Timothy wrote:
On a heading, no, but I wonder what the acceptable tolerances of a Direct are?
There are no such tolerances from a regulatory point of view, in the same way that there are none for a heading (in ATM — not FCL checkrides). Direct is a convenience for the controller, but from a procedural point of view it’s equivalent to a heading. That’s becuase there are only two ways of being separated laterally:
If you’re not on a route (note that I didn’t say, “close to a route”), then the separation is tactical using radar, whether using a heading or a direct.
In practice therefore, I would regard the tolerance to be about the same as ATC would expect on a heading: +/- 5 degrees of the track to the fix.
Ultranomad wrote:
Is there anything in the regulations about that? I’d be inclined to think it would still be PBN at least when flying in CTR/TMA.
NCO.OP.116 Performance-based navigation — aeroplanes and helicopters
The pilot-in-command shall ensure that, when PBN is required for the route or procedure to be flown:
(a) the relevant PBN navigation specification is stated in the AFM or other document that has been approved by the certifying authority as part of an airworthiness assessment or is based on such approval; and
(b) the aircraft is operated in conformance with the relevant navigation specification and limitations in the AFM or other document mentioned above.
(My bold)
But it’s more fundamental than that. Direct-to not part of the PBN concept. What’s the path definition error? What’s the path? You might say: “just join the aircraft location when the direct-to instruction is received to the fix — that’s the path”. But there’s usually a turn involved first, which means that the path would start from different places for different aircraft speeds.
So, going back to my original question, which has been lost in thread splits and merges, if you are given a direct to a point, say, 50-100nm away, and you needed to weave somewhat to avoid small buildups, would you say anything or just go for it?
Timothy wrote:
So, going back to my original question, which has been lost in thread splits and merges, if you are given a direct to a point, say, 50-100nm away, and you needed to weave somewhat to avoid small buildups, would you say anything or just go for it?
I would and do always ask for left or right of track. With mode S they can see your heading selected (well they can with me). I have never been denied a diversion due to weather unless there is another aircraft there.
The counter to that is that it can result in you asking every two or three minutes and they end up saying something like “you are free to avoid as necessary, tell me when you are back on track to XYZ”.
Also, you can often see at the levels I fly at, 110 and 120, that there is no traffic within 40nm, putting any worries about going 1nm off course into perspective.
Is your heading squitted if you hand fly?
Timothy wrote:
The counter to that is that it can result in you asking every two or three minutes and they end up saying something like “you are free to avoid as necessary, tell me when you are back on track to XYZ”.
Sure but that is fine. I also said this summer in the US that I am weaving through CBs and request clearance to deviate left and right as neccesary.
And yes depending on implementation heading is a squitter output.
If I am operating on a point to point route segment, I don’t bother asking for deviations that require a heading change of +/- 10 degrees and I am able to stay within a NM or two of the center line. If I need a greater deviation for weather, I will usually pick a point and request a route change. If I can’t do that, I will ask for deviations as needed.
NCYankee wrote:
If I am operating on a point to point route segment, I don’t bother asking for deviations that require a heading change of +/- 10 degrees and I am able to stay within a NM or two of the center line. If I need a greater deviation for weather, I will usually pick a point and request a route change. If I can’t do that, I will ask for deviations as needed.
EU or US?
I have only flown in the US, Canada, Mexico, and Bahamas.
To Timothy’s point (if I get why he asked), I wouldn’t try that approach over here…
(1) Unless otherwise authorised by the competent authority, or directed by the appropriate air traffic control
unit, controlled flights shall, in so far as practicable:
(i) when on an established ATS route, operate along the defined centre line of that route; or
(ii) when on any other route, operate directly between the navigation facilities and/or points defining
that route.
