AF 447 Thread No. 12
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Clandestino
I will be the first 
Indeed but incomplete ...
30 cases with different A330 model as the 200 (this is a difference between 200 and other when AP disconnect due to bad speed reading by Pitot tube)
Indeed he pitched down when AP disconnected (virtually indicated on instrument)
30 cases with no scratch by luck (pilots not followed the procedures in force)
Luck = not a factor of security
How many in the 30 cases happened at night ? (different environment)
What about the Pitot problem ? (ice problem) well appreciated or not ?
30 cases = also hindsight .. no ?
Why the case 31 was needed ?
Now back to our usual reaction eliciters.
Yes. Thirty cases with not as much as scratch to anyone or anything were appreciated enough... till the 20-20 hindsighters took over.
30 cases with different A330 model as the 200 (this is a difference between 200 and other when AP disconnect due to bad speed reading by Pitot tube)
Not in AF447 case as it didn't pitch up with neutral stick.
30 cases with no scratch by luck (pilots not followed the procedures in force)
Luck = not a factor of security
How many in the 30 cases happened at night ? (different environment)
What about the Pitot problem ? (ice problem) well appreciated or not ?
till the 20-20 hindsighters took over.
Why the case 31 was needed ?
Last edited by jcjeant; 26th Oct 2014 at 06:12.
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...and add a Nz control on the the top of the stick like gums'jet (controllability),to don't be glued in nz=1 by the THS, and improve he observability of the trim wheel ...
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Originally posted by Clandestino
Quote:
Originally Posted by Owain Glyndwr
The question is WTH was this not carried over to Alternate laws???
Because ALTN laws are made (inter alia) for cases of air data getting screwed up! It would be no good if false data unnecessarily rob the pilot of control authority. No matter what John Cashman, Bernard Ziegler or CONF iture might say, in FBW Airbi pilot still has the ultimate responsibility to recognize the problem and more than enough control to solve it properly
Quote:
Originally Posted by Owain Glyndwr
The question is WTH was this not carried over to Alternate laws???
Because ALTN laws are made (inter alia) for cases of air data getting screwed up! It would be no good if false data unnecessarily rob the pilot of control authority. No matter what John Cashman, Bernard Ziegler or CONF iture might say, in FBW Airbi pilot still has the ultimate responsibility to recognize the problem and more than enough control to solve it properly
Last edited by Owain Glyndwr; 26th Oct 2014 at 08:07. Reason: spelling
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Quote:
Originally Posted by gums
The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.
Clandestino
Not in AF447 case as it didn't pitch up with neutral stick.
Originally Posted by gums
The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.
Clandestino
Not in AF447 case as it didn't pitch up with neutral stick.
Final report page 187,
"However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall."
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Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...
NBAA: Dassault's Trappier pokes fun at rival Gulfstream - 10/22/2014 - Flight Global
“And we are pleased to see that our friends in Savannah have finally decided to move towards sidesticks.”
But Trappier obviously avoids mentioning how the sidestick concept adopted by Gulfstream is different ...
Originally Posted by Clandestino
It would be no good if false data unnecessarily rob the pilot of control authority
2- False data unnecessarily rob the pilot of control authority here but you're nowhere to comment.
I agree with the report. You just have to define "stability".
In "normal" the AoA/stall protections are in place. But as the report says, in that particular alternate law that night ( or anytime) there was no AoA/stall protection, but the system still tried to achieve one gee corrected for pitch attitude, regardless of speed or AoA. In other words,the plane has no significant positive static stability that we normally think of.
It doesn't have a conventional "trimmed" state until in direct law and that's because once there it does not keep trying to reach the default gee and its basic aerodynamic design takes over, which apparently is damned good and exhibits good static stability and exceptional directional stability ( if you ask me). It tries to reach the trimmed AoA according to its c.g., center of pressure and the state of all the control surfaces. Get slow and it will nose over and get fast it noses up.
Hope I am making my position clear, and it was harder us to duplicate the AF447 scenario since our pitch law included a stong AoA limiter - 15 degrees at 9 gees then almost linear function until 27 degrees and 1 gee. If we got real slow in level flight it would eventually nose over to maintain the trimmed gee, not an AoA. With gear down, we added the AoA to the mix and could actually trim for an AoA.
