AF 447 Thread no. 4
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Deviation - too little too late
BOAC
Quote:
Originally Posted by OC
BOAC - Apologies for the slow reply. Details of other aircraft deviating round the weather front can be found in already released BEA reports and in various posts in the threads on this subject. I am sure that if you look you will come across them.
- is it perhaps that you have missed the 12 deg deviation of AF447 in the report? As far as I know there is no evidence that they 'flew into a CB'.
There is nothing but evidence they flew into a CB.
But I want to add what we know and what we don't about this.
First the mission of the BEA, or any modern country’s investigative body’s is to assess the facts, try to make a determination of Probable Cause, and make recommendations for corrective action. Or lessons to prevent it from happening again.
It sometimes is implied that they “will leave no stone un-turned to arrive at a resolution.”
That is incorrect and is used when there are reasons for the outcome to be delayed.
In the Air Force where I served as an accident investigator for fighter squadrons, the mission was slightly different. And we had many more accidents to deal with. The AF did not have the luxury of waiting for the up to two year time lag waiting for results, as national security was at stake. Thus their mission was a Safety Investigation. All of the parties were immune from prosecution, legal suits did not apply, and the object was urgency, so that we could get back in the air again. Their goal is to make a determination of Probable Cause also and make recommendations to avoid or prevent.
The definition of probable cause is simply, more likely than not. Or technically 50.1% versus 49.9. A very low level of certitude, but considering all of the many unknowns very practical.
Here we know some things for sure, many many more we know literally nothing about.
1) We know: thunder storms along the track. No one knows how severe.
2) We know there are severe up and down drafts in them.
3) We know all 3 pitot tubes iced up. No one knows precisely why.
4) We know critical airpeed indicators went out.
5) Auto-pilots failed.
6) Auto-throttles failed.
7) Uncommanded 7000 fpm climb. Despite the plane being at it’s maximum cruising altitude. Evidence of 60-70 kt updrafts according to meteorological analysis.
8) Airspeed falling to below 60 kts.
9) Flight controls ineffective below 120 kts.
10) I know, you cannot control an airplane with trim alone.
11) No one knows for sure what a plane will do in a deep stall.
12) No one knows for sure whether a plane can recover from a deep stall especially with limited flight controls.
Questions I have:
Why was the flight dispatched into a known line of thunderstorms?
Why is there so little concern about the effects of flight into thunderstorms?
Despite all of the warnings on the subject?
To me there is no mystery.
Quote:
Originally Posted by OC
BOAC - Apologies for the slow reply. Details of other aircraft deviating round the weather front can be found in already released BEA reports and in various posts in the threads on this subject. I am sure that if you look you will come across them.
- is it perhaps that you have missed the 12 deg deviation of AF447 in the report? As far as I know there is no evidence that they 'flew into a CB'.
There is nothing but evidence they flew into a CB.
But I want to add what we know and what we don't about this.
First the mission of the BEA, or any modern country’s investigative body’s is to assess the facts, try to make a determination of Probable Cause, and make recommendations for corrective action. Or lessons to prevent it from happening again.
It sometimes is implied that they “will leave no stone un-turned to arrive at a resolution.”
That is incorrect and is used when there are reasons for the outcome to be delayed.
In the Air Force where I served as an accident investigator for fighter squadrons, the mission was slightly different. And we had many more accidents to deal with. The AF did not have the luxury of waiting for the up to two year time lag waiting for results, as national security was at stake. Thus their mission was a Safety Investigation. All of the parties were immune from prosecution, legal suits did not apply, and the object was urgency, so that we could get back in the air again. Their goal is to make a determination of Probable Cause also and make recommendations to avoid or prevent.
The definition of probable cause is simply, more likely than not. Or technically 50.1% versus 49.9. A very low level of certitude, but considering all of the many unknowns very practical.
Here we know some things for sure, many many more we know literally nothing about.
1) We know: thunder storms along the track. No one knows how severe.
2) We know there are severe up and down drafts in them.
3) We know all 3 pitot tubes iced up. No one knows precisely why.
4) We know critical airpeed indicators went out.
5) Auto-pilots failed.
6) Auto-throttles failed.
7) Uncommanded 7000 fpm climb. Despite the plane being at it’s maximum cruising altitude. Evidence of 60-70 kt updrafts according to meteorological analysis.
