ATC 'Maintain present heading' instruction
Join Date: Mar 2002
Location: Euroland
Posts: 2,814
Likes: 0
Received 0 Likes
on
0 Posts
Ferris,
In the old days of VOR-VOR-NDB-MARKER navigation your comments regarding flights suddenly veering off to some unknown place held some truth - you tracked beacon to beacon and every beacon was identified prior to use and the system ensured that you could never receive two VORs/NDBs with the same ident even up to 50,000ft.
The same can not be said today in the world of FMS and GPS databases...........direct to say DUB could take the aircraft towards a place near you or direct to Ireland...........Thus an aircraft in your area of the world passing a intersection and then the FMS being told to go direct to DUB..........the tired pilot misses the fact that there are two DUBs in the database, the aircraft may suddenly head 30deg right of the expected course............just when you are on the phone and not watching the screen..........before you know it.........that flight is getting toooooooo close to another climbing throught it'slevel and you could have prevented it.
You sould have a read of Attachment A and B to Annex 11.
In annex A, the spacing for parallel routes defined by VORs is basically 18nm with a reduction to 16.5nm for traffic going in the same direction on both.
In annex B, the separation for traffic on RNP5 routes is 10 to 15nm.
There is more involved. However, taking the lowest of the above figures - traffic has to be atleast 10nm parallel and radar monitored to continue on own nav at the same level............try that round Europe and the movement rate would halve or worse.
As a pilot being on a vector or locked on a heading is no big problem........unless I am being taken all over the place - which route direct and continue the headig when established is definitely not.
Regards,
DFC
In the old days of VOR-VOR-NDB-MARKER navigation your comments regarding flights suddenly veering off to some unknown place held some truth - you tracked beacon to beacon and every beacon was identified prior to use and the system ensured that you could never receive two VORs/NDBs with the same ident even up to 50,000ft.
The same can not be said today in the world of FMS and GPS databases...........direct to say DUB could take the aircraft towards a place near you or direct to Ireland...........Thus an aircraft in your area of the world passing a intersection and then the FMS being told to go direct to DUB..........the tired pilot misses the fact that there are two DUBs in the database, the aircraft may suddenly head 30deg right of the expected course............just when you are on the phone and not watching the screen..........before you know it.........that flight is getting toooooooo close to another climbing throught it'slevel and you could have prevented it.
You sould have a read of Attachment A and B to Annex 11.
In annex A, the spacing for parallel routes defined by VORs is basically 18nm with a reduction to 16.5nm for traffic going in the same direction on both.
In annex B, the separation for traffic on RNP5 routes is 10 to 15nm.
There is more involved. However, taking the lowest of the above figures - traffic has to be atleast 10nm parallel and radar monitored to continue on own nav at the same level............try that round Europe and the movement rate would halve or worse.
As a pilot being on a vector or locked on a heading is no big problem........unless I am being taken all over the place - which route direct and continue the headig when established is definitely not.
Regards,
DFC
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
DFC.
Once again, I beg to differ. I think in the pre-RNAV days, the tracking of aircraft would've been less accurate (scalloping etc), than with the dead-on multiple GPS gismos today. Perhaps you should have a read of your own post, in that RNP5 separation quoted is less than for VORs.
If you are trying to say that pilot error is the negating factor, then that applies equally to any instruction (such as flying a heading). We are talking about a specific situation; where the instruction has been issued to track to direct to somewhere. If the controller doesn't check the tracking, before basing sep on it, what's the difference to issuing a heading and not checking the a/c is approximating that?
As for all the stuff about route separation....I'll bear that in mind if the radar fails. I'll give you a tip; just because an aircraft is left on it's own nav, on it's route, radar separation doesn't stop applying.
Once again, I beg to differ. I think in the pre-RNAV days, the tracking of aircraft would've been less accurate (scalloping etc), than with the dead-on multiple GPS gismos today. Perhaps you should have a read of your own post, in that RNP5 separation quoted is less than for VORs.
If you are trying to say that pilot error is the negating factor, then that applies equally to any instruction (such as flying a heading). We are talking about a specific situation; where the instruction has been issued to track to direct to somewhere. If the controller doesn't check the tracking, before basing sep on it, what's the difference to issuing a heading and not checking the a/c is approximating that?
As for all the stuff about route separation....I'll bear that in mind if the radar fails. I'll give you a tip; just because an aircraft is left on it's own nav, on it's route, radar separation doesn't stop applying.
Join Date: Oct 2004
Location: surrey
Posts: 239
Likes: 0
Received 0 Likes
on
0 Posts
This is verging on the ridiculous now, and getting very tedious.
