Many pro-NAS people here have commented upon the fact that the aircraft came within 300 or 400FT, or were within 1NM or 2.7NM etc.
The important point is that, prior to November 27, the aircraft would have been positively separated, with minimum distances. The
only factor impacting on the distance between the aircraft here was luck. They could have missed by 100NM. They also could have hit. The system did sweet FA to affect the outcome. It was factors outside NAS which saved the day.
1) The C421 was in Class E airspace, without squawking Mode C. (He had no way to know this, because the system is deliberately designed to exclude him. This is a major failing of NAS which it's architects are aware of. It only took 6 days for it to happen.)
2) The C421 was approaching one of the major IFR inbound tracking points.
3) By
chance the C421 called up, requecting a clearance into the
adjacent class C airspace.
4) As a result, for better or worse, Mode C failure is detected, Mode C is selected, traffic information is passed, and a TCAS RA occurs.
Now, if the C421 pilot had remained silent
as he is supposed to do in Class E, what would have been the result:
1) No Mode C
2) No traffic information to the B737
3) No last minute 'save' by the controller.
4) No TCAS RA
5) The absolute last resort - see and avoid unknown traffic by the B737 (even with DTI the C421 never saw the B737 - 300 FT and 2.7NM away!)
This, ladies and gentlemen, is the sytem that is now going to cost you MORE money, for less safety.
Of course it is safe........ They were nearly 3 miles apart.
And what kept them 'nearly 3 miles apart'? Luck. Great system!.