Originally Posted by Frangible
I differ with PBL on the likely causes of the Bashkirian crew’s decision to descend.
I didn't say it was a likely cause. I said it was a rational choice.
Originally Posted by Frangible
I don’t see any evidence for worries about two other aircraft in the Russian cockpit in the report or the CVR.
I take it you didn't yet check Section 2.2.2 of the (english version of the) report, which says "
According to CVR data it can be concluded that the instructor searched the airspace in front and to the right in vain."
Originally Posted by Frangible
PBL’s point 1 is strange. Is this really the TCAS “philosophy”? If that is printed somewhere, I would like to see it
For example, see Section 2.1,
The Functional Requirement of Ed William's paper at
crpit.com/Vol47.html
I quote:
TCAS is a system of last resort and hence should have the following characteristics:
* Should only intervene when all "normal" means of separation have failed
........
* Should have minimal reliance on other systems
...
Section 2.2 elucidates the meanings of
"normal" means and
other systems.
My observation that ATC is considered to be "out of the picture" follows from this second stated requirement.
Originally Posted by Frangible
Finally, to say, as PBL does,
“I cannot think it wise to advise people to *always, without exception* follow an RA..”
is the height of irresponsibility.
Let me invent an acronym, HoI. People like to say "HoI this" and "HoI that" when talking about collision avoidance, as a way of trying to say they are worried about something. Well, it's good to be worried about something as important as collision avoidance, but it is not necessarily helpful to resort
to moral judgements in advance of having understood the technical claims.
Frangible, do you consider it HoI not to do a risk analysis on the situation of TCAS failing to resolve a conflict? Do you consider it HoI not to analyse the possible causal interactions between controller information and RAs?
If not (for extra credit
), why not?
Originally Posted by Frangible
All sorts of incidents have been recorded where pilots thought their visual intepretation of a TCAS situation was better than the gizmo’s, and they were wrong every time.
I infer that you know of lots of midair collisions in which pilots did not follow their TCAS advisory. I only know one.
If you think that pilots should always, without exception, follow the RA, would you change your mind if it turned out that the risk was relatively high that the TCAS algorithm could not resolve a given three-airplane conflict? If not (again, for extra credit), why not?
PBL