henra

No nothing wrong with it.
You need to distinguish between the ADR disagree due to the icing which was the event that lastet less than a minute and initiated this accident and the invalid airspeed due to the high AoA which occcured much later and was a consequence of it..

PH-OY-73

Gentlemen, ladies,

Although the airplane was apparently never in an extreme attitude, the pilot somehow did not recognize the stall condition, or the position of the horiz. stabiliser. Could it be overreliance on Airbus' Flt Ctl Systems and mentally 'ruling out' basic indications?

In any case, the following statement, especially its last paragraph, in the Airbus Flight Crew Training Manual (OP-020, Abnormal Attitudes) reflects what I believe is a fundamental problem in the attitude of Airbus, and their design philosophy, and could be a contributing factor to the fate of AF 447.

"It is very unlikely that the aircraft will reach these attitudes, because fly-by-wire provides protection to ensure rapid reaction far in advance. This will minimize the effect and potential for such aerodynamic
upsets.
The effectiveness of fly-by-wire architecture, and the existence of control laws, eliminate the need for upset recovery maneuvers to be trained on protected Airbus aircraft.

peplum

Why did they not rely on the ground speed to regulate their thrust ?

sustaining 400kts ground speed @FL300 or 350kt ground speed @FL200 could have save them.

Why in case of IAS malfunction they do not use the ground speed (GPS AND inertial both provided it) to evaluate their air speed ?

davionics

peplum: The pitot-static system provides Air Data, relative to the medium which the aircraft flies in, unlike the other sources you listed. An analogy; think of a boat on a river - if the river is moving at 30kts and the boat is going against the flow at 30kts, then it's GPS and INS might show 0kts... but the boat would see a flow of 30kts at it's hull.

I've finally caught up on the day's messages, and I'm intrigued and saddened that with such safety-critical data sources (Air Data sensors), there is still little redundancy in design offered. I.e. Are there 3 different air data sensors designed by 3 different companies, based on 3 different sampling principles, and then 3 of each onboard?! Pilots, and computers/software, can only compute and respond effectively (without error) if their senses / sensors can guarantee dependable data.

This could well be a systemic disease inflicting mankind lately, take for example the design of Fukushima and other BWR's around the globe... listen to what ArnieG has to say about that...
The Implications of the Fukushima Accident on the World's Operating Reactors | Fairewinds Associates, Inc

peplum

We're not on a river but a jet in the atmosphere.

The wind could be evaluated at max +-75kts in this cas. Even if you add or remove 75kts you're always in the flight domain of the plane using my values !

Anyway think one moment. To fly a plane to must evalute the air speed. Because they were high altitude, and the 3 pitot was off, the only indicator effective at this moment was ground speed.
unless you prefer to open the window and reach out to assess !
I'm not Einstein but I hardly imagine none of the 3 pilots try to use this evident method to adjust thurst and sustain a correct FL.

chaz88z

As JCjeant said it, >300 posts over speculation, human-vs-computer battle.

But this accident is like any-other a combination of several factors and their consequences, I'll try to summarize those :

1°/ Pitot failures
- No more valid speed indication
- A/P A/T disconnection (corrective actions taken by crew : "I have controls")
-Switching to alternalte law (Identified by PM "Alternate law")

2°/ Climb to FL380
-The report says that after the initial right bank the pilot performed a corrective action with a left and up S/S deflection.
-Pitch gradually increase over 10°UP. Vertical speed goes to 7000fpm (corrective action : Pitch down)
-Bank values oscillating between 12°right and 10°left. (Corrected by the pilot, but maybe a hint of the flight enveloppe limitation and turbulences)

3°/ First stall warning and pilot corrections
-PF sets TO/GA, and Up-stick force (Seemingly an approach to stall procedure on a non-FBW aircraft : power and initially a small up-stick force as a reflex to maintain constant pitch)
-Consequence of the up-stick force on the A330:
-The pilot fly a G-acceleration, thus constant upward acceleration is commanded as long as the stick is in the 'up' sector
-Auto-trim sets THS up to 13°

4°/ Stall At one point between 02h10'51 and 02h11'40
AoA rises to 16° which is the basic stall AoA at low altitude, at FL380 stall will surely occur at a lower AoA.

5°/ Entering "deep-stall" Between 02h11'40 and 02h12'02 ---> Lasting 22sec only. At a maximum altitude of FL380 the A330 is now completely stalled and descending.
-AoA reaches 40°(Computers switches to 'Abnormal attitude law' (AoA>30°) and auto-trim is disable (Trim wheel is now stuck at 13° up even if it could have been moved by the PF, but with no force-feedback on the stick how to use the trim without QRH/FCOM references?)

6°/ Stall warning 'bugs' begin
-The AoA is so high that Pitot airflow might stall, showing speed below 60kts
-Stall Horn STOPS (IMHO one of the key info that kept the crew in a wrong situation awareness)

7°/ More corrective actions from PF at ~02h12'17
-Pitch down input (correct action to get out of the stall)
-As airfow gets back in the pitots 'speed became valid' and Stall Horn rings again.
(IMHO this is the other key info given to the pilots: the PF brain might have taken it as a logical computer :
Alarm rings ---> Erroneous Action ---> What was my last action? ---> Pitch down input <---CONCLUSION---> Pitch-down input = Error)



As the aircraft is still in a stall with a more than 10.000ft/min rate of descent, the BEA did not communicate on the period between FL350 and FL100 but a major brainstorm/communication or even actions might have taken place in the flight deck.