8) Airspeed falling to below 60 kts.
9) Flight controls ineffective below 120 kts.
10) I know, you cannot control an airplane with trim alone.
11) No one knows for sure what a plane will do in a deep stall.
12) No one knows for sure whether a plane can recover from a deep stall especially with limited flight controls.
Questions I have:
Why was the flight dispatched into a known line of thunderstorms?
Why is there so little concern about the effects of flight into thunderstorms?
Despite all of the warnings on the subject?
To me there is no mystery.
wallybird7: The ITCZ is a well understood area, that routinely presents challenging weather conditions. However EVERY flight traveling North<>South in this region of the World will transit the ITCZ. So your question "why were they dispatched into a known line of thunderstorms?" is rather misrepresenting the situation. This area of weather is not a rare occurrence, more so a common situation, and in fact the conditions that night were NOT particularly severe, with the term being "moderate thunderstorms" being the one most often applied after skilled analysis.
There were many other flights that passed through the SAME weather system, however the majority applied some diversion to a much greater extent than anything AF447 attempted. THAT to me is the most problematical concern of mine - WHY didn't they divert around the system?
There were many other flights that passed through the SAME weather system, however the majority applied some diversion to a much greater extent than anything AF447 attempted. THAT to me is the most problematical concern of mine - WHY didn't they divert around the system?
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Hi Smilin_Ed
I must disagree with your first sentence. If the auto-trim followed the crew's orders (via the sidestick) then the crew had unrestricted control.
Perhaps you interpreted "unrestricted" as "full manual" ? That's not what I meant. For me "unrestricted" means just that : the planes follows the crew's inputs, and the computers don't prevent manoeuvers because it "thinks" they're of no good.
Maybe a full manual reversion (direct law, no auto-trim, as you promote it) is easier to understand. But IIRC, on the A320 which crashed near Perpignan, the trim was manual (only) ; the crew didn't notice it either, and the plane crashed.
-----------
@ DozyWannabe (post #406) :
Sir.
AZR:
Except, in this case, they didn't have unrestricted control. The flight control system kept changing the pitch trim. While this was result of an inexplicable nose-up command on the side stick, the pilots apparently didn't notice it. As I've said several times before, when the system gives up, it needs to turn off autotrim along with the autopilot.
Except, in this case, they didn't have unrestricted control. The flight control system kept changing the pitch trim. While this was result of an inexplicable nose-up command on the side stick, the pilots apparently didn't notice it. As I've said several times before, when the system gives up, it needs to turn off autotrim along with the autopilot.
Perhaps you interpreted "unrestricted" as "full manual" ? That's not what I meant. For me "unrestricted" means just that : the planes follows the crew's inputs, and the computers don't prevent manoeuvers because it "thinks" they're of no good.
Maybe a full manual reversion (direct law, no auto-trim, as you promote it) is easier to understand. But IIRC, on the A320 which crashed near Perpignan, the trim was manual (only) ; the crew didn't notice it either, and the plane crashed.
-----------
@ DozyWannabe (post #406) :
Sir.
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DEVIATE
GarageYears
Yes a slight misrepresentation -- and yes I know CB's are common. But every other flight deviated. Perhaps 447 did not deviate enough. But with all the glitches to me crystal clear the thunderstorm probably had "something to do" with the entire chain of events. The icing, the updrafts, the out of control climb. Something.
Every pilot I know says the same thing. Deviate, a lot.
I do not understand the casual dis-respect for the power of a thunderstorm.
Yes a slight misrepresentation -- and yes I know CB's are common. But every other flight deviated. Perhaps 447 did not deviate enough. But with all the glitches to me crystal clear the thunderstorm probably had "something to do" with the entire chain of events. The icing, the updrafts, the out of control climb. Something.
Every pilot I know says the same thing. Deviate, a lot.
I do not understand the casual dis-respect for the power of a thunderstorm.
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BOAC,
From the BEA reports to date, it would appear they did not perceive the Wx ahead to be extraordinary.
While the BEA report does provide the number of rotations each of the pilots had flown on South American sectors, it does not indicate when these rotations were flown, and on what sectors. So their actual experience in transiting the ITCZ over various seasons is yet to be revealed, and may never be.