If a/c are on own nav, of course radar separation continues to apply, as it does if they are on radar headings... it's all about the degree of monitoring. If a pilot is on his own nav, he can turn to avoid weather etc (by the way - route direct to you may mean one thing, but to a pilot, following company policy it may mean another - they may have to go via certain waypoints etc (this is stretching it a bit far I know but when we are talking about pilots with different first languages, continue heading or fly heading is unambiguous))... if he has been instructed to fly a heading, he is more likely to ask before he turns - it's basic human nature.
and before more pedantry prevails regarding the fact that the pilot should always ask before making a heading change in CAS. we know this and pilots know this, but the fact of the matter remains; if a pilot is on his own nav, he is more likely to deviate first then ask later than if he had an assigned RADAR HEADING.
and just to cover my back a bit better (and this does not apply to you DFC - you, at least, sound like you have a modicum of common sense), most pilots will understand without having to be told in the most minute detail, that if they are on a radar heading, it is for a reason and will therefore have a bit more savvy about them regarding turning on their own whim.
If a/c are on own nav, of course radar separation continues to apply, as it does if they are on radar headings... it's all about the degree of monitoring. If a pilot is on his own nav, he can turn to avoid weather etc (by the way - route direct to you may mean one thing, but to a pilot, following company policy it may mean another - they may have to go via certain waypoints etc (this is stretching it a bit far I know but when we are talking about pilots with different first languages, continue heading or fly heading is unambiguous))... if he has been instructed to fly a heading, he is more likely to ask before he turns - it's basic human nature.
and before more pedantry prevails regarding the fact that the pilot should always ask before making a heading change in CAS. we know this and pilots know this, but the fact of the matter remains; if a pilot is on his own nav, he is more likely to deviate first then ask later than if he had an assigned RADAR HEADING.
and just to cover my back a bit better (and this does not apply to you DFC - you, at least, sound like you have a modicum of common sense), most pilots will understand without having to be told in the most minute detail, that if they are on a radar heading, it is for a reason and will therefore have a bit more savvy about them regarding turning on their own whim.
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
if he has been instructed to fly a heading, he is more likely to ask before he turns - it's basic human nature
You have absolutely no evidence of this, it's just your opinion. In my experience, it makes no difference. A/c have a no higher rate of compliance whether on own nav, or on an assigned heading ( radar heading- you guys crack me up).
If a pilot is on his own nav, he can turn to avoid weather
Cheers.
Join Date: Nov 1999
Location: Wivenhoe, not too far from the Clacton VOR
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Let's put it this way. When training radar controllers of the Approach incination, any student who failed to lock aircraft on headings to prove the separation, would be taken outside and given a serious slap with a wet fish. In an exam situation, the student would be almost certainly failed. Whether this is logical, sensible or totally over the top I care not. It is what was taught, and in the few months since I retired I doubt anything has changed.
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
on headings to prove the separation
If you were failing students because they weren't applying what they were taught to do, then that's one thing. But if you were actually failing them for failing to prove separation, then you may want to rethink your position, because as yet no-one seems to be able to state how this technique proves anything. Other than how popular herd mentality is......
Whether this is logical, sensible or totally over the top I care not. It is what was taught
Join Date: Nov 1999
Location: Wivenhoe, not too far from the Clacton VOR
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
ferris, you have two aircraft opposite direction. For simplicity's sake they are flying on separate airways that run parallel and actually join at the edges, each delineated by VORs. Effectively then we have a chunk of CAS, say 17 miles wide, with two parallel tracks 7 miles apart. Our two aircraft are on their own nav, one requiring climb ('cos it is a departure) and one requiring descent ('cos it is an inbound). At some point their levels will cross and all other things being equal they will be 7 miles apart laterally.
I grant you the arguement that before altering heading away from own nav the pilot should inform/ask ATC. I grant you also that if you had told both aircraft to "route direct" to whatever VOR marked the end of that airway then everything should be OK. However, in aviation we all know that things don't always go according to plan. Congested frequency, CBs, first language not English, nav-aid failure (a/c or ground), misheard call-sign, you name it. The only sure way of proving you did everything to ensure separation is to lock both aircraft on headings, and of course, listen to the read-backs. It may well be the headings you use are the ones they were already on - great. That makes "resume own nav" dead easy when the crisis, sorry, confliction is past.
When I wrote this I was trying to separate (pun unintended) the rationale of the method from the immediate reason why it is used. It is used because controllers are taught it.
The rationale as to why it is taught is as above. Leaving pilots to do their own thing proves nothing, other than the controller has "assumed" that all will be well. He has done nothing to "ensure" separation. And at the subsequent Court of Enquiry, if you did not prove the separation then the possibility of a manslaughter charge is on the cards. The cynical but realistic person could describe it as an arse-covering exercise. Experience teaches to watch your six o'clock because no-one else will.
Oh, and by the way ferris, I never was a manager - I thought too much!
I grant you the arguement that before altering heading away from own nav the pilot should inform/ask ATC. I grant you also that if you had told both aircraft to "route direct" to whatever VOR marked the end of that airway then everything should be OK. However, in aviation we all know that things don't always go according to plan. Congested frequency, CBs, first language not English, nav-aid failure (a/c or ground), misheard call-sign, you name it. The only sure way of proving you did everything to ensure separation is to lock both aircraft on headings, and of course, listen to the read-backs. It may well be the headings you use are the ones they were already on - great. That makes "resume own nav" dead easy when the crisis, sorry, confliction is past.
