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LF vs AoA
For whom it may interest: a crossplot of normal load factor (gee) against AoA at entry into stall from the graph on page 45 of the french report #3 - LF vs AoA at stall entry.
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It may be pertinent to the discussion to note that Level D full flight simulators do NOT include sound cues for:
- Ice crystals (hail, yes, one size fits all generally, but smaller ice crystals no) - Air impact cues from anything other than CAS/Mach related airspeed (i.e. any aircraft velocity that is not horizontal in nature will likely not cause any air impact noise cues. So an aircraft dropping at 10,000ft/min vertically with at 0 knot CAS would be totally silent in the simulator.... |
Linktrained:
Closing down BOTH engines to flight idle might be the right thing to do - but would FEEL very wrong. Descending at night through a Cb without any clear Airspeed...I know that my Penetration speed should be between 240 and 260 kts, but how can I tell... I must try to keep my wings fairly level if I can... GerardC: You make some excellent crew points in re "age" not being the end all be all of who is a better choice to have the deck and the con. In regards the assignment of roles and responsibilities, if the Captain tells one pilot "you are in charge" that does not change what sound CRM principles call for. But yes, there is potential for CRM problems. http://www.pprune.org/tech-log/45687...ml#post6621097 0210:16, speeds could have been coherent again for a very short time and FDs were back, disapearing almost immediately. safetypee: Amen http://www.pprune.org/tech-log/45687...ml#post6621211 Altitude is "indicated altitude", as well as speeds, and UAS is causing a loss of "indicated" altitude (but ISIS is barely not affected, about 100 ft). It is obvious when you compare pitch vs V/S curves and altitude altogether: the former increased but altitude indicated change is delayed by 10-15 seconds. |
@SaturnV:
a33zab, I don't have the answer, but is it possible, without significant turbulence, to get these g accelerations after N1 was just decreased? 2 h 10 00 > 2 h 10 08, N1 decreases from 100 percent to 84 (or 83) percent (in response to a commanded decrease in Mach) 2 h 10 07 > 2 h 10 18, vertical acceleration varies between 0.9 g and 1.6 g. 2 h 10 23 > N1 begins to increase [from 83 percent]. experienced by the accelerometers and refelected by the corresponding graphs. The -normal accell- (Nz) graph is composed of flight control elevator deflections; THS trim; roll influences; speedbrake and thrust-changes but also environmental disturbences. For thrust-changes: If ∆Nz is the difference between the actual Nz and Nz(1g) and the goal is to maintain a 1g flight: ∆Nz = positive above 1g ∆Nz = negative below 1g At decreasing thrust and a positive ∆Nz this will result in a less ∆Nz to be compensated for with elevator. If the ∆Nz is negative (Nz below 1g) this will result in a higher ∆Nz to be compensated for. Off course it's the other way around with increasing thrust. Hard to explain when english is not the native, if anyone feels the need to correct and/or make additions he is most welcome. |
safetypee, thanks.
GY, perhaps the lack of sound effects in the simulator may explain this somewhat awkward phrasing in the English version, The background noise changed rapidly around 2 h 09 min 46. This change in the background noise was identified as possibly being characteristic of the presence of ice crystals but did not give rise to any specific comments from the crew, the phenomenon being little known to pilots at the time. The PNF then took the initiative to reduce the Mach towards 0.8 and the engine anti-ice devices were triggered. |
Hi HazelNuts39,
Thank you sir, and VERY good work (as usual) That's exactly what I expected: https://docs.google.com/leaf?id=0B0C...zZDlm&hl=en_GB Better posting a smaller representation directly for discussion: http://takata1940.free.fr/CASfromGS.jpg
Originally Posted by HazelNuts39
Airspeed from groundspeed, V/S, windspeed and temperature is shown on this graph: CASfromGS, It is based on wind 45 kt @125 deg, ISA +11 deg C, DFDR data for v/s, altitude and HDG.
