Lodown, ftrplt et al
I havent seen the new charts yet, has anyone looked at the steps to see if there is an issue for RPT on descent into airports where Class A overlies Class C? (i.e 747 descents into Sydney etc). Is it going to only be an issue for descent into Class D 'Airspaced' airports?
Yes, it most certainly is an issue for jets into Sydney. Class E will be outside 45NM, down to 8,500ft – ensuring that B747s etc. will have to fly in E when arriving at Sydney. In some configurations, aircraft are required to be at 10,000ft by 45NM, so staying up at FL190 to 45NM is not even a theoretical option, never mind a practical one.
Class D towers often have the additional risk of little or no radar coverage.
4711, doesn't TAAATS provide a level of protection by alerting controllers to conflicting traffic in conjunction with transponder-equipped aircraft and SSR? Obviously you wouldn't want to use this as a last line of defense, but this is something, like TCAS and GPS that we didn't have some years ago.
Yes, TAAATS does have a STCA function. As has been mentioned elsewhere, it is not 100% reliable for real conflicts (often giving its first alert
after the aircraft have passed) - quite apart from the already significant problem of ‘false’ alerts. The new procedures (as well as older methods of reduced separation such as visual separation etc.) will lead to an increasing number of these false, ‘desensitizing’ alerts.
GPS, paradoxically,
increases the risk of a collision, as its very accuracy ensures that two aircraft which are on reciprocal tracks will be right on track. In the ‘old days’, NDB VOR or dead reckoning errors would increase the likelihood that aircraft would miss each other, even when they were one the same ‘nominal’ track.
Whatever it was, I know I'd put my trust in modern technology over the system we had then. Taken in isolation, each one of these technologies would not be trusted as a 'last line of defense' but when the entire system is considered, then I don't have a problem with this aspect of NAS.
I concur most heartily. Perhaps our difference on emphasis is that I would prefer to see our current system
enhanced by new technology, rather than
replaced by it, especially when the equipment was designed as a fall-back, rather than as a primary system of defence.
I am still in two minds about NAS, but surely if the technology allows us to advance and make the airspace more user friendly for all while raising capacity and at the same time without impinging on the operations of the big boys, then I am all for it.
Two minds are always better than none at all. I am yet to be convinced that the current system is as user ‘unfriendly’ as it is made out to be. Unfortunately, introduction of E, both inside and outside radar coverage does impinge on the ‘big boys’. It reduces their current level of safety.
Consider the following scenario:
A Boeing 737 on descent, with a ground speed of 450KT and a rate of descent of 2,500fpm. The weather is overcast at 13,000FT, VMC below. It is night time.
Ahead of the 737 is a light twin, maintaining FL125 (VFR) with a ground speed of 150KT.
The 737 breaks out of cloud at FL130, and has
12 seconds (500ft at 2,500 fpm ROD) to see the lights of the twin against the lights of the town below, identify it as an aircraft, identify it as a collision risk, and either arrest the rate of descent or take lateral avoiding action. The distance between the aircraft at first visual contact opportunity would be one mile (300KTS closing speed for 12 seconds)
The light twin, not being equipped with rear view mirrors, never has an opportunity to see the 737 at all.
Yes, this is a ‘worst case’ type scenario, but most accidents tend to be. I ask you to consider whether this is the basis for a safe system.
The current option is for the VFR aircraft to be known to the ‘system’ and the aircraft to be separated.
Aussie Andy
Lest any of our more 'sensitive' characters draw any unwarranted inferences from the refence to the timing of NAS vs the next election, the only implication is that NAS is supported by the current minister and is opposed by the ALP. Thus, it would need to be impelemented before the election in case the coalition was voted out.