Air France 447 - On topic only!

[Fear_of_Flying]

Originally Posted by Gabriel

"PAN PAN, Jetphotos 1234

*Off-topic* So I was curious about the origin of "PAN PAN PAN" and looked it up. It comes from a French word (not for "bread", which is kind of what I thought it sounds like), but for mechanical failure. The article went on to explain that various bacronyms have been applied to PAN, such as "Possible Assistance Needed". Well, I had never heard of a bacronym before, either, so this was a learning experience (a bacronym is when you come up with suitable words for the word that already exists). Then came the most interesting part. The article listed uses of PAN PAN PAN in modern aviation, and one of them was from May 5th of this year. I hadn't heard about this incident, and I'm not sure if there's a thread here or not - I don't see it if there is. But here's the summary, kind of funny in a scary sort of way:

An Air Berlin Airbus A330-200, registration D-ALPA performing flight AB-9721 from Palma Mallorca,SP (Spain) to Munich (Germany), was on approach to Munich about 15 minutes prior to landing, when the crew declared PAN PAN reporting they were fatigued and needed to perform an automatic landing. The airport needed to temporarily invoke procedures to protect the ILS category III zones to permit an automatic landing. The aircraft continued for a safe landing on runway 26L about 15 minutes later at 10:27L (08:27Z).

(From Aviation Herald)

Too tired to land the plane? That's a new one.

[MCM]

Pan Pan is not a particularly rare event FoF. The would have been plenty used since the 5th of May.

They just achieve radio priority, and ultimately (if required) priority handling.

The incident you mention is an interesting one. I am lead to believe that the order of events was slightly different to that reported. I may well be wrong, but I believe the pilots reported that they were fatigued and going to do an autoland. The airport would have said fine, but the ILS critical areas are not protected. The crew may have decided they wanted them protected, and by declaring a PAN ATC are required to comply and protect them.

Its an interesting policy they have about requiring autolands, and I'm sure it will be closely examined by airlines everywhere.

Gabriel - declaring a PAN and descending is obviouly what you would do. That wasn't exactly my point. My point was that this thread seems to be very much discounting the "coffin corner" concept as one that seriously affects civilian jetliners, when that is not the case. There seemed to be concentration on normal aircraft operations, but not considering the effect of increased G force (be it by turbulence or even just enroute track changes), or by environmental changes. You are correct that accelerating to that speed normally would take time, but it is environmental factors that are more likely to actually cause the problem.

Evan,

You would have more idea about what an airbus does when faced with that scenario than I do! I know very little about airbii. For what its worth, I'm not sure I agree with the the "blended" approach. I think too often confusion comes from not understanding what the aircraft is doing. Too many different, subtle modes. I personally prefer the Boeing method - either the autopilot is doing it, or it isn't doing it. At least I know for sure what my control inputs are doing.

[Evan]

Originally Posted by MCM

Evan,

You would have more idea about what an airbus does when faced with that scenario than I do! I know very little about airbii. For what its worth, I'm not sure I agree with the the "blended" approach. I think too often confusion comes from not understanding what the aircraft is doing. Too many different, subtle modes. I personally prefer the Boeing method - either the autopilot is doing it, or it isn't doing it. At least I know for sure what my control inputs are doing.

Maybe 'blended' isn't the word, but something like a five-second warning that the autopilot is about to disengage. I realize a lot can happen in five seconds, but the pilot could always take it immediately by pressing the instinctive button. I think the sudden handover can be disorienting when a pilot is least expecting it.

My question put more simply is what will the autopilot do at cruise altitude if environmental factors suddenly put your airspeed below stall?

[Gabriel]

Originally Posted by Evan

My question put more simply is what will the autopilot do at cruise altitude if environmental factors suddenly put your airspeed below stall?

It's not exactly what you are asking, but AFAIK, in many airplanes (all that lack envelope protection?), in situations of diminishing airspeed, the autopilot set in alt or vert speed mode will have no problem to increase the AoA all the way into the stall (or at least stall warning).
We have Turkish and Pinnacle as examples.
What I don't know is if, when the stall warning is reached, the AP will self disconnect or not.

[Gabriel]

Originally Posted by MCM

Gabriel - declaring a PAN and descending is obviouly what you would do. That wasn't exactly my point. My point was that this thread seems to be very much discounting the "coffin corner" concept as one that seriously affects civilian jetliners, when that is not the case. There seemed to be concentration on normal aircraft operations, but not considering the effect of increased G force (be it by turbulence or even just enroute track changes), or by environmental changes. You are correct that accelerating to that speed normally would take time, but it is environmental factors that are more likely to actually cause the problem.