The blue dots are Mach from ADR, pink is Mach from GS, wind and v/s, and the green dots show the corresponding CAS. "Sensed/indicated" airpseed drops below 60 kt, alarm stops because alpha is NCD. At first sight, it seems fair considering the very remote possibility that an aircraft would still be "flying" at such a low airspeed. Also, IAS went below limits of 30 kt "sensed", hence NCD is displayed on main instruments (only ISIS displays IAS down to 0) While in reality, this aircraft airspeed was never under 100 kt but stayed in the range of 105-175 kt, where, of course it was not "flying" but "stalling". During about 1 minute, 0211:45 - 0212:45, airspeed was not that far from "flying again" values. The reversal of airspeed tendency happened when engines were set to IDLE. With correctly interpreted informations (and test pilot skills) this aircraft might have been fully recoverable during this whole minute, as late as 0212:45, and maybe later providing enough altitude remained; Even THS setting is not an issue at such a low airspeed. Elevators are powerfull enough to overide it and trim back; this aircraft is longitudinaly very stable and thrust management could have made the difference for pitching down to "flyable" alpha. |
Reply to HazelNuts39 fascinating post 5 Aug 11 #1592 of LF vs AoA – some thoughts
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HN39 or takata:
Does the graph ( http://www.pprune.org/tech-log/45687...ml#post6621344 ) take into account, or synchronize with, the change in heading to the right over the course of the descent, which would thus vary the airspeed depending upon what winds were at a given level ... or, did you average the winds from what data is known to get the airspeed numbers from ground speed? |
GY, perhaps the lack of sound effects in the simulator may explain this somewhat awkward phrasing in the English version, Quote: The background noise changed rapidly around 2 h 09 min 46. This change in the background noise was identified as possibly being characteristic of the presence of ice crystals but did not give rise to any specific comments from the crew, the phenomenon being little known to pilots at the time. The PNF then took the initiative to reduce the Mach towards 0.8 and the engine anti-ice devices were triggered. Italics mine. The RAeS ICATEE working group is doing some very good work related to upset training requirements, modeling approaches and similar. I am pretty sure many related to that effort are monitoring this thread. |
Hi Lonewolf,
Originally Posted by Lonewolf_50
the change in heading to the right over the course of the descent, which would thus vary the airspeed depending upon what winds were at a given level
Originally Posted by HazelNuts
It is based on wind 45 kt @125 deg, ISA +11 deg C, DFDR data for v/s, altitude and HDG.
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Originally Posted by Lonewolf
Does the graph ( AF 447 Thread No. 5 ) take into account, or synchronize with, the change in heading
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Group of graphs on Stall Warning
Here is a set of graphs illustrating the association between certain pilot commands, Pitch variation, and Stall Warning OFF/ON/OFF, and the consequences on the confusion in the cockpit.
Unfortunately, the confusion took place during the time window in which the recovery was still possible (35000 ft to approx 6000ft). http://farm7.static.flickr.com/6139/...4400eb0a_b.jpg
Originally Posted by airtren
(Post 6618125)
.... The AF 447 pushed the system to its limits, and two problems surfaced: a) the STALL WARNING stopped during the STALL, with a confusing effect - the a/c was still in STALL. b) the STALL WARNING started during the transition from STALL to NON-STALL, with a confusing effect - the pilot commands were ND, or lower Thrust, to take the a/c out from the STALL, and the start of the STALL WARNING meant that the commands were wrong, and so they stopped/reverted the commands. |
airten:
But you omit two key parameters from your graphs? Airspeed and AoA.... and since these two are fundamental to the generation of the Stall Warning itself I think you are painting a directed picture. Take a look at the BEA data and it is clear that the Stall Warning basically follows CAS - the rest is coincidental to my eye at least. Take just one Stall Warning occurrence - the one centered around 2.14.00 - on page 107 of the English version of the 3rd Report.... and exactly coinciding is a period where airspeed becomes greater than 60 knots. There is clearly some hysteresis around the airspeed value since short periods where CAS exceeds 60 knots don't trigger it, but when the value is there for a 'reasonable' period. I suspect the problem is that excessive AoA leads to invalid CAS due to pitot characteristics - effectively the dynamic pressure is no longer being read since the inlet aperture is no longer 'inline' with the airflow, and the drain opening is exposed... all in all the problem is a vicious circle, driven by the insane AoA value. Once IN THE STALL many of the systems necessary to understand the situation are compromised. Solution = avoid STALLING |
Originally Posted by Takata
[The PNF] wasn't sure of his own understanding of events.
