AF447

Pretty amazing they where able to find both the FDR & CVR and retrieve data from them. looks like they have pretty well determined what happened already:

http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai20 11.en.pdf"]http://ca.reuters.com/article/topNews/idCATRE74N0AN201 10524


Not the first time a crew was overwhelmed by alarms but I thought the industry had taken steps to address this.


The report released on May 27 that adds much more to this incident then the article above:

http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af44 7.27mai2011.en.pdf

and a summary and some discussion from over at airdisasters.com:


"- The pitot tubes were blocked or otherwise rendered ineffective.
- That triggered an unreliable speed event.
- The crew correctly identified the unreliable speed event and the fact that the autopilot and autothrottle had disconnected.
- A pilot took manual control of the plane.
- He should have applied the memory items for unreliable speed: Point the nose 5º above the horizon and set the throttles to climb thrust.
- Instead, he didn't set climb thrust and pointed the nose more than 10º above the horizon.
- The plane climbed, lost speed, and stalled.
- The pilot never recovered from the stall because he didn't apply the correct control inputs, as you know by now, so the plane kept falling stalled for 38,000ft and three minutes.

I think that that very much summarizes it. Gabriel"


"Originally Posted by Harding
What is this "memory items"? At first i thought it was a emergency checklist of some kind - but i changed my mind after reading the report. Seems like they actually didnt know they where in an emergency for quite a while?"


"No. They correctly noticed the unreliable speed at once.
There is a two-fold procedure for an unreliable speed event:
1- Fly the plane at a given initial pitch and thrust that ensures that the plane remains safe. This are the memory items because you have to know them by heart. There's no time to go grab the book and look up for the correct procedure.
2- Now, with the plane stabilized as said above, one pilot keep flying the plane according to these two memoty item values, and the other calmly grabs the book, looks up for unreliable speed, and with a few parameters (aircraft weight, altitude and temp) look up in a table for fine tunned values of pitch and thrust that not only will ensure safety but also will keep the altitude. Gabriel"




"The pilots were obviously not well trained for this. They failed to perform the two basic memory items. I think they might also have ignored the stall warnings because they knew the airspeed was erroneously low and considered this the cause of false stall warnings. However, the QRH specifies that pilots are to RESPECT STALL WARNINGS and to ignore any ECAM message warning them of RISK OF UNDUE STALL WARNING.

I'm also wondering if the altimeters and VSI could have been affected. The FPV was lost during the sequence. The FDR has them at 40° AoA and -10,000 ft/min V/S, but only 15° pitch with 100% N1 thrust. How is that possible? Did they reduce thrust at FL380 to remain in the envelope and let it fall, and then firewall it as they were falling out? This is not explained in the briefing. Or is it possible that the pitch indications were erroneous, both on the PFD and on the FDR? And why did they subsequently bring thrust back to IDLE in a developed stall, when airspeed was obviously needed? Did the PF do this or the Capt?

The best I can make of this is that thrust lock, a bit of load factor and pitch input caused an initial stall warning and an excessive rate of climb. They momentarily recovered by reducing pitch but the thrust setting remained too low and the pitch trim raised the AoA once again. With the second stall warning they initially applied TOGA thrust and pitch in excess of 10° This resulted in an excessive rate of climb until they reached their maximum FL380. Then it would seem that to reduce the V/S, they reduced thrust too aggressively while not reducing pitch and stalled, and then returned thrust to TOGA after the stall had developed, too late to prevent it, and then reduced again to IDLE fearing overspeed at at high rate of descent (apparently unaware of their pitch or AoA). That's the best I can make of it.

I am not surprised to hear that the pilots did not do the memory items correctly. That seems to be what killed them. Obviously, there was an industrywide training deficiency on this issue, and perhaps a deficient set of procedures issued by Airbus. The threat was obviously underrated, since ice-related pitot failure is not supposed to be happening at FL350, based on conventional wisdom at the time, and doesn't seem to occur outside the ITCZ. But it had been happening and both Airbus and the operators were aware that a threat existed. Neither seem to have reacted properly with training and procedures.

But I can't accept that such an experienced crew would not be well versed on general stall avoidance and recovery procedure either. They must have been deprived of vital positional awareness beyond airspeed data to get into the mess described in the report.

Or perhaps we still have a lot more to learn about human factors. I hope we will see the FDR plots and get a CVR translation soon. There are too many new questions in my head. Evan"