Originally Posted by Right Way Up
The reason the TL issue is a primary cause, but the slippery runway is only a contributary factor, is that whilst other aircraft that night landed on a slippery runway and did not crash, the only aircraft that did not retard the thrust levers did crash!
That is certainly a potential criterion. It is related to the criterion in Mill's Method of Difference. Let's look at it further.
The same reasoning exonerates any features of the design of the A320 controls, for they have been used in millions of successful landings. Given the number of people on this thread who have been arguing that the design of the A320 controls was a major factor, it would seem that they are not using this criterion for identifying main factors.
Consider the accident to AA 587. The first officer's use of rudder to control yaw at other than low speed had been noted by others he had flown with, in successful flights. Lots of people have flown A300's without the fin separating. And lots of people have encountered wake turbulence, and yaw in turbulence, without their airplanes breaking. So it seems as if this criterion is not applicable to prioritising the factors in the AA 587 accident. So it doesn't apply everywhere.
In the Warsaw accident, people had landed A320s before carrying 20 kts over VRef (it was in the Ops Manual). And the pilots performed according to SOPs and the weather info from the tower and a Pirep. And people had landed before with outdated weather information. And people had landed before him. But the front had just gone through and the wind changed. Applying the criterion, the primary cause would then be the weather, and everything else is just "contributory".
In the Strasbourg (mont St.-Odile) accident, many crews had used the V/S / descent angle controls many times successfully, as well as not paying so much attention to each other and their tasks, so again there is no application of this prioritisation criterion.
In the midair collision in Überlingen, the particular difference between this and other TCAS encounters would be that one crew thought they were in conflict with two other aircraft and resolved the conflict in favor of the "phantom" rather than the real "intruder" (in TCAS parlance). And that happened because the controller misspoke once (advising of a conflict at 2 o'clock rather than the 10 o'clock on which they had a visual).
In the Cali accident, the particular difference would be that they were withing reception range of two NDBs with the same frequency and the same identifier (that is, though, not unique - the NTSB identified two other such situations worldwide).
In the Birgenair B757 accident off the Dominican Republic, again all the factors (INOP ASI, confused crew) were not particular to that accident, so again the criterion could not be applied to prioritise.
It should now be clear through these few examples that
* the proposed criterion does not always apply to prioritise causal factors, and
* in cases in which it does apply, there are apparently other prioritisation criteria which take precedence
So why would it be the predominant prioritisation criterion in the Congonhas case?
PBL