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Originally Posted by GarageYears
I suspect the problem is that excessive AoA leads to invalid CAS due to pitot characteristics - effectively the dynamic pressure is no longer being read since the inlet aperture is no longer 'inline' with the airflow, and the drain opening is exposed... all in all the problem is a vicious circle, driven by the insane AoA value.
Once IN THE STALL many of the systems necessary to understand the situation are compromised. Solution = avoid STALLING |
Thanks, HN. Winds vary (often considerably) from FL 380 to the surface in both direction and velocity ... so
I chose a wind speed and direction that produced a match between the calculated Mach and the recorded Mach pior to the airplane going to very large AoA, One has to keep in mind that the DFDR wind is obtained by comparing IRU- or GPS-based groundspeed to the ADR-derived airspeed, and also that wind speed and direction may change in the interval shown. That said, it only makes a difference if one is trying to sort out whether or not, when the airspeed on your chart increased late in the event, there was a chance to resume flying (how close to unstalling the aircraft might have been with some nose down) .... but that's all after the fact, as the inputs required to do so were not made. |
I'm deeply impressed about all the knowledge and enthuiasm to find out how this accident occurred.
About 1/3 of my career I flew Boeing, 2/3 I drove various Airbusses. Day after day I'm asking myself, could this happen on a 737, 747, 767, 777.... ? How far did Airbus go to put three qualified pilots out of the loop? thx |
airtren:
I can also see now, that the slight Altitude loss (if the BEA graph is accurate) |
@takata/airtren (thanks for your recent posts)
Originally Posted by takata
Agreed 100%. I'll add that, beside being told to avoid stalling, pilots should be informed of what would eventually happen (as precisely as possible) to their systems if they missed the first part of the drill.
However how do you identify a real stall from a false stall? Keep in mind that 6-9 months prior to AF447 incident we had a couple of false indication incidents on A330. Were these events fresh in the minds of the AF447 pilots? If so then it might be understandable to ignore stall warning and nose up! Exhibit A: QF72 (extract follows...) At 1240:28, while the aircraft was cruising at 37,000 ft, the autopilot disconnected. From about the same time, there were various aircraft system failure indications. At 1242:27, while the crew was evaluating the situation, the aircraft abruptly pitched nose-down. The aircraft reached a maximum pitch angle of about 8.4° nose-down, and descended 650 ft during the event. After returning the aircraft to 37,000 ft, the crew commenced actions to deal with multiple failure messages. At 1245:08, the aircraft commenced a second uncommanded pitch-down event. The aircraft reached a maximum pitch angle of about 3.5° nose-down, and descended about 400 ft during this second event. Exhibit B: QF71 |
GarageYears, re noise simulation - enhanced requirements for training devices.
I recall that the PSM+ICR report identified a similar problem with poor simulation of engine failure sounds / indications. When all of the ‘relevant’ conditions were identified and programmed in simulation, the ability of a pilot to experience them all, would have taken longer than the total simulator sessions in a career. Crews could end up permanently in the simulator, in ice, approaching the stall, recovering from upsets, etc, etc. All that might be achieved is avoiding the accident that someone else has just had; to avoid the potential for 'the next accident', the training solutions have to be more generic. Some critical issue w.r.t. ice crystals are knowledge that the conditions exist, and judgement (risk assessment) in avoiding the hazard. Crews must avoid any complacency encouraged by modern technology, e.g. with a better WXR picture the closer that the ‘legal’ Cb misdistance can be flown. Always add a safety margin, ask what if, and have an 'undo' option' (CtrlZ). Knowledge and judgement are aspects of airmanship – these are the core (or application) of professionalism. These qualities can be taught using a range of example situations, from basic training through refresher training, but perhaps most of all continuously exercised in daily operations with a ‘learning’ debrief – self improvement – striving to be a professional. SaturnV, I interpreted “… the phenomenon being little known to pilots at the time …” as implying that the A330 engines had not suffered from ice crystal problems thus the safety threat had not been highlighted (A330 engines true/false?). However, the ice crystal problem could have been known by all A330 crews based on previous pitot incidents with the appropriate dissemination of information – shared experiences / events. Within this I include the EASA decision to accept a delay in modifying pitots (a practicality) on the assumption that a crew could maintain control (in all foreseeable circumstances) for the duration of a ‘short’ encounter and potential loss of speed displays – enabling opportunity for an operator training action check. The latter conclusion, could be biased by hindsight, but if we can turn that into foresight (foreseeable circumstances) then we might avoid similarly extreme or remote events. Operators should share safety experiences, and then both management and individuals should consider ‘what if’ for a range of scenarios – reinforcing knowledge, providing a basis for situation and risk assessment – a professional approach to operating in the modern world. |
Thanks for your comments.