Whether this is logical, sensible or totally over the top I care not. It is what was taught
The rationale as to why it is taught is as above. Leaving pilots to do their own thing proves nothing, other than the controller has "assumed" that all will be well. He has done nothing to "ensure" separation. And at the subsequent Court of Enquiry, if you did not prove the separation then the possibility of a manslaughter charge is on the cards. The cynical but realistic person could describe it as an arse-covering exercise. Experience teaches to watch your six o'clock because no-one else will.
Oh, and by the way ferris, I never was a manager - I thought too much!
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
Bern, an excellent post. I agree with almost everything you say, except that 'locking on headings proves separation'. I went thru why in earlier posts, so I won't go over and over it. Suffice to say that at that subsequent court of enquiry, you would have a hard time proving that locking on headings is safer than a perfectly servicable modern a/c flying on it's own nav (IMHO). It's exactly the sort of thing clever lawyers get you with.
I can argue that every single thing you name as a reason for why you lock them on headings, is not neccesarily right. eg
Freq congestion: A great reason not to add to RT loading with instructions that are a waste of time (headings). How congestions is a problem for a/c on their own nav, I'm not sure.
CBs. In my experience, a/c approaching CBs will deviate whether on an assigned heading, or not. If (by issuing headings) we have fostered the belief that it's OK to deviate if on your own nav, then that's our fault and needs correcting.
First language not English: In my experience (and we have a lot of non-native speakers around these parts!), "track direct to XXXXX" is as equally well understood as "continue on present heading" or "fly heading XXX"
Nav failure. This is probably the best reason you give. However, if someone actually did some research, I'd reckon that nav equip failure, in modern a/c, would be about as common as altimeter or transponder failure, yet we take no special precautions against these failures (which involve the a/c actually being much closer together). Ground aids aren't even required these days (witness the approach of ADS-B).
Mis-heard callsign. I would say that actually works against your argument, as the 'locking heading' technique involves more RT than saying nothing.
So, as you see, I disagree with the basic premise that this technique proves anything.
I can argue that every single thing you name as a reason for why you lock them on headings, is not neccesarily right. eg
Freq congestion: A great reason not to add to RT loading with instructions that are a waste of time (headings). How congestions is a problem for a/c on their own nav, I'm not sure.
CBs. In my experience, a/c approaching CBs will deviate whether on an assigned heading, or not. If (by issuing headings) we have fostered the belief that it's OK to deviate if on your own nav, then that's our fault and needs correcting.
First language not English: In my experience (and we have a lot of non-native speakers around these parts!), "track direct to XXXXX" is as equally well understood as "continue on present heading" or "fly heading XXX"
Nav failure. This is probably the best reason you give. However, if someone actually did some research, I'd reckon that nav equip failure, in modern a/c, would be about as common as altimeter or transponder failure, yet we take no special precautions against these failures (which involve the a/c actually being much closer together). Ground aids aren't even required these days (witness the approach of ADS-B).
Mis-heard callsign. I would say that actually works against your argument, as the 'locking heading' technique involves more RT than saying nothing.
So, as you see, I disagree with the basic premise that this technique proves anything.
Join Date: Jun 2001
Location: Somewhere on the warm side!
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
P-RNAV
Precision Area Navigation (P-RNAV) is being introduced as the standard to use throughout ECAC Terminal Airspace, if you wish to introduce RNAV routes. The option of conventional procedures is retained.
P-RNAV is predicated upon a lateral track accuracy of 1NM for 95% of the time. There are detailed design criteria to be followed for P-RNAV routes that are published in a Eurocontrol document. However, fly-by turns are required to be used for most procedure designs when using P-RNAV. The design criteria contains a multitude of formulae and tables that let the procedure designer determine when aircraft will start to turn prior to a fly-by waypoint. Factors such as the speed of the aircraft, turn angle, bank angle are taken into account. A minimum distance between successive waypoints is required for stabilisation. This minimum distance also varies depending on speed, bank angle, turn angle, etc. The point is that P-RNAV enables procedure designers to determine when an aircraft will start to turn prior to a fly-by waypoint. All aircraft, if flying P-RNAV, should turn so as to remain within 1NM of the published track. There are several rules for P-RNAV design. One such rule is that no single turn should exceed 120 degrees. This is to avoid aircraft having to initiate the turn, even in Terminal Airspace, at a substantial distance prior to a fly-by waypoint.
Work is currently on-going to determine the required spacing that should be provided be P-RNAV routes. Initial noises from the CAA suggest that 5NM is an appropriate distance to apply between P-RNAV routes. This is presumably based on the fact that aircraft fly within 1NM of published track, and allows for a 3NM separation criteria even if both aircraft are at the edge of their respective 1NM tolerances.
It is also being suggested that in the near future the CAA will look favourably upon separation criteria such as Aircraft A on a P-RNAV route, being separated by xNM from Aircraft B that is on a radar heading. Historically in the UK both aircraft A & B would have been provided with headings to fly (or be 'locked' on).
