation loop. The pilot is required to be in command. What may need some tweaking is making a better fit for him in the control loop to better enable his exercise of command. It come's with the pilot's badge. I suspect that the crux of this accident is not hardware or software, but a human condition, i.e. industry, management, training and CRM, that needs to be addressed. |
loma - don't forget that 'names' here are not 'names' and an accusation that posters are 'misleading' folk is potentially equally wrong, may yet turn out to be part of a different 'agenda' and needs to be clarified.
"Point and counterpoint will suffice for most of us" - therein lies the rub - whose 'counterpoint' do we listen to? So far, AB software 'expert' opinion has been challenged repeatedly so that none of us know who is right, and as I said earlier, what hope for a crew in an upset? . Now then - anyone willing to answer my queries - definitively, correctly and without fear of contradiction? Lonewolf - spot on. |
In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae of that knowledge to advance their agenda' and we can then disregard these other posts, since for those of us who are not 'experts' it is exceedingly difficult to know who is spouting rubbish.when statement after statement is challenged by someone else 'claiming' to be expert. I once convened my production test pilots, all very experienced, to discuss a simple power margin procedure that customer pilots were using and getting different results from ours. They all wondered why I asked since it was so straightforward and well known. Then each of the six told me how they did it, none exactly the same, maybe eight ways in total since a couple of the guys had alternatives. And the dispersion of the results when I had them fly the same aircraft was unacceptably large. It took a while but we finally agreed on and documented a specific procedure that gave reasonably consistent results. So it's no surprise to me that pilots disagree amongst themselves. Also see the debate about what controls airspeed and flight path (n.b. I use stick and throttle together or one or the other as required.) In that regard, one of the things that is apparent from the discussion is that the Airbus protections and fall backs are very, very complicated. Even the knowledgeable and/or formally trained appear to disagree (or at the least quibble) about how the software and computers work. That doesn't seem like a good thing... |
Tailspin Turtle:
I use stick and throttle together or one or the other as required. next bit Deleted as irrelevant to A330. Part of the idea behind teaching that way was to keep the student from trying to fly by just moving the stick. (I wonder if autothrottle lends itself to that functional habit? ) Next bit deleted as irrelevant to A330. EDITED per BOAC's valid complaint. |
This is so irrelevant as to be unbelievable! Please continue on the Flying Instructors' thread? What ON EARTH has this to do with AF447?:mad:
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