Air France jet missing

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Gabriel
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Re: Air France jet missing

Postby Gabriel » Tue May 31, 2011 4:59 pm

Thanks for the link, great read . This about sums it up:
- When the aerodynamic flow on the wing is stalled, the only possible mean to recover a normal flow regime is to decrease the AoA at a value lower than the AoA STALL.
- Stall is an AoA problem only. It is NOT directly a speed issue.

The traditional approach to stall training consisted in a controlled deceleration to the Stall Warning, followed by a power recovery with minimum altitude loss. Experience shows that if the pilot is determined to maintain the altitude, this procedure may lead to the stall.

Even if the traditional procedure can work in certain conditions if the pilot reacts immediately to the SW, or if he is not too adamant on keeping the altitude, the major issue comes from the fact that once the Stall Warning threshold has been crossed, it is difficult to know if the aircraft is still approaching to stall or already stalled. Difference between an approach to stall and an actual stall is not easy to determine, even for specialists.
Several accidents happened where the “approach to stall” procedure was applied when the aircraft was actually stalled. For those reasons, the pilots should react the same way for both “approach to stall” and “stall” situations.
Are you quoting me or Airbus? :?

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Re: Air France jet missing

Postby flyboy2548m » Tue May 31, 2011 9:07 pm

Are you quoting me or Airbus? :?
Why bother quoting Airbus when you're around?
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Re: Air France jet missing

Postby 3WE » Wed Jun 01, 2011 2:32 am

Are you quoting me or Airbus? :?
Why bother quoting Airbus when you're around?
I blame Wolfgang Langewische.
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Re: Air France jet missing

Postby flyboy2548m » Thu Jun 02, 2011 12:58 am

Are you quoting me or Airbus? :?
Why bother quoting Airbus when you're around?
I blame Wolfgang Langewische.
I blame THS logic. Evan told that's the problem.
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Re: Air France jet missing

Postby flyboy2548m » Sun Jun 19, 2011 2:40 am

An report about a scientific experiment.

This evening on my request we modeled an UAS situation in a CRJ-700 simulator. The event ended with me making a safe landing at only 9 knots above normal speed.

Now, Bombardier has no QRH procedure for unreliable airspeed as such. Furthermore, it's not even possible for the simulator to model the failure of all three indicators. What Bombardier does say is that if the PFDs disagree, the procedure is to switch to the ISIS and should one of the PFDs agree with the ISIS, that PFD may be used for "cross-reference". So, what we did was cover the ISIS with a very high-tech Post-it(R) note, thus leaving ourselves with no valid airspeed data. Everything else was operating normally, as was allegedly the case with AF447. To try to model the problem as closely as possible automation was not used at all, no AP, no FDs.

The scenario we made up was that both ASIs failed on climbout. At around 3,000' one went to 300kias, the other to 110kias. The weather conditions were OVC003, 1sm at night. The airport was CVG.

Once aware of the problem, I leveled the airplane off and asked the NFP to set 70% N1. Why? Because I know that at 70% N1 with the nose level a CR7 will do around 250kts. Once the airplane was stable we asked for vectors for the ILS to 36R. We were given a descent to 2,400'. Once there, I asked for 60% N1 and that's where the thrust levers stayed all the way until landing flair. On base leg I called for flaps 1, then 8, then 20. I know that at 60% N1 with flaps 20 and nose level the airplane will do around 170kts. An additional speed cue here is that with flaps at 20 the airframe buffets noticeably above 200kts. So, when the buffeting stopped I knew we were below 200kts.

Once we were established on the glideslope with full flaps my next cue was whether or not my descent rate was close to normal. It was between 800 and 900fpm. Remember, I hadn't even touched the thrust levers yet.

Once we broke out, I flew the airplane like on any other approach, the visual picture looked spot-on, the roundout and touchdown were normal. Once we stopped the airplane, the instructor advised me that at 500' AGL I was at 153kts (Vref+18) and at the flair I was at 144kts (Vref+9).

Conclusions: obviously we were expecting the failure, we were in a simulator and the only caution message we got was EFIS COMP MON due to PFDs disagreeing by more than 10kts. We were in night conditions, but without a thunderstorm and the alleged severe turbulence AF447 encountered. On the flip side, we didn't have 38,000' to work with.