In "normal" the AoA/stall protections are in place. But as the report says, in that particular alternate law that night ( or anytime) there was no AoA/stall protection, but the system still tried to achieve one gee corrected for pitch attitude, regardless of speed or AoA. In other words,the plane has no significant positive static stability that we normally think of.
It doesn't have a conventional "trimmed" state until in direct law and that's because once there it does not keep trying to reach the default gee and its basic aerodynamic design takes over, which apparently is damned good and exhibits good static stability and exceptional directional stability ( if you ask me). It tries to reach the trimmed AoA according to its c.g., center of pressure and the state of all the control surfaces. Get slow and it will nose over and get fast it noses up.
Hope I am making my position clear, and it was harder us to duplicate the AF447 scenario since our pitch law included a stong AoA limiter - 15 degrees at 9 gees then almost linear function until 27 degrees and 1 gee. If we got real slow in level flight it would eventually nose over to maintain the trimmed gee, not an AoA. With gear down, we added the AoA to the mix and could actually trim for an AoA.
Last edited by gums; 26th Oct 2014 at 15:17. Reason: typo, clarification of Viper control law
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Originally Posted by Clandestino
While precise and correct answer could be provided only by Airbus FBW experts - and I strongly suspect any of them reading AF447 threads must be howling with laughter
While precise and correct answer could be provided only by Airbus FBW experts - and I strongly suspect any of them reading AF447 threads must be howling with laughter
It's nothing to laugh about, but answers must be drawn
Hé ! qu'est-ce qu'il fait !? here
Ja it's pitching up all the time!!!
But what is happening? here
waaay too much even for the most corruptostupid aerogovernmental people inhabiting the imagination of PPRuNe's resident Airbus bashers
Originally Posted by Owain Glyndwr
... in alternate this THS movement inhibition could be triggered by stall warning rather than alpha protection. Only AOA data involved there, no false airspeeds; and I can see no good reason to trim into a stall situation.
... in alternate this THS movement inhibition could be triggered by stall warning rather than alpha protection. Only AOA data involved there, no false airspeeds; and I can see no good reason to trim into a stall situation.
THS position instrument and AOA indicator must be part of any cockpit instrumentation, with improved awareness for extreme positions.
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AF447 : un accident d'une extraordinaire complexité
certification:
BEA:
The A330 meets the requirements of the regulations in force at the time of application for the license type, namely the JAR 25 change 13 or 14 and the special conditions issued by the DGCA.
...
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
ECAM on the AF447, for 2 minutes and 39 seconds there was no message NAV ADR DISAGREE or NAV ADR DISCREPANCY.
It is these messages that moving towards doubtful IAS, procedure adapted to the situation
BEA:
The A330 meets the requirements of the regulations in force at the time of application for the license type, namely the JAR 25 change 13 or 14 and the special conditions issued by the DGCA.
...
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
ECAM on the AF447, for 2 minutes and 39 seconds there was no message NAV ADR DISAGREE or NAV ADR DISCREPANCY.
It is these messages that moving towards doubtful IAS, procedure adapted to the situation
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@JC
ECAM on the AF447, for 2 minutes and 39 seconds there was no message NAV ADR DISAGREE or NAV ADR DISCREPANCY
The remaining ADRs are compared to the average value > 16kts for 1s.
If true then the NAV ADR DISAGREE is set.
Since the message was only set after 2 min 39s this means that the above values were not exceeded before.
Remember the RH display was switched to ADR 3 at 02:10:40.
NAV ADR DISCREPANCY does not exist.
a DISCREPANCY message is preceded by a parameter, e.g. NAV IAS DISCREPANCY or NAV AOA DISCREPANCY.
The availability of this message (IAS) depend of the installed FWC standard.
Last edited by A33Zab; 29th Oct 2014 at 05:45.
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So we agree that nothing indicated a speed value problem on ECAM before 2 min 39s after the AP disconnected
And JAR 25
Is 2 min 39S is a acceptable delay for indicate such problem ? (speed reading)
And JAR 25
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
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Within that time period of 02:39, during the 'STALLSTALL' ADR1 and ADR2 were consistent and accurate for at least 1:04s.
