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Were all these calculations made using Flight Idle ? Or TOGA ? Or what ?
The latest advice appears to show a difference. |
It requires most talent, training, and practice. But is not this exactly what is expected of professional pilots? Or professional pilots position is now .. only be able to pilot planes when all is smooth but not when problem arise ? |
Originally Posted by rudderrudderrat
(Post 6665015)
In ALT LAW - when stick free, the FBW computers would maintain the same attitude and probably apply more nose up elevator and trim in an attempt to maintain 1g during the stall.
On a quick eyeball check of the FDR traces (after the post-apogee slam to the backstick stops), the aircraft is indeed maintaining roughly one g in the stall with the elevators slammed up, except for the two periods where backstick is released, the elevators start to return to neutral and the g traces show a change in value - suggesting that letting go of the stick would have had some effect on what the load factor protections would command. What that effect would have been - let alone would it have been enough - I don't have the information to answer. |
Henra, correct, thanks and sorry for any confusion
Additionally: Significant drag is contributing to NU trim when and if the tail does stall Additionally: Significant drag is contributing to ND trim when and if the tail does stall |
Hello QwainGlyndwr,
What I had in mind is the 'g load factor' involved in the pitch control (elevators and auto-trim) that may be an impediment to a very quick, but very short (time wise) set of actions, that involve also Elevators and possibly (tbd) THS, which a successful Stall Recovery may require. "rudderrudderrat" had a quite similar perspective:
Originally Posted by rudderrudderrat
(Post 6665015)
Hi Henra,
Originally Posted by henra
I'm quite confident this aircraft would have dropped the Nose upon stall if this hadn't been so vigorously countered by the massive NU inputs and subsequent THS following.
In ALT LAW - when stick free, the FBW computers would maintain the same attitude and probably apply more nose up elevator and trim in an attempt to maintain 1g during the stall.
Originally Posted by Owain Glyndwr
(Post 6664855)
airtren
Originally Posted by airtren
Without having a Normal Acceleration in the picture, is there any indication that in order to being able to quickly and effectively react and have full control of the control surfaces at Stall, would have been better achieved by being in Direct Law?
It depends a bit on where you consider 'Stall' to be. By the time the stall was fully developed the actual details of how the system would respond to control inputs are far less important than the fact that there were no control inputs. If you are considering the actual entry to stall in the first place then the better pitch damping given by Alternate might have been a factor for good. I don't think much of the harmonisation of roll and pitch given by Alt2, but I suspect that a 'double whammy' of direct law in both axes might have led to even worse results. But I trespass into pilot territoryhttp://images.ibsrv.net/ibsrv/res/sr...lies/wink2.gif |
Taking this one stage further from Owain's analysis etc. isn't it now likely that Airbus (on behalf of BEA?) have simulated the 330's recovery from such a fully developed stall attitudes and trajectories.
If the speculation that Airbus really intends to test-fly such a profile at some point holds water,.then they must be very sure that it's doable. A tail chute might be a consideration, as some of the early T-tailled test aircraft had to start using here. I would think a fairly good dynamic model of stall recovery has been attempted and the likely recovery profile, loads and altitudes known - which will hopefully feature in a report one day. |
@airtren - Speaking purely theoretically and from the technical evidence I have, if the manual trim wheel is moved then there isn't a damn thing any protection can do to stop it, and if you hold it in position, there's nothing it can do to change it either. It's way outside normal procedure, but let's face it - this flight profile was nothing if not way outside anything that went into the book.
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jcjeant,
Someone mentioned at one point the Challenger Shuttle accident happening in front of so many watching it, and the O-rings problem that was known for quite some time. This was mentioned before perhaps....There are many components in the lessons of AF 447, but at least 3 of them are related to flying/pilots: one is flying with lack of speed indications, second is avoidance of High Altitude Stall, and the third is High Altitude Stall Recovery (in night conditions). Like after the Challenger accident, there are many signs that this may be somewhat of a turning point in training and practicing, as I am sure talent is there, or was always there. A new generation of Flight Simulators for training is in order, better curriculum, including a wider span of theoretical physics and basic principle of flying, better documentation, better procedures... and the list can get very long..... These are just a few...
