AF 447 Search to resume

[PJ2]

CONF iture;

I don't think it was necessary to select one or both Flight Path Directors ON to get the FPV red flags.

Agree, thank you for the catch and correction.

Sigh, going from memory isn't working as well as it used to.

"FPV | Red flag under initial position of horizon line (has a
steady position and does not follow pitch and roll
variations). It is displayed in TRK FPA mode when
attitude is valid but drift angle or flight path angle

are not valid. Flashes for 9s then is steady."

[techgeek]

FBW design goals and aircraft performance

The following quote is taken from a document comparing B777 and A330 flight control design vis a vis aircraft performance limitations and pilot authority developed during the recent USAF tanker competition (emphasis is mine):

"The Airbus design allows the pilot to obtain, in a repeatable fashion, a consistent level of aircraft performance. However, the pilot may be prevented from obtaining maximum aircraft aerodynamic performance. The procedure for the CFIT escape maneuver in the Airbus aircraft as recommended by Airbus, is for the pilot to pull full back on the stick and apply TOGA thrust. Speed brakes if extended, will automatically retract. Control laws either stabilize the AOA at an optimum value or adjust pitch rate to obtain maximum allowed g. With the Airbus CFIT escape maneuver pilots can quickly and easily achieve a repeatable consistent level of performance allowed by the envelope limiting system. This ease of handling might, in certain cases, result in optimum CFIT escape performance, even though full aerodynamic performance may not be achieved. The argument can be made that pilot authority is limited in the “hard” design by the fact the pilot is prevented from exceeding the limits of the flight envelope. The Airbus design allows the pilot to rapidly obtain maximum allowed aircraft performance to avoid ground contact. However, the pilot is prevented from obtaining all possible aircraft aerodynamic performance. That last bit of available but not attainable performance may be all that is necessary to avoid ground contact."

For those so willing to cast doubt upon the flight crew you should give thought to the more likely event that they were trained to take specific actions on the assumption of control laws being in operation with valid inputs. The aircraft may well have betrayed the best intent and effort of the pilots in this circumstance.

[cuddieheadrigg]

Thanks to Chris and JD-EE

Trying to look at this through inexperience eyes, and with as little speculation as possible, another few questions:

ACARS Timings: are they accepted as mirroring the duration of the event?
(As in from first signs to or near impact - if any doubt - 'no')

If above is 'yes' then is it accepted the aircraft went very rapidly from normal flight to rapid descent?

Weather: is this ABSOLUTELY determined to be THE or merely a contributory factor?

The Aircraft:
As the commander has final authority for the safety of the aircraft - we have no indication of diversion or messages RECEIVED (or sent) regarding any such action. Regardless - is this in any way relevant to events? (That is IF a turn was implemented, or an intentional descent would this have ANY material bearing on events in terms of any contribution - or if it is a concurrent event demanded by the situation is it irrelevant to the outcome?)

Crew awareness: Assuming all crew alert - and weather a factor - is there any relevance to saying the crew 'should' have noticed via weather radar any anomolies, or were the general conditions not a factor of concern until 'too late'? (That is, there was no reason to be concerned and possibly no way to know what lay ahead?)

Finally: assuming rapid descent - again irrespective of the ACARS messages - if the pilots had a non respoding aircraft - there are obviously countless variations on the theme - but the question would seem to boil down to;

Is there a possibility or indication of 'loss of control'?

If control was lost or reduced - what is MORE responsible - mechanical action (by ice or any other damage) - or the Airbus computer system?

[AlphaZuluRomeo]

@ techgeek :

I'm not sure the statement you posted apply to an A330 under ALTN 2 FBW law ?

Furthermore, accepting the conclusion (based on hard evidence - floating debris analysis) that the aircraft impacted water with a high vertical speed and a low forward speed (i.e. stalled), what would a bit more performance have changed ? It's not a CFIT situation, as far as we know...

[Mr Optimistic]

'BOAC, discussions here led me to believe it was standard practice for one of the cockpit crew to have his mask on so that if something went wrong with the air supply he'd still be alert enough to fix it.

{^_^}'

Is this a coded message pilot to pilot or can it be read literally ? The only alternative is that there is some scuttlebutt on what the rov's have seen ?

