AF447 wreckage found
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We don't know if the ND picture was normal - until we know the tilt setting on the WXR it's difficult to conclude anything, but, I think At the time the FCTM/FCOM says something like" CRZ ALT - set tilt "slightly" negatively down," if that's what actually was set they may have been over scanning and had a false picture. Over water ITCZ type flying needs aggressive down tilts and short ranges(80nm and 3.5 ish down tilt etc)
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fgrieu, I think you'll find the A/C was in Alt Law 1 or 2 depending if it had concluded a ADR disagree or fault, either way the pitch control in Alt law 1 or 2 is the same, with normal THS movement dependent on the load factor command from the sidestick deflection.
Once the A/C exceeded 30 degrees AOA however the abnormal attitude would have kicked in remaining in ALT law however the THS auto trim would have stopped.
So the initial nose up inputs caused the THS to trim for the new commanded load factor from the sidestick deflection (full nose up at times) and frozen at 13 degrees probably when the AOA exceeded 30 degrees.
Once the A/C exceeded 30 degrees AOA however the abnormal attitude would have kicked in remaining in ALT law however the THS auto trim would have stopped.
So the initial nose up inputs caused the THS to trim for the new commanded load factor from the sidestick deflection (full nose up at times) and frozen at 13 degrees probably when the AOA exceeded 30 degrees.
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The PF experience has nothing to do with the accident .. it's not a reference.
( Laws of "too loose"? )
BOAC, I read that article again, and it seems to be contradictory.
That doesn't answer the mail for dealing with a stalled aircraft. From from a common sense perspective, in terms of operations, "do better at NOT stalling" it certainly makes sense as a training objective.
{AF 447} After stalling, the A330's angle of attack stayed above 35°. But while this exceeded the threshold for the abnormal attitude law, the flight control computers had already rejected all three air data reference units and all air data parameters owing to discrepancy in the airspeed measurements.
{My thought: does this mean that AoA greater than 30 deg does not trigger Abnormal Law, or that there are some more tie ins to the comparisons {summed inputs into the flight computer} requiring (valid?) airspeed input before that law is selected?}
Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.
The BEA is still attempting to explain why AF447's crew failed to rescue the aircraft after it climbed to 38,000ft and stalled. The pilot's control inputs were primarily nose-up, despite the stall condition.
There has been no indication that the aircraft switched into any other control law, other than alternate, during the accident - suggesting that auto-trim was available throughout the descent.
{skip a bit}
In its conclusions over the {Perpignan} accident the BEA highlighted the rarity of the need to trim manually, which created a "habit" of having auto-trim available made it "difficult to return to flying with manual trimming".
"One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training," it said. "However, in this case, the exercises generally start in stabilised situations."
In the wake of the A320 accident, near Perpignan in November 2008, the BEA recommended that safety regulators and manufacturers work to improve training and techniques for approach-to-stall situations, to ensure control of an aircraft in the pitch axis.
{My thought: does this mean that AoA greater than 30 deg does not trigger Abnormal Law, or that there are some more tie ins to the comparisons {summed inputs into the flight computer} requiring (valid?) airspeed input before that law is selected?}
Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.
The BEA is still attempting to explain why AF447's crew failed to rescue the aircraft after it climbed to 38,000ft and stalled. The pilot's control inputs were primarily nose-up, despite the stall condition.
There has been no indication that the aircraft switched into any other control law, other than alternate, during the accident - suggesting that auto-trim was available throughout the descent.
{skip a bit}
In its conclusions over the {Perpignan} accident the BEA highlighted the rarity of the need to trim manually, which created a "habit" of having auto-trim available made it "difficult to return to flying with manual trimming".
"One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training," it said. "However, in this case, the exercises generally start in stabilised situations."
In the wake of the A320 accident, near Perpignan in November 2008, the BEA recommended that safety regulators and manufacturers work to improve training and techniques for approach-to-stall situations, to ensure control of an aircraft in the pitch axis.
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So auto-trim was still active throughout the stall and continued stick-down inputs, had they been applied, would have moved the THS down and thus aided the recovery?
@Lonewolf: my reading of this, and the BEA report, is that the AOA data is lumped together with other air data measurements and accepted or ignored together... either all or none. (thoughts... does this apply to altitude and ROC too?)
No abnormal law for the same reason as no stall warning.
@Lonewolf: my reading of this, and the BEA report, is that the AOA data is lumped together with other air data measurements and accepted or ignored together... either all or none. (thoughts... does this apply to altitude and ROC too?)
No abnormal law for the same reason as no stall warning.
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fgrieu -- note that the expert is said to be an ex-airbus pilot. When listening to the testimony of experts who have had previous links with manufacturers or employers, one should be sure to check that there is no axe to grind. Even a small chip on a shoulder can cause a man to walk with a pronounced limp. Demanding the entire fleet to be grounded until the phenomenon is 'adequately explained' (to whom?) is a serious step that could financially cripple or even destroy the manufacturers, airlines and their employees.