P-RNAV is likely to be introduced on a more widespread basis as new runways, requiring revisions or additions to SIDs, STARs and new airspace come into effect in the UK. Work is on-going to ensure that P-RNAV is introduced in such a way as to ensure a safe and efficient operation continues to exist in UK Terminal Airspace.
P-RNAV is predicated upon a lateral track accuracy of 1NM for 95% of the time. There are detailed design criteria to be followed for P-RNAV routes that are published in a Eurocontrol document. However, fly-by turns are required to be used for most procedure designs when using P-RNAV. The design criteria contains a multitude of formulae and tables that let the procedure designer determine when aircraft will start to turn prior to a fly-by waypoint. Factors such as the speed of the aircraft, turn angle, bank angle are taken into account. A minimum distance between successive waypoints is required for stabilisation. This minimum distance also varies depending on speed, bank angle, turn angle, etc. The point is that P-RNAV enables procedure designers to determine when an aircraft will start to turn prior to a fly-by waypoint. All aircraft, if flying P-RNAV, should turn so as to remain within 1NM of the published track. There are several rules for P-RNAV design. One such rule is that no single turn should exceed 120 degrees. This is to avoid aircraft having to initiate the turn, even in Terminal Airspace, at a substantial distance prior to a fly-by waypoint.
Work is currently on-going to determine the required spacing that should be provided be P-RNAV routes. Initial noises from the CAA suggest that 5NM is an appropriate distance to apply between P-RNAV routes. This is presumably based on the fact that aircraft fly within 1NM of published track, and allows for a 3NM separation criteria even if both aircraft are at the edge of their respective 1NM tolerances.
It is also being suggested that in the near future the CAA will look favourably upon separation criteria such as Aircraft A on a P-RNAV route, being separated by xNM from Aircraft B that is on a radar heading. Historically in the UK both aircraft A & B would have been provided with headings to fly (or be 'locked' on).
P-RNAV is likely to be introduced on a more widespread basis as new runways, requiring revisions or additions to SIDs, STARs and new airspace come into effect in the UK. Work is on-going to ensure that P-RNAV is introduced in such a way as to ensure a safe and efficient operation continues to exist in UK Terminal Airspace.
Join Date: Nov 1999
Location: Wivenhoe, not too far from the Clacton VOR
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
ferris, we may have to disagree on this one. However I will take you up on one small point. You said
. What I actually said was
(my italics). There is a difference. All I would have to prove in court is that I did what has been, until now, the accepted (and SRG approved) way of ensuring lateral separation. I would contend that if I could not prove this, then I am in trouble.
Frequency congestion and CBs. If an aircraft has been told "route direct XYZ", the pilot does not know if this is for separation purposes or the ATCO is being nice today. He wishes to avoid a build-up ahead, the frequency is humming, he is, in his mind, on his own nav. He deviates from track and tells ATC when he can get a word in sideways. Ooops! On the other hand, if told to "fly heading XXX" it should suggest that it is for a reason, probably separation. Heading deviation without clearance is far less likely IMO.
Nav aid failure. Well I suppose it depends what airspace you are in and what traffic you get. Not everyone has super-duper modern aircraft with fancy glass cockpits and all the gizmos. The system has to cater for the poor sods at the bottom if the IFR food chain i.e. the lowest common denominator surely?
First language not English. We obviously have different experiences of this!
So, some disagreement but hey, that's life.
you would have a hard time proving that locking on headings is safer than a perfectly servicable modern a/c flying on it's own nav
The only sure way of proving you did everything to ensure separation is to lock both aircraft on headings,
Frequency congestion and CBs. If an aircraft has been told "route direct XYZ", the pilot does not know if this is for separation purposes or the ATCO is being nice today. He wishes to avoid a build-up ahead, the frequency is humming, he is, in his mind, on his own nav. He deviates from track and tells ATC when he can get a word in sideways. Ooops! On the other hand, if told to "fly heading XXX" it should suggest that it is for a reason, probably separation. Heading deviation without clearance is far less likely IMO.
Nav aid failure. Well I suppose it depends what airspace you are in and what traffic you get. Not everyone has super-duper modern aircraft with fancy glass cockpits and all the gizmos. The system has to cater for the poor sods at the bottom if the IFR food chain i.e. the lowest common denominator surely?
First language not English. We obviously have different experiences of this!
So, some disagreement but hey, that's life.
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
All I would have to prove in court is that I did what has been, until now, the accepted (and SRG approved) way of ensuring lateral separation
Agree to disagree (as long as you're not checking me
).
Join Date: Sep 2001
Location: Sandpit
Posts: 312
Likes: 0
Received 0 Likes
on
0 Posts
Ferris, what planet did you actually manage to pass a licence exam on? (Or is it simply that you're best buddies with a certain S'african!)
I would love to know if anyone out there can calculate the required change in windspeed through a 2000ft climbthrough to erode separation between two aircraft that have been locked on parallel headings with, let's say, 7 miles initial separation to give a bit of a margin to see just how far out Ferris's theory of drift is.
At the 7 units in 3 countries (Abu Dhabi included) where I have been Valid, I have never, ever heard of even a proposal of "Track to " separation. Has anyone else?
