Airspace Design - Some Background
We noticed that an exchange is taking place on a parallel site - dealing with proposed new radio procedures. We noted the detailed reference to incidents, and were surprised to see how many of those incidents were apparently resolved by ACAS systems - not design, and not procedures.
This is a very good example of mis-interpretation and mis-direction attempting to lead you AWAY from a point and not towards it.
As we indicated in previous postings, the use of ACAS systems as a system design tool is specifically and categorically discouraged - not only by the International Civil Aviation Organization - but also by ALL major States and Eurocontrol. Both the International Federation of AirLine Pilots Associations [IFALPA], and the International Federation of Air Traffic Controller Associations [IFATCA] have strong positions on the use of ACAS systems as anything other than last line of defence systems. Even the United States of America would not design a system that relies on ACAS systems. We suspect that a question to the right authority in the Federal Aviation Administration would validate this statement.
Your respondent cites numerous examples where the activation of ACAS systems - whilst preventing a collision - allowed aircraft to operate in dangerous proximity. ACAS systems can and do fail - witness the unfortunate accident at Uberlingen.
What we are saying is that you should NOT be bated by the seemingly "convincing" statistics - they are just that - statistics. We have looked at the web-site of your air investgaion body, and if we are correct, a classification of 4 or 5 means that your investigator was not overly concerned by the incidents.
And yet, in the same breath, your airspace design people are [seemingly] advocating a system that RELIES on ACAS systems to be effective.
We would play this straight back to your designers - challenge them to demonstrate how it can be a dangerous set of incidents on the one hand - yet a key safety design feature on the other.