It does not matter which Flight control law the A/C is in, (as long as the Autothrust is not u/s), it will kick in at the pre determined angle of attack and give Toga thrust, even with the thrust levers in the idle position.
OK...thank you for that info.
Does "u/s" mean Unservicable, or 'Deferred'? If so, what happens with the throttles in idle?
A question for aircrew doing check or test flights.
When performing test flights, as you go through the list of checks, in what frame of mind are you ?
When performing an action, do you expect a normal response, or are you prepared for an abnormal response, or are you prepared for "anything to happen" ?
Back to the Perpignan thread: is it possible that towards the end of a checkflight where everything has been routine, the crew were in a frame of mind expecting that all responses would continue to be routine/as expected ?
I'm thinking back to commissioning many newly-launched spacecraft, and working with ground stations, where it was esssential to be in the correct frame of mind when doing systems checks, and how after the initial burning-in phase where one was very wary, one "got used" to all responses being nominal.
The aircraft went straight to Direct Law while performing an ALPHA PROT at low altitude in landing config, I think that this is the final reason of the crash.
We dont need to go much futher to know what caused the accident.
The Control Laws didnt catch the plane while performing the deep Stall and later the dive. Instead, the loss of auto trim in Direct Law and the full up position of the stab limited de manouver envelope for a recovery when the control transited to Alternate Law.
Probably it get to the limit of 2,5G during the pull up, this is pretty scary in a commercial jet, but it wasnt enough.
I dont know if the plane structure would have resisted 2,6 or 2,7 Gs, but I prefer to wreck the plane rather than being wrecked by the plane.
It does not matter which Flight control law the A/C is in, (as long as the Autothrust is not u/s), it will kick in at the pre determined angle of attack and give Toga thrust, even with the thrust levers in the idle position
I am not sure about the above. This is my interpretation :
Alpha Floor protection (TOGA thrust and AOA "stall" protection) only works in NORMAL LAW !!
Alternate Law has a Low Speed Stability which may be overridden and the aircraft may stall
Direct Law has no such protections as all, and once again, you may stall !!
DC, It does not matter which Flight control law the A/C is in, (as long as the Autothrust is not u/s), it will kick in at the pre determined angle of attack and give Toga thrust, even with the thrust levers in the idle position."
You are absolutely wrong, the protection you are speaking about is ALPHA FLOOR and it is ONLY available in NORMAL LAW.
Regarding the STALL WARNING in NORMAL LAW, it is available, but the threashold is way below V ALPHA MAX, it is impossible for the A/C to reach this threshold and still be airborne. The ONLY way to get a stall warning in NORMAL LAW is for the AoA probe to break or be stuck to reach this threashold. The reason that it is on the FCOM is because it has happened before.
For the avoidance of doubt - I have checked the relevant FCOM:
Alpha - floor (which incidentally is simply an A/THR mode independent of FBW protections) signal is provided by the FAC, when the AOA is above a predetermined threshold, which is a function of the configuration. It is available from lift-off until the a/c reaches 100 ft. RA in approach.
Alpha-floor is lost under alternate or direct flight control law. (one of eight loss-making conditions).
i.e Alpha-floor is only available in Normal Law
Regarding who is "drivers" and who ain't - unless a PPRuNer's profile states licence type and a/c - I assume they are not pilots. But I don't assume they don't know what they are writing about, unless it is obvious from what they write. TP
TP - may I summarise with a question? As you know, I have no knowledge of AB technology, but I assume it true to say that if the AoA vane had been 'jammed' in its rest (ie hanging straight down) position, it would never sense AoA near the stall and therefore not trigger AFloor, nor, I guess might any indications of such a position be apparent in 'normal' flight? Does all of this depend on a serviceable AoA vane and pilot monitoring of speed/attitude? How many AoA vanes are there on the 320?
I am confused (as are some 'apparent' AB pilots) as to what (if anything) happens then to pitch/power/A Throttle with the onset of subsequent stall - presumably no stick shake, just a classic stall with possible wingdrop - I guess the a/c would not 'know' it had stalled? I also understand that by then the tail would have been trimmed well noseup and it appears (if I understand this correctly) that the a/c could then prevent you from recovering from the ensuing dive by limiting 'g'?
