RV8builder
Excellent questions. Herewith my thoughts:
1. Why did the 737 need to go through the E airspace? At 50 DME and above FL180 he could delay his descent to stay in the class C steps and still not need to exceed 3000fm.
I guess he could have, unless there are STAR requirements, such as those at Sydney, which would not permit this. I fact, at Sydney, aircraft are often
required to be as low as 10,000 by 45NM. Avoiding class E is impossible in this case.
More to the point – why? The only reason to avoid a certain class of airspace would be if the airspace is not conducive to safe operations. That is precisely the point of the argument.
2. It was eight minutes from when the C421 requested an airways clearence into Essendon until he was advised VFR not available, then a further six minutes for an IFR clearence to be given. Is this considered an acceptable level of service, at 10:00 am on a weekday?
I am not sure about the timing in your post (a total of 14minutes), but even so, the ‘delay’ mentioned was not a delay to the aircraft. As far as I am aware, the clearance was issued
when the aircraft required it. Of course, the change from VFR to IFR, the requirement to obtain flight plan details etc. and the requirement to rearrange the traffic to facilitate IFR separation will cause additional workload. This may lead to delays which would not have occurred under pre-NAS2B operations.
3. If the controller was concerned about a potential conflict why didn't he simply ask the C421 to do a orbit or standard rate turn at his current position. This would have given an immediate 2 minute increase in seperation. Happens going into CBR all the time.
The point here is that the controller was
not required to be ‘concerned about a potential conflict’. There is no requirement for the controller to separate - - only to provide traffic information and allow Class E procedures to kick in. The
system should have allowed the B737 to descend straight through the C421’s level with no intervention by the controller. Of course, in this case, the controller did not sit idly by and let it all go bad.
Fortunately, this incident amply demonstrates the potential short-comings of NAS. Many of the ‘holes in the swiss cheese’ lined up on the day. Happily, some of them did not.
Failed defences
1) VFR aircraft was operating in an area of high levels of IFR traffic, and in fact at a major IFR tracking and holding point.
2) Mode C was not operating correctly, resulting in radar and TCAS defences becoming unusable (until later when the problem was rectified).
3) Despite the relatively close proximity, the C421 pilot failed to see (and therefore was unable to avoid) the B737 at any time, despite the fact that it was undoubtedly VMC at the time.
Successful defences
1) A spot of luck – in that the C421 called up, and the Mode C problem was rectified.
2) Traffic information was passed correctly.
3) The controller intervened.
4) The B737 pilot saw the C421 – with the benefit of directed traffic information.
5) TCAS provided a further defence.
What can we learn from this incident? What would have happened of the C421 had not chosen that moment to call? Can we make the system safer? Please, let us all learn from this.