Air France 447 - On topic only!

[Fear_of_Flying]

They've listened to the CVR. You have to wonder if they already know what happened. Hopefully someone will leak it to the public soon.

The first leaks, reported by Le Figaro in France, are that the data are pointing squarely to pilot error.

There are several explanations for this, not the least of which is the press is trying to encourage a quick release of information to dispel swirling rumors.

There is also the possibility that something rather egregious took place in the cockpit that overshadowed what we think was the principle factor (the airspeed problems), something like the Colgan accident. That's where I'm putting my early money.

[Gabriel]

Do you mean static longitudinal stability? Are you referring to Sec. 25.173?

For example. It's all across the FARs, but 25.173 is a good example.

If I get you right, you are saying that the idea of the FCC maintaining a load factor that slows the aircraft below trim speed after stick force has been released, as opposed to it returning to the trim attitude as a result of static stability, is inherently dangerous in the absence of stall protections? Is that right?

Yes, more or less. Maintaining a load factor of 1.

If you release the stick force, the FCC will keep a load factor of 1 (corrected for pitch and bank angles, but let's leave this at a side by now).

That means, for example, you are steadily flying straight and level. Then you pull up on the stick, thus increasing the load factor, the climb rate and the pitch (all while the pull force lasts), then you release the stick (or the force on it), the FCC will maintain 1G again, which means:
1- The climb rate and pitch will stop increasing.
2- Unless you add thrust, the plane will start to slow down.
3- The lift then would tend to diminish, but that would result in a load factor of less than 1, and the FCC will prevent that by increasing the AoA (and hence the pitch).
4- The climb rate will remain constant which, with a diminishing speed, will result in a steeper climb slope.
5- The loop will continue (speed goes down, pitch goes up to keep the same lift).
6- Depending on how close were you from the "back of the power curve" (where you need more power to fly slower) when you started the maneuver, and how much you initially pulled up, the plane might settle at a speed below the initial one but above the start of the "back of the power curve", OR find its way in that "back of the power curve". Once there, if there is no proper intervention (by the human pilot or the envelope protection), the plane will eventually but unavoidably stall.

Example 2: Same initial condition. The upset, instead of a pull up, is a reduction in thrust. Start from point 2 above and the cycle is almost identical (the only difference being, in point 4, that the trajectory will be constant). Again, if the thrust set is not enough to sustain flight at any speed between the initial one and the start of the "back of the power curve", the plane left alone will eventually but unavoidably stall.

Oh, and with a computer that keeps 1G, there is no such a thing as a trim speed.

I think Airbus gets around this (it was written in 1965, long before FBW technology was practical) by taking into account part (d)

I don't think so. This point (d) applies "Within the free return speed range specified in paragraph (b)", which in cruise flight is +/- 7.5% of the initial trim speed. The FCC maintaining 1G will have no problem to stabilize the speed beyond that range even into a stall.

And have you checked paragraph (c)?

(c) The average gradient of the stable slope of the stick force
versus speed curve may not be less than 1 pound for each 6 knots.

How, do you think, does Airbus get around that?

[fmedina]

Wow, what could exonerate airbus so quickly..

http://blogs.star-telegram.com/sky_talk/2011/05/lefigaro-says-black-boxes-exonerate-airbus-in-air-france-447-accident.html

Must be a horrible mistake by crew.. anyone got any insight?

[Jpmkam]

http://blogs.star-telegram.com/sky_t...-accident.html

Must be a horrible mistake by crew.. anyone got any insight?

I wouldn't rush to judgment based on this one report so soon.

[Gabriel]

The news report by Le Figaro

My advice? Don't read it. It says nothing.

Just in case, google translation of part of it:

According to sources in government and close to the investigation interviewed by Le Figaro , the first elements extracted from the black boxes would Airbus harmless in the tragedy

Investigators from the Bureau of Investigation and Analysis (BEA) were able to operate from this weekend's Flight Data Recorder data (FDR), one of the two black boxes, which recorded the flight parameters and conclude fairly quickly as the Airbus A 330 was harmless. The work of the BEA will now be to determine what happened in the cockpit, and if mistakes are the responsibility of the crew or that of Air France, especially because of security procedures imposed by the company. To do this, investigators have two sources of information: the FDR, which also indicates the actions of the crew in the cockpit and the Cockpit Voice Recorder (CVR) which recorded the conversations in the cockpit.
According to sources interviewed by Le Figaro , new features of the liability of Air France and its crew will be provided by the BEA in the day Tuesday. The final report of the BEA survey should be prepared for several months but it is possible that the scenario of the drama is finalized by the weekend.