(Bring back the 'overstress' ability you and I recall - the days of popped rivets and being alive for the boss's reprimand....)
This thread is getting away, as usual, onto Airbus perceived faults bythose who don't have any idea how good it is and how safe it can be compared to the geriatrics many of us pilots, including me, have flown. May I just point at at the fact that , in all intents and purposes, this crew had managed to escape from the first stall situation and all they had to do was manually trim the aircraft and reduce the thrust - get out of TOGA-. It should have been the end of the scare... but it wasn't as SA was no longer there (only explanation , IMO). Another fact is on the final plunge, why accelerate / retract the high lift devices...? People are talking about protections that are no longer available in their actual laws...A slower speed, with flaps/slats out at 2.5 gs could have saved them too...
Regarding who is "drivers" and who ain't - unless a PPRuNer's profile states licence type and a/c - I assume they are not pilots. But I don't assume they don't know what they are writing about, unless it is obvious from what they write.
OK.....I didn't put a 'smiley' behind the word driver. I would think that anyone with any sense of humor would've recognized that. Wrong again.
As to Ratings: ATR DC-6/7, B-737, DC-8. Not current...RETIRED, thankfully!
Does anyone have a comment on the wild fluctuations of 'recorded' CAS between 45:42 and :52, where little pitch change is taking place? <60kts to >240kts several times in 10 seconds? 3 times - just not possible. What are we looking at - some gross Pressure errors? If those speeds were being displayed to the crew.............................
They performed the planned (?) low speed test, involving an entry - and an immediate exit from - into α floor.
The altitude for the test is lower than the recommended FL120-140 by all documents
In this exercise, they expected to see successively Vls, Vmin, α prot and α floor, marked by an automatic trigger of TOGA thrust. They even talked about the ATHR handling at that point ( "push, disengage, reengage" )
They never saw that succession of events... Instead, they had a "stall warning" (we can safely assume that it was the "STALL...STALL" call-out and not the "SPEED...SPEED" one would get in normal law.
They selected a manual TOGA thrust and then,
They experienced some difficulty with the flight path control, ending in a plunge into the sea.
In the report there are two major issues that the investigators have not commented upon but just mentioned as "in passing" :
The frozen -"frozen" as in "not moving due to a blockage" of any sort - AoA sensors, probably feeding the FACs erroneous data critical to the speed limits info displayed and the computation of the AoA protection speeds. As the print-out shows the AoA1 and 2 unmoving parameters, one can also assume that the stall warnings came from the - unrecorded - stby AoA.
The stabilizer (THS) was automatically - and correctly, in view of the deceleration - trimmed to max nose-up and stayed at that value for the remainder of the flight. On this subject, in "Normal Law", the auto-trim stops when the airplane enters an α prot situation...and in "Direct Pitch Law" it is unavailable, the crew is reminded by a message urging them to use the manual trim wheel.
But, because of the unavailable AoA data, they never entered α prot and got instead a stall warning They did enter the "Direct Pitch " mode because of the landing gear been extended... and yet, the stabiliser still showed no movement : jammed or un-utilised ?
That un-moving stabilizer, stuck at max nose-up (for want of another word) couldn't be overcome by the full nose-down demand by the PF, especially when one considers the not-so-light pitch-up moment that the engines at TOGA thrust would induce.. In other words, the sidestick authority in pitch wasn't enough to check the increasing pitch attitude of the airplane, leading to the two subsequent successive stalls. I have left out all the reversions that could have occurred during that maneuver, because in my opinion, they all lead to a further complication of the crew situational awareness. Because in the end, I believe that they entered a totally unexpected situation they were not either prepared or trained for, with major handling difficulties and, in my opinion, some disorientation... A situation that was unrecoverable so close to the sea.
This thread is getting away, as usual, onto Airbus perceived faults by those who don't have any idea how good it is and how safe it can be compared to the geriatrics many of us pilots, including me, have flown.
That is true. However, as I said early on.....like it or not.....had this been a 'conventional' airplane, there would have been no reason for such a test, would there? I just won't go away, will I?