Funnily enough, parallel headings were accepted at all. Funny thing that, isn't it?
I would love to know if anyone out there can calculate the required change in windspeed through a 2000ft climbthrough to erode separation between two aircraft that have been locked on parallel headings with, let's say, 7 miles initial separation to give a bit of a margin to see just how far out Ferris's theory of drift is.
At the 7 units in 3 countries (Abu Dhabi included) where I have been Valid, I have never, ever heard of even a proposal of "Track to " separation. Has anyone else?
Funnily enough, parallel headings were accepted at all. Funny thing that, isn't it?
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
This is the sort of entrenched thinking that I am talking about. Put up one decent argument, just one, and I might reconsider my position.
Perhaps you haven't read the thread thru. Just because a technique has been perpetuated since the 1950s, doesn't mean it has any relevence today. Regardless of how many countries perpetuate it.
I am not proposing a "track to" standard (although obviously you haven't been valid in the UK- or you would realise that "track to" separation is being applied at aerodromes there right now {read the thread
}). I am merely questioning the technique described by the thread starter. The standard is a radar standard, and the query surrounds that standard's assurance. I am not even querying 'parallel headings' ( a technique that is still very useful in certain situations).
You can't even work out the drift in order to argue. You just assume and use derision. The old "my positions right, and anyone who questions it is a fool" routine.
Funny? Yep.
Perhaps you haven't read the thread thru. Just because a technique has been perpetuated since the 1950s, doesn't mean it has any relevence today. Regardless of how many countries perpetuate it.
I am not proposing a "track to" standard (although obviously you haven't been valid in the UK- or you would realise that "track to" separation is being applied at aerodromes there right now {read the thread
}). I am merely questioning the technique described by the thread starter. The standard is a radar standard, and the query surrounds that standard's assurance. I am not even querying 'parallel headings' ( a technique that is still very useful in certain situations).You can't even work out the drift in order to argue. You just assume and use derision. The old "my positions right, and anyone who questions it is a fool" routine.
Funny? Yep.
Join Date: Sep 2001
Location: Sandpit
Posts: 312
Likes: 0
Received 0 Likes
on
0 Posts
Sorry Ferris, wrong again - multiple previous validations in the Uk albeit before any "track to " separation was acceptable. (maybe I'm getting too old!)
I will grant you that I jumped the thread a bit - screaming kids in the background tend to be a bit distracting. However, I beg to differ on who's showing entrenched thinking here. I suggest that you re-read Bern Oulli's two previous posts, he's much more eloquent than I am but I think is trying to express the same idea. ie, we are not only required to provide separation but to ASSURE it. Big difference. As we all know and BO (unfortunate that) has already stated, there are any number of reason that an aircraft may change track while on "own Nav", the risks of which are greatly diminished by the use of parallel headings. I know which I prefer to stake my licence on.
p.s. very disappointed to see the old US of A's lazy spelling methods have reached the rest of the colonies!! Thru
I will grant you that I jumped the thread a bit - screaming kids in the background tend to be a bit distracting. However, I beg to differ on who's showing entrenched thinking here. I suggest that you re-read Bern Oulli's two previous posts, he's much more eloquent than I am but I think is trying to express the same idea. ie, we are not only required to provide separation but to ASSURE it. Big difference. As we all know and BO (unfortunate that) has already stated, there are any number of reason that an aircraft may change track while on "own Nav", the risks of which are greatly diminished by the use of parallel headings. I know which I prefer to stake my licence on.
p.s. very disappointed to see the old US of A's lazy spelling methods have reached the rest of the colonies!! Thru
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
Apology accepted.
Now...
Who was talking about parallel headings? The example was a/c on own nav (laterally separated) being put on headings to "assure" sep. You see, I don't think you can support that position with any actual evidence . Prove it. All I ever get in reply is "well, it's common sense". Where is it stated anywhere that a/c on own nav can divert around wx, track to mysterious intermediate waypoints etc etc? The pilots aren't handflying anymore. If they are told to track direct XXXXX, then they push buttons and the a/c does it. Doing anything else requires intervention. As I have stated over and over, I have seen just as many a/c divert around wx while on own nav, as on an assigned heading. If you are under the misapprehension that an a/c on an assigned heading will not divert, then you are setting yourself up for a fall. As I previously said, if pilots are under the misapprehension that if on own nav, they can divert, then that is something that ATC has probably fostered and needs correction.
If you are going to argue that the a/c may not track to XXXXX due to database errors, pilot error, etc etc, it's no different to an assigned heading error. If you don't check the tracking before 'setting and forgetting', it's the same as assigning a heading and not checking.
Furthermore, if a/c are changing level, I don't think you can assure anything with headings. See earlier posts. You even acknowledge that you don't know how much wind shear would be required for you to lose separation in your example (and it would depend on the time involved ie rate of level change). More to the point, we don't plan/buffer for failure of altimeters or transponders, and the a/c are far closer together there. Why do it for 7nm lateral sep (that the a/c will achieve without our intervention)?
