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AF447 wreckage found

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AF447 wreckage found

Old 30th May 2011, 18:14
  #1061 (permalink)  
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Danger Automation paralysis? Inexperience? Temporary Insanity?

At 2 h 10 min 51 , the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs
The Flight Data Recorder recorded airspeed and altitude as displayed on the left primary flight display (PFD), and on the integrated standby instrument system (ISIS).

"There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for less than one minute."

Even if the pilots were confused about momentary airspeed deviations and had no longer trusted the displayed airspeeds: It's a mystery as to why the Pilot Flying would pull back on the stick and climb from FL 350 to FL 380 during multiple stall warnings. Elementary, basic flying instinct learned from day one in flying school, should have made him do just the opposite. That is, to get the nose down, not up during a stall warning.

Curiously, the captain in the Colgan Air DH-8 crash in upstate New York had also pulled back on the yoke during the stall warning and active stick pusher...

Inexperienced pilot graduates from the same school...?
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Old 30th May 2011, 18:15
  #1062 (permalink)  
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To override the NU of the THS, in Alternate Law, one pulls back on the SS.

Yes? Was there confusion about the origin of the chronic NU on the way down?
I would assume so. To clear this, does one pull back to the stop and release?

"during" and "continuous" mean different things, yes?

If the cg was even partially ng, could the PF have confused the a/c insistence on climb with a 'stuck' "Law" command? One which he continually tried to 'Clear'? With intermittent full back ss to override??

see touch 'n oops below
Old 30th May 2011, 18:18
  #1063 (permalink)  
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nitpicker330 BACK TO THE BOOKS.

For someone who is "supposed" to know their aircraft, you really do spout a load...

Alternate 1
Alternate 2
What is that supposed to mean???

Don't you mean:
Alternate WITH protections
Alternate WITHOUT protections




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Old 30th May 2011, 18:26
  #1064 (permalink)  
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We know ?
We know almost nothing. So little data has been made public that making any assumptions and conclusions is quite premature, if not simply stupid. Nothing can be said for sure without going through the entire CVR transcript, while at the same time looking at the FDR data.

I have an unrelated question. One of the error messages transmitted by the aircraft was
Meaning: This message indicates that the TCAS is inoperative.
Is there any explanation why TCAS would fail? It seems completely unrelated to airspeed...
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Old 30th May 2011, 18:31
  #1065 (permalink)  
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@jcjeant - I'm just going by the bea rpt. The PF says "we're going to arrive at level one hundred." The report also says "the inputs made by the PF were mainly nose-up." It doesn't say that the last, simultaneous, inputs were nose down, so I assume they were nose up.

Still, my question is whether they might have thought they were in a dive?
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Old 30th May 2011, 18:31
  #1066 (permalink)  
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Is it possible to get a stall warning when pulling out of a dive?

It's called "high speed stall" or maybe "accelerated stall", and it occurs any time you're asking the wing to work beyond its max CL. The attitude of the aircraft is immaterial.

In fact, what we usually call a common stall (1.0 g) is a special case; in general a stall occurs whenever (mass x g) exceeds the wing's aerodynamic lifting capacity.
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Old 30th May 2011, 18:32
  #1067 (permalink)  
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There is some confusion among posters here, and in the press, about the flight path. The pitch attitude is reported to be around 15-16 degrees nose up, and the angle of attack to be 35-40 degrees. This translates to a flight path angle of -20 to -25 degrees. If the vertical speed is around 10,000 fpm (~100 knots), then the slant speed has to be the vertical speed divided by the sine of the descent angle, or somewhere around 250 knots. This is the true airspeed. The airplane was not fluttering down vertically like a leaf, and its forward speed was not 60 knots or 107 knots or whatever.
There is ample opportunity for confusion, since at different points in the report ground speed, AIS, and the erroneous speeds on the displays are mentioned. To understand what they are saying you have to keep the context of each separate in your mind.

As far as the forward speed, it was 107 knots when last recorded, according to the report. I assume that's GPS derived, so it should be accurate. However, that was ground speed, not the speed through the air. For your 250 knot estimate of airspeed to the true, that would imply a headwind speed of around 120 knots, which is unlikely. It was a thunderstorm, not a category 4 hurricane.

The report also mentions that the AOA in the final moments of the flight was always in excess of 35 degrees. It did not say how high it reached, nor what it was at the end of the recording. Thus, your assumption of only 40 degrees is probably an underestimate.

To put a perspective on it, if the wind was calm, then the actual flight path would be about 45 degrees down, AOA of about 61 degrees, with an actual speed through the air of about 151 knots.
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Old 30th May 2011, 18:43
  #1068 (permalink)  
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As for TCAS failing: might be completely unrelated to events. We sometimes have it momentarily failing in the CRZ and then rapidly coming back soon after.
However (speculation) it could be due to enormous amount of static (St Elmos) around the direction sensing receiving antenna etc.

In the grand scheme of things it's completely irrelevant to proceedings.

There but for the grace of God.
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Old 30th May 2011, 18:44
  #1069 (permalink)  
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ok you're in the cruise and the pitots ice up. airspeed/mach will stay at current values. Crew decides to reduce to turbulence speed., thrust reduces to achieve this. As actual a/c speed reduces autopilot starts to slowly pitch the nose up to maintain altitude and whilst doing so applies nose up trim. Maybe the thrust even reduced to idle at this point.

This continues until ths is at aft limit (remember the indicated speed/mach are still at original cruise values but the actual aircraft speed is much lower. Autopilot and autothrust disengage and a/c reverts to Direct law giving immediate pitch up due trim and a/c gains circa 3,000 ft and then enters dynamic stall. Presumably this zoom would give a slight reduction in static pressure, therefore the indicated speeds would increase.