Originally Posted by jcjeant
(Post 6665354)
Happy to read that.
But is not this exactly what is expected of professional pilots? Or professional pilots position is now .. only be able to pilot planes when all is smooth but not when problem arise ? |
Tried to make the point in #494, and quite frequently before; I see you bring it up above (#499): Relative g demand Law. If in DIRECT LAW, wouldn't the PITCH have been non reliant on this "slowpoke", and the PF would have STALLED far sooner than the AL2 "normed" ascent allowed?
Not a BAD thing, and perhaps with a higher level of energy, the NOSE drop and Buffet may have contributed to a more straightforward STALL ID and recovery? |
Dozywannabe,
It's in the realm of talent, training and practicing. I am aware of two Airbus 310 day light Successful Stall Recoveries in Europe - Interflug and Tarom, both A310 - in which pilots, in spite of the mistakes that created the Stall situations, were able to prove their airmanship, and mastering of their profession and tools in the cockpit, including the THS wheel, by recovering from what would have been unrecoverable situations, and landed safely, with no injuries, or damage to the airplanes. It was not some corporate procedure document they've read at Stall that saved them. From what I understand, those pilots, were from a generation in which training was not different than that of the military pilots. So they had it in their reflexes, didn't have to think much, what to do right away in a stall. From what I've read, at 4100ft, and 30kt AoA NU at 60 degrees, - yes forty one hundred feet - from where the Tarom A310 recovered, there was not much time. The Captain and FO leveled the plane at 800ft, from nose dive to regain speed. The captain used the THS Wheel, like the Stick, with quick, soft, short (time-wise) commands....
Originally Posted by DozyWannabe
(Post 6665401)
@airtren - Speaking purely theoretically and from the technical evidence I have, if the manual trim wheel is moved then there isn't a damn thing any protection can do to stop it, and if you hold it in position, there's nothing it can do to change it either. It's way outside normal procedure, but let's face it - this flight profile was nothing if not way outside anything that went into the book.
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Why loss of AP
If loss of airspeed was the only underlying fault in AF447, can anyone explain why the Autopilot needs to disengage? Isnt the AP taking inputs from pitch, roll and yaw only? I can understand that the autothrottle needs to disengage as obviously that needs a reliable airspeed input. But Ive flown plenty of less sophisticated types where the AP will happily keep functioning despite airspeed and many other system failures. This would allow you to focus on the problem whilst AP aviates and you manually set throttle to an appropriate N1 setting.
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@ChrisJ800 - depends on the type of autopilot. Older types would be limted in the amount of roll, pitch and yaw they could command (and as such should theoretically not induce LOC as long as you keep an eye on them). Modern types are "Full authority", and can theoretically command anything.
For an example of what pitot failure can do to an autopilot, check the Birgenair 757 case. During climb, the blocked pitot indicated overspeed and the A/P commanded nose-up to the A/P's limit of control - the overspeed warning continued, so the Captain reduced thrust manually and almost immediately stalled and never recovered. |
Chris, I think the autopilot engineers didn't want the AP flying the airplane if there were two competent pilots to take over if the inputs to the computer were lost. The AP if programmed to keep flying without airspeed input would have held 3 degrees nose up until altitude hold required a different attitude, and the last N1. The AT would eventually have no way to know if it needed to change with no AS. I think that is why they wouldn't let it keep flying level. It could get too fast or too slow with no AT help. Letting the pilots fly it manually to keep it in proper speed range was their solution.
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airtren
Following link re: Interflug/Tarom (not sure the latter Captain was ex-military, although he was certainly ex-BAC 111 with all that entails re: stall alert....)
