Re Überlingen, one of the alternative views of this accident was that it involved ‘poor’ worldwide/industry communication.
ACAS / TCAS evolved from a US concept (to solve a specific US problem) into something that the industry found to be of great value and thus was approved by ICAO. The ‘failure’ was that the procedures (operational assumptions and crew actions) that evolved in the US were not communicated worldwide – they are now via ICAO. I suspect that there are still many operators / countries who do not appreciate the need to follow the system’s instructions. I recall that at the time of the accident one PPrune poster suggest that in his country (Africa), every pilot would turn when responding to TCAS!
I wonder if the semi-circular / quadrangle flight level system would have prevented Überlingen? Was the lack of this feature a failure to ‘defend in depth’, - over reliance on radar systems, need to handle more aircraft in a crowded airspace, or the human desire to help others by giving them direct routing?
I note similarities with the TAM overrun accident re worldwide communications; i.e. the knowledge of, adoption, and training for the revised crew procedure for the MEL single thrust lever operation.
Re EGPWS; several ‘Saves’ are in the paper
“Celebrating TAWS ‘Saves’: But lessons still to be learnt”. To my knowledge none of these events have been claimed as saves by the crew, primarily as the pilots were unaware of the severity of situation that they encountered. Many of the HF contributions / human behaviors in these incidents can be seen in TAM and other overrun accidents, and the issues of situation unawareness and the failure in ‘the last defense’ - the crew - failing to react or reacting inappropriately to warnings, arises in the discussion in this thread.
: is a new Ueberlingen possible today : alas ‘yes’ as humans are part of the system.