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At the apogee the AC was above the lift- and propsion ceiling, a level off was therefore not possible. EDIT:: Apogee, by definition, is level flight. |
I agree with Contacted.
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Originally Posted by studi
... as was said before, we don't know why Bonin pulled.
Section 2.1.3.3.1 of the final report deals with the PF's reaction from the triggering of the STALL 2 warning, as perceived by the HF group (I think the crucial moment is when he starts to pull just before the SW): Some of the PF’s actions may be interpreted as indicative of a perception of a risk or of a diagnosis of overspeed. Firstly, the PF reduced the thrust during the seconds preceding the activation of the STALL 2 warning and the onset of buffet. Secondly, 51 s after the triggering of this warning, the PF said “I have the impression we have speed” then moved the thrust levers to the IDLE detent. He reformulated his impression a few seconds later, combined with an attempt to extend the speedbrakes. Other factors which may have prompted the PF to fear an overspeed situation were: - The display on the ECAM (max speed 330/.82) combined with the reconfiguration to alternate law which may have been read; - The fact that, in cruise, the upper red strip on the speed tape (MMO) is about ten knots above the current speed, whereas VLS is barely visible at the bottom of the tape (thirty knots less); - The dangers associated with overspeed situations embedded in the collective consciousness of pilots. Nevertheless, the PF was also confronted with the stall warning, which conflicted with his impression of an overspeed. The transient activations of the warning after the autopilot disconnection may have caused the crew to doubt its credibility. Furthermore, the fact that the flight director was advising a nose-up attitude may have confirmed the PF’s belief that the stall warning was not relevant. During previous events studied, crews frequently mentioned their doubts regarding the relevance of the stall warning (see 1.16.8.4). The application of maximum thrust was probably the consequence of the perception of the stall warning. However, the PF may have assimilated the triggering of the warning as a consequence of the reduction in thrust, which he had applied four seconds earlier; he should then have applied full thrust to return to the earlier situation. A few seconds later, the PF said “I’m in TOGA, right?”. Either he was unsure whether or not he had set the thrust controls to the TOGA detent, as he intended, or he did not understand why this action was ineffective in clearing the stall warning. This second case might therefore indicate that the PF had built an erroneous mental representation of the aeroplane’s flight model, and that he had hoped that he could resolve the situation by applying TOGA thrust at high altitude and a pitch attitude oftwelve degrees, a strategy similar to that recommended at low altitudes. The fruitless result of his actions possibly heightened his mistrust of the warning. Just my opinion, FWIW. |
I think you guys are trying to make too much out of this. Round and round and round again, in technical circles. What are the most important things that pilots need to do/understand to avoid similar accidents? Here are a few I can think of, in no particular order: - Have a working knowledge of performance attitudes in all phases of flight. - Pulling back on the controls for an extended period of time is rarely the solution to a problem. - Crew communication/interaction is vital during an emergency in a multi-pilot aircraft. - Know how your airframe behaves when you lose part/all of the protections/automation. Competence in just one of those areas might have prevented the accident under discussion... |
Originally Posted by Contacted
I think you guys are trying to make too much out of this. Round and round and round again, in technical circles. After flying jets for 20 years. I'm with Studi post #746: : ..... If a simple AP disconnect and THR lock of a perfectly stable flying airplane puts the pilot into overload, it has nothing to do with the machine, but with the guys training and skill. It wasnt. |
hazelnuts Quote: At the apogee the AC was above the lift- and propsion ceiling, a level off was therefore not possible. Agreed, but you're overreacting. Apogee was at 02:11:10, 13 seconds after the airplane stalled at 02:10:57 EDIT:: Apogee, by definition, is level flight. No, it is the farest point away from earth and has nothing to do with level flight. At that point level flight was not possible. Only possible thing to do was to lower the nose and align pitch angle roughly with flightpath angle. That way stall would have been broken and aircraft would have been recovered. What Dozy told and others accept without thinking "level off at apogee" was the final killer in the event. @dozy I come back to some posts of you on monday, present no time due to driving on the road. But i would suggest, that you try to align your wordfull explanations of the event with the final report. For now, check, wether the Vs presents itself when speeds are lost, afaik no colours when no protections. |
RetiredF4;
Let's not quibble about semantics. |
Originally Posted by Contacted
Look. The aircraft was flying fine (attitude/thrust) when the technical problem occurred.