The graphs I've posted were intended as complementary to the information and the points made by a set of my previous posts, as at the time, I didn't have the graphs available. The goal of those posts was limited only to the explanation of the relationship between certain elements that are under pilot control, the Stall Warnings and the confusion in the cockpit. I have not made any claims of completeness on the set of graphs, so it may be the case, that more graphs could be added for more information. The reasons of WHY the STALL WARNING functioned the way it did was a NON-GOAL, was not in my intention to explain with those graphs, and post. An analysis of WHY the STALL WARNING functioned the way it did, can be a topic for a different post, and set of graphs. Your suggestions are useful for such a set of graphs, and post. I think, these clarifications should help with the use of the word "omit" as well.
Originally Posted by GarageYears
(Post 6621507)
airtren:
But you omit two key parameters from your graphs? Airspeed and AoA.... and since these two are fundamental to the generation of the Stall Warning itself I think you are painting a directed picture. Take a look at the BEA data and it is clear that the Stall Warning basically follows CAS - the rest is coincidental to my eye at least. Take just one Stall Warning occurrence - the one centered around 2.14.00 - on page 107 of the English version of the 3rd Report.... and exactly coinciding is a period where airspeed becomes greater than 60 knots. There is clearly some hysteresis around the airspeed value since short periods where CAS exceeds 60 knots don't trigger it, but when the value is there for a 'reasonable' period. I suspect the problem is that excessive AoA leads to invalid CAS due to pitot characteristics - effectively the dynamic pressure is no longer being read since the inlet aperture is no longer 'inline' with the airflow, and the drain opening is exposed... all in all the problem is a vicious circle, driven by the insane AoA value. If we consider the causality chain, that the STALL is caused by a "lack of sufficient lift", which is caused by the range of the actual "airspeed" and/or "AoA", it may become clear that if we could sense, or measure directly "the lift", and thus the "lack of lift", then that would be perhaps an additional parameter, that would add to the reliability of the STALL detection/calculation mechanism. Once IN THE STALL many of the systems necessary to understand the situation are compromised. Solution = avoid STALLING |
If we consider the causality chain, that the STALL is caused by a "lack of sufficient lift", which is caused by the range of the actual "airspeed" and/or "AoA", it may become clear that if we could sense, or measure directly "the lift", and thus the "lack of lift", then that would be perhaps an additional parameter, that would add to the reliability of the STALL detection/calculation mechanism. Lack of lift typically results in descent. What happens at stall is the dramatic change in lift generation due to the disruption of airflow at a critical angle of attack. Before that, lift and drag are generated in a particular manner. Beyond that, the manner in which the airflow interacts with the airfoil changes. (More turbulent flow, less laminar ... etc) If you know your AoA, and your critical AoA, then you know how close you are to a change you'd rather avoid. To measure lift, just what frame of reference are you going to use? :confused: |
Originally Posted by takata
(Post 6621554)
Agreed 100%. I'll add that, beside being told to avoid stalling, pilots should be informed of what would eventually happen (as precisely as possible) to their systems if they missed the first part of the drill.