They already noticed the speed difference because they switched RH display to ADR 3, unfortunately the most deviating and faulty source at that time.
i.e. they took action before the announcement.
Do you consider 16kts difference for 10s from median value acceptable?
Do you agree that an aircraft, which purpose is to transfer humans, should always be modified to the highest standard?
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
i.e. they took action before the announcement.
Is 2 min 39S is a acceptable delay for indicate such problem ? (speed reading)
Do you agree that an aircraft, which purpose is to transfer humans, should always be modified to the highest standard?
Last edited by A33Zab; 29th Oct 2014 at 10:23.
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Do you consider 16kts difference for 10s from median value acceptable?
Do you agree with JAR 25 or not ?
JAR 25
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
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Do you agree with JAR 25 or not ?
There are 7 lines of ECAM messages in view, in priority NAV ADR DISAGREE is only #114th.
#48 F/CTL ALTN LAW (PROT LOST) was always in view, (PROT LOST) = NO PROTECTIONS = keep away from limits!
Audible STALLSTALL means something and requires an appropriate action.
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We know that the failure was Pitot tubes
The AP was alerted of this failure and so he disconnected
The FBW system was alerted and so go in alternate law
Is the crew was alerted of this failure (for take appropriate actions .. so follow the procedure in force for IAS) and when in the time scale of the event ... ?
The AP was alerted of this failure and so he disconnected
The FBW system was alerted and so go in alternate law
Is the crew was alerted of this failure (for take appropriate actions .. so follow the procedure in force for IAS) and when in the time scale of the event ... ?
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The abiliy of pilots to be concerned with the good priorities is overloaded in flight by sofware variety and imagination. Their world of lift gets a cold untasted soap impossible to drink.
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We know that the failure was Pitot tubes
The AP was alerted of this failure and so he disconnected
The FBW system was alerted and so go in alternate law
Is the crew was alerted of this failure (for take appropriate actions .. so follow the procedure in force for IAS) and when in the time scale of the event ... ?
The AP was alerted of this failure and so he disconnected
The FBW system was alerted and so go in alternate law
Is the crew was alerted of this failure (for take appropriate actions .. so follow the procedure in force for IAS) and when in the time scale of the event ... ?
The PCPCs reverted to ALTN LAW by comparison of the median/average value of the speed data from ADIRUs.
The crew is alerted by comparison of the speed displays (NAV IAS DISCREPANCY) if the a/c was updated to the highest standard available (we know it is was not!).
The message NAV ADR DISAGREE didn't show up in phase 1 of the event because -unfortunately- it didn't exceed the delta/time limits.
This crew at that time needed to do the comparison themselves and take the appropriate action (pitch and power) like it was done for many years.
An exact failure description is simply not feasible, even the ADIRUs don't know the PITOT icing, the only know (by comparison) that Pt is not equal.
Above that all pitot failures will lead to the same appropriate action: pitch and power.
Last edited by A33Zab; 30th Oct 2014 at 09:53.
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An exact failure description is simply not feasible, even the ADIRUs don't know the PITOT icing, the only know (by comparison) that Pt is not equal.
Above that all pitot failures will lead to the same appropriate action: pitch and power.
Above that all pitot failures will lead to the same appropriate action: pitch and power.
Above that all pitot failures will lead to the same appropriate action: pitch and power.
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No we don't agree, pitot failures are clustered and result in NAV ADR DISAGREE (if value and time constraints are exceeded).
As such it is certified by the authorities so it complies to JAR 25 or FAR equivalent.
Name one A/C manufacturer who do announce PITOT ICING by means of message, warning light or such.
As such it is certified by the authorities so it complies to JAR 25 or FAR equivalent.
Name one A/C manufacturer who do announce PITOT ICING by means of message, warning light or such.
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Name one A/C manufacturer who do announce PITOT ICING by means of message, warning light or such.
If not all follow a regulation or make respect a regulation that does not mean they are therefore correct
JAR 25
"Systems and associated alarms" must be developed to minimize the risk of error by the crew
Pitot is not a new technology .. icing and deicing of Pitot is not new knowledge
I think this was enough time for find a system for alert the crew that a Pitot is out of use .. by audible or visible alarm