If the time had been daylight, and they had seen a Cb towering 20,000 feet above their FL ahead on the airway, I suspect they, like nearly every pilot, would have deviated off the track, and put their plane at a safe distance from that cell. What might be the appropriate, one adjective characterization of a pilot who would fly into a Cb whose top is 15 or 20 thousand feet above their FL in the cruise?
I don't know whether the BEA will ever provide more information on AF459 following on the same airway 35 minutes behind, and compare the reaction and response of the AF459 cockpit to that of AF447. It might be quite telling.
________________________
Given the relatively higher percentage of cabin crew bodies recovered floating, unless they were in crew rest modules, it would suggest that the cabin crew were not instructed to take their seats and tighten the straps. More about this will be known once the autopsies and identifications are completed on the 100+ bodies retrieved in their seats.
From the BEA reports to date, it would appear they did not perceive the Wx ahead to be extraordinary.
While the BEA report does provide the number of rotations each of the pilots had flown on South American sectors, it does not indicate when these rotations were flown, and on what sectors. So their actual experience in transiting the ITCZ over various seasons is yet to be revealed, and may never be.
If the time had been daylight, and they had seen a Cb towering 20,000 feet above their FL ahead on the airway, I suspect they, like nearly every pilot, would have deviated off the track, and put their plane at a safe distance from that cell. What might be the appropriate, one adjective characterization of a pilot who would fly into a Cb whose top is 15 or 20 thousand feet above their FL in the cruise?
I don't know whether the BEA will ever provide more information on AF459 following on the same airway 35 minutes behind, and compare the reaction and response of the AF459 cockpit to that of AF447. It might be quite telling.
________________________
Given the relatively higher percentage of cabin crew bodies recovered floating, unless they were in crew rest modules, it would suggest that the cabin crew were not instructed to take their seats and tighten the straps. More about this will be known once the autopsies and identifications are completed on the 100+ bodies retrieved in their seats.
Last edited by SaturnV; 26th Jun 2011 at 23:25.
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Restricted control
AlpaZulu
I must disagree with your first sentence. If the auto-trim followed the crew's orders (via the sidestick) then the crew had unrestricted control.
Auto Trim is not a primary flight control. Therefore the crew's control was restricted. You cannot recover an out of control plane with trim alone.
I must disagree with your first sentence. If the auto-trim followed the crew's orders (via the sidestick) then the crew had unrestricted control.
Auto Trim is not a primary flight control. Therefore the crew's control was restricted. You cannot recover an out of control plane with trim alone.
Ah, then wallybird7, you and I ARE on entirely the SAME page then. Because that is the root of the mystery here - why didn't they deviate? Everything that follows is a consequence of this fundamental issue. And we can postulate alternate trim functionality, this law or that, until we are blue in the face, but were it not for a simple 100nm East or West (name your distance/direction), we would not be having this discussion, which makes this all the more sobering.
"unrestricted" vs "full manual" ?
@AZR:
OK, AZR, I yield to your semantics.
But I hope the pilots did not really intended for the trim to go full nose up. I don't like to use the word panic to describe the situation but things sure are pointing in that direction. That's what happened in Buffalo and it was 100% fatal there too.
Perhaps you interpreted "unrestricted" as "full manual" ?
But I hope the pilots did not really intended for the trim to go full nose up. I don't like to use the word panic to describe the situation but things sure are pointing in that direction. That's what happened in Buffalo and it was 100% fatal there too.
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From a pilot's perspective, if someone hands me the controls and says "You have it." I want him to keep his hands off until I hand it back to him. I don't want him to touch the trim unless I ask him to do so. Maybe not all pilots agree with that but I was trained to evaluate the "Flying Qualities" of aircraft. I made my living doing just that and my opinion is that the autotrim needs to come out when the confusers get thoroughly confused and give up trying to fly the aircraft.
@Dozy: Yes, the ability to manually control the trim is there but they didn't use it. We don't yet know why but it is clear that they let the system trim them up into a stall. In the world of pilots, that is a big no no.
@Dozy: But, in this case, the system did hinder the pilots. The pilots were remiss in not catching the fact that trim had run full nose up, but the system put it there when it shouldn't have, reducing their ability to fly it out of the stall.
@Dozy: But, in this case, the system did hinder the pilots. The pilots were remiss in not catching the fact that trim had run full nose up, but the system put it there when it shouldn't have, reducing their ability to fly it out of the stall.
