Radar Vectors along the flight plan

[Gazeem]

In the London sectors quite frequently I find myself being vectored along my flight plan route.

Often this vectoring is precisely following waypoints and turning points.

Not having a dig just wondering the reason for it.

For us without the bigger picture - radar vectoring a/c capable of accurately flying the airway structure seems to be putting more workload on already busy sector controllers.

Interested to hear any answers,

G'day

Gaz

[AlanM]

Because if you were told to route direct blah - you may not go the direct way - you may wander around avoiding weather, letting the pax on the left see Paris etc.

If you are locked on headings then you cannot hit another.

Guarentee's separation which is good. Also justifies lots of ATCO's which is especially good :)

[Gazeem]

I hear what you are saying but if I'm told to route direct I will, if I need to divert due to Wx I will ask first, unless it's a big angry storm and the freq is blocked! As I probably would on a radar heading(!)

Does that mean the official definition of direct is not direct??

Regards

Gaz

[Northerner]

Hi Gaz,

It's more that you are on your own navigation, ie that you navigate to that point however you wish. As AlanM says you might do that in a non 'direct' manner, and we can't take a chance on that if we need to separate you against other traffic. That's when we lock you (and the other plane most of the time) on a heading so we know you won't deviate without request. It's worth remembering that the plane you're being separated from may also not be on the same frequency as you are.

We try (or some do anyway) to let you fly your own plane as much as possible, and I'd rather not take you miles off route, so when you can be own nav you will be, and if you are vectored it is likely to be fairly close to the route you would expect anyway.

Hope this helps.

You could always come and visit a centre sometime and see how we do it!

Cheers,
N

"Keep smiling, it makes people wonder what you're up to..."

[055166k]

At any particular moment in time the controller must be able to prove separation from other aircraft. If you are in level flight on airways and an aircraft is coming the other way [for example] it may well be that vertical separation is assured; however if you or the other aircraft are climbing/descending through each others level the controller may be using Radar separation, and in order to demonstrate the safety you may be instructed to fly an assigned heading.....sometimes called "radar heading" although the "radar" part is not strictly necessary but it is in common usage as a recognised and unambiguous phrase.......!
If the routes or tracks of the respective aircraft are sufficiently separated from each other a "heading" may not be required, but in the very dense UK environment the tightly packed airspace means that positive control in the form of heading assignment is the norm......basically it means that ATC can be absolutely certain that you will not deviate from your heading and can therefore climb/descend traffic through your level using radar separation standards such as 5 miles.
The point you raise is simple....ATC need to "lock" you on a heading for radar separation purposes.....but there may be no need to take you off your flight-plan track.....you can be cleared direct to somewhere and then "locked on". What we can never do is to think "well he probably won't turn and so I'll take a gamble and climb/descend through with the other one, who likewise probably won't turn"
We don't do "gamble".

[VectorLine]

For example,

This morning there were lots of CBs over UR8 near GIBSO. Most pilots asking for Wx avoidance, except for one BAW pilot who just turned anyway - good thing the ATCO noticed it.

Pilots don't always tell us that they are deviating from route.

'Aviate, Navigate, Communicate' the old excuse goes.

[BEXIL160]

Gaz,

Airliners flying along the "flight planned route" don't always adhere strictly to the route. For example the Airbus' tend to smoothe out the corners when turning over waypoints, unless there is pilot intervention on the FMS to overfly them.

Nothing wrong in that, RNP5 and all that, but when a controller is trying to maintain 5 miles between a/c and one turns "early", well, embrassment all round followed by form filling. Not good.:O

Hence, "Continue on your present Heading". Less paperwork.

Rgds BEX

[ifleeplanes]

At 200+ knots if we dont 'smooth' out the corners we will overshoot them and go though the otherside....cant have it both ways.....:{

[cdb]

Yeah Gazeem, but its a question of HOW early. A couple of miles is fine, but I've seen A330s/A340s start a turn 4 miles before the VOR. That can screw you!

[Euroc5175]

According to info from an RNAV Coding Workshop, certain Airbus types, above FL180, can be limited to a 5 degree Angle of Bank for pax comfort. If the angular change at a fly-by waypoint is significant, Airbus types can potentially initiate a turn upto 20nm prior to a fly-by waypoint!!

[TrafficTraffic]

Airbus types can potentially initiate a turn upto 20nm prior to a fly-by waypoint!!

Next you will be sending us breaking news that they dont climb very well either!

RNAV Coding workshop hey - worth every cent by the sound of that.

[BEXIL160]

Curious isn't it, how things have "Improved".

I don't remember BA11s, or B737s or HS121s having a problem flying OVER a VOR, picking up the outbound radial and flying along it, even at 420kts+ TAS.

In some sectors we're using the same VORs with the same turns, and yet certain a/c can't be guaranteed to stay withing 4nm of the VOR.

BEX

[Lon More]

Curious isn't it, how things have "Improved".
It's what happens when pilots are replaced by system monitors:\ (Repeats old joke about pilot and dog to self)
I note they never fly past the fix and turn later. In the past I saw quite a few cases of early turns right into active danger areas

[Bigears]

This (http://www.faa.gov/atpubs/atbarc/03-5.htm) may be useful (starts about quarter way down, under 'RNAV Flight Behavior').
Don't try and involve me in a discussion- I'm just supplying the link! :O

[West Coast]

If you anticipate a problem of an early turn on a tract change, tell the crew not to turn prior to it. This is easily achievable with a minimum of fuss in the cockpit.

[Lon More]

West Coast It shouldn't be neccessary to tell them,There have been enough complaints on these boards from pilots annoyed that ATC is flying their aircraft.

[West Coast]

"It shouldn't be neccessary to tell them"

In the US it's neccessary. Unless the fix is a flyover fix (rare) the pilot or the FMC will lead it as to not overshoot the tract outbound from the fix.

I don't see it as ATC trying to fly the plane for me if they tell me not to turn prior to the fix, just controlling.

[Lon More]

West Coast Sorry, I didnt clarify my post. In Europe most airways are still a nominal 10n.m. wide. I was refering to turns which brought the aircraft outside these limits which can mean that they have entered an active military area.

[missioncontrol]

I got "vectored" from EDI to LHR this evening via Prestwick!

When asked if we "could fly towards London at some point", I was reminded that quote "there are others in the sky apart from you".

Sorry for asking , but when I am given a rather long vector on a route I have operated for quite a few years and it seems unusual, is it so wrong for me to ask an innocent and legitimate question?

[West Coast]

Lon

I understand, can see you concerns.

[Fly Through]

mission control,
It's not what you say but how you say it.
FT

[missioncontrol]

"Fly Through"-

I absolutely agree with you, - you have summed up the scenario precisely!

Best wishes

mc