I would go even further. There should be an increased effort to help pilots understand the very basic laws of physics involved, in very simple, and practical terms. That would make clear the very important causality chain, which forms a logical chain in the systems algorithms, which is not that different than the logic that one should apply mentally. The training should be clear also about the limitations of the system, and how be able to detect when the system has reached its limitations, and how to use any other available indication for complementing the system and diagnosing the STALL. "xcitation" mentioned, if I recall correctly, using a bottle of water for attitude indication..... great idea.... maybe add also an Emergency Kit, of very simple tools, which can function independent of anything else.... |
Good call. However how do you identify a real stall from a false stall? Higher than normal nose (pitch) attitude + High rate of descent They could also have noticed that the sound of the airflow was indicative of low airspeed. I thnk that PNF had the clues; what a shame he did not take control and act upon them. |
However how do you identify a real stall from a false stall? It's my sincerest hope that a professional "pilot" would never have to ask that question! I'm presuming those of you asking it are not pilots, because I can't imagine a pilot who could ever not know if he's stalled, PDQ, after the fact. The fact that recent years have shown us that those kind of pilots do exist - even while they earn their Darwin awards, ought to cause us all to have a really good look.... If any pilots reading here have any doubts, have no doubt that you DO need some training. |
Apologies if I mention things that were covered already.
(*I speculate*) Could the PF's initial response to pitch up have been to regain his original altitude of FL350? - Perhaps his altimeter showed a gradual loss in altitude as blockage occurred? (as happened in previous events. See pg48 and pg51 of the following document: http://www.bea.aero/docspa/2009/f-cp090601e2.en/pdf/f-cp090601e2.en.pdf) The PNF's action of switching the F/O displays to ADIRU 3 info seems to also suggest he felt ADR2 was less reliable. Later on, after the captain is in the cockpit: 2 h 12 min 15 to 2 h 12 min 19 CAP: Là je sais pas là ça descends There I don't know, there it's going down His comments coincide with the AIR DATA and ATT-HDG selector being positioned to 'CAPT on 3'. Seems like a lot of confusion in the cockpit about what is happening with the altitude. The airplane is pitched nose-up, by this stage the PF claims to no longer have any V/S indication, and there continues to be doubt as to whether the airplane is gaining or losing altitude. 2 h 12 min 27 PNF: Tu montes ... You're going up ... PNF: Tu descends descends descends descends go down go down go down go down 2 h 12 min 30 PF: Je suis en train de descendre là? Am I going down? (Pardon my French, but could the 'là' be the PF referring to PFD1 or the ISIS? As if to say "those instruments there say I'm descending???" PNF: Descend ! Go down 2 h 12 min 32 CAP: Non tu montes là No you're going up there (WHERE does it show them climbing??? I am not so sure he is referring to pitch attitude) 2 h 12 min 33 PF: Là je monte okay alors on descend There I'm going up ok so let's go down (Once again - what is indicating to him that they are going up?) There are only two things which I can think of which indicate up and down in an airplane (excluding the V/S indicator). 1) Pitch Attitude (in which case the whole discussion of up and down is in reference to attitude). 2)Altimeter information (in which case one of them is indicating an increase or constant altitude, while the other(s) indicate a decrease in altitude. I am baffled by what could have been happening, and as the ADR2 data is not recorded by the FDR it leaves us wondering whether it was behaving in a similar fashion to ADR1 and 3, or doing something else. Otherwise...how could there be so much discussion about whether one is climbing or descending?!? I strongly believe the captain's comment was in reference to this conflict of information: 2 h 12 min 44 CAP: (…) C’est pas possible It's not possible And I would be inclined to say the same - I don't think it's possible for one ADR to somehow be frozen or to be indicating an increase in altitude. Nor do I know whether it's possible for IR2 to be displaying different attitude information compared to IR1 and 3. But the entire talk of climbing/descending leads me to envision such scenarios. As a final point - I do not doubt the experience or professionalism of the crew. I believe they did their best with the information that was presented to them, and I don't think it was as simple as the PF simply being 'behind the airplane' and not noticing where he was pointing the airplane - it's possible, but I imagine there's more pieces missing to this puzzle. Nor do I think he was chasing the intermittent FD bars. I think a pilot with his experience on the Airbus would know not to follow the FD bars blindly - it would serve no purpose in such a situation and I'm willing to bet he was aware of that. PS - If it wasn't mentioned already, the airplane switched to Alternate 2 - meaning roll control was DIRECT. Maybe this contributed to his 'over controlling' in roll. |
DJ77 & Neptunus Rex
DJ77
Quite - hence my unease at the entire SS concept (#1535) Neptunus Rex Agreed re: PNF. If he had seen PF's control inputs between FLT350 and FLT380, he would have been there..... |
He did not need to see the control inputs...he could see the results.