This is why I try to be really careful with language here because I don't want to give anyone the impression that I'm disrespecting the piloting profession when nothing could be further from the truth. We all make mistakes in our day-to-day lives, some of which have more far-reaching consequences than others. Being in charge of a two hundred-ton metal tube moving through the sky just below the speed of sound with a couple of hundred people behind you means that for line pilots, those consequences tend to be more far-reaching on an almost constant basis. When I hear the phrases "I don't believe a pilot would do that", "No pilot in his right mind would do that" or "A pilot would never do that" I get a sinking feeling (with no instruments to reference to confirm my physical perception
). This is because we're all human, and pilots - some of whom were below average, but many of whom were experienced, skilled and respected - have nevertheless done things like attempting a take-off without clearance/in snow conditions with engine anti-ice off/with high-lift devices not extended, shut down a working engine leaving the aircraft to fly on the damaged one, pulled back on the control column turning a stall warning into a full stall... the list is a long and sad one. To be clear, I'm not bashing pilots here - I'm simply stating that the consequences that the men and women of the piloting world face for the kind of momentary lapse in judgement that would be easily resolved in almost any other workplace are far more severe, and that's why I personally have a lot of respect for all of you. But being almost hair-trigger defensive in the way that I see sometimes on here does you a disservice, when what I'm sure engineers all want is to make your (and our) lives as easy and safe as we can.
Right now we're speculating on information that was barely more than a press release. The people that designed these systems weren't stupid, and I'm sure there are very logical reasons for the system being designed the way it is. Remember that this was designed to be the next generation of flight controls - doing things a certain way because that was the way they'd been done since WW2 (or even beforehand!) wasn't a valid design input. Being as friendly and logical to the pilot as possible certainly was, the only problem with that being that some pilots prefer different things.
In every fixed wing aircraft that I have flown, directional stability and pitch stability are positive and only lateral stability is neutral. The Wright brothers initially thought that they wanted neutral pitch stability but after a couple of flights, they began to realize that pitch stability had to also be positive. If not, when they pulled the nose up, it would stay there until the aircraft stalled. That's when they changed their design to positive pitch stability which brought the nose back to the trim speed when they let go of the controls. Having the autotrim follow the sidestick commands essentially gives the aircraft neutral pitch stability. Neutral pitch stability is fine as long as the autopilot is functioning properly, but when it quits, you really need it to be positive when you are hand flying.
Last edited by DozyWannabe; 27th Jun 2011 at 00:08.
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The crew obviously didn't just fly through a CB. Every crew finds their own way around them. No evidence of any major turbulence is reported in the BEA report. They iced up as had many Airbuses prior to this event. All indications are they lost airspeed indications and for some reason pulled back on the side stick until they went into a deep stall. No reports of severe turbulence or vertical drafts. I think it best to wait for the report rather than add personal concepts of what might have happened. The BEA report has nothing to report of any significant turbulence.
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Hi,
They don't report .. ? .. but the pilot report ...
BEA 27 May 2011 note
And ..
Now of course .. are they warning CC of significant turbulences .. when they add "you should watch out" ?
The BEA report has nothing to report of any significant turbulence.
BEA 27 May 2011 note
Between 1 h 59 min 32 and 2 h 01 min 46 , the Captain attended the briefing between the
two co-pilots, during which the PF said, in particular "the little bit of turbulence that you just saw
[…] we should find the same ahead […] we’re in the cloud layer unfortunately we can’t climb much
for the moment because the temperature is falling more slowly than forecast" and that "the logon
with Dakar failed". The Captain left the cockpit.
two co-pilots, during which the PF said, in particular "the little bit of turbulence that you just saw
[…] we should find the same ahead […] we’re in the cloud layer unfortunately we can’t climb much
for the moment because the temperature is falling more slowly than forecast" and that "the logon
with Dakar failed". The Captain left the cockpit.
At 2 h 06 min 04, the PF called the cabin crew, telling them that "in two minutes we should enter
an area where it’ll move about a bit more than at the moment, you should watch out" and he
added "I’ll call you back as soon as we’re out of it".
an area where it’ll move about a bit more than at the moment, you should watch out" and he
added "I’ll call you back as soon as we’re out of it".
Originally Posted by PA 18 151
In this situation. The aircraft knew it was stalled, knew it's pitch angle, and had consistent and valid airspeeds. What more info do you want before you start to lower the nose?
You have returned us to the issue of not knowing the AoA.