[HazelNuts39]

Originally Posted by AlphaZuluRomeo

... the conclusion (based on hard evidence - floating debris analysis) that the aircraft impacted water with (...) a low forward speed (i.e. stalled) ...

Where did you read that?

[jcjeant]

Hi,

Podrían haber encontrado las cajas negras del Air France que cayó al Atlántico en 2009 – RT

[Chris Scott]

cuddieheadrigg,

Forgive me, but I can't help feeling as if we're being asked to take part in some kind of consumer survey by an organisation that has only a passing interest in the subject, that has insufficient time/inclination/ability to phrase all its questions with intelligible syntax, demands yes/no answers, and which may have an agenda it is unwilling to reveal.

Am I being uncharitable?

JD-EE,

Re "gentle descent unlikely": yes, admittedly I do occasionally lapse into tongue-in-cheek understatement.

[AlphaZuluRomeo]

@ HN39 : High vertical speed is from the BEA. Low forward speed is my interpretation of BEA's Report 2 data (*) + declarations following the wreckage found + photos showing a relatively intact frame (compared to SW111).

(*)

(...)From these observations it can be deduced that:
- The aircraft was probably intact on impact.
- The aircraft struck the surface of the water with a positive attitude, a low bank and a high rate of descent.(...)

Am I misleaded, here ? Any other reasonnable interpretation I cannot see ?

- - - - - -

@ techgeek : After checking : g protection still in effect in ALTN 2 law, so you're right, then.
I still can't see that (correct) info as relevant to AF447, though.

[paull]

Was the A330 actually certified for the flight plan it filed?

It seems based on the first BEA report that at FL350 the temperatures were EXPECTED to be lower than. -40C and there is nothing unusual about that I assume, yet according to Appendix 4 of the second (interim) report this was the very limit of the Certification of the Pitot tubes.

So, if the pitot tubes are not certified below -40C, then how can the A330 be, or are we just relying on "Ice will not be a problem below -40C" ?

After all the previous examples of Incorrect Airspeed, below -40C, why did we have to wait for this loss before recommending that the certification needed adjusting to encompass what is after-all a fairly routine temperature range?

[cuddieheadrigg]

Chris Scott:
Forgive me, but I can't help feeling as if we're being asked to take part in some kind of consumer survey by an organisation that has only a passing interest in the subject, that has insufficient time/inclination/ability to phrase all its questions with intelligible syntax, demands yes/no answers, and which may have an agenda it is unwilling to reveal.

Am I being uncharitable?

I would say so.

I've actually followed all these threads for a long time - I have not added to them as I have nothing to input - but as the threads expand, it becomes difficult to see any comments that are either not theorising, and are 'simple' to understand.

I shall try and put into words how the events appear to me (with no technical knowledge). I have no interest other than A: finding the various theories difficult to comprehend and B: being an occasional air traveler.

So: in terms I understand, you need lift and thrust to move an aircraft through the air. If either of these factors change or are lost then the aircraft will not fly correctly.

From reading and rereading the events seem to point to an incident which lasted a short period of time - indicating that the aircraft descended rapidly.

The ONLY relevance to the type (Airbus) that I can possibly see in terms of the accident is IF the computer shut down or operated in some way as to either stop or inhibit control inputs being corectly applied, or the computer sent the aircraft into a dive.

Otherwise, disregarding the weather, the only other possibilities are that the aircraft lost thrust - how? or it lost lift - how? - or - it lost one or a combination and did not descend as rapidly as may be believed, and ditched.

If the aircraft lost thrust it will descend rapidly even if full control is available elsewhere. If it breaks up midflight then it will plummet. If control is lost then it has to be exceptionally severe if thrust and minor controls cannot restore any form of controlled flight - so ultimately, the questions have to be - short of the aircraft being pitched down deliberately - if an aircraft stalls, and has diminished controls, is it really not possible to get some measure of control back in 30 odd thousand feet? Can weather totally disable an aircraft?

It seems otherwise, that it could in theory be anything from engine to system failure, or even fuel starvation. There are no posts which say, for instance 'if the computer failed then all control would be lost' (that I can find) - which may give a clue. All we know is it fell or flew from the sky.

[Lonewolf_50]

Originally Posted by JD-EE

Lonewolf_50, sorry I phrased it badly. I was suggesting you might have been derelict not to mention that point to support your argument. It's a very telling point, at least to me.

