Originally Posted by
Advance
Sir, you are missing the point. It does not matter in the slightest what actually failed. What matters is that a failure has occurred such the the system is so degraded that ongoing capacity is now limited - as you point out. But at the time of failure, there could have been more aircraft in the airspace around Sydney than could safely be managed without the radar. Had the failure happened at 0820 instead of 0520 for example?
The safety management system and its oversight is intended to ensure that no single failure (or failure 'chain' consequent on a single failure) can prejudice the safety of any aircraft.
The very fact that traffic handling is now limited is proof that whatever fault did occur, so limited traffic handling that aircraft in the airspace between the time of failure and the time at which the traffic numbers were reduced suffered a reduction in safety assurance.
The safety system and its oversight is intended to preclude that situation.
Beg to disagree, sorry. As I wrote, the information available so far does not point to a failure of surveillance feeds. What happened was a system degradation (whose full nature and extent is yet to be revealed) at Sydney that resulted in a response to limit traffic to rates that could be safely managed commensurate with the extant state of the system. So of course capacity is reduced, what else could be expected? This response is all planned, documented and obviously has had the appropriate safety, risk and audit rulers run over them, both internally and by CASA. It's just a matter of pulling out the checklist and initiating the appropriate response to a system degradation.
Reduced traffic volumes do not mean a reduction in safety. In contrast, traffic volumes would be reduced as required to assure the maintenance of safety assurance in the absence of some element of ATC's technology.
As for time of day - please bear in mind that Sydney ATC only manages the traffic in the vicinity of Sydney itself and typically only deals with traffic in the flight phase that is within 15-odd minutes from Sydney. The overlying and surrounding airspace is controlled from Melbourne and Brisbane.