Then we agree 100%.
The "enroute track change" effect can be highky mittigated, nearly eliminated, by limitting the bank angle to a max of 15 degrees. I would definitivelly not make a 25 or 30 deg bank turn if I'm just 10 or 15 knots IAS above the slow speed buffet or stall warning. Agreed?

[Taliesin]

Originally Posted by MCM

Taliesin,

A few big assumptions you've made there!

That said, yes, AF447 was not operating in coffin corner.

That's true, but I believe that my assumptions are reasonable. An aircraft with the same wing flying at the same density altitude is very likely going to have a similar weight, barring adverse winds, it would not fly at that altitude if the weight were not similar.
Either way, even if the weights are not similar, the density altitude and Mach numbers are, which were the details in question.

In the end, we agree

[Evan]

BBC reporting a bit ahead of the release of the final report:

One of the mistakes of the crew, according to investigators, was to point the nose of the aircraft upwards, after it stalled, instead of down.

The father of one of the flight's victims says that investigators have told him, ahead of the final report's release on Thursday, the reason for this incorrect move was that the flight director system gave "erroneous information" that the jet was diving.

Which is why the QRH procedure specifically instructs pilots to turn off the flight directors. THis is why you MUST adhere to procedure.

[TeeVee]

Originally Posted by Evan

BBC reporting a bit ahead of the release of the final report:



Which is why the QRH procedure specifically instructs pilots to turn off the flight directors. THis is why you MUST adhere to procedure.

interesting: when the machine clearly makes a mistake, it is still the human's fault because he failed to shut the machine off. when does it ever become the machine's or its' engineers' fault?

[Evan]

Originally Posted by TeeVee

interesting: when the machine clearly makes a mistake, it is still the human's fault because he failed to shut the machine off. when does it ever become the machine's or its' engineers' fault?

The machine isn't "making a mistake". The machine is deprived of data (airspeed) necessary to function. Therefore the manufacturer specifically directs the pilots to deactivate components that might be unreliable in that state, and take the plane into their own hands.

This is what the pilot is there for.

If he is properly trained...

[Peter Kesternich]

Originally Posted by TeeVee

interesting: when the machine clearly makes a mistake, it is still the human's fault because he failed to shut the machine off. when does it ever become the machine's or its' engineers' fault?

Going down that road and giving the last responsibility to the machine will lead us to single pilot flight crews and eventually fully automated planes. And that is the day I will stop travelling on aircraft.

[TeeVee]

final report out: http://www.bea.aero/en/enquetes/flig...ght.af.447.php

[Gabriel]

Originally Posted by TeeVee

interesting: when the machine clearly makes a mistake, it is still the human's fault because he failed to shut the machine off. when does it ever become the machine's or its' engineers' fault?

TeeVee, I think you are not oversimplifying, but doing it the wrong way too.

It is a known fact that current airspeed indicators, no matter how many of them you install and no matter from how many different source you feed them, are not fully redundant because they are all based on Pitot tube probes, which are all vulnerable to the same atmospheric event (icing), so it is possible that if one of them fail due to this vulnerability, all the others may also fail.

Because this vulnerability is known, there are procedures designed to deal with those situations. This procedure is one of the few that must be memorized (at least its first steps to stabilize the situation and gain time to grab the checklist). Among these few first steps there is a "flight director disconnect" instruction.

Now, one of the main reasons for the pilots to be there is to deal with malfunctions. So yes, there was a malfunction, there was a procedure to deal with this malfunction, there were two pilots there, and the malfunction was not handled properly. But wait, there is more to this.

Not only the "flight director disconnect" was omitted. The full unreliable speed procedure was omitted, not even called for, despite the fact that the unreliable speed situation was recognized and called for.

And not only that, but even if you don't know the procedure, the right and very obvious thing to do is to keep a typical cruise attitude and power. The plane was flying before loosing the airspeed and can keep doing so without them. The wings don't care what the airspeed indicators are showing.

Certainly, and above all, pointing the nose 12° up and 2000ft at 7000fpm when you were already near your operative ceiling is NOT the right thing to do. I don't know if those not familiar with airplanes' performance are aware of the ridiculous of this situation. 12° is close to a typical take-off attitude (15°) and 7000fpm is twice the typical take off climb rate, and that at an altitude where the plane cannot sustainably climb anymore (and they knew that because they had briefed and decided before that they could not climb to 37000 as planned because the temperature was warmer than expected and hence they lacked the performance). This is comparable to trying to turn around the corner when you are driving at 100MPH.