8°/Approaching FL100
-Less than one minute before impact
-The other pilot takes over (or maybe the captain from behind)
-Only info is 'AoA remained over 35°'
(We do not have any info on the last minute inputs, possibly a desperate maneuver)


I hope this will help picture out the overall situation, so people don't only focus only on one computer or one pilot input.

peplum

False. IAS is OFF but GS is OK.
Air speed can be sufficiently evaluated from ground speed to adjust thrust and do not stall.

Caygill

Sure you can create models to handle any situation, but the risks are naturally increasing with each missing parameter. It's no fuzzy logic, although that would be a good concept to start with

I read many inputs on random newspaper forums, asking why cannot GPS-data be used calculate speed if pitots freeze... Beyond the obvious of not understanding the difference between air speed and ground speed, I came to think about something:

Would it be out of question to create an automation graceful degradation, which:

a) would use a pattern of ground speed vs IAS to judge faulty airspeed readings. Give an advisory to pilots before actually making the call to consider it faulty (less voting of three pitot readings).

b) in case of actually loosing reliable IAS and forced switching to alternate law or what ever mode, would use GPS for displaying pilots an educated guess of airspeed, and would use GPS for calculating altitude and a safe attitude and power setting, which would keep the plane in the air in those conditions. The pilot would then have the option of flying the plane manually or rely on an rude "autopilot" using only pre-calculated values to keep the plane in a safe as possible envelope with data available.

c) use GPS to judge whether the plane is stalling or IAS too far out to be considered reliable (re: no stall warning below 60kts).

chaz88z

Will GS appear on the PFD?
Then they will have to check on the ND or FMS, okay it is just a few inches away but then the aircraft was on full auto and released to full manual the workload must have significantly increase in the first seconds, and one might consider the 7000ft up vertical speed to illustrate the amount of workload and a related lack of visual scanning

peplum

You're right. I'm very surprised to not read in the official media the air speed evaluation from the ground speed. I'm quite sure that it's too complicated to recognize the pilots were too clueless and accustomed to use their computers and to consider this simple tips that could save their lives.

peplum

On A320 it does. GS and TAS.

They were 3 pilots. None of them had this simple idea to read the ground speed. Damn, the wind would be at max 75kts (may be more we don't really care).

Open the window and evalute the wind !
No, just read the ground speed.

You're at FL300, sustain as much you can 400 kts GS
You're closer of FL200, aim 350 kts GS.

Automatic pilots makes intelligent people too stupid when deconnected.

And please indicate air incidence should be considered main indicators.

paull

Genghis,
"these chaps were experienced and current pilots unlikely to make such an elementary error. "

Only one of them made the mistake, the other two did not know what he was doing. PF used up 27'000 feet and PNF then had a go with less than 10'000 feet left. You are there to monitor the other guy but cannot see what he is doing, so you assume he is getting it right, at least to start with? In my book that gives you a single point of failure and that is a bit naughty.

davionics

I grossly over simplified, but sometimes 'simple' provides us the best analogy - fluid mechanics aside. As the last resort option (beyond having desirable sensor redundancy etc), GPS or INS could have been the only, albeit inaccurate substitute for air data available during the reported pitot icing. Can a 'bus pilot tell us what the safe operating airspeed margin 447 might have had at FL370?

Zorin_75

Temporary pitot failure may have been a factor, but it's not a good enough reason in itself for an otherwise fully intact a/c to fall from the sky. They recognized UAS, there's a procedure for it, why didn't they apply it? Or at least common sense? The plane was flying well before the pitots failed, it would very likely have continued to do so if they had maintained pitch and thrust. Instead for reasons yet unclear they performed a manoeuvre leading into a stall. Then they either failed to interpret the situation or didn't / couldn't apply appropriate measures to recover from it. Again for reasons unknown yet.
There's still far too much open questions and to most of them 'pitots' doesn't seem to be a good answer.

peplum

What are you looking for, Vs @FL370 ?

eswdev

chaz88z

Your 2nd item omits to say that there were two stall warnings after the PF corrected the bank to the right. Subsequently the aircraft climbed at a high rate. The high climb rate must mean that the stall warnings were not valid; could they be triggered by invalid airspeed rather than excess angle of attack?

HarryMann

Eeek! - What is this ridiculous fascination with minimising height loss everyone is quoting (modern pilots) as having during cruise ... ???

At 35,000 goddam feet... really... who is dreaming up these latest training schemes ?

busTRE

Peplum and others:

You simply cannot use ground speed.

The wind could easily be 150kts or more in any direction ( I don't kow where you get the idea that 75 is a maximum Peplum, it just isn't). So, if you maintain 400lts GS as you suggest you might be doing 250 or 550 or anything in between. i.e. you have no idea. At near to service ceiling the safe speed range can be as little as 30 kts wide and yet you think it is fine to use a method that has a 300 kt (or more range of error). I can only assume you are not professional pilots to have made such a basic error.

peplum

I've read the stall alert is invalid when AoA is too high bevcause AIR speed measure cannot be intrepated as valid.

Why did they sustain a such AoA ? Do the plane displays (sufficuently) it on instruments ?

Bus Driver Man

"...on protected Airbus aircraft"

Once in alternate law, the aircraft was not protected anymore and the reaction to a stall warning is like in any other airplane.
Ofcourse a correct pilot action is needed.

So calling this a fundamental problem in the attitude of Airbus and their design philosophy seems incorrect.
Alternate law and stall recovery should be included in the training of the pilots.