As I said, times have changed.
Maybe it's time to rethink some of these techniques. Alas, I find many minds are closed on the subject (except maybe the people writing those "track sep" procedures in the UK you aren't aware of, Guy ).
Now...
there are any number of reason that an aircraft may change track while on "own Nav", the risks of which are greatly diminished by the use of parallel headings
If you are going to argue that the a/c may not track to XXXXX due to database errors, pilot error, etc etc, it's no different to an assigned heading error. If you don't check the tracking before 'setting and forgetting', it's the same as assigning a heading and not checking.
we are not only required to provide separation but to ASSURE it
As I said, times have changed.
multiple previous validations in the Uk albeit before any "track to " separation was acceptable. (maybe I'm getting too old!)
).
Join Date: Oct 2004
Location: surrey
Posts: 239
Likes: 0
Received 0 Likes
on
0 Posts
wind and its effects on climbing A/C
Ferris - the amount of difference in wind speed/direction required to make putting a/c a dangerous proposition would be immense and unheard of within close band levels.
You talk about people not being able to do the calculations to work out how much wind would be required to move the aircraft in question; so what???
I assume you do not know how to work it out either, or you would realise that it would be too complicated, and would need additional information from the pilot to work it out rapidly when controlling aircraft.
However, whether you know how to go about working it out or not is a moot point - though I would be interested in watching any ATCO performing such an in depth geometric calculation whilst on radar - the fact is, the difference in wind being experienced by two a/c in such proximity needed to create such a phenomenon would be akin to divine intervention. And if that happened, we may as well hang up our headsets and let the ethereal beings get on with it.
You talk about people not being able to do the calculations to work out how much wind would be required to move the aircraft in question; so what???
I assume you do not know how to work it out either, or you would realise that it would be too complicated, and would need additional information from the pilot to work it out rapidly when controlling aircraft.
However, whether you know how to go about working it out or not is a moot point - though I would be interested in watching any ATCO performing such an in depth geometric calculation whilst on radar - the fact is, the difference in wind being experienced by two a/c in such proximity needed to create such a phenomenon would be akin to divine intervention. And if that happened, we may as well hang up our headsets and let the ethereal beings get on with it.
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
difference in wind speed/direction required to make putting a/c a dangerous proposition would be immense and unheard of within close band levels
You talk about people not being able to do the calculations to work out how much wind would be required to move the aircraft in question; so what???
the difference in wind being experienced by two a/c in such proximity needed to create such a phenomenon would be akin to divine intervention
Now as a very basic example, lets work thru one (just so you get the idea.
). In the example used earlier in the thread, we have a square a b---------------------c ------ d
Aircraft 1 is tracking c to d, a B738 FL230, and a/c 2 is tracking b to c, an A345 climbing from FL200 to FL380and will pass each other at the roughly the midpoint by roughly 7-8 nm. Assuming the controller is comfortable with this margin he locks the headings. The wind at FL200 is 300/30, the wind at FL230 is 300/120, and at FL380 is 300/140. As the wind speed increases as a/c2 climbs, the FMS would normally adjust heading to the right to make good the track from b to c. But with the heading locked, a/c 2 begins to drift left, at potentially 90kts, as he climbs into the stronger wind. As a/c 2 is an A340, so may take up to 3 hours to climb over the 738
, the drift could be enormous (and in the example may take as little as 2 minutes to lose sep, depending on the wind gradient). Even worse, this drift will not be immediately apparent. Only if you keep monitoring the situation will it become so.You think this sort of wind would be divine? Well, in the Gulf we work with this sort of wind for about 3 months of the year (now).
Just trying to get people to think about something often considered 'gospel'
Join Date: Sep 2001
Location: Sandpit
Posts: 312
Likes: 0
Received 0 Likes
on
0 Posts
I'll keep this quick since I'm on a break at work.
1. Ferris, in the climbthrough you just mentioned, the level change takes place between FL220 and FL 240, therefore, wind speeds at FL 380 are irrelevant.
2. Fact. Pilots are on own Nav have been known to "deviate" the odd mile or so around weather etc. without mentioning it.
3. Fact. Pilots are required to advise any deviation from an assigned heading.
4. Fact. Pilots are required to advise a rate of climb below a pre determined level, according "local" AIP - often 1000fpm.
I have to say that in my experience, pilots are much more likely to advise a change of assigned heading than a small deviation while on own nav. Let's face it, they're not really stupid and don't tend to have a death wish so most recognize that if we assign headings, it's for a reason.
You seem very keen to quote extreme examples of winds etc. and to assume that, knowing of the existence of such winds, we would all choose to ignore them when allocating headings. We're not all stupid either. It's not too difficult to apply a rate of climb or a slightly different heading to acheive the desired result. Going by previous posts, I think I am correct in saying that most of those here in most normal situations would use a heading to do so. To make no allowances in extreme situations would be nothing short of reckless.
Have a pint of black for me next time you're in Dubliners. Cheers
1. Ferris, in the climbthrough you just mentioned, the level change takes place between FL220 and FL 240, therefore, wind speeds at FL 380 are irrelevant.