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peefactor
3. But the entire talk of climbing/descending leads me to envision such scenarios. Airmanship again. |
Neptunus Rex
I am not talking objectively as to what should have happened/been triggered. I am talking subjectively as to what actually happened that particular night, based on what has been disclosed so far (shortly after his rest break, in the early hours). PNF was almost there, and just needed one or two more clues, and that is a separate question to what he should have needed under a proper training environment that properly equipped both pilots to deal with the situation they encountered (but then modern planes fly themselves and pilots are just a cost that reduces shareholder dividends, or so too many senior line management believe....).
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Neptunus Rex,
How do you know which instruments are valid and which are bogus. You might only have seconds to figure it out! I recommend you read the QF72 interim factual 1, to see what the Quantus captain said. He was not certain of the "varacity" of all of them. Fortunately he had visual + good weather so the situation was less confusing than AF447. QF72 interim factual 1, an extract. The flight crew reported that the weather was fine and clear and there had been no turbulence during the flight. At about 1239, the first officer left the flight deck for a scheduled rest break. The second officer then occupied the right control seat. At 1240:28, the autopilot disengaged. The crew reported that there was an associated ECAM3 warning message (AUTO FLT AP OFF) and that they also started receiving master caution chimes. The captain took manual control of the aircraft using the sidestick. He reported that he attempted to engage autopilot 2 and then autopilot 1, but neither action was successful.4 The flight data recorder (FDR) showed that, during this period, the aircraft’s altitude increased to 37,200 ft before returning to the assigned level. The crew reported that they cleared the AUTO FLT message from the ECAM. They then received a NAV IR1 FAULT message on the ECAM.5 The crew were also receiving aural stall warning indications at this time, and the airspeed and altitude indications on the captain’s primary flight display (PFD) were also fluctuating. Given the situation, the captain asked the second officer to call the first officer back to the flight deck. At 1242:27, while the second officer was using the cabin interphone to ask a flight attendant to send the first officer back to the flight deck, the aircraft abruptly pitched nose-down. The captain reported that he applied back pressure on his sidestick to arrest the pitch-down movement. He said that initially this action seemed to have no effect, but then the aircraft responded to his control input and he commenced recovery to the assigned altitude. The aircraft reached a maximum pitch angle of about 8.4 degrees nose-down during the event, and a maximum g loading of -0.80 g6 was recorded. The aircraft descended 650 ft during the event. The flight crew described the pitch-down movement as very abrupt, but smooth. It did not have the characteristics of a typical turbulence-related event and the aircraft’s movement was solely in the pitching plane. They did not detect any movement in the rolling plane. During the initial upset event, the second officer activated the seatbelt sign to ON and made a public address for passengers and crew to return to their seats and fasten their seatbelts immediately. The flight crew reported that, after returning the aircraft to 37,000 ft, they commenced actions to deal with multiple ECAM messages. They completed the required action to deal with the first message (NAV IR1 FAULT) by switching the captain’s ATT HDG (attitude heading) switch from the NORM position to CAPT ON 3 position, and then cleared that message. The next message was PRIM 3 FAULT.7 The crew completed the required action by selecting the PRIM 3 off, waiting 5 seconds and then selecting it on again. At 1245:08, shortly after the crew selected PRIM 3 back on, the aircraft commenced a second uncommanded pitch-down event. The captain reported that he again applied back pressure on his sidestick to arrest the pitch-down movement. He said that, consistent with the first event, that action was initially unsuccessful, but the aircraft then responded normally and he commenced recovery to the assigned altitude. The aircraft reached a maximum pitch angle of about 3.5 degrees nosedown, and descended about 400 ft during the second event. The flight crew described the event as being similar in nature to the first event, though of a lesser magnitude and intensity. The captain announced to the cabin for passengers and crew to remain seated with