Originally Posted by
Stanley Eevil
If your ultimate strategy is to divert to an airfield `abeam` or an airfield `behind you` then you will have to leave the track centreline to ensure separation from other OTS traffic.
Because your eventual diversion route is not (yet) subject to a formal ATC clearance then changing level by +/- 500 ft (assuming you were cruising below FL410 and not thrust limited) will be necessary to give you some degree of vertical separation from other traffic.
You are NOT obliged to descend below FL285, even if diverting `across` the OTS (weather issues i.e. CB below you, or shortage of fuel?). You could divert from Track `D` to Keflavik maintaining FL355 if you wanted to (NAT doc 007 refers).
If your intention is to divert to an airfield ahead of you, then it may not be necessary to leave the NAT track in the first place. Because you are then complying with an existing oceanic clearance, if you still have sufficient thrust, no change in FL would be necessary.
Thanks for the reply. What you said is my thoughts also. Turning around around would require a 500ft change I understand that part. But If your going to an abeam airfield as you said, I could not see the the point of descending to FL285 other than avoiding the Tracks.
At my current OP we only flying T16 and T9 but the the contingency still applies. The wording in our OPs manual says we need to descend FL285 before considering a divert. Deviating 500ft and diverting would make more sense.