AF447

[Hyperveloce]

Short summary of the new BEA interim report

Hi there,
Here is a short summary of the report:
-From the visual inspection of the varied debris (toilet doors, partitions, galleys, cabin crew rest module, spoiler, aileron, vertical stabiliser):
The aircraft was probably intact on impact.
The aircraft struck the surface of the water with a positive attitude, a low bank and a high rate of descent.
There was no depressurisation
The report does not put forward any descent rate, deceleration figure (except the 36 g /120 000 N for the VS) or other figures resulting for exemple from an accurate metallographic analysis of well chosen debris.

-The medical and pathological Information drawn from the autopsy reports does not add so much, and does not enable to know whether the Captain was in the flight deck at the time of the crash.

-The ACARS analysis is refined, 21 of the 24 can be related to a failure of the anemometric loop, at least one more ACARS message (a class 2 fault message about the ADR2) should have been transmitted between the last ACARS (02:14:26Z) and 02:15:14Z.

-The meteorological analysis is slightly refined (surface to mid altitude convection cells using the Tropical Rainfall Measuring Mission / Cloudsat data): it suggests the presence of strong condensation towards AF447’s flight level (10 000 m) probably associated with convection towers.

-The BEA studied thirteen events on Airbus A330 / A340, losses of or temporary anomalies in indicated speeds occurring for which it had both crew reports, parameter recordings the PFR: Air France (4 cases); TAM (2 cases); Qatar Airways (4 cases); Northwest (1 case); Air Caraïbes Atlantique (2 cases).
It can be noted from this analysis that:
In seven cases, the autopilot was reconnected during the event. In two of them, the re-connection occurred when the two speeds were consistent with each other but were erroneous;
The autothrust disconnected in ten cases, leading to the activation of the Thrust Lock function. In five of them, this function remained connected for over one minute;
In 2 cases, the autothrust did not disconnect and the flight directors did not disappear. The recording of the engine RPM parameters shows fluctuations in thrust with N1 values of between 48% & 100% ;
Nine cases of triggering of the stall warning were observed.
With regard to crew reactions, the following points are notable:
Five cases of a voluntary descent were observed, of which one was of 3,500 feet. These descents followed a stall warning;
Four crews did not identify an unreliable airspeed situation.
The duration of the engagement of the Thrust Lock function indicates that there was no rapid autothrust disconnection actions then manual adjustment on the thrust to the recommended thrust;

To explain the exiting of the flight enveloppe, the BEA thinks to the risk of an attitude/thrust mismatch, when the A/THR disconnection occurs with a low N1 value. Woudn't the greatest danger be when the A/THR goes off with a high N1 index (or full thrust), this being maintained "several dozens seconds" or "over a minute", the plane being put in descent following a stall warning ?
Jeff
PS) Nowhere in the report, it is said that the false alarms may have played a major role in the accident but in a paragraph about "Operator training for the Unreliable IAS / ADR check emergency / backup procedure", it is concluded that the key points for a correct management of the situation are: detection of the problems, interpretation of the alarms and coordination in processing.