seatbelts fastened. The second officer made another call on the cabin interphone to get the first officer back to the flight deck. The first officer returned to the flight deck at 1248 and took over from the second officer in the right control seat. The second officer moved to the third occupant seat. After discussing the situation, the crew decided that they needed to land the aircraft as soon as possible. They were not confident that further pitch-down events would not occur. They were also aware that there had been some injuries in the cabin, but at that stage they were not aware of the extent of the injuries. At 1249, the crew made a PAN8 emergency broadcast to air traffic control, advising that they had experienced ‘flight control computer problems’ and that some people had been injured. They requested a clearance to divert to and track direct to Learmonth, WA.9 Clearance to divert and commence descent was received from air traffic control. Figure 1 shows the track of the aircraft and time of key events. Following the second upset event, the crew continued to review the ECAM messages and other flight deck indications. The IR1 FAULT light and the PRIM 3 FAULT light on the overhead panel were illuminated. There were no other fault lights illuminated. Messages associated with these faults were again displayed on the ECAM, along with several other messages. The crew reported that the messages were constantly scrolling, and they could not effectively interact with the ECAM to action and/or clear the messages. The crew reported that master caution chimes associated with the messages were regularly occurring, and they continued to receive aural stall warnings. The captain reported that, following the first upset event, he was using the standby flight instruments and the first officer’s primary flight display (PFD, see Appendix A) because the speed and altitude indications on his PFD were fluctuating and he was unsure of the veracity of the other displayed information. After the second upset event, he had observed that the automatic elevator trim was not functioning and he had begun trimming the aircraft manually. He later disconnected the autothrust and flew the aircraft manually for the remainder of the flight. The flight crew spoke to a flight attendant by interphone to get further information on the extent of the injuries. The flight crew advised the cabin crew that, due to the nature of the situation, they did not want them to get out of their seats, but to use the cabin interphones to gather the information. At 1254, after receiving advice from the cabin of several serious injuries, the crew declared a MAYDAY10 and advised air traffic control they had multiple injures on board, including a broken leg and some cases of severe lacerations. The crew continued attempts to further evaluate their situation and, at 1256, contacted the operator’s maintenance watch unit11, located in Sydney, by SATPHONE to seek assistance. There were several subsequent communications during the flight between the flight crew and maintenance watch, who advised that the various faults reported by the crew were confirmed by data link, but that they were not able to diagnose reasons for the faults. During one of the conversations, maintenance watch suggested that the crew could consider switching PRIM 3 off, and this action was carried out. This action did not appear to have any effect on the scrolling ECAM messages, or the erratic airspeed and altitude information. |
It has been said before but I d like to add my voice to this opinion. English is a much more factual language then French.
The French language is in my humble opinion too ambivalent to be used in a factual environment like a cockpit in distress. Là is such a word which could be used in the sense of indicating a position (there) or a given time (then), and there are more. Perhaps there has been no misunderstanding between pilots on the deck about the intentions of whoever spoke in this specific case. I do not feel qualified to judge this, despite having been raised in part in French, but others should. I realize some French natives may object to my humble opinion, French are notoriously protective of their language, as it is a fundamental part of their cultural heritage (just think of the French laws requiring French broadcasting stations to broadcast a certain % of music in French), but I do think the discussion should be had. Time for a quick exit.... |
xcitation (QF72)
The crew reported that master caution chimes associated with the messages were regularly occurring, and they continued to receive aural stall warnings. The cry of "wolf," or the cricket chirp of "wolf" could be a case here. |
Lonewolf 50
Definitely a cricket chirp:ok:
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3hole...
