Lonewolf_50

Nemrytter, a rather thorough analysis of the g-data from the FDR shows that no significant turbulence was encountered that would have hampered handling. They DID in fact encounter the icing problem, and if we do a very tight root cause analysis, we discover that without iced-up pitot tubes NONE of the rest follows.

The point a lot of people have made, pilots and others, is that UAS from frozen up pitots is a known malfunction for which there are some effective procedures. Likewise, if the FD goes wrong, or if UAS is the general problem, you turn the FD's off and take some other concrete actions, work through the procedures step-by-step, and get yourself back into the flying condition you desire.

Also of note, the data show that the UAS itself was intermittent, which to me means that the pitot's being rendered INOP sort of cleared itself up, but apparently not all at once. Trouble is, that wasn't necessarily obvious to the pilots, but a UAS procedure was available to deal with the fact that the airspeed input was acting up.

I appreciate your point on Wx avoidance, and also Robert's resetting the radar to a more suitable mode, which I concur let to the (late?) heading correction made (12 deg IIRC) to at least partly avoid what he diagnosed as Wx he'd rather not hit.

That leaves the crew with a malfunction which, had it been handled one way, we'd never have known about unless it was added to the other 36 UAS events that have been discussed at some length on the Tech Log forums.

The response instead included a possible misdiagnosis, and what appears to have been a low-alt tailored response to a high alt UAS event ... and it all ended in tears. (Points on training, recency, and currency apply here in the human factors facets of this event).

It isn't as simple as Wx penetration being the cause.
There was still plenty of room NOT to end in tears, even with entering a bit of rougher weather than they intended to.

To make a rough analogy of a different way to die while hauling pax from place to place ...

I can make a turn in the wrong direction in bad weather near an airport. (perhaps on the way into Islamabad in rainy weather somewhat recently???)
If I notice my mistake (or hear from ATC that I am off course?) and make the proper correction to that error, I don't hit the mountain. If I instead keep my error in, and then do something that isn't correcting my heading error, I hit the mountain and it ends in tears.

The Wx didn't cause that, but poor Wx contributed to it -- right?

Nemrytter

I never said that it was, I was correcting the guy who said that they never encountered intense weather. As I figure you know bad weather doesn't necessarily mean turbulence (+vice-versa) but it can cause other problems - like the icing you mention. Convection can raise warm air to altitude and that can cause the icing problems. Whilst the cloud tops were very cold it looks (based on the data I have) that the temperature at lower altitudes (i.e: ~FL350-400) were quite a bit warmer than normal. This matches the BEA report. What's clear is that it was a rather rare set of circumstances.

To be clear: The Wx was an important factor in the crash, acting as a trigger perhaps, but far from a singular cause. The only reason I posted was to correct the other chap and I definitely didn't mean for it to dominate the discussion.

(edit)Yes, agreed!

Lonewolf_50

nemrytter:
We have an accord.

Apologies if I took your remarks out of context. Oops.

Flight Safety

I don't understand the stall warning logic of the A330. If you have an indicated airspeed of less than 60kts, and there is no weight on wheels (i.e. the airplane knows it's airborne), aren't you stalled?

Why the arbitrary cutoff of the aural stall warning at 60kts? I understand the AOA won't be reliable at that speed, but who cares, if you're airborne at less than 60kts IAS in an A330, you're stalled.

Diamond Bob

I found an article which expands on this theory that the PF was following the Flight Director and that this might explain his pitch-up inputs.

Final AF447 Report Suggests Pilot Slavishly Followed Flight Director Pitch-Up Commands | Aviation International News

glad rag

I don't know for certain [] but I think it may come down to the certification requirements of primary flight instruments viz reliability modus of wow sensors...