If the aircraft "knows it is stalled" but the pilots don't, what are your suggestions?
Follow on to that is: what were they trained to do in the case that they had stalled the aircraft?
There was posted either in this thread, or in the one at Rumors and News, a graphic depicting a 16 deg nose up on a display. You might see that on a departure climb, but how often in cruise?
This takes me to BOAC's question about a crew allowing their aircraft to head into orbit: what airline pilot, flying at altitude, would find a 16 deg nose up attitude something other than abnormal?
Why would either let that nose attitude sustain?
This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?
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This takes me to BOAC's question about a crew allowing their aircraft to head into orbit: what airline pilot, flying at altitude, would find a 16 deg nose up attitude something other than abnormal?
Why would either let that nose attitude sustain?
This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?
Why would either let that nose attitude sustain?
This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?
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BOAC
It may be losing sight of the wood for the trees but to dismiss the aircraft entering turbulent weather as not relevant is rather rash. The fact that the crew of AF447 did not deviate round the weather front is highly significant. The pitot tube failure whilst clearly a contributory factor is not the reason for the accident. The actions of the flight crew in responding to the situation and entering the thunderstorm when others didn't are. I am not assigning any value judgment here just noting an event.
It may be losing sight of the wood for the trees but to dismiss the aircraft entering turbulent weather as not relevant is rather rash. The fact that the crew of AF447 did not deviate round the weather front is highly significant. The pitot tube failure whilst clearly a contributory factor is not the reason for the accident. The actions of the flight crew in responding to the situation and entering the thunderstorm when others didn't are. I am not assigning any value judgment here just noting an event.
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Hi,
I wonder if it's not a usual behavior of some AF pilots to take at least some risks on this route or in case of similar weather ..
It's to remind sometime after the AF447 disaster .. the AF445 "mayday" on same route and somewhat same conditions ...
It was "apparently" a non event (but passengers were strongly shacked for longtime .. big turbulences) and plane lost altitude (was it stalling also ??) .. but happy end ..... in this case .
We will never know what really happened as the recorders were erased or datas convienently missing ...
Another "cas d'école" .........
Go figure .......
BOAC
It may be losing sight of the wood for the trees but to dismiss the aircraft entering turbulent weather as not relevant is rather rash. The fact that the crew of AF447 did not deviate round the weather front is highly significant. The pitot tube failure whilst clearly a contributory factor is not the reason for the accident. The actions of the flight crew in responding to the situation and entering the thunderstorm when others didn't are. I am not assigning any value judgment here just noting an event.
It may be losing sight of the wood for the trees but to dismiss the aircraft entering turbulent weather as not relevant is rather rash. The fact that the crew of AF447 did not deviate round the weather front is highly significant. The pitot tube failure whilst clearly a contributory factor is not the reason for the accident. The actions of the flight crew in responding to the situation and entering the thunderstorm when others didn't are. I am not assigning any value judgment here just noting an event.
It's to remind sometime after the AF447 disaster .. the AF445 "mayday" on same route and somewhat same conditions ...
It was "apparently" a non event (but passengers were strongly shacked for longtime .. big turbulences) and plane lost altitude (was it stalling also ??) .. but happy end ..... in this case .
We will never know what really happened as the recorders were erased or datas convienently missing ...
Another "cas d'école" .........
The BEA has launched an investigation on December 1, the day after the landing of the aircraft. Air France has meant that when the plane had already left for Bangalore in India and the data of the CVR black boxes, the registration of trade in the cockpit, and the FDR, the parameters of the flight had been "crushed". A plane is indeed equipped with two black boxes supposed to provide the data theft. The recording of conversations is valid only four hours while recording parameters covers 25 hours. After a return trip to India, there remained nothing more data.
The companies also have an additional record the QAR to the use of its maintenance crews. Unable to access both legal records, the BEA has requested that the QAR was not available. "Air France has said that the data were not recorded because of poor formatting," says spokesman BEA. For its part, Air France states that "the QAR was recovered on November 30 just before noon and the time to send it and realize that it was a virgin, the plane had left for Bangalore."
