Airbus crash/training flight
Joined: Oct 2007
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From: Miami
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.
G
G
Joined: Feb 2007
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From: Not here
From processing the flight data in the prel report and from pages 34 and 35 I get:
at 2000 ft (when the flaps are selected to pos 0):
IAS 165
Pitch -47
AOA: 0 deg
at 389 ft:
IAS 263
Pitch: -24
AOA: 11 degs (I wonder if it reached alph-prot)
Also there's at least 2 data errors in the report.
.
at 2000 ft (when the flaps are selected to pos 0):
IAS 165
Pitch -47
AOA: 0 deg
at 389 ft:
IAS 263
Pitch: -24
AOA: 11 degs (I wonder if it reached alph-prot)
Also there's at least 2 data errors in the report.
.
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From: Miami
"It is so comforting to see all the Airbus/FBW drivers NOT in agreement on how their aircraft operates!"
G
Joined: Sep 2008
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From: MI
guiones -
I'll bet that chapter is a book all by itself.
I used the term 'driver' loosely. Actually, I guess I should have said "observer" instead.
I hope Raven77 is not an Airbus FBW "driver" as you put it; if you are qualified on any Airbus FBW, one of the first things you learn is the chapter on Flight Controls and Protections!!
I used the term 'driver' loosely. Actually, I guess I should have said "observer" instead.
Joined: May 2000
Posts: 1,021
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From: Glorious West Sussex
Alpha-floor
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
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
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
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From: UK
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....)
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....)
Sun worshipper
Joined: Dec 2001
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From: Paris
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...
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...
Joined: Sep 2008
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From: MI
TyroPicard -
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!
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.
As to Ratings: ATR DC-6/7, B-737, DC-8. Not current...RETIRED, thankfully!
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
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From: UK
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.............................
Sun worshipper
Joined: Dec 2001
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From: Paris
My view of the events
First the facts, as they appear in the report :
• 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.
• 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.
Joined: Sep 2008
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From: MI
Lemurian -
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?
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.
Trash du Blanc
Joined: Mar 2001
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From: KBHM
Don't know about the Diesel Eight but the DC-10 has alpha floor protection that brings up the throttles. And I assure you it is tested during acceptance/maintenance check flights.
If the Ten is not "conventional" then you're stuck in the sixties....
If the Ten is not "conventional" then you're stuck in the sixties....
Joined: Dec 2008
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From: DXB
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.
Sun worshipper
Joined: Dec 2001
Posts: 494
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From: Paris
You think a plane automatically trimming the aircraft out of control range without warning or feedback and keeping it like that while it should had been trimmed back to normal is safe ?
At that moment, they went into a stall warning and probably because the system sensed both FACs failed, it went - correctly - into direct law, because of the extended gear.
The crew had at that point two ways of identifying their flight control status :
1/- the lack of the warnings associated with "normal Law" (SPEED, SPEED)
and the lack of automatic TOGA that should have been triggered by an "alpha floor" sensed situation
2/- the change in the PFD and the "Use Man Pitch Trim" message.
As I said earlier, the stickforward movementfrom the PF and the application of manual TOGA was enough to exit tyhe stall situation and had they used the manual trim, it would have been just a classic stall recovery.
With the data we have at our disposal, we can't define the whys of the law changes (logic about failed inputs to the DMCs, comparison with the stby AoiA sensor....)
What we can , IMO, safely surmise is that the failed AoA sensors are at the top of the causes of the crash.
SFLY, there is more to piloting than moving throttles and sidesticks. And your arguments are at least specious. To say that they are what caused a crash is dishonest (just think of the THY 738 in AMS).
Joined: Aug 2003
Posts: 259
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From: FR
The conclusion that two of the AoA sensors failed, comes from the fact that the values "do not make sense" at some point in time; and also from the fact that the values are not changing. Of course I don't know, but I presume neither of these clues is taken into account by the system to (in)validate the data? The two wrong AoA values do seem to agree with each other, though. Would the third (supposedly good) data be discarded in such a situation, without any sort of warning?
Joined: Jan 2008
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From: southwest
When Airbus issued an AOT in January saying...
..during painting and maintenance it is important to protect all aerodynamic data sensors.... and that tests such as low speed tests "must be performed at safe altitude and be preceded by a recall of basic rules as regards to minimum speeds and recovery actions".
they did so after getting all the FDR data available at the time. They had a VERY good idea what happened, if not why.
..during painting and maintenance it is important to protect all aerodynamic data sensors.... and that tests such as low speed tests "must be performed at safe altitude and be preceded by a recall of basic rules as regards to minimum speeds and recovery actions".
they did so after getting all the FDR data available at the time. They had a VERY good idea what happened, if not why.