But let's keep with your argument. What the flight directors were showing after loosing the airspeed was not know until the last report, because that parameter is not recorded in the FDR. That said, I find hard to find a program logic that would command the flight director to 12° nose up. And even then, if the judge calls you to the stand, you go. If the judge tells you to jump out the window, you do? I guess you don't, even he threatens to declare you in contempt. It should be absolutely OBVIOUS for an Airbus pilot that if he is already flying at or very near the ceiling putting the plane in a 12°, 7000fpm climb is jumping out the window, EVEN if the flight director tells you to do so. (the attitude indicator that shows pitch, the altimeter, and the vertical speed indicator, are all there in the PRIMMARY flight display together with the flight director, in particular, the attitude indicator has priority, so if the flight director tells you to roll inverted you don't).

But wait, there's even more. Finally sort of levelled off at 37500ft at an angle of attack (and deck angle) of about 4 degrees, there they had the chance to recover by stop pulling up and maintaining if only a healthy pitch attitude.

But the AoA increased to 6 degrees, point at which the stall warning triggered. some 45 seconds had elapsed since the beginning of the event (the disconnection oft he AP and AT). Now, they knew that they were in alternate law and that they had lost some protections (they had called alternate law protections early along the incident). The must (or should) have known that AoA protection was one of the lost ones. And they should have known (even if from the private pilot course) that stall is a matter of too much AoA. How did they react?

They pulled up again. With the little margin they had between the stall warning and the actual stall, and consuming the little energy in the form of speed they had left, they managed to climb and reach (always with the stall waring sounding) 38000ft with a deck angle and AoA of 16 degrees, and then the plane started to go down (with the nose pointing up). The stall warning sounded uninterruptedly for 54 seconds!!! Did any of the two pilots say "Hmm Joe, it looks like a stall", or "Maybe we should lower the nose", or said nothing but lowered the nose? No! They just kept (mainly) pulling up!!!

Maybe they were still following the flight director? I very seriously doubt it. As far as I know, these planes are equipped with a PLI, or Pitch Limit Indicator. What is it? It's very simple: A mark in the attitude indicator that shows "if you pull up to this point, the stall warning will trigger". It is taken as an upper bound for any pull-up. And the flight director is programmed not to go up past the PLI mark.

Again, even if the flight director (which should have been disconnected by the pilots from the beginning because it was part of the procedure to deal with what their recognized as an unreliable speed situation) was "commanding" them to pull up, following that command with the stall warning sounding is not like jumping out the window anymore but like blowing your brains out.

So yes, in this case, very much, the pilots screwed it up BIG time, beyond any "machine" problem.
The question remaining is why. (a simple "lack of training" is not enough in this case).

[TeeVee]

Originally Posted by Evan

The machine isn't "making a mistake". The machine is deprived of data (airspeed) necessary to function. Therefore the manufacturer specifically directs the pilots to deactivate components that might be unreliable in that state, and take the plane into their own hands.

This is what the pilot is there for.

If he is properly trained...

more excuses... the machine was missing one thing only: airspeed. out of that, the unimaginable cascade of failures that occurred is simply mind boggling. practically the entire aircraft fails to operate properly, or at a least those parts that make the pilots able to fly, namely the instruments.

then, you expect the humans, faced with a problem they cannot understand, and apparently couldn't fix, to remember (1) memory item for UAS, (2) shut-off flight director (3) what else? oh yeah, hand fly a plane they almost NEVER fly by hand. all of this in turbulent conditions, in pitch blackness. umm my bet is that many, too many, pilots will fail at this. and the reason is not because the machine is a pos. it's because the humans that built it expect the humans that fly it, to let it fly itself 99% of the time but react with 100% perfection and efficiency when the damn thing fails--for whatever reason.

[TeeVee]

obviously it will take a while to get through the whole thing, but start with this fault: "However, no explicit indication that could allow a rapid
and accurate disgnosis [sic] was presented to the crew."

strike 1 airbus

[Evan]

Originally Posted by TeeVee

more excuses... the machine was missing one thing only: airspeed.

It was missing two things: airspeed and a competent crew.

Gabriel just explained everything to you in patient detail. God knows why because by now we all know what good that does. Rant on. You can join the chorus of ignorance that continues to protect the truth from the light of day.