Lyman

For everyone who thinks PF blundered in 'neglecting to turn off his FD', remember the drill, and try to focus on when the crew became sufficiently sure of UAS to mention it. For to turn off the FD without knowing if UAS drill obtains, remember that in an emergent situation, it is very difficult to consider 'options' rather than pressure one's self to act decisively. The PF did not turn off his AP, either. It remained for the Captain to switch it off mere seconds before the impact. Please know that in the first several seconds, the solution rapidly lost focus for anyone, even you. It is clear that the plot became lost for both quite rapidly, even PNF lost his confidence quickly.

To follow a drill, one must first establish the need for it. It is not wrong to say that once these pilots got behind, catching up became extremely difficult. The FD seems seductive enough to have tempted PF, and the counter intuitive SW was no help. The planning for this "common" event (UAS), at the program level, seems to me to be arbitrary, even haphazard. The complexity of the challenge was in so many ways artificially induced; at the time when one needed simple, one was deluged, and having no training in the necessary skillset seems to me to be wildly negligent on the part of both Airline and Airframer.

Comes Captain, and he too is immediately drenched in a deluge of data, to the extent that he did not notice some truly simple things.

Is there a ready explanation for the very smooth line of THS increase to max, vice a more herky response to actual (commanded) pilot inputs? It looks graphically as though the THS was deploying to a "target" position, independent of pilot command?

xcitation

The word "stall" was stated about 70 times surrounded by chirps/crickets by the flight systems. Not once did any of the 3 pilots acknowlegde the stall verbally nor did they follow the stall recovery procedure. This is very hard to understand as it trumps all other warnings.
Training in the airline transport industry was focussed on avoiding the stall rather than recovering from it. This contrasts with light aircraft training where stall recovery is experienced and practiced.

Lyman

Has anyone bravely listed all possible reasons the Stall (Warn and actual) was never acknowledged?

Clandestino

Nice example of paternalistic appeal to authority. I'd be happy to see more details.

Sure. You have proposed a method whereby 100 x 3-man crews would be put in a multi-day full-experience simulator. At some point, each crew would get on 1% of their flights an AF447-type scenario. No warning, it just happens. From this you would see what percentage "flubs" the scenario and determine from this whether it was pilots or machine the root cause of the AF447 demise. So far so good. Methodology seems sound, logic too. So it could be scientific. Why is it bad?

Because it is based on monumental misunderstanding of aviation and human factors in it. Logically correct conclusion from false premises is still false!

So whatever we conclude from study, the premise of human-machine interface being inadequate must be confirmed. Why making the study at all if initial bias is confirmed no matter the outcome?

If you crash in the simulator, you can restart. Nonavailability of this feature in real life is very important factor when proverbial hits the fan and largely increases chance of inadequate response and panic.

While they are demanded by certification standards, mother nature has shown total indifference to righteous demands of outraged public that demands the letter of the certification laws be followed. There is no AoA probe that will work well and reliable both at 1 kt and 0.82 Mach. Make fame and fortune by inventing one.

So wealth of data available to make good case studies out of a few occurrences is just thrown away to make one-or two conclusions out of very small sample statistics? I'm glad BEA took different path.

At least you could have properly credited your quotes to Popular Mechanics article mainly based on Jean-Pierre Otelli book. Monsieur Otelli had valid commercial reasons to make his book a bit more sensationalist than very technical and dry BEA report on AF447 since sales figures are of more practical value to any author than truth.

Fact that CM1 changed the mode of WX absolutely does not imply it was set incorrectly! It is perfectly normal to change range, elevation and gain to get the complete picture of weather systems ahead!

As it is possible on each and every radar with wx brightness adjustment. All of them nowadays come with such a feat so it is possible to set it too low on any wxrad equipped aeroplane. What is the point of singling out the Airbus?

Interim report number two was published on 30. Nov 2009. By that point, it had been clear from AF447 ACARS messages its pitots were blocked. Analysis of 13 similar incidents in cruise was made and all of them happened near the storms but never inside the convective cloud.

