Turn without permission - did it happen to you too?
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Blocka - just wondering if you are sure that is right.
My lowly ill-educated impression was that Direct to meant Direct to and Own Navigation meant you can either route direct to or return to the flight plan route.
The difference between the two is subtle and only really comes in to play when the waypoint concerened is further down the route. ie NOT the next waypoint.
On a separate issue and I ask only out of curiousity (promise) what is the smallest turn you can pick up on radar? I guess this probably depends on a few factors like windspeed and climb rates etc but would be interested to know a rough figure.
My lowly ill-educated impression was that Direct to meant Direct to and Own Navigation meant you can either route direct to or return to the flight plan route.
The difference between the two is subtle and only really comes in to play when the waypoint concerened is further down the route. ie NOT the next waypoint.
On a separate issue and I ask only out of curiousity (promise) what is the smallest turn you can pick up on radar? I guess this probably depends on a few factors like windspeed and climb rates etc but would be interested to know a rough figure.
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Guzzler,
I used to fly professionaly, and now work as an ATCO in the LTMA.
I agree with your interpretation having worked both sides of the mic.
'Route direct to XXX' means, (in my book), that you go direct to the point specified, even if it is 3 or 4 waypoints down the route. You are still under your 'own navigation' i.e. you are responsible for getting directly to that point without radar vectors from me.
'Resume own Navigation to XXX' means, (again as far as I am concerned), that you are no longer having to maintain radar vectors, and that you are on your own navigation to the point specified (and beyond).
If that point happens to be 3 or 4 waypoints further down the route, you are within your right as a pilot to either route direct to the specified point (then pick up the rest of the route), or go via the 3 or 4 waypoints that precede it on your route.
The two instructions are distinctly different IMHO, if an ATCO wants you to make your next point a waypoint 3 or 4 fixes down the line, they should, IMO, say 'route direct to XXX' (thereby instructing you to miss out the waypoints in-between). The instruction 'Resume own navigation' means you can pick up the full route to the point specified if you wish.
I believe (if through no other reason than plain old pedantry) that a lot of ATCOs who have never flown, or who haven't thought it through, use the two phrases incorrectly.
Although it is quite pedantic, if an ATCO tells you 'resume own navigation to XXX' (expecting you to go directly there) and you go via the intervening waypoints A,B and C, you may be doing something that the ATCO has not expected, but only because they don't understand the instruction they have given you, not because you have done anything wrong!
I also often hear the phrase 'resume your own navigation direct to XXX', again I think this is used due to ATCOs not understanding what the separate instructions actually mean in the cockpit.
What they are really saying is 'route direct to XXX' but using more words than required, possibly because they don't understand that both phrases mean that you are under your own navigation to the specified point, it's just what happens in between your present position and the specified piont that (may) differ(s).
'Resume your own navigation direct to XXX' is actually a contradiction if XXX is 3 or 4 waypoints further down your route (if really being pedantic)!
As for the smallest turn you can see on radar - realistically about 10 degrees plus. If you have Mode 'S' though, that figure goes down to 1 degree, if monitoring the Mode S readout.
The main thing is ATCOs get very used to the profiles of routes on their sectors, and even what headings look like on a particular day (giving variation for wind), therefore it is not so much the degree of turn, but the deviation from the SID/STAR/Route that will get picked up - much easier to spot small deviations on routes defined by aircraft track than it is to spot subtle wanderings from assigned headings.
I used to fly professionaly, and now work as an ATCO in the LTMA.
I agree with your interpretation having worked both sides of the mic.
'Route direct to XXX' means, (in my book), that you go direct to the point specified, even if it is 3 or 4 waypoints down the route. You are still under your 'own navigation' i.e. you are responsible for getting directly to that point without radar vectors from me.
'Resume own Navigation to XXX' means, (again as far as I am concerned), that you are no longer having to maintain radar vectors, and that you are on your own navigation to the point specified (and beyond).
If that point happens to be 3 or 4 waypoints further down the route, you are within your right as a pilot to either route direct to the specified point (then pick up the rest of the route), or go via the 3 or 4 waypoints that precede it on your route.
The two instructions are distinctly different IMHO, if an ATCO wants you to make your next point a waypoint 3 or 4 fixes down the line, they should, IMO, say 'route direct to XXX' (thereby instructing you to miss out the waypoints in-between). The instruction 'Resume own navigation' means you can pick up the full route to the point specified if you wish.
I believe (if through no other reason than plain old pedantry) that a lot of ATCOs who have never flown, or who haven't thought it through, use the two phrases incorrectly.
Although it is quite pedantic, if an ATCO tells you 'resume own navigation to XXX' (expecting you to go directly there) and you go via the intervening waypoints A,B and C, you may be doing something that the ATCO has not expected, but only because they don't understand the instruction they have given you, not because you have done anything wrong!
I also often hear the phrase 'resume your own navigation direct to XXX', again I think this is used due to ATCOs not understanding what the separate instructions actually mean in the cockpit.
What they are really saying is 'route direct to XXX' but using more words than required, possibly because they don't understand that both phrases mean that you are under your own navigation to the specified point, it's just what happens in between your present position and the specified piont that (may) differ(s).
