Tom Laxey

1. I think AoA sensors are different from speed sensors, but could the pilots have believed that both were invalid?

2. I would like to know how this sequence of events was particularly affected by this being an Airbus - couldn't any make of airliner not suffer defective speed sensors, and the crew not have to control the plane in the dark using a basic understanding of the altitude/ attitude and AoA?

3. If the pilots did believe the stall warning, their AoA increase was so much that the stall warning went away, which they may have interpreted as success. However should it not have rung alarm bells that this was the result of nose-up inputs? What would the artificial horizon have been showing?

4. In the later stages, it appears they attributed their altitude loss to being in an unstalled dive, and only at a much lower altitude did they push-down, perhaps confusingly turning-on the stall signal (still deep in stall), and by then there was too much altitude loss to recover steady flight? Did the pilots ever notice that their speed signals were in alignment? And wouldn't their slow speed have been an indicator that they were not in a dive?

grizzled

BananaAir

I agree with promani re your jumping to conclusions. At this stage, your use of the word "negligence" to refer to the Catapin's actions is most unfair and irresponsible.


Promani

Your reference to wishing the USA was conducting this investigation sounds somewhat parochial. In my experience, Dozy is correct re his comment above that the BEA is an entirely different organisation than it was a few years ago. (A fact that is also true, BTW, of many other countries' avation investigative boards.)

bubbers44

I've flown through that zone and it should be manageable on a normal night without needing the captain to be in the cockpit if it is his rest time. We are normally deviating around weather. They both seemed happy with the 12 degree left deviation. A bit of turbulence is normal in that situation so the FO advised the FA's. Somehow the pitot tube icing up caused the pilot flying who hadn't probably handflown the airplane much before lost his airspeed thought Airbus says it won't stall so pulled back so when the static source at his higher altitude gave him with the trapped pitot pressure caused the overspeed warning he retarded the throttle, then came the stall warning which he ignored so put it in a deep stall 3,000 ft above his assigned altitude. You cannot zoom climb an airplane that large without running out of airspeed. Everybody knows that. Other than monitoring the autopilot I wonder how many hours he had flying manually in an airliner. I heard he had 800 hrs in type and less than 3,000 total hours. How many hours was not monitoring the autopilot?

This new generation of low time pilots might not cost much pay wise but what do you think Air France paid for this crash?

deSitter

techgeek said
That misses the point completely. I know there are great people writing software - the problem is not with the people, it's with the methodology, or philosophy, or whatever you want to call it. The problems are bent around the idioms, instead of creating or using natural idioms based on the problem. It doesn't matter how good you are, you end up making reality bend to the design document, only it won't bend in the end.

HarryMann

I think it was bratschewurst who suggested there may well have been no need for any (substantial) pilot stick input at first knockings.

That I can get behind, possibly one of the better observations here

Another might be that if the Captain upon entering the cockpit could have seen immediately a very obvious AoA and a very obvious stick position, perhaps this thread wouldn't exist...

..which leads also to the thought that he surely must have noticed the deck angle upon his return ot the cockpit, if only by energy exerted per yard of progress ?

If so, then did he realise what the PF was doing, indeed is there any CPN and PF dialogue along those lines?

JD-EE

Tom Laxey, in relation to your first question if my memory serves way back on the first thread it was revealed this particular A330-200 did not have AOA sensors mounted. That should be checked as it has tremendous bearing on some of our bloviating here.

(And I did say "our", guys.)

bearfoil

syseng68k

The autopilot drops out involuntarily for other than UAS ADIRU disagree.
The input limits have been posted before, so subject to correction, I believe they are 45 degrees roll, 13 degrees Nose up, and 9 degrees nose down. for reasons other than max deflection, there are trend issues and off phase limiting? When the auto pilot is overwhelmed, the pilots get the a/c back in non degraded Law, Normal, ALTERNATE LAW is self selected if the cause is ADIRU disagree. Again, this is subject to a type guy.

You are precisely on point, for from the moment of A/P drop the pilots know they are in command subject to the Law selected, and they must be 'au courant' instantly. Without putting too fine a point on things, "I have the controls" is a professional and expected thing to say by the PF. He said this, and made a correction just after a/p had dropped, so an out of trim condition is not cause for concern.

I have a bit of a problem understanding why others don't see this handover as the "beginning" of things going rapidly pear.

alex_brin

Newbie here, not a pilot, but I've been following this since it happened and here is a link to a detailed meteorological analysis posted at the time, so none of the current information being discussed was known then.

I'm not posting this because of their attempts to understand what happened with the limited knowledge at the time, rather because of the extensive weather information and analysis given at the time. I wonder from the pilots here, if any of this analysis might explain the mystery of the continued nose up.

Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

GarageYears

AoA sensor or AoA INSTRUMENT/DISPLAY?????

How does the plane figure a stall without AoA sensors? Or compute AoA protection in Normal Law?

Answers on a post card....

There are Three Angle Of Attack (AOA) sensors, one on left (#1),
two on right (#2, #3) of airplane nose...

glhcarl

Did Airbus have a idea what happen to AF447 a year and a half ago?

www.flightglobal.com/articles/2009/09/09/331991/aa09-pilot-handling-skills-under-threat-says-airbus.html

bearfoil

Garage Years

Quote:
"...From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input...."



Things don't CENTER for the pilot when he gets it back from Otto. Something made the slave go poof, and why does it have to be UAS? It may well have been. His first inputs seem to be an adjustment for something the ap had trimmed out. It doesn't look like Pitch and Power to me. It looks like "give me a lower speed and some energy when I arrive at the top." Overspeed in still air is a bad thing, in turbulence it is to die for. Power is Altitude, Attitude is airspeed. PF was transacting business, who on God's Earth has enough data to question him at this point? OR believe me? Sherlock is rolling his eyes mon freres.