Interim report number 3 was issued at 29.07.2011. FDR and CVR were found and analyzed. They absolutely confirmed conclusions of interim2: UAS events happen near the storm tops, not in them. AF447 was avoiding the weather well, G trace shows only light turbulence as speed dropped to unrealistic values, quickly reducing to no turbulence at all. That's definitive proof that no storm penetration occurred!
That contradicts the BEA report. What is the source for this statement?

That's beyond reasonable doubt.

Plane did no such thing. Aeroplane keeps flying out of its own accord and no matter the law, it remains aerodynamically the same. Protections are discarded so their untimely application based on false data does not chase the aeroplane out of envelope or into the ground.

Complexity still does not imply intelligence.

While being exposed to constant 1G acceleration. That's the luxury we don't have in the aeroplanes.

One look at PFD is sufficient.
Painting the elevator actuators yellow is already reserved for flight controls failure!

PITCH HOLD is flight director mode. Airbus doesn't have it. Airbus FD has less modes than those fitted to modern turboprops. It's not a bad thing.

Me too. Today. Both our experiences are completely irrelevant and absolutely unrelated to AF447. RTF report.

It maintains flightpath. Constant pitch is consequence of neutral stick and constant speed.

If bad weather definition encompasses fog, true. Active storm cells always come with a lot of turbulence.

barek

From the report:

jcjeant

A simple question
What are the effects (in general) generated by descent from 37,000 feet to 0 feet in a time of 4 minutes on the ear drum (pressurizing system operating normally)
Personally (frequent traveler) I feel symptoms during descents or climbs (normal) of the aircraft
If there are symptoms .. is that this does not be also be an input (sensory) for pilots?
This could be as a source of concern in the cabin ? (Ref CVR multiple calls from a cabin attendant to cockpit)

Clandestino

Because flight controls computers must constantly crosscheck AoA info against measured airspeed and known weight to see whether they are valid and can be safely applied when alpha protection is needed. Firing AoA protection based solely on alpha info seemingly did not sit well with fellows developing and certifying Airbus flight controls. Firing stall warning is fine - it still leaves the last line of defence, the pilot, to determine whether AoA vane measures realistic AoA and its advice is best heeded or it got damaged and stall warning is to be disregarded.

EDIT: I have to stand corrected on this; system is a bit simpler as FCCs don't crosscheck AoA vs speed, they just check whether both signals are valid, not consistent with each other. Inconsistency won't trigger law degradation, jut CHECK GW mesage on MCDU.

Life in a cockpit can get tough sometimes.

svhar

I do not know what equipment you have been using, but you are talking about things you have no idea about. All weather radars display level of precipitation.

Source: Boeing.

I once knew a guy who talked like a professional pilot in the cafeteria with endless stories of his adventures in Africa, but there always where holes in his stories. He was able to fool everyone for a long time and was adored by lots of guys and girls. No one really cared to blow his cover because he was in fact good company. Always called "The Captain". He had a PPL and worked as an ambulance driver. Reminds me of BOAC.

soylentgreen

Well, on the one hand, that's not appeal-to-authority precisely, since I was prepared to tell you why I disagreed (rather than just saying "Trust me, I'm a doctor"), but upon re-reading my words, they did come across snarky and like a cheap shot, so I apologize.


To be fair, I did not mean to suggest this was the perfect experiment that would end all debate. I said "it would be fun" and "The outcome would be quite interesting."

Obviously, simulator-based research has a number of flaws, the biggest one (which you mention) is called Ecological Validity though I think that it could be argued that simulator research might present a lower bound on the %crash% estimate. The logic being that the pilots may suspect this is not a routine test, and they know they aren't going to actually die, may be less likely to panic, etc.

Again, I'm not familiar with this research, so I'm just speculating.


Not at all. Some things (bad weather in the ICTZ, human frailty) we can't change. Some things we can: training and machines. I'm simply saying that
we should think of the big picture here, and improve the things that we do control.

Agreed -- see above.