After two minutes of pilot input, in wasn't flying. It was falling. Despite 2 wings, 2 engines, an artificial horizon, 35,000 feet of airspace and sufficient control authority. Full wings is spot on:
Originally Posted by FullWings
- Have a working knowledge of performance attitudes in all phases of flight.
- Pulling back on the controls for an extended period of time is rarely the solution to a problem. - Crew communication/interaction is vital during an emergency in a multi-pilot aircraft. - Know how your airframe behaves when you lose part/all of the protections/automation. I just feel we need to re-iterate, once in a while, the vital tasks of the pilots. The importance of flight path control and cockpit co-ordination in those first few critical moments of a serious non-normal. Amongst all the bells, whistles, lights, g forces, etc. I'm not convinced the importance in which this is taught in simulator training is really hitting home. Their machine failed them during two separate phases, first in the seconds after the A/P disconnect the displays/indicators/attention getters/attention demanders didn't give clear and pointed information, and secondly the FD inconsistency confused the PF during his attempts to control the aircraft. I say this because I believe I'm repeating what the BEA wrote in the final report. I do not place blame on the system because it offered a confusing environment, but I think that the confusion was a significant factor in their failure to recognize their true state. |
At apogee, the aircraft had no influence on her flight path. She was Nose high, AoA thirty degrees, and climbing, and her flight path was "level" for a brief millisecond, before she started falling at 1G. She started rolling, and was accelerating quickly toward her reported maximum ROD of 15000 fpm.
'Level' had nothing to do with what Dozy wants to say... The THS kept cranking in NU until she hit her stops, at 13+ degrees, never to budge off the dogs. Nose down past this point did nothing to move the THS off the max NU position. I think she was basically flat plate, any guesses as to what elevators were doing is moot, the THS never moved, the computer never sensed the g necessary to command the HS ND.....at the last, when Captain said, "Pitch at ten", they started to pull, and pull had gotten them nowhere. Question, Could ND have budged the THS? It did not. What was wrong with the computer/Pitch control? Nothing? That is a guess.....Something? Also, a guess. |
At apogee, the aircraft had no influence on her flight path. She was Nose high, AoA thirty degrees, and climbing, and her flight path was "level" for a brief millisecond, before she started falling at 1G. She started rolling, and was accelerating quickly toward her reported maximum ROD of 15000 fpm. Nose down past this point did nothing to move the THS off the max NU position. |
HazelNuts39
Use of the word "Level" is misleading, for it implies that she lingered at level. She did not, it was fleeting, and since the trajectory was ballistic, ("momentum", per BEA), she had no level component at any time, not even a second. To remain level whilst moving implies lift, she had none, she was above the Lift ceiling. Her controls had no purchase, her engines were above propulsive ceiling, and so on. BEA say she fell at the same Pitch she carried to and through the peak of climb. Certainly, her AoA increased, and drag, to it's limit (terminus). "Yes, the nose-down inputs were too small and too brief to change the position of the THS." This is puzzling, and not what I expect. What is the lag between actuation of ND elevators and screw jack actuation? It would seem the design would actuate the HS straightaway, else the elevators could lead by sufficient time to over stress? |
Lyman;
Use of the word "Level" is misleading, for it implies that she lingered at level. To remain level whilst moving implies lift, she had none, she was above the Lift ceiling. Her controls had no purchase, her engines were above propulsive ceiling, and so on. What is the lag between actuation of ND elevators and screw jack actuation? |
This is puzzling, and not what I expect. What is the lag between actuation of ND elevators and screw jack actuation? It would seem the design would actuate the HS straightaway, else the elevators could lead by sufficient time to over stress? The only way for have a immediate move of the trim surface is to manually change the trim position ..... |
Above Lift ceiling means insufficient lift to remain at specified altitude, including controls, yes?