However, investigators have recently received a new report, more substantial than the first. "He has no objective value, says one close to the investigation. The company has just said it was a non-event and that the crew may have overreacted. " The side of the BEA, the investigators' regret not having the AF445 flight data that could shed new light on what occurred on Flight 447. "
The companies also have an additional record the QAR to the use of its maintenance crews. Unable to access both legal records, the BEA has requested that the QAR was not available. "Air France has said that the data were not recorded because of poor formatting," says spokesman BEA. For its part, Air France states that "the QAR was recovered on November 30 just before noon and the time to send it and realize that it was a virgin, the plane had left for Bangalore."
However, investigators have recently received a new report, more substantial than the first. "He has no objective value, says one close to the investigation. The company has just said it was a non-event and that the crew may have overreacted. " The side of the BEA, the investigators' regret not having the AF445 flight data that could shed new light on what occurred on Flight 447. "
Last edited by jcjeant; 27th Jun 2011 at 04:03. Reason: Add press comment
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DW:
What design change? Are you still hung up with your misinformation that the Birgenair Capt didn't have an AIR DATA: NORM/ALT switch on the panel in front of his left knee? That switch was there from the beginning of production of the 757/767.
The Capt. cocked up, that's all. DW, why are you trying to blame the 757, and let the A330 off free?
As for CB, thousands or millions of flights have successfully negotiated the ICTZ at flight levels since the day of the 707, with Wx radars far more primitive than what AF447 had, yet how many crashed?
(and indeed a design change to the 757) over the years,
The Capt. cocked up, that's all. DW, why are you trying to blame the 757, and let the A330 off free?
As for CB, thousands or millions of flights have successfully negotiated the ICTZ at flight levels since the day of the 707, with Wx radars far more primitive than what AF447 had, yet how many crashed?
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Graybeard:
I think you'll find that you've missed the point I was trying to make. This isn't about A v B, USA v EU, pilots v engineers or any of that rubbish.
There seems to be a point at which the human brain can only process so much information. In the case of Birgenair it seems that the PF was unable to determine from the ADI that he was nose-high and stalling because he was still focused on the initial false overspeed warning. In the case of AF447 it appears that the PF repeatedly pulled back on the stick despite this being the precise opposite action to what was required for recovery - his ADI was right in front of him and presumably working throughout. If this is indeed the case why does this happen?
(The information that the 757's design was changed to make it easier to switch air data after the Birgenair crash comes from the ACI/Mayday episode on the subject - it is possible they got it wrong...)
I think you'll find that you've missed the point I was trying to make. This isn't about A v B, USA v EU, pilots v engineers or any of that rubbish.
There seems to be a point at which the human brain can only process so much information. In the case of Birgenair it seems that the PF was unable to determine from the ADI that he was nose-high and stalling because he was still focused on the initial false overspeed warning. In the case of AF447 it appears that the PF repeatedly pulled back on the stick despite this being the precise opposite action to what was required for recovery - his ADI was right in front of him and presumably working throughout. If this is indeed the case why does this happen?
(The information that the 757's design was changed to make it easier to switch air data after the Birgenair crash comes from the ACI/Mayday episode on the subject - it is possible they got it wrong...)
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Originally Posted by Lonewolf_50
This takes me to BOAC's question about a crew allowing their aircraft to head into orbit: what airline pilot, flying at altitude, would find a 16 deg nose up attitude something other than abnormal?
Why would either let that nose attitude sustain?
This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?
This takes me to BOAC's question about a crew allowing their aircraft to head into orbit: what airline pilot, flying at altitude, would find a 16 deg nose up attitude something other than abnormal?
Why would either let that nose attitude sustain?
This goes back to what may not be answerable: what did each member of that cockpit crew see in front of him, and what was he paying most attention to?
Originally Posted by DozyWannabe
This is where (and why) I keep going back to Birgenair - where a very experienced pilot stalled and span his 757 despite the fact that the only fault on the aircraft was a single blocked pitot tube.
This is where (and why) I keep going back to Birgenair - where a very experienced pilot stalled and span his 757 despite the fact that the only fault on the aircraft was a single blocked pitot tube.
I'm with Savrin here. The a/c systems need full scrutiny, if only to understand what made the pilots react the way they did. The problem with explaining away PF action is that it is just too persistent.
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Hi,
I hope that after your explanation above .. you do not more critisize my informations sources .. because it seems that your sources can not be described as more serious than mine
(The information that the 757's design was changed to make it easier to switch air data after the Birgenair crash comes from the ACI/Mayday episode on the subject - it is possible they got it wrong...)