Not me, but perhaps someone else? This video Google's next driverless car goal? 1,000,000 miles is interesting and relevant: Google claims to have driven 160,000 miles in their robot car with only one fender-bender (which they claim was human error).

How many miles do we need google's robot cars to have accident-free before we trust them?

Seems like this technology (using LIDAR, GPS, and a bunch of other data) could be useful as a "third eye" autopilot that normally sits in the back and is quiet, but occasionally speaks up "Hey guys, uh, I know you are the bosses here, but we seem to be falling towards the sea in a strange attitude. I can show you on this 3D display just what I'm seeing..."


I'm not sure I understand you here, but I'll try to make my points again.

The "naturalistic" study shows that 1 of 37 crews in similar situations crashed. As I mentioned, that's such a small sample size that we can't say whether the actual percentage is closer to 0% or closer to 10%.

I hope that if the actual number is 10%, you'd agree with me that something is wrong, either with pilot training, or with the human-computer interface, yes?

My proposed simulator study would vastly increase the N to, say 100.

The statistics show that if 1/100 crashed, our confidence range narrows to roughly (0% to 3%).

If we had 1000 crews run through the simulator, and 1 crashed, then the interval shrinks further (about 0.5% to 1.5%).

Then, a naive analysis could be made (*with a ton of assumptions which we shall ignore*)

Let p1 be the % of flights on which the pitot tubes freeze and the autopilot drops out.
Let p2 be the % of times where the crew crashes when the autopilot drops out.

Then the overall risk of this = p1 * p2.

To me (again, not a pilot, but interested in cognitive psychology and statistics) both of these numbers are relevant here.

From what I know, the airline industry likes the risks to be in the one per million range or lower, and if there's a suggestion that it's anywhere near to 1% or 3% or even 10%, yikes!

Interlude

I understood that BOAC was commenting on the satellite images ironbutt57 presented in post #281 rather than the aircraft radar.

svhar

These images are totally useless. They only display what can be seen from above.

Clandestino

... though the page ironbutt57 linked to is somewhat useful as it very often used for those still peddling the idea AF447 entered the storm.

Northwest 705 was high altitude upset that resulted in low altitude break-upWho would have thought it is possible to make large longitudinal control displacement with yoke?

NLM 431 hit tornado, not something you meet at high levels. I can't find exact reference what was its altitude at the time but I don't expect that flight shorter than 100 km would climb very high.

Pulkovo 612 is example of trying to climb above ceiling in aeroplane that is prone to deep stalls. I couldn't find any reference to in-flight disintegration or any damage prior to ground contact in flat spin.

I cannot doubt Tim Vasquez's expertize on meteorology but filing these accidents under "high altitude weather-induced breakups" is quite a bit of stretch.

While AF447 operated in the area of storm activity, all the data collected so far point that the crew was aware of the severe weather and circumnavigated it successfully. "Don't fly into storm" is valid lesson yet it was heeded by the AF447 crew so you can't make them poster-children for it.

Nemrytter

An analysis of the Wx conditions done by UK met office and the owner/operator of the satellite used in Vasquez's webpage. It's not yet published but should be in a month or two. If you're interested (and I remember!) then I can PM you a copy when it's out.

Also, it doesn't contradict the BEA: They state that with the - very limited - data they had available they couldn't conclude if the conditions were exceptional.

Not strictly true, by using different wavelengths of radiation you can gain some insight into vertical structure. As I said before the area was also overflown by a radar satellite (TRMM) that has a decent vertical capability.
Even for instruments that can only see the cloud tops it is possible to use computer models to determine the internal structure of the cloud with a reasonable degree of success (better than a forecast could manage, for instance).

However this is irrelevant to the AF447 discussion, so if there's anything else to talk about then maybe it'd be appropriate to continue in a thread in jetblast.

deSitter

Several questions..

At what point was the "deep stall" unrecoverable? What exactly is a deep stall? Was the trim issue the main obstacle to recovery? Thanks in advance.