Fair to say I left out an important point, particularly considering that on this forum, copilot and captain experience is frequently raised as a troubling issue for the current state of the airline industry. (See the Hudson River Landing, two experienced pilots did well in a tough situation ... the Buffalo crash / icing rather the inverse ... )

There was an old Aviation Safety Maxim that goes something like this:

Gravity and physics don't care how many hours you have in your log book, you still have to know your aircraft and fly it professionally ... experience is no proof against mishap, nor against the vagaries of Mother Nature.

@cuddieheadrigg:

Trying to look at this through inexperience eyes, and with as little speculation as possible, another few questions:
ACARS Timings: are they accepted as mirroring the duration of the event?

Probably not. I'd be careful in attempting to correlate too closely a text based maintenance message system (with a comparatively low baud rate) with a flight data system. You are asking for more than what that system is designed to give.

To give you some perspective: if the "wait in line" message interval is six seconds, a number of things can happen all at once (let's say four) and it takes 24 seconds to get all of the faults transmitted to the maintenance system. In the meantime the pilots have been busy dealing with malfunctions. For perspective: I could enter a training spin, let the aircraft spin for a few revolutions, and recover, in less than 24 seconds, (altitude reduced by a few thousand feet) when I was an instructor in T-34C's. I could also, in the same aircraft, in six seconds or less, be at the 90 (base) in the landing pattern, get into a skidded turn stall, and be dead on impact with the ground. A whole lot more than error messages would have gone on in the interim for both of the above events.

Weather: is this ABSOLUTELY determined to be THE or merely a contributory factor?

"Merely a contributory factor?" Weather is a contributory factor to a lot of what happens in flight, for fair and foul. You question makes zero sense as phrased.

The Aircraft:
As the commander has final authority for the safety of the aircraft - we have no indication of diversion or messages RECEIVED (or sent) regarding any such action.

That might be due to the CVR and FDR not having been found yet. Info from ACARS is intended to assist the maintenance crew in their trouble shooting and remedy of faults to some aircraft systems. Also, the protocol when flying, the iron rule of the sky, is Aviate, Navigate, Communicate. If and when things went all wrong, the last thing the crew is going to do is talk. They'll first address getting the plane flying, then getting on course/speed/altitude/route, etc, and then talk about it.

- is this in any way relevant to events? (That is IF a turn was implemented, or an intentional descent would this have ANY material bearing on events in terms of any contribution - or if it is a concurrent event demanded by the situation is it irrelevant to the outcome?)

This question makes no sense. Increasing your Angle of Bank will change your stall margin, but people turn aircraft left and right every day with no ill effects. You can stall from straight and level flight, or in turning flight. I did both with some frequency as an instructor pilot. It was a controlled situation, however. What has become clear to me in this family of threads and posts, in re AF 447, is how difficult it is to handle a big passenger jet that has actually stalled, rather than approached stall, and how many thousands of feet it requires to recover from that stall, if recovery can be managed. It has been a real eye opener.

Crew awareness: Assuming all crew alert - and weather a factor - is there any relevance to saying the crew 'should' have noticed via weather radar any anomolies, or were the general conditions not a factor of concern until 'too late'? (That is, there was no reason to be concerned and possibly no way to know what lay ahead?)

The reason weather radar is on modern transport aircraft is to allow a crew to avoid surprise, damage, and worse as a consequence of running into severe weather. How one uses that tool is a factor of training and practice. How one arrives at decisions based on info from the weather radar is a function of airmanship. "Should have" is a vague assessment, when lacking data. Numerous posts in AF 447 threads, and a few recently here, point out some of the nuances and limitations of weather radar.

People have keyed on weather as a contributing factor for a variety of reasons (see references to other posts on this topic about a pitot tube issue over the Pacific a few years ago) but the major reason is as follows: without significant phenomenon influencing AF 447, and given how well modern aircraft can be trimmed for level flight at altitude, and given the system redundancy designed into modern passenger aircraft, there is little rational reason for AF 447 to have done other than maintain altitude and course selected to eventually arrive in Paris. Something interrupted that, and given the weather in the area, and other flights using course deviations to avoid significant weather, that factor has been considered as a key to solving the mystery of AF 447's loss.

