ASI 2
Quote from PA_18_151:
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications".
That, to me at least, indicates confusion. Either
1) There were no valid indications
or
2) They misunderstood, or were confused by, what they were being shown
My money is on 2)
Agree. It's a puzzling exchange, and the reason I'm still not entirely convinced that ASI2 was giving similar, intermittent, under-readings as ASI1 and the ISIS ASI. On the face of it, Pitot1 and Pitot2 might be expected to suffer similar icing characteristics, as they are symmetrically situated. But their heating performance might not have been identical on the night. This brings me back to a possibility others were discussing yesterday, which has been nagging me since May27.
It is possible to infer from the PF's remark that he had recently been relying on an indication that had just been removed. The words seem to have been spoken some time after they had passed FL350 in the descent. If the Pitot2 had been blocked both at intake and drain-hole, this would not explain the INITIAL pitch-up that we assume the PF made from FL350. But once the climb had been started, the ASI2 readings would have gradually increased to the FL380 apogee, then gradually decreased in the (stalled) descent. Simplistically, if Pitot2 remained completely frozen, the ASI2 reading would have dropped to the original cruise value when the static source (thought) the aircraft was passing FL350 in the descent. After that, the ASI2 reading would progressively drop to zero.
Although I think the above scenario is unlikely, because the trap is understood by most pilots, it would be frustrating if it cannot be disproved by QAR data or otherwise.