'Resume your own navigation direct to XXX' is actually a contradiction if XXX is 3 or 4 waypoints further down your route (if really being pedantic)!
As for the smallest turn you can see on radar - realistically about 10 degrees plus. If you have Mode 'S' though, that figure goes down to 1 degree, if monitoring the Mode S readout.
The main thing is ATCOs get very used to the profiles of routes on their sectors, and even what headings look like on a particular day (giving variation for wind), therefore it is not so much the degree of turn, but the deviation from the SID/STAR/Route that will get picked up - much easier to spot small deviations on routes defined by aircraft track than it is to spot subtle wanderings from assigned headings.
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However, on RNP routes pilots need to remember that RNP 5 means that the aircraft will be +/- 5nm 95% of the time that the indicator shows the aircraft to be on track. Unlike the VOR when one could wander from -5 to +5 degrees (a 10nm cross track distance at 60nm from the VOR) and remain "within limits", with RNP being 1 dot left of track could mean that one is actually more than 5nm from the track already!!!
I think you're confusing regulatory RNP requirements with practical ANP.
The vast majority of B-RNAV boxes will deliver accuracy far in excess of the 5nm 95%. More like .03 nm 99.99% of the time for GPS based, and not much worse for non GPS, in most populated parts of the world anyway.
re: the OP. Yes, its bad form and should generally be avoidable. Having said that, sh1t happens. More likely on a busy freq after a SID turn >60 degrees as other have mentioned.
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Blocka - just wondering if you are sure that is right.
My lowly ill-educated impression was that Direct to meant Direct to and Own Navigation meant you can either route direct to or return to the flight plan route.
My lowly ill-educated impression was that Direct to meant Direct to and Own Navigation meant you can either route direct to or return to the flight plan route.
1. A pilot is required to comply with an ATC clearance.
2. Unless otherwise authorized by the appropriate
ATS authority, or directed by the appropriate air traffic control
unit, controlled flights shall, in so far as practicable:
unit, controlled flights shall, in so far as practicable:
a) when on an established ATS route, operate along the
defined centre line of that route; or
defined centre line of that route; or
b) when on any other route, operate directly between the
navigation facilities and/or points defining that route.At the end of vectoring you are cleared "own navigation abc". In that case the two points defining your cleared route are your current position and abc.
Taking the above, when ATC have finished vectoring they issue a clearance to a specific point - (they are supposed to provide position info as well as magnetic track etc to the point but that is seldom complied with these days and in RNAV airspace is not really necessary).
According to b) above it is clear that when cleared to a point by ATC the flight is expected to operate directly between current position and the point one is cleared to. If flying a C172 with just VOR and ADF, you are entitled to ask ATC for either vectors back to the original route so that you can use the VORs or vectors to the waypoint if it is not a VOR or NDB within DOC.
On a separate issue and I ask only out of curiousity (promise) what is the smallest turn you can pick up on radar?
That depends on many issues. However, for a single plot extracted and processed radar feed, it is possible in a relatively slow aircraft to turn (agressively) left and right 60 degrees and provided your progress along track is not below the threshold for the moving traget indicator, it will show you on a constant track i.e. ATC will not see a track change however the position symbol may wander about a bit but that can happen for several rasons other than the aircraft moving about. Again in something like a Pits if you don't have mode C, you can do a quick loop and the person would have to be looking very closely at your position symbol to detect what you did. (the moving target indicator filters out radar returns that are not moving above a certain speed i.e. ground clutter).
With primary radar you can take advantage of tangental fade and other issues to play hide and seek with ATC.
However, the important point is that unless ATC are vectoring you they do not care about your heading and do not care if you are turning provided that your track complies with the clearance - If you fly on a constant track initially with a tailwind then into an area with 50 knots from the left then a headwind followed by 50Knots from the right think of how your heading will be changing (you will be turning) but ATC will not see it or care.
So I think that we should be talking about non-compliance with ATC clearance which better describes having to make a turn to avoid weather without first obtaining clearance.
Regards,
DFC
Last edited by DFC; 28th Jul 2009 at 22:36.
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anotherthing and DFC - thank you for your thorough responses.
Clears things up nicely.
The reason I asked about what turns are normally detectable is that sometimes (particularly on departure) a turn of 2 or 3 degrees for a mile or so may be really handy for dodging a cloud. When the frequency is really busy it seems ridiculous to add to the controllers workload and equally stupid to fly through the cloud!
Clears things up nicely.
The reason I asked about what turns are normally detectable is that sometimes (particularly on departure) a turn of 2 or 3 degrees for a mile or so may be really handy for dodging a cloud. When the frequency is really busy it seems ridiculous to add to the controllers workload and equally stupid to fly through the cloud!
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The reason I asked about what turns are normally detectable is that sometimes (particularly on departure) a turn of 2 or 3 degrees for a mile or so may be really handy for dodging a cloud.
Having said that, you are expected to fly the aircraft +/- 5 degrees of the required heading so being 2 or 3 degrees from your chosen heading is not unusual for a time.
However, these days you have to fly the departure as accurately as possible not just for safety but to ensure that the noise to cash generating machines dotted round under the departure don't send your company a bill.
Regards,
DFC