Finally: assuming rapid descent - if the pilots had a non respoding aircraft - there are obviously countless variations on the theme - but the question would seem to boil down to; Is there a possibility or indication of 'loss of control'?

The aircraft hit the water. An aircraft in control most likely won't do that when the selected altitude is 35,000 or 37,000 feet. Between the pilots and the aircraft systems, being "in control" would avoid unintended water impact. How and why controlled flight was compromised is the great unanswered question of this crash.

If control was lost or reduced - what is MORE responsible - mechanical action (by ice or any other damage) - or the Airbus computer system?

The answers to that question are pending retrieval of the CVR and FDR. Attempting to attribute a major cause by guesswork (as has been going on in the various speculative posts in this extended discussion, including mine) has limited utility.

The facts available to date do not lend themselves to the terse summation you require without FDR and CVR confirmation.

[cuddieheadrigg]

I should also have mentioned: on the face of it weather, human factors (bad design, negligence, human error etc) an 'unforeseen circumstances' (which could be a combination of the above) always seem to factor highly in any accident, aviation or not.

Now, if weather alone was a primary cause in the case of AF447, then has avaiation been incredibly lucky, or did we see unknown weather in the area? If not, then surely logic will say that such events should be more common: how many windshear events have caused incidents at airports, even when known about? If similar weather events could cause total loss of conrtol then surely statistically there would be more cases even if the particular area sees less traffic? I don't know.

I also do not think crew incompetence or absence or whatever has much if anything to do with AF447 - but as we are told it did not break up in mid air, it really leaves only the options previously mentioned - which may or may not have much in common with the prevailing weather.

[Lonewolf_50]

Now, if weather alone was a primary cause in the case of AF447

I am going to be a bit of a nitpicker here. The intent is to assist with understanding.

"If weather alone was a primary cause"

If weather alone was the cause, weather being the sole cause, then there is no resort to primary, secondary, or tertiary causes ... but I think that the way your framed that isn't the right lens through which to view this aviation accident.

For what it's worth, I have learned over the years to look at aviation mishaps and crashes as being shaped by contributing factors, some with greater weight than others, but all being linked together in combination to provide a combined cause for the effect, which is a crash or other mishap.

I invite you to consider the infamous Swiss Cheese model.

Colorado Firecamp - HFACS, the "Swiss cheese" model, Introduction

What you might be looking at is the issue of being necessary and or sufficient.

"Without the Wx as the trigger, would this mishap event chain have been broken?"

That is one way to look at it. Weather has been around us (and a hazard) since Orville and Wilbur took to the skies. How we mitigate the numerous risks that weather provides to the flying environment is one of many factors in flying safely. (You alluding to wind shear is a well placed example).

[Mr Optimistic]

Quoting from HazelNuts from way back last August (hope he doesn't mind)

'So, based on the ACARS messages alone, the ROD in the final seconds could have been anywhere between 2463 and 16320 fpm, while the average ROD in the preceding descent was of the order of 7850 fpm: 35000 (2:10:10) - 2176 (2:14:21).

I also believe that the airplane probably stalled one or more times in those final minutes. Is it certain that it was stalled in the final seconds?

Quote:
some juggling of a flight termination time could give a v/s that fits with the BEA reports (high vertical speed, 'en ligne de vol', and 'arm 36 g' etc..).
The 320 ditched in the Hudson at 780 fpm, 125 kt, 9.5 deg pitch. Its fuselage received substantial damage but stayed in one piece.

The Turkish 737 in Amsterdam impacted stalled at 3000 fpm, 100 kt, 22 deg. pitch, its fuselage broke into three sections.

AF447's stall speed (Vs1g; V_alphamax) was 158 kCAS; 162 kTAS; 274 fps. The corresponding alphamax can be estimated as 14.5 degrees. Interpreting "avec une assiette positive, une faible inclinaison et avec une vitesse verticale importante" as 2.5 degrees nose-up, leaves an FPA of 12 deg. down, or 3418 fpm.

So was it stalled?'

Based on straightforward kinematics, an impact at 20000m from LKP within 300 seconds assuming constant ROD gives an average ground speed of about 140 kts, about 65 kts vertically, flight path angle -26 degrees, average speed about 170 kts and with linear deceleration gives a starting speed of 340 knots.