[Fear_of_Flying]

The news report by Le Figaro

My advice? Don't read it. It says nothing.

Just in case, google translation of part of it:

Early reports are notoriously inaccurate and need to be viewed with healthy skepticism. Added to that is the fact we are all so desperate to learn something that we are ready to take the first thing we hear and run with it.

Having said that, I have found that early reports do often contain a kernel of truth: bin Laden didn't die in a drone attack, but he was killed.

I'm not convinced there's nothing to this report; it depends on why this information was published.

[Gabriel]

I see it this way:

The report says too things:

1) The plane was perfect. We know it's not true. The chain of ACARS messages prove it. Pilot error can't cause it, which take's us to...

2) Pilot error. We knew it, or at least it was a very likely scenario. We know that unreliable speed alone, if correctly managed, doesn't down a plane. At the same time, pilot error alone doesn't either. If the pilts just magically dissaperaed fomthe universe, in that phase of flight (cruise), the plane would have eventualy reached Africa or Europe by itslef.

I don't say that the report doesn't contiain some turth. What I say (or meant to say) is that it adds nothing new to waht we already knew. And then it adds some things that we know are not true.

[Highkeas]

The A330 has the capability of up to four seats in the cockpit (plus access to a sleeping area perhaps). What is the minimum number of qualified pilots who must be in the flight deck at all times for aflight such as AF447? Just curious as to how many voices we might hear on the CVR.

[Fear_of_Flying]

I see it this way:

The report says too things:

1) The plane was perfect. We know it's not true. The chain of ACARS messages prove it. Pilot error can't cause it, which take's us to...

2) Pilot error. We knew it, or at least it was a very likely scenario. We know that unreliable speed alone, if correctly managed, doesn't down a plane. At the same time, pilot error alone doesn't either. If the pilts just magically dissaperaed fomthe universe, in that phase of flight (cruise), the plane would have eventualy reached Africa or Europe by itslef.

I don't say that the report doesn't contiain some turth. What I say (or meant to say) is that it adds nothing new to waht we already knew. And then it adds some things that we know are not true.

The discussion for a long time now has been how much the situation was exacerbated by inappropriate pilot actions, as opposed to being just an impossible set of circumstances to overcome. To me, the implication of the article - this initial report - is that the weight of the accident falls heavily on the pilots.

Another question, setting aside the issue of the faulty pitot tubes, is how much did the Airbus's interrelated systems, so dependent on sensor data, contribute to the accident? Again, it could be interpreted that the gist of the article provides an early answer: not much.

However, the article could just as easily be a ploy or a mistake.

[Black Ram]

I agree it is too early to draw conclusions. However, wasn't it again Le Figaro who did the exact same thing with the last Air France accident - the A340 at Toronto - and ended up being right about the reversers?

[Myndee]

I am very glad that the data was recovered and soon we will know what happened. I will follow the thread for any leaks. I won't be posting too much in this thread as it seems there is a troll amongst us. I will wait to see if he/she falls out like trolls so often do.

[tone]

Well done BEA!
They issued a press release just to slam the newspaper Le Figaro (still just in French).

http://www.bea.aero/fr/enquetes/vol.af.447/com17mai2011.fr.php

[Evan]

The discussion for a long time now has been how much the situation was exacerbated by inappropriate pilot actions, as opposed to being just an impossible set of circumstances to overcome. To me, the implication of the article - this initial report - is that the weight of the accident falls heavily on the pilots.

I think what it is getting at is that there is no other 'smoking gun' on the FDR, no other indication of a major system or structural failure beyond what we already know. IF THIS IS TRUE then the implication is that the situation should have been manageable by the crew, but this assumes two key things: (a) the crew was properly trained and had realistic and effective procedures for UAS under these conditions. and (b) a recovery under these conditions was achievable despite the cascade of the Airbus interdependent system failures.

So no one and nothing is exonerated yet even if this is true. It may turn out to be a recipe of pilot error, insufficient pilot training, flawed procedural (QRH) development and an aircraft design that is particularly unsafe under these rare circumstances. That's where my money is right now.

[MCM]

What is the minimum number of qualified pilots who must be in the flight deck at all times for aflight such as AF447

Minimum is 1.

Usually there would be 2

If they were doing a crew changeover there could be three or four

[Evan]

And have you checked paragraph (c)?
How, do you think, does Airbus get around that?

Probably the same way they got around this:

Sec. 25.497
Tail-wheel yawing.

But I see your point about the potential danger, particularly since the diminishing speed would result in uncommanded pitch during manual flight and that pilot inattention would result in increased AoA rather than simply a loss of altitude.

I think (keeping the AIrbus philosophy) the solution to this could be a software fix though.