2. Fact. Pilots are on own Nav have been known to "deviate" the odd mile or so around weather etc. without mentioning it.
3. Fact. Pilots are required to advise any deviation from an assigned heading.
4. Fact. Pilots are required to advise a rate of climb below a pre determined level, according "local" AIP - often 1000fpm.
I have to say that in my experience, pilots are much more likely to advise a change of assigned heading than a small deviation while on own nav. Let's face it, they're not really stupid and don't tend to have a death wish so most recognize that if we assign headings, it's for a reason.
You seem very keen to quote extreme examples of winds etc. and to assume that, knowing of the existence of such winds, we would all choose to ignore them when allocating headings. We're not all stupid either. It's not too difficult to apply a rate of climb or a slightly different heading to acheive the desired result. Going by previous posts, I think I am correct in saying that most of those here in most normal situations would use a heading to do so. To make no allowances in extreme situations would be nothing short of reckless.
Have a pint of black for me next time you're in Dubliners. Cheers
Join Date: Mar 2002
Location: Euroland
Posts: 2,814
Likes: 0
Received 0 Likes
on
0 Posts
Ferris,
You seem to have missed the whole idea of issuing a heading to an aircraft..........i.e. for the controller to position that aircraft where the controller chooses and not rely on the pilot hopefully positioning the aircraft where the controller hopes it will go.
Note the frequent use of "hope" in the above.........not good to say after........."I had hoped the pilot would.....".
What would you say the equivalent RNP for an experienced controller in enroute airspace under moderate traffic load is........i.e. when they put aircraft on headings, how close will they keep the aircraft to the desired track for 95% of the time? (assume an area where 5nm separation is permitted)
I would guess that it is about RNP2.........i.e. controllers frequently vector aircraft along one side of the airway 2 miles from the edge without going outside. Provided that the resultant radar returns or responses do not get closer than the required minimum radar separation (say 5nm) then the required separation has been acheived in a compact piece of airspace.
Compare this theoretical RNP2 figure to the figures I quoted earlier for traffic on own navigation.
As for calculating the drift it is not hard at all.........we simple pilots do it day in day out even when we are half asleep!
Simply put - at 420 Kt for every 7 Kt of crosswind there will be 1 degree of drift.
Each degree of drift puts the aircraft 1nm off track in 60nm
However here comes the crunch - being a good controller and aware of the upper winds you will momnitor the actual tracking of the aircraft atleast every minute or two and issue a correction to the heading. So the most the aircraft is going to get off track is 2nm 95 % of the time provided you do your job properly.
You quoted an extreme case but provided you take charge of the situation and you do you job well the only person who can be blamed for a loss of separation is you.
Note the frequent use of "you" in the above situation.
If you did loose separation, the question I would ask is why knowing the wind situation did you not climb to 1000ft below initially to check that separation was being ensured?
Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately.
Never assume.
We can quite happily fly the aircraft in heading mode- we change the heading to try and acheive the required tracking or we can even manually fly the aircraft as accurately as we can (wandering over the sky if the winds are shifting and the bumps are hard!). What is important is that we do not have to tell you how we are flying the aircraft provided we acheive the required RNP.
Do you not think that a large part of controller workload in busy enroute airspace comes from having to vector aircraft? If so then do you not also think that moves would have been made to increase capacity (reduce workload) by reducing the requirement for vectors?..........The answer lies in the Eurpean study from where I got those separation figures for parallel tracks earlier.
Regards,
DFC
PS as Captain I don't trust you to save my licence - that's my job.............don't expect me to do anything to save yours!
You seem to have missed the whole idea of issuing a heading to an aircraft..........i.e. for the controller to position that aircraft where the controller chooses and not rely on the pilot hopefully positioning the aircraft where the controller hopes it will go.
Note the frequent use of "hope" in the above.........not good to say after........."I had hoped the pilot would.....".
What would you say the equivalent RNP for an experienced controller in enroute airspace under moderate traffic load is........i.e. when they put aircraft on headings, how close will they keep the aircraft to the desired track for 95% of the time? (assume an area where 5nm separation is permitted)
I would guess that it is about RNP2.........i.e. controllers frequently vector aircraft along one side of the airway 2 miles from the edge without going outside. Provided that the resultant radar returns or responses do not get closer than the required minimum radar separation (say 5nm) then the required separation has been acheived in a compact piece of airspace.
Compare this theoretical RNP2 figure to the figures I quoted earlier for traffic on own navigation.
As for calculating the drift it is not hard at all.........we simple pilots do it day in day out even when we are half asleep!
Simply put - at 420 Kt for every 7 Kt of crosswind there will be 1 degree of drift.
Each degree of drift puts the aircraft 1nm off track in 60nm
However here comes the crunch - being a good controller and aware of the upper winds you will momnitor the actual tracking of the aircraft atleast every minute or two and issue a correction to the heading. So the most the aircraft is going to get off track is 2nm 95 % of the time provided you do your job properly.