All that being said, I must admit that while the experiment wasn't particularly fun, it certainly was no great challenge. It seems that at least in the CR7 the pitch/power approach works rather handsomely, a lot better than I thought, actually. I didn't think I'd end up within less than 10kts of Vref, I figured I would be somewhere in the Vref+10-15 range, which on most runways is not a problem. Moreover, with ASIs working, I usually do a lot of thrust tweaking, while here the thrust was set midway on the downwind and wasn't moved again until 50' AGL. Which makes me think all my usual tweaking is unnecessary.

So, the main conclusion is that it seems not only possible, but not even all that hard to fly an airliner at night, in IMC with no valid airspeed data.
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Re: Air France jet missing

Postby Ed » Sun Jun 19, 2011 2:11 pm

That's an interesting experiment.

This all boils down to human factors and airmanship in my humble (or not) opinion. Nik and Pik in the cockpit, trying to figure out what to do to battle the airbus computers, and then, likely at a critical moment, the Captain comes in and mucks things up even more (wasting precious time coming up to speed and trying to understand what is going on himself...basically going through the processes the two flying pilots did 30 seconds or more before he got there (Basically, what should have been a sterile cockpit during problem debug, became contaminated).

Stop
Breathe
Think
Act

Works in every situation.

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Re: Air France jet missing

Postby Gabriel » Sun Jun 19, 2011 7:29 pm

Flyboy, if you have the chance, try it at high a altitude cruise (close to the ceiling for the condition). Not that I think it's especially difficult. I'm just curious about how it feels in a situation where all the margins (except altitude) are small.

I also find it strange that there is no procedure for UAS as such. Ok, so you've get a warning when the sped in the two PFDs disagree, and the procdure for that is to use the ISIS. But this is the part that lost me: [b]should [/b]one of the PFDs agree with the ISIS, that PFD may be used for "cross-reference".

So it's a simple voting: Where you have two in agreement and one in disagreement you take the two that tell the same story. But the part that I don't get is that, according to what understand from your description, if you have no agreement, then you must trust the ISIS. What makes the ISIS especially trustful? Isn' the airspeed shown by it computed from the dynamic pressure provided for a Pitot tube, just like in the PFDs? Isn't the pitot tube that feeds the ISIS as vulnerable to icing, clogging, insects or whatever as the other pitot tubes? And what if you were flying at say 250kts and suddenly one PFD and the ISIS show a rapidly decaying speed, but the plane keeps flying at constant altitude with the same pitch? Will you believe the ISIS? (or that's what you are supposed to do?)

I know that it's impossible to foresee every single abnormal situation as to make procedures for all of them, and that in those cases is where pilot's knowledge and judgement are needed most. But for some reason, other manufacturers considers the UAS situation not only probable enough as to place a procedure, but also important and urgent enough as to be one of the few cases that require memory items.

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Re: Air France jet missing

Postby Gabriel » Sun Jun 19, 2011 7:34 pm

This all boils down to human factors and airmanship in my humble (or not) opinion. Nik and Pik in the cockpit, trying to figure out what to do to battle the airbus computers, and then, likely at a critical moment, the Captain comes in and mucks things up even more (wasting precious time coming up to speed and trying to understand what is going on himself...basically going through the processes the two flying pilots did 30 seconds or more before he got there (Basically, what should have been a sterile cockpit during problem debug, became contaminated).
While I agree with that in general, that doesn't seem to be the case here.

Nothing of that, and nothing related to the automation that I can think of, explains why, having positively identified the auto pilot and autothrottle disconnect ("I have the controls") and the UAS ("We've lost the speeds"), they didn't follow the memory items or, at the very least, stabilized the plane in a normal cruise pitch and thrust setting as they were flying just up to then, but instead pulled up 10 deg nose up without increasing the thrust, climbing from FL350 to FL375 at vertical speeds that reached 7000 fpm, and then, when the stall warning sounded, they PULLED UP AGAIN until reaching 38000ft with an attitude of 16 deg nose-up. And the captain was not in the cockpit yet.

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Re: Air France jet missing

Postby flyboy2548m » Mon Jun 20, 2011 2:27 am

I also find it strange that there is no procedure for UAS as such. Ok, so you've get a warning when the sped in the two PFDs disagree, and the procdure for that is to use the ISIS. But this is the part that lost me: [b]should [/b]one of the PFDs agree with the ISIS, that PFD may be used for "cross-reference".

