Air France 447 Debris Found Underwater

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plutocrat03
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Re: Air France 447 Debris Found Underwater

Postby plutocrat03 » Mon May 16, 2011 9:39 am

Reports today are that that the flight data is intact and that there are approx 2 hrs of voice recordings. With luck thy are right and the speculation can be put to rest.

Three cheers for silicon memory.

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champguy
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Location: Florence, (Coastal) Oregon

Re: Air France 447 Debris Found Underwater

Postby champguy » Mon May 16, 2011 12:13 pm

Last words on FDR
"Oh S----"
"What was that?"
"Oops!"
I hope they can learn something more than "don't fly into a thunderstorm", and fix or make more robust any electronic systems that lives depend on.
Remember, not all who wander, are lost.
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plutocrat03
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Re: Air France 447 Debris Found Underwater

Postby plutocrat03 » Fri May 27, 2011 1:48 pm

First release of data from BEA in English can be found here http://www.bea.aero/fr/enquetes/vol.af. ... 011.en.pdf

Looks like they stalled it and never recovered.....

DCFlyer
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Re: Air France 447 Debris Found Underwater

Postby DCFlyer » Fri May 27, 2011 2:36 pm

From what I have read in the press the pilot made a rookie mistake by stalling the plane. I am not buying the reports that it was that simple. Secondly, if anyone can shed some light on how large aircraft like this one stalls. It seems strange not to be able to recover from a stall at that flight level.

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champguy
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Re: Air France 447 Debris Found Underwater

Postby champguy » Sat May 28, 2011 12:23 pm

A professional can explain it better, but when flying as fast and as high as they can to save fuel, time, and money, those big heavy monsters are very close to both VNE and stall at the same time.
Remember, not all who wander, are lost.
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Greg Bockelman
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Re: Air France 447 Debris Found Underwater

Postby Greg Bockelman » Sun May 29, 2011 5:08 pm

champguy wrote:A professional can explain it better, but when flying as fast and as high as they can to save fuel, time, and money, those big heavy monsters are very close to both VNE and stall at the same time.


That is called "Coffin Corner". And it isn't as big a deal with the more modern jetliners as it was in the past.

Swept wing aerodynamics are rather complex. Bottom line is that if an airliner is actually stalled, it is very difficult, if not impossible, to recover from. That is why there are stick shakers, stick pushers, and all sorts of other things to wake up the pilots to the fact that something VERY BAD is about to happen.

As far as the AF 447 thing goes, from what I have read so far, the crew did some things that make me scratch my head. But I am not sure, in fact I am positive that, not all of the facts are in yet.

Greg Bockelman
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Re: Air France 447 Debris Found Underwater

Postby Greg Bockelman » Sun May 29, 2011 5:10 pm

DCFlyer wrote:From what I have read in the press the pilot made a rookie mistake by stalling the plane. I am not buying the reports that it was that simple. Secondly, if anyone can shed some light on how large aircraft like this one stalls. It seems strange not to be able to recover from a stall at that flight level.


As I said to Champguy, in a lot of cases it isn't possible to recover from a stall in a big airplane. That is why the designers go to great lengths to prevent it from happening in the first place.

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ATC_Ben
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Re: Air France 447 Debris Found Underwater

Postby ATC_Ben » Mon May 30, 2011 9:58 pm

From what I remember of swept wing aerodynamics the tips stall first which actually pushes the nose further up. The airspeed being invalid (as well as the AoA at times) put the aircraft into 'Alternate' law, in which the normal 'Alpha Floor' protections are not available. In 'Normal' law the Airbus logic infact prevents a stall from occuring by limiting the AoA to a maximum value, even full aft stick won't stall it. In 'Normal' law the aircraft is UNABLE to be stalled and any approach to minimum airspeed triggers the Alpha Floor protection mode which automatically applies full power. But the AoA is limited so even with no thrust the aircraft will just descend at max AoA.

In 'Alternate' law everything changes, you loose a heap of the protections normally offered by 'Normal' law. See http://www.google.com.au/url?sa=t&sourc ... BQ&cad=rja

It's not the full story yet, but it would seem that situational and mode(law) awareness are factors. No-one seemed to mention that the aircraft was in alternate law, or make any account for it. I'm sure there is a checklist for alternate law that spells out clearly what protections have been lost (important in a FBW aircraft!). But the inputs the PF was making were at odds with the law that was active, it also seems to indicate that he was actually over-riding (with his aft stick inputs) the aircraft trying to get the nose down under 'low speed protection'. Nor did anyone mention (bar the SO once) the altimeter unwinding at an impressive rate. In excess of 10,000fpm descent should have gotten someones attention, as should have the excessive deck angle that would have come with over 35deg Alpha unless it was stuck in one almighty downdraft. Unfortunately they didn't put together the bits of airspeed and AoA information they did get together with the altimeter and work out they were stalled. At this juncture it looks like the crew were perplexed by the problem and the aircraft was lost not by the problem (although it didn't help), but by the age old problem that no-one was effectively flying the aircraft! Because the aircraft executed a 270deg turn and lost 35,000ft in just over 3 minutes.

No judgement against the crew until we have the full story, but IFR 101 is Attitude + Power = Performance. If you loose your airspeed but you set cruise power (no autothrottle because that needs airspeed to work!) and about 4-6 deg nose up you should stay relatively in the same place. Sure the turbulence will upset you a bit, but just ride it out and fly the pitch and power.

Of course it's much easier to Monday morning quarterback from the comfort of your home.
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