Video Wanted - Interflug A310 Stall Incident - JetPhotos.Net Forums - The Friendly Way to Fly Useful pre-AF447 Discovery Channel "automation" documentary, now with an added resonance. Interview with ex-Lufthansa safety pilot, which draws the battle lines. Chill Lyman, chill......! |
Originally Posted by Welsh Wingman
(Post 6665529)
Useful pre-AF447 Discovery Channel "automation" documentary, now with an added resonance.
Interview with ex-Lufthansa safety pilot, which draws the battle lines. |
DozyWannabe
And your opponents (of which I am not one in the wider context) will argue he was spot on.....
To the extent that I have an issue with "Airbus", if I am to be dragged in to such a debate, it is limited to the "leap" from Concorde/A300 to the A320. More than incremental, and it should have been limited (at that stage) to the FMS move forward and not concurrently removed artificial feedback from the cockpit. I cannot stress enough, as a pilot to a software engineer, the Pandora's box that was opened up in relation to line management perceptions on flight operations and training and which is at the very heart of what went spectacularly wrong with AF447. Airmanship plus - forget it. |
jcjeant Personally I do not think the AF447 accident has any relation (or could be explained) by trigonometry .. geometry or other formulas .. academic or by the curvature of THS The accident was related to the actions of the pilot(s) This aircraft was built according to specifications and apparently he has met these requirements since it was authorized to make commercial flights. And since the AF447 accident he continue to perform commercial flights This aircraft is equipped with up to date flight and navigation aids So .. it indicates to pilots (in the case of 447) that there may stall ... or if this warning is not followed by appropriate reactions of the pilots .. he will warn that the aircraft is experiencing stall The pilot did not have appropriate responses to deal with the event and did not have appropriate responses to correct his first mistake The aircraft systems were all put in place to prevent the pilot from his mistake The stall alarm has been running for 54 seconds continuously The artificial horizon presented a large blue area The altimeter showed a rapid loss of altitude The origin of the event is the icing three pitot probes at the same time (same manufacturer .. same type .. no luck for redundancy) There was also 3 pilots icing (brain icing) .... The three pilots, however, were of different types .. but of the same brand (AF) Even there .. redundancy has not worked ... I still recommend to watch Mayday (or whatever the name is in your country) Season 11 Episode 2. Mayday | Episode List Note: The final report was written in Spanish. |
Hi Aitren,
So they had it in their reflexes, didn't have to think much, what to do right away in a stall. The pilot's did not have to go through the "W.t.f. is it doing now?" It is simply - "what you feel on the elevator is what you get." Hi bubbers44, Letting the pilots fly it manually to keep it in proper speed range was their solution. Hi jcjeant, The accident was related to the actions of the pilot(s) The only question is why 3 qualified pilots could not recognise that they were in a stalled condition. Edit. The stall alarm has been running for 54 seconds continuously When overloaded, the brain processes auditory senses last or not at all. |
Hi,
I agree. The only question is why 3 qualified pilots could not recognise that they were in a stalled condition. What is a qualified pilot ? On which basis (in AF) they are named "qualified" ? On which basis are they recruited ? What are the level of qualification and how is the recruitment in other companies ? different .. more .. less ? What is the following of their qualification .. rate of refreshing courses ... etc ... What is the security policy of the company .. the general atmosphere on such safety within the company .. I want to remind the Colin report about Air France |
So, the Elevator to THS surface ratio is 3:7, which is 1: 2.33. .... But as the THS moves itself, the Elevators move/angle is relative to the THS, and absolute to the a/c body, and thus "complex" - it has two components: its own, and that of the THS. At this quick writing I am not sure if I am clear. As the pitching momentum depends on the angle, the complex angle has a complex effect on the pitching momentum. Imagine cruise AoA, and THS and Elevators at corresponding position. What would Manual Trim NU of THS do? It considers only: max NU, with both THS and Elevators at max NU, and max ND with both THS and Elevators at max ND, and leaves out the other two combinations, which are part of the set of possible positions see my original post bellow: question: are there any other forces (with their respective arms) involved? at that AoA? |
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