[TeeVee]

this seems to go against everything that has been discussed here:

"However, the number and the type of manifestation (ECAM
messages, speed changes, etc) linked to erroneous speed indications makes training and exhaustive information for pilots impossible"

this will make the boeing guys happy:

"He may therefore have embraced the common belief that the aeroplane could not stall, and in this context a stall warning was inconsistent."

i have to say that this has to be a belief among some pretty uneducated folks. that or airbus trainers are really screwing up.

"No failure message is provided that identifies the origin of these other failures: in particular, the rejection of the ADR’s and of the speed measurements."

strike 2?

"One may therefore question the suitability of the automatic reappearance of the flight directors once they have disappeared."

strike 3?

"The “situational awareness“, “decision-making“ and “crew resource management“ causal factors were inseparable and were by far the most significant contributing factor in many events;
ˆˆ The piloting abilities of long-haul and/or ab-initio pilots were sometimes poor;
ˆˆ A notable loss of good sense and general aeronautical knowledge;
ˆˆ Weaknesses in terms of representation and awareness of the situation during system failures (reality, severity, danger level, induced effects …)."

strikes 1, 2, 3, & 4 for AF

[TeeVee]

Originally Posted by Gabriel

TeeVee, I think you are not oversimplifying, but doing it the wrong way too.

It is a known fact that current airspeed indicators, no matter how many of them you install and no matter from how many different source you feed them, are not fully redundant because they are all based on Pitot tube probes, which are all vulnerable to the same atmospheric event (icing), so it is possible that if one of them fail due to this vulnerability, all the others may also fail.

Because this vulnerability is known, there are procedures designed to deal with those situations. This procedure is one of the few that must be memorized (at least its first steps to stabilize the situation and gain time to grab the checklist). Among these few first steps there is a "flight director disconnect" instruction.

Now, one of the main reasons for the pilots to be there is to deal with malfunctions. So yes, there was a malfunction, there was a procedure to deal with this malfunction, there were two pilots there, and the malfunction was not handled properly. But wait, there is more to this.

Not only the "flight director disconnect" was omitted. The full unreliable speed procedure was omitted, not even called for, despite the fact that the unreliable speed situation was recognized and called for.

And not only that, but even if you don't know the procedure, the right and very obvious thing to do is to keep a typical cruise attitude and power. The plane was flying before loosing the airspeed and can keep doing so without them. The wings don't care what the airspeed indicators are showing.

Certainly, and above all, pointing the nose 12° up and 2000ft at 7000fpm when you were already near your operative ceiling is NOT the right thing to do. I don't know if those not familiar with airplanes' performance are aware of the ridiculous of this situation. 12° is close to a typical take-off attitude (15°) and 7000fpm is twice the typical take off climb rate, and that at an altitude where the plane cannot sustainably climb anymore (and they knew that because they had briefed and decided before that they could not climb to 37000 as planned because the temperature was warmer than expected and hence they lacked the performance). This is comparable to trying to turn around the corner when you are driving at 100MPH.

But let's keep with your argument. What the flight directors were showing after loosing the airspeed was not know until the last report, because that parameter is not recorded in the FDR. That said, I find hard to find a program logic that would command the flight director to 12° nose up. And even then, if the judge calls you to the stand, you go. If the judge tells you to jump out the window, you do? I guess you don't, even he threatens to declare you in contempt. It should be absolutely OBVIOUS for an Airbus pilot that if he is already flying at or very near the ceiling putting the plane in a 12°, 7000fpm climb is jumping out the window, EVEN if the flight director tells you to do so. (the attitude indicator that shows pitch, the altimeter, and the vertical speed indicator, are all there in the PRIMMARY flight display together with the flight director, in particular, the attitude indicator has priority, so if the flight director tells you to roll inverted you don't).

But wait, there's even more. Finally sort of levelled off at 37500ft at an angle of attack (and deck angle) of about 4 degrees, there they had the chance to recover by stop pulling up and maintaining if only a healthy pitch attitude.

But the AoA increased to 6 degrees, point at which the stall warning triggered. some 45 seconds had elapsed since the beginning of the event (the disconnection oft he AP and AT). Now, they knew that they were in alternate law and that they had lost some protections (they had called alternate law protections early along the incident). The must (or should) have known that AoA protection was one of the lost ones. And they should have known (even if from the private pilot course) that stall is a matter of too much AoA. How did they react?