Does anyone have a clue about what these gents were (may have been) IN?

Anyone ever hear a Stall chirp at speed?

wozzo

Couldn't find neither "overspeed warning" nor "retarded the throttle" at this stage in the report. Wouldn't at least an overspeed warning have been mentioned?

Also, the PF didn't ignore subsequent stall warning: "The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs" (curious thing, TOGA, if PF was thinking being in overspeed).

Are we maybe reading different reports?

JD-EE

alex, thanks for posting that. It's nice to have that link handy again. It's been around this group since mere days after the accident. It's an excellent analysis. It'll be interesting to see if anybody sees anything more in it that would bear on this accident. (I suspect somebody was thinking of this and the BEA analysis of the weather might be why 200km off normal line of flight was mentioned.)

JD-EE

wozzo, I went back to the 17 Dec, 2009 Interim Report and found a description of the stall procedure. At altitude it's TOGA for thrust and slight nose down. So he did it half right. There is a valid question what he had in mind for his continue pull on the stick. And I suppose there is question whether he wanted TOGA for stall or for getting above it all. (If the latter, why did he almost level off after only 500' altitude gain?)

bratschewurst

My understanding (which may well be incorrect) is that, when the a/p drops out, alternate law will maintain the pitch/roll status current at a/p disconnect. The implication in the report is that the right roll began after a/p disconnect, presumably as a result of turbulence. My understanding (again, possibly incorrect) is that the computers would have corrected the roll to the previous (presumably straight-and-level) setting without pilot input. But that doesn't explain why the PF believed he needed to get the nose up.

The question left by the report is why the PF did anything at all. Obviously there was a reason for what the PF did, even if not doing anything might have produced a better result. If it was the airspeed displayed on the right side display, it wouldn't be recorded in the FDR, which does seem to be a design oversight.

A related question is why the crew didn't work the QRH for unreliable airspeed.

mm43

I haven't gone back and re-read it, but far as I remember he didn't see anything out of the normal in the data he had at hand. The OAT was forecast around -46°C, and the actual data will be available from the FDR, including a complete temperature sampling all the way from FL380 to FL0 provided the probes could keep up with the rate of change.

The following pilot comment is probably pertinent, "... we’re in the cloud layer unfortunately we can’t climb much for the moment because the temperature is falling more slowly than forecast". I note from Tim Vasquez's profile chart that he has indicated the FL350 temp as -43°C.

The crew knowing the OAT was on the high side and they were level FL350 at 205 tonnes, had already formed the opinion that climbing to FL370 per the FP wasn't an option. So, why a few minutes later when the AP/ATHR disconnected did they engage in this "zoom" climb?

It would seem that they were in the anvil cloud out-flowing from the prime Cb's, and this cloud was carrying a lot of moisture just ready to turn into ice crystals as it struck the pitots etc.. Did they at any time get on a thermal elevator?? I don't think so ... the only elevators in use were the ones attached to the airframe.

For the record, Tim has stated that thermal updrafts can reach speeds of 4 ~ 5,000 ft/min, but as far as I am aware that didn't occur that night .. daytime, maybe.

There is much more to what happened than has been revealed, and I suspect the real meat will be in the detail.

CogSim

The last recorded values were a vertical speed of -10,912 ft/min, a ground speed of 107 kt, pitch attitude of 16.2 degrees nose-up, roll angle of 5.3 degrees left and a magnetic heading of 270 degrees.

ground speed: 107 kt
vertical speed: -10,912 ft/min = -107 kt

Coincidence? Maybe.

The mathematician in me says this a/c achieved some sort of exotic aerodynamic stability during its descent. Wish I had more info about a/c heading during its descent.

mm43

Thanks to ACARS being free to transmit the CVS advisory in real-time, here is what actually happened:-

Two independent pneumatic safety valves prevent the cabin pressure from going too high (8.85 psi above the external ambient pressure) or too low (- 1 psi below ambient pressure).

* hcbn = 7350 – (750 ft/min x 251/60) or 7350 ft - 3138 ft = 4212 ft

As a 2.03625437 inHg pressure change gives approximately a 2036 ft altitude change, and as the external pressure is 1 psi more than the cabin pressure, the external or aircraft altitude (hacft) is simply:

* hacft = 4212 - 2036 ft = 2176 ft

2:14:16 - 2:14:28 = 12 sec > rate of descent = (2176/12) x 60 = 10,880 ft/min.
BEA's Rate of Descent at impact = 10,912 ft/min.

The 10,880 ft/min rate uses the earliest time the Cabin Vertical Speed advisory could have originated, i.e. coincident with commencing transmission of the preceding fault report message [02:14:16] with time of receipt 2:14:20. A further assumption is that the flight terminated coincident with the Cabin Vertical Speed warning receipt confirmation by the aircraft [02:14:28].

NOTE: WRN messages take precedence over FLR messages.
2:14:20 FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT
2:14:26 WRN/WN0906010214 213100206ADVISORY CABIN VERTICAL SPEED

The final satellite link with AF447 terminated a few milliseconds prior to the aircraft's impact.

gums

Good math, Cog. Maybe go further and calculate the AoA required for those parameters.

Then re-read my re-post about the Viper deep stall AoA and descent rate and indicated airspeed.

jcjeant

Hi,

Unreliable speed:
Airbus presentation dated 26-28 September 2006.
Unreliable Speed – Latest Improvements. Presented by Sourya Kahoul and Marie-Helene
Combes.
http://www.iag-inc.com/premium/Airbu...ableSpeeds.pdf