You quoted an extreme case but provided you take charge of the situation and you do you job well the only person who can be blamed for a loss of separation is you.
Note the frequent use of "you" in the above situation.
If you did loose separation, the question I would ask is why knowing the wind situation did you not climb to 1000ft below initially to check that separation was being ensured?
Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately.
Never assume.
We can quite happily fly the aircraft in heading mode- we change the heading to try and acheive the required tracking or we can even manually fly the aircraft as accurately as we can (wandering over the sky if the winds are shifting and the bumps are hard!). What is important is that we do not have to tell you how we are flying the aircraft provided we acheive the required RNP.
Do you not think that a large part of controller workload in busy enroute airspace comes from having to vector aircraft? If so then do you not also think that moves would have been made to increase capacity (reduce workload) by reducing the requirement for vectors?..........The answer lies in the Eurpean study from where I got those separation figures for parallel tracks earlier.
Regards,
DFC
PS as Captain I don't trust you to save my licence - that's my job.............don't expect me to do anything to save yours!
Join Date: Apr 2001
Location: Adrift upon the tides of fate
Posts: 1,840
Likes: 0
Received 0 Likes
on
0 Posts
Guy
Once again...
Fact. Pilots are required to advise of any deviation from track.
Fact. Pilots have been known to deviate a mile or two when on an assigned heading, as well.
So does that make you more right?
The windspeed at FL380 was mentioned just to indicate that the windspeed is increasing with altitude.
It is really irrelevent what rate the a/c climbs at (the time the risk is experienced will be the same whatever the technique). The point being that 'locking headings' has just as much, if not more, inherent risk than saying nothing and leaving a/c on their own nav.
No, I wasn't. But it became apparent that people holding entrenched views don't believe they could be wrong. Hence the verbosity. All this talk of proving or assuring separation. Just trying to demonstrate that it isn't neccessarly the case.
Cheers, except that I don't drink.
edited because DFC slipped his post in ...
DFC.
A long post, full once, again, of waffle.
If you had followed the thread properly, you would've read that the original question was why lock a/c on headings they are already doing.
There are many reasons why controllers vector a/c, I just happen to disagree with one of them- the one this thread is about. It is a technique that I have thought about long and hard, and has nothing to do with 90% of your post. I don't expect you to understand, as you are not a controller, but nor do I expect to receive advice on my job from you. The piloting aspects of what happens when we do certain things, sure, I would welcome your input, but I just cringe when you have NFI about what is being discussed.
Yep, with todays modern a/c, I believe they can track at least as accurately, in the situation described, as a controller locking headings.
As mentioned by someone else earlier, this technique is supposed to be a 'set-and-forget' thing, allowing the controller to move his attention to other things. This is one reason why it has always been touted as superior to leaving a/c on own nav. Alleged sep assurance.
BTW- would you deviate around a cell, or fly thru it, if you were flying an assigned heading?
Don't you agree that we are wasting everybody's time by applying this technique, when the a/c are so far apart, and the real risk of collision is so small, yet we take no preacautions about other lapses/failures, which involve the a/c being much physically closer together?
Personally, I am quite happy to front an interview about a loss of sep, armed with the excuse "the pilot deviated from track without informing me". No different to a level bust. Why do we treat it as such?
Once again...
Fact. Pilots are required to advise of any deviation from track.
Fact. Pilots have been known to deviate a mile or two when on an assigned heading, as well.
So does that make you more right?
The windspeed at FL380 was mentioned just to indicate that the windspeed is increasing with altitude.
It is really irrelevent what rate the a/c climbs at (the time the risk is experienced will be the same whatever the technique). The point being that 'locking headings' has just as much, if not more, inherent risk than saying nothing and leaving a/c on their own nav.
You seem very keen to quote extreme examples of winds
Cheers, except that I don't drink.
edited because DFC slipped his post in ...
DFC.
A long post, full once, again, of waffle.
If you had followed the thread properly, you would've read that the original question was why lock a/c on headings they are already doing.
There are many reasons why controllers vector a/c, I just happen to disagree with one of them- the one this thread is about. It is a technique that I have thought about long and hard, and has nothing to do with 90% of your post. I don't expect you to understand, as you are not a controller, but nor do I expect to receive advice on my job from you. The piloting aspects of what happens when we do certain things, sure, I would welcome your input, but I just cringe when you have NFI about what is being discussed.
Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately
As mentioned by someone else earlier, this technique is supposed to be a 'set-and-forget' thing, allowing the controller to move his attention to other things. This is one reason why it has always been touted as superior to leaving a/c on own nav. Alleged sep assurance.
BTW- would you deviate around a cell, or fly thru it, if you were flying an assigned heading?
Don't you agree that we are wasting everybody's time by applying this technique, when the a/c are so far apart, and the real risk of collision is so small, yet we take no preacautions about other lapses/failures, which involve the a/c being much physically closer together?
Personally, I am quite happy to front an interview about a loss of sep, armed with the excuse "the pilot deviated from track without informing me". No different to a level bust. Why do we treat it as such?
Last edited by ferris; 22nd Feb 2005 at 12:33.