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Lemain We have been here before
BBC ON THIS DAY | 10 | 1954: Comet jet crashes with 35 on board
Tinker at the edges until there is another crash into the sea?
Tinker at the edges until there is another crash into the sea?
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Lemain
Oh yeah. After BA038, there was a similar refrain. Two rollbacks, simultaneous on a twin. A somewhat more serious event than UAS?
UAL recalled its entire fleet, but supposedly, for a deferred item (firebottle #5 in the Hold), then released them to the line after the inspex. Huttig plus salt shaker, please. (Chip on shoulder equals "limp" priceless!)
Oh yeah. After BA038, there was a similar refrain. Two rollbacks, simultaneous on a twin. A somewhat more serious event than UAS?
UAL recalled its entire fleet, but supposedly, for a deferred item (firebottle #5 in the Hold), then released them to the line after the inspex. Huttig plus salt shaker, please. (Chip on shoulder equals "limp" priceless!)
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In answer to Lemain:
I am just trying to understand what happened, and what lessons can be learned. I did link to an article echoing a voice asking to ground the planes, but that's not an endorsement of that opinion.
If (that's far from evident, at least to me) the THS remained nose up 13° despite the pilot commanding a nose down circa 13000 ft due to a characteristic of the flight law then active, then I think pilots on the type should be trained to trim manually in order to get out of stall in that flight law, rather sooner than later. Anyway, if that's true, I expect many if not most pilots on the type have read the BEA report and came to that conclusion by themselves.
Full disclosure: I'm not a pilot, I am an engineer working on security (not safety) critical systems.
I am just trying to understand what happened, and what lessons can be learned. I did link to an article echoing a voice asking to ground the planes, but that's not an endorsement of that opinion.
If (that's far from evident, at least to me) the THS remained nose up 13° despite the pilot commanding a nose down circa 13000 ft due to a characteristic of the flight law then active, then I think pilots on the type should be trained to trim manually in order to get out of stall in that flight law, rather sooner than later. Anyway, if that's true, I expect many if not most pilots on the type have read the BEA report and came to that conclusion by themselves.
Full disclosure: I'm not a pilot, I am an engineer working on security (not safety) critical systems.
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there is a lot of stuff left to cover by the BEA...... they have barely addressed the cockpit conversation, they have not addressed at all many of the ACARS messages that were sent during the last four minutes (PRIM1/SEC1 faults et al)
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I would say that in hindsight we all know that they should have stay clear of the ITCZ weather; well in that part of the world they could have deviated a hundred miles off course with no problem from ATC with respect to parallel airways.
However in the Atlantic or Pacific with closely spaced airways and random tracks, sometimes ATC is pretty slow or outright deny any request to deviate. I guess the junior crew members were reluctant to exercise the emegency option of deviating without clearance. Some airlines come down hard on pilots deviating without clearances.
You may say, ask for deviation clearance early, but with the modern flat plate weather radar system, severe weather returns sometimes only pop up within 40-60 miles ahead. ATC like Tokyo takes hours to reply or authorise deviations. How do you veterans deal with this situation........exercise your emergency contigency procedures and deviate without clearance and risk a TCAS event followed by loads of explaining to do?
However in the Atlantic or Pacific with closely spaced airways and random tracks, sometimes ATC is pretty slow or outright deny any request to deviate. I guess the junior crew members were reluctant to exercise the emegency option of deviating without clearance. Some airlines come down hard on pilots deviating without clearances.
You may say, ask for deviation clearance early, but with the modern flat plate weather radar system, severe weather returns sometimes only pop up within 40-60 miles ahead. ATC like Tokyo takes hours to reply or authorise deviations. How do you veterans deal with this situation........exercise your emergency contigency procedures and deviate without clearance and risk a TCAS event followed by loads of explaining to do?
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BOAC, cheers, what are the odds, a failure allows the THS to still be used and unfortunately for whatever reason a significant nose down input is not made.
Perhaps Airbus should freeze the THS after an ADR failure and not wait until an abnormal attitude is reached leaving you with an A/C that is possibly trimmed just outside the range of a UA.
Perhaps Airbus should freeze the THS after an ADR failure and not wait until an abnormal attitude is reached leaving you with an A/C that is possibly trimmed just outside the range of a UA.
BOAC, cheers, what are the odds, a failure allows the THS to still be used and unfortunately for whatever reason a significant nose down input is not made.
Perhaps Airbus should freeze the THS after an ADR failure and not wait until an abnormal attitude is reached leaving you with an A/C that is possibly trimmed just outside the range of a UA.
Perhaps Airbus should freeze the THS after an ADR failure and not wait until an abnormal attitude is reached leaving you with an A/C that is possibly trimmed just outside the range of a UA.
1. What do you mean by "freeze the THS": cancel or pre-empt all commands to move it, up or down, unless the pilot manipulates the trim wheel?
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Stop auto trimming with an ADR problem, which would have left the trim at 3 degrees which was speed stable for FL350. Once the problem was resolved allow the auto trim to resume.