Possible Updraft Effects
There are a number of unresolved (at least for me) queries based mainly on the information in the BEA Interim Report 2 and the Update on Investigation report of 27 May 2011. A possible scenario that might answer these queries is rather than one of blocked pitots, instead a moderate to severe updraft.
Queries:-
a) A/C rolls to right: The “go left a little” at 02:08:07 would put the turbulence to the right of a/c, with the a/c flying at a tangent to any column of rising air. A moderate to severe updraft under the right wing would probably then cause EFCS to respond with right wing down.
b) PF inputs left and nose-up: In an Updraft air is being forced up by the air beneath so static air pressure would increase. This would cause Baro Alt to very rapidly decrease, giving the impression the a/c was descending, possibly then causing the PF to pull the nose up. Also a “barometric vertical speed higher, as an absolute value, than 20,000 ft/min”would cause the FPVs to disappear.
c) TCAS fail: this could be due to failure of the altitude credibility check
d) A/S "sharp fall" from 275 > 60kts Captain's PFD: In an updraft the raw reading of dynamic pressure would be affected(as the airflow would be partially across the end of the tube) by cosine of AoA plus any venturi effect. Also in an updraft, with a rapid increase in local static pressure, calculated AS would rapidly decrease. The subsequent calculations of AS would be affected by the various changes in AoA and static pressure causing a number of fluctuations. Other air speed related faults could also be due to the effects of an updraft, e.g. ISIS and ADIRU.
e) PRIM 1 and SEC 1 fault:Possibly the PF turns them off in desperation, believing that the apparent erratic behaviour of the a/c was because the EFCS was faulty.