They pulled up again. With the little margin they had between the stall warning and the actual stall, and consuming the little energy in the form of speed they had left, they managed to climb and reach (always with the stall waring sounding) 38000ft with a deck angle and AoA of 16 degrees, and then the plane started to go down (with the nose pointing up). The stall warning sounded uninterruptedly for 54 seconds!!! Did any of the two pilots say "Hmm Joe, it looks like a stall", or "Maybe we should lower the nose", or said nothing but lowered the nose? No! They just kept (mainly) pulling up!!!

Maybe they were still following the flight director? I very seriously doubt it. As far as I know, these planes are equipped with a PLI, or Pitch Limit Indicator. What is it? It's very simple: A mark in the attitude indicator that shows "if you pull up to this point, the stall warning will trigger". It is taken as an upper bound for any pull-up. And the flight director is programmed not to go up past the PLI mark.

Again, even if the flight director (which should have been disconnected by the pilots from the beginning because it was part of the procedure to deal with what their recognized as an unreliable speed situation) was "commanding" them to pull up, following that command with the stall warning sounding is not like jumping out the window anymore but like blowing your brains out.

So yes, in this case, very much, the pilots screwed it up BIG time, beyond any "machine" problem.
The question remaining is why. (a simple "lack of training" is not enough in this case).

i was busy reading the report when you posted this. thanks for explaining it but i think the final report basically calls out the truth behind what happened, and it wasn't only shitty pilots. far from it in my layman's interpretation.

[TeeVee]

Originally Posted by Evan

It was missing two things: airspeed and a competent crew.

AND, according to the BEA:

1) an AoA indicator
2) a method for informing the crew WHY HAL shut itself off, i.e., "UAS you idiots"
3) my favorite of all, "no explicit indication that could allow a rapid
and accurate disgnosis [sic] was presented to the crew."

so, you build a futuristic, fbw, fly-by-computer aircraft that is vaunted for its ability to save the world from stupid/incompetent pilots, hand it over to some pilots that are not properly trained and perhaps have very little experience in manual flight (basic airmanship), certainly very little experience manually flying this super-computer aircraft, have ZERO training for high altitude manual flight, and then you DEMAND that they perform appropriately at high altitude when HAL says, "I give up. You take over. Oh and by the way, a big chunk of the aircraft's systems are failing."

don't get me wrong, i'm not defending the incompetent crew here. they f'd up in a big way. but even the BEA has recognized that they may never have been equipped for the situation they faced. they may have been sent into harm's way without being properly prepared for this. MAY... it's like giving a soldier the most sophisticated weapon known to man, training him only how to hold it, sending him into combat, and expecting him to use the weapon perfectly.

but this type of human failure is bound to happen and keep on happening the more things are automated. humans naturally become complacent. skills rapidly degrade if gone unused. not a perfect situation.

add to this a very complex and sophisticated machine that does a whole litany of stuff and leaves you in control with something clearly wrong yet fails to tell you what that something is and 200+ people die.

[Gabriel]

Originally Posted by TeeVee

and it wasn't only shitty pilots

Of course not. It NEVER is.
But...

"The “situational awareness“, “decision-making“ and “crew resource management“ causal factors were inseparable and were by far the most significant contributing factor in many events;
ˆˆ The piloting abilities of long-haul and/or ab-initio pilots were sometimes poor;
ˆˆ A notable loss of good sense and general aeronautical knowledge;
ˆˆ Weaknesses in terms of representation and awareness of the situation during system failures (reality, severity, danger level, induced effects …)."

By the way, the "human factors" part really dissappointed me. Paraphrasing:

"The pilots maybe didn't notice the stall 2 warning due to the aural saturation due to the prolonged C chord warning coupled with the stress of the situation, or maybe they heard it but considered it irrelevant (as other crews declared), or maybe they didn't trust it because they were in a mindset that the danger was overspeed, not stall, and that's why they kept pulling up, or maybe they did believe in the stall warning after all, as they applied TOGA which is a more consistnt reaction for a stall than for overspeed, but failed with the rest of the recovery, or maybe not, or the opposite, or something else"

Yes, sure that some of the above has to be true. "And therefore, it is proved that the murdered is either the defendant or someone else".

Yet, even them don't understand the pilot sustainedly climbing 12° and 7000fpm in a plane that was already flying at the limit of its capabilities.

[Gabriel]

Originally Posted by TeeVee

i was busy reading the report when you posted this.

And I was busy writing that post when the BEA published the final report. To support my post I had just downloaded the latest info available at the BEA site that was the third interim report.

Sometimes even real-time is not even real-time.