So it's a simple voting: Where you have two in agreement and one in disagreement you take the two that tell the same story. But the part that I don't get is that, according to what understand from your description, if you have no agreement, then you must trust the ISIS. What makes the ISIS especially trustful? Isn' the airspeed shown by it computed from the dynamic pressure provided for a Pitot tube, just like in the PFDs? Isn't the pitot tube that feeds the ISIS as vulnerable to icing, clogging, insects or whatever as the other pitot tubes? And what if you were flying at say 250kts and suddenly one PFD and the ISIS show a rapidly decaying speed, but the plane keeps flying at constant altitude with the same pitch? Will you believe the ISIS? (or that's what you are supposed to do?)
The ISIS is fed by the standby pitot tube which differs from the others in that it's mounted elsewhere and, possibly more importantly, is shaped differently. I think even you would agree that it would take a trio of very precise insects to nail all three tubes at once. As for ice, my airline is, depending on how you define it, either the most or the second-most experienced CRJ operator in the world and, according to our central safety department, we have not had even one case of an ASI failure due to pitot icing.

However, that doesn't mean that it can't happen. So, to answer your question, if what the ISIS is showing is not jiving with pitch attitude/thrust setting, I would do what I did last night and ignore it and proceed as I did.

Again, all this presupposes that the only thing off-kilter is the airspeed. If I have three indicators disagreeing on everything, now I better hope for some VMC, so I can get my attitude information from looking outside and fly the darn thing like a Piper Cub where the altimeter lies almost by design, the ADI is not even present and the ASI works only if it wants to. I sure wouldn't want to be in IMC with that problem.
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Re: Air France jet missing

Postby Gabriel » Mon Jun 20, 2011 4:12 am

we have not had even one case of an ASI failure due to pitot icing.
That's remarkable, with so many cases around in the rest of the world / fleet (ok, not soooo many, but certainly not unheard of).
Again, all this presupposes that the only thing off-kilter is the airspeed. If I have three indicators disagreeing on everything...
Now that's as close from impossible as it gets. To begin with, in each instrument the airspeed and altitude is fed by the pitot-static system, while the attitude is fed by laser gyros or other form of AHRS (mostly solid state these days). So to have a failure of both just in one PFD is unlikely. Ok, the PFD might fail itself (for example, the screen might stop working), but for that to happen in both PFDs, again extremely unlikely. Next would be a total electric system(s) failure, including the batteries. Then both PFDs will die (along with a good bunch of things you might need to keep it flying), but the ISIS has it's own, independent, dedicated battery (does it?). So to have all the (air data and attitude) information disagreeing or failing on all three instruments, you need one terrible event (like crashing against a mountain or a PEM made by a nuke exploding next to you), case in which you would not care about this (or any other thing), or an extremely unlikely series of unrelated failures.
..., now I better hope for some VMC, so I can get my attitude information from looking outside and fly the darn thing like a Piper Cub where the altimeter lies almost by design, the ADI is not even present and the ASI works only if it wants to.
Been there, done that (in the Tomahawk). Ok, all the non-electric instruments were working (I conclude), including the vacuum powered attitude indicator and gyro compass, the ASI, altimeter and VSI, the RPM-meter, and even the whiskey compass, only that I could not see them in the dark. It was a training exercise too: the famous "you've lost all the electrical system and you forgot the flashlight" emergency at night VMC. Sound of wind, engine noise, view through the windshield and seat of the pants were the only "instruments" available.

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Re: Air France jet missing

Postby Ed » Tue Jun 21, 2011 1:40 am

This all boils down to human factors and airmanship in my humble (or not) opinion. Nik and Pik in the cockpit, trying to figure out what to do to battle the airbus computers, and then, likely at a critical moment, the Captain comes in and mucks things up even more (wasting precious time coming up to speed and trying to understand what is going on himself...basically going through the processes the two flying pilots did 30 seconds or more before he got there (Basically, what should have been a sterile cockpit during problem debug, became contaminated).
While I agree with that in general, that doesn't seem to be the case here.

Nothing of that, and nothing related to the automation that I can think of, explains why, having positively identified the auto pilot and autothrottle disconnect ("I have the controls") and the UAS ("We've lost the speeds"), they didn't follow the memory items or, at the very least, stabilized the plane in a normal cruise pitch and thrust setting as they were flying just up to then, but instead pulled up 10 deg nose up without increasing the thrust, climbing from FL350 to FL375 at vertical speeds that reached 7000 fpm, and then, when the stall warning sounded, they PULLED UP AGAIN until reaching 38000ft with an attitude of 16 deg nose-up. And the captain was not in the cockpit yet.
That is what I mean. If they thought they were going down and pulled up while simultaneously trying to figure out configuration and then the Captain entered, it may have mucked up the scenario enough to affect the outcome. It looks like they may not have known what normal cruise was, for whatever reason. The Captain may have been able to figure it out, but not enough time to act and react to the pilots flying. CRM may have come into play here as well.