By how the aircraft behaves, of course! It's my sincerest hope that a professional "pilot" would never have to ask that question! I'm presuming those of you asking it are not pilots, because I can't imagine a pilot who could ever not know if he's stalled, PDQ, after the fact. The fact that recent years have shown us that those kind of pilots do exist - even while they earn their Darwin awards, ought to cause us all to have a really good look.... If any pilots reading here have any doubts, have no doubt that you DO need some training. This was a stall in an a/c with degraded instruments, ALT LAW, no visual in chop. Not a trivial case. The inexperienced PF did try stick forward however a/c still stays nose up no response, as elevator is at -30 deg due to full THS! So behaviour is bizarre and only explained if you have a full understanding of the situation in 60 seconds. Even then you would be faced with stall recovery - also not trained for and not trivial. Bus pilots have stated that ALT LAW behaves like no other a/c you have flown! So if you have not tried it don't you think it is a bit presumptive/over simplistic to "see how a/c behaves". Even the QF72 CAP with the help of experience, day time, normal law, good weather still doubted varacity of all his instruments. Fortunately he could correctly ignore his stall warnings. IMHO given the details of AF447 incident it was a difficult and exceptional situation. |
Originally Posted by takata
It seemed normal to me and no, BEA would not comment something "normal" without good reasons to do so.
I am very curious of that kind of normality. BTW, is the AoA1 value stuck at 2.1 deg part of the normality too ? Following, something I'm not sure to understand - How things work - What's the logic behind ? Maybe A33Zab could explain ... Thanks. http://i45.servimg.com/u/f45/11/75/17/84/wiz_pi11.gif |
Back up instruments - not inadequate training
As an electronic engineer and pilot of 50 hours, before a pacemaker intervened, I an astonished that all the blame is being put on the pilots and “lack of training”. The cause of the accident is absolutely plain. The automatic systems and glass cockpit completely failed the pilots by providing erroneous and variable indications. With a carefully designed back-up of dependable instruments such as gyros and inertial navigators, and others, pilots would not be without believable data. When the automatics fail catastrophically, as in this case, they should be cut out. The so called stall would never have been believed and subsequently would not have been turned into a real stall. The fault lies with (ALL) modern aircraft design.
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Lonewolf
I've expressed an idea, in a quick post ... and you're nit picking on that.:) giving me the opportunity to muse on semantics.... I could say that I disagree with you, based on how you describe the "descent" as being caused by a "lack of lift". I could say, a "descent" is caused by "a gradual diminishing of lift" not a "lack of lift". ;) "Lack of lift", means (to me) "absence of lift". and thus "fall". You called it "drastic change in lift".... well, yeah,.... it is a change that results in "lack of lift".... But we can also say that "fall", is a "descent", with the qualifier "at high or very high vertical speed".... :). That's BEA's language? So, we can say, that the "stall/lack of lift" is a subset of the larger set which is "change of lift", which includes the other subset, which is the normal "descent/gradual change of lift". For that AoA, isn't that bottle of water that "xcitation" mentioned a genial idea????
Originally Posted by Lonewolf_50
(Post 6621740)
I respectfully disagree, and mostly in how you phrased that.
Lack of lift typically results in descent. What happens at stall is the dramatic change in lift generation due to the disruption of airflow at a critical angle of attack. Before that, lift and drag are generated in a particular manner. Beyond that, the manner in which the airflow interacts with the airfoil changes. (More turbulent flow, less laminar ... etc) If you know your AoA, and your critical AoA, then you know how close you are to a change you'd rather avoid. To measure lift, just what frame of reference are you going to use? :confused: |
@xcitation
Worry not, sir. I'm no Chuck Yeager. I don't even fly any more. But I'm certain that a stalled aircraft behaves just like a stalled aircraft, and ALL pilots should know that behaviour. In this case you can clearly see in the traces the A/C was indeed behaving just like a stalled aircraft. Keep on training! |
Originally Posted by vanHorck
(Post 6621916)
It has been said before but I d like to add my voice to this opinion. English is a much more factual language than French.
Speaking as another Dutchman, who's spent half his life in France (aircraft industry), but with English as the 'family' language at the same time (long story, and not really 'on topic' here). |
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