@RetiredF4:
Thanks for your perspective on things...
Originally Posted by
RetiredF4
What are the limits, within those the VSI needle displays vertical speed?
And what is the picture, when vertical speed is greater then the display available?
Could somebody post a picture with VS pegged?
02:11:50 PF: ........"I have a problem, itīs that i donīt have vertical speed indications"
..............Captain: ."OK"
I was catching-up with the thread yesterday after some time away, and I saw you mentioned the VSI / VVI a few days ago also. I've searched for the info on the VSI display, but can't find it yet.
I remember reading (I think in a BEA report?) that when some barometric parameters are exceeded (including CAS < some value???) that VSI display is
inhibited and a flag was shown instead of a value. So there were times when the PF had no valid VSI shown (my memory is that NCD was set in the SSM of the ARINC data, to indicate it was not valid, but I'm happy to be corrected when the actual reference is found). I'll look again when I have a bit more time.
This might also be what is shown on the graphs in BEA report 3 (English) pages 106 and 111 (but that is not the presentation which I remember reading) - we can see that at times, the recorded VSI is shown switching to zero, then back again to a high value. At the times when the FDR trace records zero that will be NCD in the ARINC stream since, of course, the VSI was not really switching rapidly to zero and back to a high value.
Personally, I think this intermittent VSI indication also played a part in the PF's behaviour. As well as intermittent airspeed indication, he
also had this intermittent VSI
and, at some times, intermittent (counter-intuitive) stall warnings e.g. ND = stall warning, NU = no stall warning.
We now know that these behaviours all had a single cause (low CAS inhibits some data & warnings), but he/they may not have made that "connection" (and may not have been trained to know that). With 3 different sources of data all behaving "strangely" to him, (not only UAS) perhaps he simply did not know that he
could (and should!) trust the artifical horizon?
At the moment, I'm not sure whether the PF (and PNF) didn't hear the repeated "Stall Stall" due to cognitive overload, or whether they heard it but chose to not
believe it, thinking it to be spurious due to having other (apparently) incomprehensible indications as I mention above?
@Ian W:
Just wanted to also say thanks for the human factors comments, very interesting and fits with my experience about cognitive overload. I do also see a significant variation between people in this respect (I overload more quickly than some other people I know - I can't give commentary to an instructor
in full sentences without the flying suffering
- but other people manage it fine!).