I apologize if this seems a parse, are we not disabusing a poster of "Levelling Off" when the a/c cannot fly? Relative to THS: If I command ND, I push the stick to a a percentage of its available travel, and release. The computer commands the elevators to deflect downward, and the a/c starts to ND. I do not have to hold the input, at what time does the THS start to move? I submit the THS did not move at all, to continue to try to establish a G....if so, the Law prohibits recovery simply because the G loading does not meet its parameter? Recovery from Stall means a good deal of sub 1 G..... Can't get there from the wrong side, according to the THS...... I have held back stick beyond the Stall break, (never with trim), intentionally, but I was doing it deliberately, to spin, why would any aircraft trim past the SW, what pilot would, in an airliner? It is one thing to hold off when the elevators can provide 1G. Then it cranks in to keep the load factor, and well past the elevators authority. So 'super' NU, and a vary strange entry to STALL. Then when negative G is required, it will have none of it? Why would anyone design an aircraft that can fly beyond its elevators to maintain a load? And then stubbornly hold it after the STALL? |
Originally Posted by Lyman
Above Lift ceiling means insufficient lift to remain at specified altitude, including controls, yes?
In alternate law without high-AoA protection the lift ceiling marks the onset of perceptible buffeting in 1g flight. Exceedence of the lift ceiling results in increasing intensity of buffet and ultimately stall. There is no direct relation between lift ceiling and pitch control. You're losing me in the remainder of your post. |
"In alternate law without high-AoA protection the lift ceiling marks the onset of perceptible buffeting in 1g flight. Exceedence of the lift ceiling results in increasing intensity of buffet and ultimately stall. There is no direct relation between lift ceiling and pitch control."
Thanks HN... How would you describe the onset of Stall, another way? Ceiling implies a pressure altitude, no? As to the THS, I take note that you believe the THS remained at full nose up due to insufficiency and/or longevity of ND commands? Without knowing the parameters of this control, how can we say this? Is it not reasonable to assume another condition.....specifically, it did not receive a command to trim down? And the command was lacking because with down elevators, the computer will not allow less G? What logic discards load parameter for flight path, and allows the THS to relax its NU? Any? |
Without the captain being in the cockpit I think these two could not have handled any emergency. They were button pushers, not pilots.
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Originally Posted by Lyman
As to the THS, I take note that you believe the THS remained at full nose up due to insufficiency and/or longevity of ND commands? Without knowing the parameters of this control, how can we say this?
1.1 History of flight: The trimmable horizontal stabilizer (THS) began a nose-up movement and moved from 3 to 13 degrees pitch-up in about 1 minute and remained in the latter position until the end of the flight. 1.16.3.3 Analysis of the flight control law: A simulation of the operation of the flight control computers was undertaken, which involved recalculating the movements of the elevators and of the trimmable horizontal stabiliser (THS) based on pilots’ inputs and compared the results against FDR parameters. This simulation was continued up until the end of the flight. The recalculated deflection angles for the elevators and the PHR are consistent with the parameters recorded. And the command was lacking because with down elevators, the computer will not allow less G? |
All the discussion of what the THS would or would not have done provokes a question... is the algorithm of THS (and other controls) operation published by the maker of the aircraft? What is known about it from "official" sources?
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HazelNuts39
Thanks, but my question is unanswered. The text says essentially that the controls worked properly, nothing about the logic. That is what I am after. How much input is required to bump the THS off the stops? What is the logic that directs the trim in AltLaw2? This is the bottom line: What allows the aircraft to isolate the pilot's options away from Manual trim? In a jet upset, this law treats recovery as it would the cruise. It is established that Autotrim is a function in AlternateLaw, but where in upset does a pilot want a "Dual track" for trim? One for short term inputs, and one that causes an input to remain trimmed, when the pilot may want agility. Once an input is "trimmed in" that deflection is the new "stability" why program stability, when a pilot may want its step sister, agility ? |
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