Are these figures that unlikely ?

[HazelNuts39]

Originally Posted by AZR

Low forward speed is my interpretation

Agreed, and not unreasonable too, but not a fact,

[cuddieheadrigg]

Lonewolf

Many thanks, that is a superb link.

Also, thanks for the input to the questions I put. I think in retrospect they are all 'worse' than speculating that the Captain was on the lavatory or whatever. Your answers actually highlight the speculative nature of the questions, even if they 'demand' yes or no answers.

I think, as you mention, with a combination of events almost always to blame for such things, it may well be something no one has thought of is in the mix somewhere, rather than one 'key'.

[HarryMann]

Originally Posted by mm43

Something tells me that the 02:10 FCPC2 (2CE) WRG: ADIRU 1 BUS ADR1-2 TO FCPC2 may have been precipitous to the whole sequence, as a wiring fault manifest itself in turbulence.

My thoughts too, since Svarin pointed out the WRG: WRN: difference

[HazelNuts39]

About stalling, generally speaking

Since we're likely to get into this again and again, a few words on stalling (apologies to all those for whom the following contains nothing they don't already know, several elements having been posted earlier).

One way to stall an airplane is to gradually reduce airspeed at approximately 1g. The speed at which the airplane then stalls is called the 1g-stall speed, or Vs1g. In the conditions of AF447, such deceleration would take of the order of 1.5 - 2 minutes. When the load factor is greater than 1g, the airplane stalls at a higher speed. That is because stall is not solely a function of speed, but occurs when the airplane exceeds a certain angle of attack, AoA, or alpha.

For the A330, alphamax is an AoA slightly below the AoA at which the airplane stalls aerodynamically, as illustrated schematically in FCOM 1.27.20. It is the highest AoA that can be obtained in normal law by gradually pulling the sidestick fully back and keeping it there. Thus it defines the minimum steady flight speed obtainable with this airplane, variously referred to as V_alphamax or Vs1g. At high altitude alpha-max corresponds to the onset of perceptible buffet.

Loadfactors greater than 1 can result from control inputs (maneuvers such as pull-ups or turns), gust encounters, or a combination of both. This graph shows the relation between between alpha, load factor and gust velocity for a rigid body encountering a sharp-edged gust. Real-life gusts cannot be sharp-edged, but are always surrounded by a mixing zone that 'softens the blow'. Other attenuating factors are structural flexibility, unsteady aerodynamics, and longitudinal stability, all not taken into account in this graph. Per regulation, the highest discrete gust velocity assumed in the design of the structure at this altitude is about 60 ft/s TAS.

Finally, it should be said that a stall is a temporarily uncontrolled, but usually recoverable condition, provided the pilot recognizes it and takes the right actions. The stall is identified by buffet of increasing intensity, usually becoming so intense that, in regulatory language, it is an effective deterrent to further reduction of speed or increase of load factor. To 'unstall' the airplane, the AoA must be reduced below that at which it stalls.

All things combined, the conclusion could be that it is not likely that the airplane stalled at 2:10, and remained stalled all the way down to the surface.

[cuddieheadrigg]

Originally Posted by mm43
Something tells me that the 02:10 FCPC2 (2CE) WRG: ADIRU 1 BUS ADR1-2 TO FCPC2 may have been precipitous to the whole sequence, as a wiring fault manifest itself in turbulence.
My thoughts too, since Svarin pointed out the WRG: WRN: difference

Funny how you ask a few questions and something pops up that seems to make a little sense: IE - normally speaking, one would expect an aircraft to avoid weather likely to be very uncomfortable or dangerous.

Any issue with the aircraft resulting in a flight proflle that is not ideal would only incease any risk from bad weather - irrespective if the issue cropped up before or during the worst of the weather - BUT if the weather 'alone' was not enough to be the decisive influence without any other problem, then any potential issue arising independently or because of (Turbulence) would certainly explain subsequent events.

Out of interest, if icing is a potential cause of the airspeed inconstencies is it equally possible a wiring fault could casue the same thing?

Looking at a whole, it seems more plausible than some of the other ACARS messages since some appear unrelated (directly) to having problems with the pitots and probes - or perhaps that was the cause alongside a seperate fault unrelated?