willadvise, can you confirm that an offset as small as 1 mile will cause the ATC computers to spit the dummy and not update an aircraft’s position on your boards? (And can your enroute radars detect a track error that small?) I can only accept that you know what you’re talking about. However, as a (very non-mathematical) flying layman, I’m surprised to learn that, given that there are many aircraft still out there that are not GPS or IRS-equipped that the ATC computers can’t cope with an aircraft that is flying extremely accurately 1 mile off the airway centreline. (Non IRS/GPS aircraft can and do wander considerably more than 1 mile off the exact airway centreline.)
I feel that there is a maybe all too human reaction on the part of many ATC people that in asking for the offset to be legalised, we pilots are somehow slagging off at ATC and impugning their abilities or professionalism. I’d like to state quite clearly here that that is not so. (The analogy would be that in practising engine failure drills, we’re impugning the abilities of our engineers – or the abilities of flocks of seagulls to find their ways into engine intakes.[!]) We just believe that it is a very easily achieved extra layer of safety – and surely, we should all be grasping any extra layers of safety available to us without quibbling? And without delay.
Groundloop, have to agree that this particular incident was not your classic opposite direction conflict. In your suggestion to pass the slower aircraft on the left, I’m assuming that you are not a professional aviator (or sailor for that matter) – but yes, yours is a good idea. However, this incident does clearly illustrate the point 410 and others have been trying to make for some time now – the extraordinary accuracy of modern navigation systems. I think we’ll have two (and possibly four) converts to the offsetting argument in the crews involved in this incident. If flying NATS tracks and overtaking same direction traffic only 1000’ above or below you, (with the wonderful aid of hindsight), commonsense might now dictate that offsetting slightly to the right until past might be a very good practice, even in absolutely smooth conditions. ‘Situational awareness’ might also dictate that in such a situation, crews keep a very close eye on exactly where traffic immediately below them is tracking to pre-plan the direction of an immediate turn (or not to turn) in the event of a sudden depressurisation or engine failure in the cruise.
Maybe we should ask for a quick survey of respondents to this thread. How many of you do fly offset some or most of the time? I’ll add my name to list – I do it nearly all the time above 10,000’, except in RNP5 airspace. I’d rather find myself standing on the mat in front of the boss or the CAA explaining the error of my ways than finding myself a (dead) statistic. I don’t want to end up in some crash comic after meeting the same fate as the Luftwaffe TU154 and USAF C141 crews who had the midair off the African coast a year or two ago.
And if someone can explain the maths to me re how offsetting increases the chances of a midair, I’d be very grateful.
[This message has been edited by Wiley (edited 29 November 2000).]