The aspect that really interests me is that neither crew member noticed the increasing pitch attitude as the speed was reducing. What would the flight director be commanding throughout all this? If during the zoom upwards it's showing fly down to regain the selected flight level this might explain the initial side stick forward to regain.

If neither pilot wasn't paying any attention to the attitude then where were they looking?

Coming back to the issue of pitots getting iced up I still don't understand with modern design why this is a problem. There are plenty of other jet transports flying around the world where, as far as am aware, this has never happened. What is intrinsically different in the design of the system on this a/c?

Last edited by fireflybob; 30th May 2011 at 19:09.
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Old 30th May 2011, 18:44
  #1070 (permalink)  
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one of the things we learn in primary flight school is "hazardous attitudes". One of them is, iirc, "that can't happen to me". I read a lot of that one between the lines here. Scary.

I am fairly certain that either of the three pilots on board knew, at least in theory, how to recover from a stall.

btw: has anyone ruled out severe icing on the wings and stabilizers?
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Old 30th May 2011, 19:08
  #1071 (permalink)  
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Originally Posted by ap08 View Post
Is there any explanation why TCAS would fail? It seems completely unrelated to airspeed...
TCAS needs to know how fast they're going. If it doesn't it only has half the information (i.e. where they are) required to transmit .
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Old 30th May 2011, 19:10
  #1072 (permalink)  
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Flight Safety
Right Way Up, about as likely as 3 engines failing at the exact same time in the exact same way, not very likely.
Not sure why not as icing is likely to affect all pitots at the same time. With regard to engines failing its worth looking up the Miami- Nassau Tristar or the Royal flight 146!
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Old 30th May 2011, 19:25
  #1073 (permalink)  
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The missing cvr transcript

"Unless I missed it, nobody seems to have mentioned that the original worst-case theory--that the airplane flew into the mother and father of all ITCZ thunderstorms because it was radar-blanked by a line of cells between it and AF447--no longer seems to hold water.

Certainly 447 flew into weather that created an unusual kind of supercooled, high-altitude icing that suddenly affected the Pitots, but the CVR transcript doesn't mention anything that might be interpreted as turbulence upset--only the apparent impossibility of dealing with multiple fault warnings and anomalous displays. "

Does anybody really believe that there wasn't a lot of chatter going on in the cockpit? Especially, "What's it doing now?"

We've been given only minimal information and so far no indication that the CVR was not intact.

Another notable absence: Any reference whatsoever to the number one item: THE CHECKLIST! With everything going "off " nothing re "reset".
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Old 30th May 2011, 19:27
  #1074 (permalink)  
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An Airbus Programming Error?

Doomed Flight AF 447: Questions Raised about Airbus Automated Control System - SPIEGEL ONLINE - News - International
Gerhard Hüttig, a professor at the Institute of Aeronautics and Astronatics at the Technical University in Berlin, considers the high angle of the horizontal stabilizer to be a failure of the Airbus' electronic flight control system. Hüttig, a former Airbus pilot himself, calls it "a programming error with fatal consequences."

"No matter how hard the crew tried to push down the nose of the aircraft, they would have had no chance," Hüttig says. He is demanding that the entire fleet of Airbus A330s be grounded until the phenomenon is adequately explained.
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Old 30th May 2011, 19:35
  #1075 (permalink)  
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@DozyWannabe. TCAS doesn't receive any speed input whatsoever. It calculates closure rates based on comparing time it takes to send a signal and receive it back at the antenna.

Post amended because of bad wording

TCAS does have one air data input for Mode C (barometric altitude) coming from the Static Port. It would be very unusual for a Static Port (which is flush on the fuselage) to ice over.
So as a source of failure for the TCAS I think not likely.

Last edited by Shaka Zulu; 30th May 2011 at 20:52.
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Old 30th May 2011, 19:48
  #1076 (permalink)  
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Originally Posted by Shaka Zulu View Post
@DozyWannabe. TCAS doesn't receive any speed input whatsoever. It calculates closure rates based on comparing time it takes to send a signal and receive it back at the antenna.
No Air Data Input.
I stand corrected - cool.

Right, so that being the case there are two questions. If TCAS doesn't require air data itself, is the way it's plumbed into the A330's avionics something to do with it? Also, at what point in the ACARS sequence did that message fire? Early on, it might raise some questions. Later, as more systems began to fail it might be a moot point.
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Old 30th May 2011, 19:53
  #1077 (permalink)  
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TCAS computation needs altitude to assess threats and should receive barometric and Radio Altimeter inputs! yes/ no?
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Old 30th May 2011, 20:19
  #1078 (permalink)  
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For those pondering lessons from this accident:

Its probably been said before in the last 55 pages but,

If you lose sensible airspeed and altimeter indications, disregard all and fly attitude and zero bank angle for normal cruise flight with relevant manual throttle setting. Been there, done that.

Try it in the sim.
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Old 30th May 2011, 20:19
  #1079 (permalink)  
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Autopilot and autothrust disengage and a/c reverts to Direct law giving immediate pitch up due trim and a/c gains circa 3,000 ft and then enters dynamic stall.
With the few precious facts that we have a this moment, why make stuff up that even contradicts those?
At the beginning of the climb:
- alternate law
- THS 3 deg up
- nose up input from PF
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Old 30th May 2011, 20:25
  #1080 (permalink)  
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If the airspeed data was erroneous/unavailable for 50 seconds or so and then became available why the aural "STALL" warning was not continuous since? I think an audible "STALL" and "SINK RATE" would be more than enough to get the crew aware. The question is: why there were no such alarms? Or why it sounded only when the sidestick was pushed forward, supposedly breaking away from the stall, or at least relieving it? Maybe I'm missing something...
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