Air France jet crashed nose-up after 4 minute ordeal

Reuters/Yahoo ^

[nuconvert]

PARIS (Reuters) – Pilots wrestled with the controls of an Air France airliner for more than four minutes before it plunged into the Atlantic with its nose up, killing all 228 people on board, French investigators said Friday.

The 2009 emergency began with a stall warning two and a half hours into the Rio-Paris flight and nine minutes after the captain had left the cockpit for a routine rest period.

The Airbus A330 jet climbed to 38,000 feet and then began a dramatic three and a half minute descent, rolling from left to right, with the youngest of three pilots handing control to the second most senior pilot one minute before the crash.

[r9etb]

Intl. overseas flight. He went back to sleep in the qtrs, so he’d be pilot on landing in France. Routine.

I know it's "routine." But given how quickly things went to hell after he stepped out, it's difficult to believe that there weren't clues about upcoming rough weather that he either missed or ignored.

And I recall at the time that there were stories about the weather along their flight path (which, IIRC, was a deviation from the normal route).

Accidents like this rarely happen for just one reason -- in my world (satellites, not airplanes) there's typically a chain of events that eventually culminates in the so-called "root cause." And thus it seems to be in this case: my recollections of the early stories are that the pilot knowingly took a risk with his flight plan due to schedule/fuel loading issues. So they flew through the weather instead of around it.

[Tzfat]

Is there some advantage to summing the inputs?

Absolutely. It is actually a very well thought-out design. The problem is the pilots need to use it the way that it was designed. Like I said, this is elementary Airbus pilot stuff, which makes this sound like inexperience or panic on at least one of the pilots' part.

[bill1952]

LOL! I’ve only had that on 2 declared emergency occasions & I’m still here to annoy you :)

[Jack Hydrazine]

You are correct. The computer did exactly what it was designed to do. In the event the computer doesn’t like what the pilot is doing the computer decides for him and locks out the pilot and flies how it wants to fly. It’s called fly-by-wire. The flight computer makes the final decision on any pilot input and can override any commands.

It’s pretty obvious the AF447 flight computer was having a bad silicon day and wouldn’t let the pilots even put the freaking nose down to get out of the stall. As far as I know Boeing airplanes don’t have this problem.

[r9etb]

I believe you ... but what is the purpose for summing the inputs from the two sets of controls? There has to be some reason why they would choose to do that, despite the dire consequences of misusing the feature.

[Jack Hydrazine]

You could have 200 pilots with their hands on the joystick and the computer still isn’t going to let you do anything the computer doesn’t like.

[DManA]

it’s difficult to believe that there weren’t clues about upcoming rough weather

This tv show I refereed to speculated on this too. They recreated the weather along the flight path that night. They noticed there was a small storm in front of them that would have hidden a much bigger storm right behind it. They avoided the little storm and found themselves faced with a big one. A meteorologist speculated that this type of storm would have had supercooled water vapor. Water vapor that could be induced to flash into ice around a pitot tube.

At least that was put forward as a possibility.

[SeeSac]

OK. Given 500 knots groundspeed and wind direction of 090 is the Airbus above or below stall speed ...

[John S Mosby]

Admittedly from reading accident followups from the past and conversation with buddies who also are long time Boeing jockeys- as such biased (bigots against airbus). So, should the focus be on the pitots (per another commentary on “freezing up”)? What would make the aircraft go into a stall on it’s own from previous level flight? With the “summing” effect in one consideration adding even more nose up commands, why would they have done that in the first place if the plane was in a stall? Do you think the computer locked them out because of false airspeed. Thanks for the admonishment and for your experience.

[John S Mosby]

Admittedly from reading accident followups from the past and conversation with buddies who also are long time Boeing jockeys- as such biased (bigots against airbus).

So, should the focus be on the pitots (per another commentary on “freezing up”)? What would make the aircraft go into a stall on it’s own from previous level flight? With the “summing” effect in one consideration adding even more nose up commands, why would they have done that in the first place if the plane was in a stall?

Do you think the computer locked them out because of false airspeed. Thanks for the admonishment and for your experience.

[DManA]

So, should the focus be on the pitots

In a way it was. All pilots of this plane were told about this potential situation and told how to recognize it and how to react to it. And the standard training course was changed to emphasize how to deal with this problem.

[Erasmus]

And also that supercooled water froze on contact with the pitots and shut them down all at once.

The NatGeo program, IIRC, was made some time before the black boxes were found.

The boxes should confirm or disprove the theory that the pitots were all out.

[raygun]

You are SO full of crap. Did you even read the BEA report?

http://www.freerepublic.com/focus/news/2720523/posts?page=18#18

The only inputs made by the pilot during the stall where nose-up.

[Jack Hydrazine]

Now why would trained pilots pull the nose up when they hear the stall horn? Any and every pilot flying an airplane from the smallest to the largest knows you don’t pull back on the stick when the aircraft is stalling.