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Re: Air France jet missing

Postby flyboy2548m » Tue Jun 21, 2011 3:13 pm

It looks like they may not have known what normal cruise was, for whatever reason.
Yikes.
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Re: Air France jet missing

Postby Ed » Wed Jun 22, 2011 12:49 am

It looks like they may not have known what normal cruise was, for whatever reason.
Yikes.
Yup.

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Re: Air France jet missing

Postby Procede » Fri Jul 29, 2011 2:51 pm

AF447 crew not trained for high-altitude stall: investigators
Inquiries into the loss of Air France flight AF447 have yet to explain fully why the pilots failed to avert the Airbus A330's fatal stall, despite its onset being characterised by buffet and the activation of a stall warning.

But the AF447 investigation has said that the two pilots had not received any high-altitude training for unreliable airspeed procedures and manual aircraft handling. It is formally recommending review of training and check programmes, and crucially the mandatory creation of specific exercises for manual handling, including stall recovery.

...

BEA has made 10 new safety recommendations in its latest update on the investigation, including an advisory that authorities should assess the requirement for angle-of-attack indicators in the cockpit. AF447's angle of attack was not displayed directly to the pilots.

...
Source: http://www.flightglobal.com/articles/20 ... ators.html

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Re: Air France jet missing

Postby flyboy2548m » Fri Jul 29, 2011 5:37 pm

Great. So, a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying, while Air France doesn't see fit to do so.
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Re: Air France jet missing

Postby PurduePilot » Fri Jul 29, 2011 5:47 pm

Great. So, a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying, while Air France doesn't see fit to do so.
I would be interested in hearing more details of your high-altitude hand-flying training.

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Re: Air France jet missing

Postby flyboy2548m » Fri Jul 29, 2011 5:57 pm

I would be interested in hearing more details of your high-altitude hand-flying training.
Ask away.
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Re: Air France jet missing

Postby Gabriel » Fri Jul 29, 2011 8:19 pm

a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying
Was it before or after the diet Pepsi dude event?

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Re: Air France jet missing

Postby flyboy2548m » Fri Jul 29, 2011 8:30 pm

a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying
Was it before or after the diet Pepsi dude event?
The autopilot on the CRJ has always been an MEL-able item, thus it was essential to teach hand-flying at all altitudes. High-altitude stalls were and are part of the PTS for the CL-65 type rating, so were always taught as well, both before and after the 9E mishap.
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Re: Air France jet missing

Postby 3WE » Fri Jul 29, 2011 10:59 pm

I succesfuly flew my simulated CRJ without airspeed data by using known power settings, known attitudes and other common clues.
I would like to nominate Flyboy for the Genious Airmanship award. :clap:
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Re: Air France jet missing

Postby flyboy2548m » Fri Jul 29, 2011 11:11 pm

I successfully flew my simulated CRJ without airspeed data by using known power settings, known attitudes and other common clues.
I would like to nominate Flyboy for the Genius Airmanship award. :clap:
Gosh, if that's all it takes for Genius award, airmanship is in more trouble than I thought.
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Re: Air France jet missing

Postby Joey » Sat Jul 30, 2011 12:21 pm

I feel so bad about the pilots trying to fly this perfectly good aircraft, without proper training (it is very obvious to everyone), into an unrecoverable situation, because they did not have proper training. It sucks. Sorry to sound a little juvenile :evil: .

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Re: Air France jet missing

Postby 3WE » Sat Jul 30, 2011 4:01 pm

Great. So, a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying, while Air France doesn't see fit to do so.
You sound just like a parlor talker- amazed at how the big boys can botch something that seems so basic. :)
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Re: Air France jet missing

Postby flyboy2548m » Sat Jul 30, 2011 4:05 pm

Great. So, a CRJ operator teaches plenty of high-altitude stall recovery and hand-flying, while Air France doesn't see fit to do so.
You sound just like a parlor talker- amazed at how the big boys can botch something that seems so basic. :)
Not so much amazed, but puzzled.
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Re: Air France jet missing

Postby reubee » Sun Jul 31, 2011 11:36 am

... Sorry to sound a little juvenile
... <antipodean humour>with a name like that it should come naturally</antipodean humour>



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