PPRuNe Forums - View Single Post - BASI "Limitations of See & Avoid" ??
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Old 8th Aug 2003, 17:01
  #17 (permalink)  
WhatWasThat
 
Join Date: Jun 2000
Location: Melbourne, Victoria, Australia
Posts: 71
NoTimtams,
A couple of points for consideration, from the ATC side of the mike.

Re ATC alerted see and avoid - this seems to me to not be see and avoid at all, but more often pilot arranged procedural separation, I can count on one hand the number of times I have passed traffic to two IFRs and they have continued on their merry way without speaking to each other to arrange something. This makes me question the pilots faith in "see and avoid". Surely if the pilots were confident that they could sight and manoevre to avoid conflicting traffic, they would not be talking to each other at all.

Re Big Sky - whilst the sky is big the number of frequently travelled aerodromes is considerably smaller, this means that the probability of two aircraft welding cannot be assessed based on the total volume of australian airspace. Aircraft don't travel on random paths, they alter altitude and speed on a fixed trajectory between point A and B, this makes it much more likely that someone going B to A will hit you. The volume of Sky within which all the planes routinely operate would be a very small fraction of the total volume of Australian airspace, it only gets smaller as improved Nav performance means aircraft are closer to the nominal track between A and B. Even if the air route system were removed and free flight became the norm, the sky would still not be as big as it seems, as aircraft would still be contained in "corridors" between aerodrome pairs.

putting aside reciprocal tracks, I am still amazed at how often aircraft on crossing tracks in the GAFA or ocean arrive at the crossing point at the same time.Even with all that sky out there, we still have to move them more often than you might think. Admittedly the closest measurement I can make is to the minute, and there is still plenty of room within that tolerance for a miss - but its close enough for me.
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