[raygun]

Why don't you ask PF of Birgenair FL301 flying your beloved Boeing (B757-200) that very question?

The Dominican Republic government's Dirección General de Aeronáutica Civil (DGAC) investigated the accident and determined the following probable cause for the accident:

"The crew's failure to recognize the activation of the stick shaker as a warning of imminent entrance to the stall, and the failure of the crew to execute the procedures for recovery from the onset of loss of control."

Investigations later showed that the plane was actually travelling at 220 knots at the time. The investigation concluded that one of three pitot tubes, used to measure airspeed, was blocked.

Or how about Continental Airlines FL3407 that landed in a Buffalo, NY house?

[Jack Hydrazine]

Lack of training?

[cynwoody]

Here's a little story posted by Orval Fairbairn not long after the crash:

I just got this email from a retired airline pilot:

From a retired NWA buddy of mine

This from Brent Stratton, a friend and NWA pilot I flew the B-757 with
out of our Tokyo base.........Now obviously on the A-330  

Well, I'm sure you have all heard of the Air France accident. I fly the
same plane, the A330.

      Yesterday while coming up from Hong Kong to Tokyo, a 1700nm 4hr.
flight, we experienced the same problems Air France had while flying
thru bad weather.
I have a link to the failures that occurred on AF 447. My list is almost
the same.
http://www.eurocockpit.com/images/acars447.php
            
      The problem I suspect is the pitot tubes ice over and you loose
your airspeed indication along with the auto pilot, auto throttles and
rudder limit protection. The rudder limit protection keeps you from over
stressing the rudder at high speed.
      
      Synopsis;
Tuesday 23, 2009 10am enroute HKG to NRT. Entering Nara Japan airspace.

      FL390 mostly clear with occasional isolated areas of rain, clouds
tops about FL410.
Outside air temperature was -50C TAT -21C (your not supposed to get
liquid water at these temps). We did.

      As we were following other aircraft along our route. We approached
a large area of rain below us. Tilting the weather radar down we could
see the heavy rain below, displayed in red. At our altitude the radar
indicated green or light precipitation, most likely ice crystals we
thought.

      Entering the cloud tops we experienced just light to moderate
turbulence. (The winds were around 30kts at altitude.) After about 15
sec. we encountered moderate rain. We thought it odd to have rain
streaming up the windshield at this altitude and the sound of the plane
getting pelted like an aluminum garage door. It got very warm and humid
in the cockpit all of a sudden.
Five seconds later the Captains, First Officers, and standby airspeed
indicators rolled back to 60kts. The auto pilot and auto throttles
disengaged. The Master Warning and Master Caution flashed, and the
sounds of chirps and clicks letting us know these things were happening.
      Jerry Staab, the Capt. hand flew the plane on the shortest vector
out of the rain. The airspeed indicators briefly came back but failed
again. The failure lasted for THREE minutes. We flew the recommended
83%N1 power setting. When the airspeed indicators came back. we were
within 5 knots of our desired speed. Everything returned to normal
except for the computer logic controlling the plane. (We were in
alternate law for the rest of the flight.)  

      We had good conditions for the failure; daylight, we were rested,
relatively small area, and light turbulence. I think it could have been
much worse. Jerry did a great job fly and staying cool. We did our
procedures called dispatch and maintenance on the SAT COM and landed in
Narita. That's it.

[Tzfat]

In the event the computer doesn’t like what the pilot is doing the computer decides for him and locks out the pilot and flies how it wants to fly. It’s called fly-by-wire. The flight computer makes the final decision on any pilot input and can override any commands.

No, you are wrong. Have you ever flown an Airbus (or anything for that matter). Your so-called "lock out" is not a function of any fly-by-wire aircraft within normal flight regimes. Period. Did you stay at a Holiday Express last night?

It’s pretty obvious the AF447 flight computer was having a bad silicon day and wouldn’t let the pilots even put the freaking nose down to get out of the stall. As far as I know Boeing airplanes don’t have this problem.

Wrong again. The cause is most likely not a software failure, but a hardware failure. A320 and A330/340 aircraft were under an Airworthiness Directive at the time to replace faulty pitot tubes. It just so happens that numerous Boeing aircraft had crashes (with loss of life) because of just such failures. A Northwest B727 crashed in 1974 with a loss of all souls for that very reason.

[Tzfat]

I believe you ... but what is the purpose for summing the inputs from the two sets of controls?

It has to do with why there are two pilots. There are times when takeover is needed - when using the override is not timely - for only momentary transitory use. In the landing flare is an example. It is highly discouraged, but technically possible and something we train for.

[r9etb]

OK.... so the summed inputs are pretty much predicated on the assumption that only one pilot is in control at a time. It would be the same as dual inputs to a purely mechanical system, and the difficulty of creating software to achieve a foolproof automatic “I’ve got it” switchover would be prohibitive.