How to manufacture a Mid-Air.
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willadvise, can you confirm that an offset as small as 1 mile will cause the ATC computers to spit the dummy and not update an aircraft’s position on your boards? (And can your enroute radars detect a track error that small?) I can only accept that you know what you’re talking about. However, as a (very non-mathematical) flying layman, I’m surprised to learn that, given that there are many aircraft still out there that are not GPS or IRS-equipped that the ATC computers can’t cope with an aircraft that is flying extremely accurately 1 mile off the airway centreline. (Non IRS/GPS aircraft can and do wander considerably more than 1 mile off the exact airway centreline.)
I feel that there is a maybe all too human reaction on the part of many ATC people that in asking for the offset to be legalised, we pilots are somehow slagging off at ATC and impugning their abilities or professionalism. I’d like to state quite clearly here that that is not so. (The analogy would be that in practising engine failure drills, we’re impugning the abilities of our engineers – or the abilities of flocks of seagulls to find their ways into engine intakes.[!]) We just believe that it is a very easily achieved extra layer of safety – and surely, we should all be grasping any extra layers of safety available to us without quibbling? And without delay.
Groundloop, have to agree that this particular incident was not your classic opposite direction conflict. In your suggestion to pass the slower aircraft on the left, I’m assuming that you are not a professional aviator (or sailor for that matter) – but yes, yours is a good idea. However, this incident does clearly illustrate the point 410 and others have been trying to make for some time now – the extraordinary accuracy of modern navigation systems. I think we’ll have two (and possibly four) converts to the offsetting argument in the crews involved in this incident. If flying NATS tracks and overtaking same direction traffic only 1000’ above or below you, (with the wonderful aid of hindsight), commonsense might now dictate that offsetting slightly to the right until past might be a very good practice, even in absolutely smooth conditions. ‘Situational awareness’ might also dictate that in such a situation, crews keep a very close eye on exactly where traffic immediately below them is tracking to pre-plan the direction of an immediate turn (or not to turn) in the event of a sudden depressurisation or engine failure in the cruise.
Maybe we should ask for a quick survey of respondents to this thread. How many of you do fly offset some or most of the time? I’ll add my name to list – I do it nearly all the time above 10,000’, except in RNP5 airspace. I’d rather find myself standing on the mat in front of the boss or the CAA explaining the error of my ways than finding myself a (dead) statistic. I don’t want to end up in some crash comic after meeting the same fate as the Luftwaffe TU154 and USAF C141 crews who had the midair off the African coast a year or two ago.
And if someone can explain the maths to me re how offsetting increases the chances of a midair, I’d be very grateful.
[This message has been edited by Wiley (edited 29 November 2000).]
I feel that there is a maybe all too human reaction on the part of many ATC people that in asking for the offset to be legalised, we pilots are somehow slagging off at ATC and impugning their abilities or professionalism. I’d like to state quite clearly here that that is not so. (The analogy would be that in practising engine failure drills, we’re impugning the abilities of our engineers – or the abilities of flocks of seagulls to find their ways into engine intakes.[!]) We just believe that it is a very easily achieved extra layer of safety – and surely, we should all be grasping any extra layers of safety available to us without quibbling? And without delay.
Groundloop, have to agree that this particular incident was not your classic opposite direction conflict. In your suggestion to pass the slower aircraft on the left, I’m assuming that you are not a professional aviator (or sailor for that matter) – but yes, yours is a good idea. However, this incident does clearly illustrate the point 410 and others have been trying to make for some time now – the extraordinary accuracy of modern navigation systems. I think we’ll have two (and possibly four) converts to the offsetting argument in the crews involved in this incident. If flying NATS tracks and overtaking same direction traffic only 1000’ above or below you, (with the wonderful aid of hindsight), commonsense might now dictate that offsetting slightly to the right until past might be a very good practice, even in absolutely smooth conditions. ‘Situational awareness’ might also dictate that in such a situation, crews keep a very close eye on exactly where traffic immediately below them is tracking to pre-plan the direction of an immediate turn (or not to turn) in the event of a sudden depressurisation or engine failure in the cruise.
Maybe we should ask for a quick survey of respondents to this thread. How many of you do fly offset some or most of the time? I’ll add my name to list – I do it nearly all the time above 10,000’, except in RNP5 airspace. I’d rather find myself standing on the mat in front of the boss or the CAA explaining the error of my ways than finding myself a (dead) statistic. I don’t want to end up in some crash comic after meeting the same fate as the Luftwaffe TU154 and USAF C141 crews who had the midair off the African coast a year or two ago.
And if someone can explain the maths to me re how offsetting increases the chances of a midair, I’d be very grateful.
[This message has been edited by Wiley (edited 29 November 2000).]
Pegase Driver
Here we go again..
Some more thoughts :
1 NM offs et is fine in RNP 10 Airspace or higher. In RNP 5, 4 or in TMAs this is too much, but as in nearly all FMS you only can manually off set full digits, it is not possible to off set less than one full mile.
Only solution would be enbedded off set.
The more the Navigation accuracy of your aircraft, the least ammount of offset you need. In fact with GPS/IRS 0,1 NM will do.
To avoid the problem encountered in the begining of this thread, the notion of applying RANDOM offset between 0, 1 and 0,4 NM would elimaniate that problem.
Problem is when do you revert to accurate NAV . 10.000 Ft as suggested won't work as there are may airports above 10.000 Ft...
Most collisions occur in low altitudes anyway...in TMAs or close to airports, . this question at the moment is a choking point,
Last : Mathematically, someone in the ICAO Working group demonstrated that if you offset, on multiple crossing points, the area of exposure to collision is greater, therefore the risk of collision is higher.(But do not ask me to give you back the formula )For this reason , legally ICAO cannot implement a measure that will increase the risk.At least this is the reason they give us. Common semse might prevail one day, but like many things in aviation, it will need a few more collisions.
Some more thoughts :
1 NM offs et is fine in RNP 10 Airspace or higher. In RNP 5, 4 or in TMAs this is too much, but as in nearly all FMS you only can manually off set full digits, it is not possible to off set less than one full mile.
Only solution would be enbedded off set.
The more the Navigation accuracy of your aircraft, the least ammount of offset you need. In fact with GPS/IRS 0,1 NM will do.
To avoid the problem encountered in the begining of this thread, the notion of applying RANDOM offset between 0, 1 and 0,4 NM would elimaniate that problem.
Problem is when do you revert to accurate NAV . 10.000 Ft as suggested won't work as there are may airports above 10.000 Ft...
Most collisions occur in low altitudes anyway...in TMAs or close to airports, . this question at the moment is a choking point,
Last : Mathematically, someone in the ICAO Working group demonstrated that if you offset, on multiple crossing points, the area of exposure to collision is greater, therefore the risk of collision is higher.(But do not ask me to give you back the formula )For this reason , legally ICAO cannot implement a measure that will increase the risk.At least this is the reason they give us. Common semse might prevail one day, but like many things in aviation, it will need a few more collisions.
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Wiley
Yes I can confirm that. Remember I am talking about FANS/ADS/CPDLC aircraft. Of course if you don't have this then there is no way of knowing (and I would prefer not to know). In radar coverage you have 3nm either side of the waypoint to be considered passing over they waypoint.
For more infomation on this have a look at the following link
http://www.pprune.org/ubb/NonCGI/For...ML/000823.html
Yes I can confirm that. Remember I am talking about FANS/ADS/CPDLC aircraft. Of course if you don't have this then there is no way of knowing (and I would prefer not to know). In radar coverage you have 3nm either side of the waypoint to be considered passing over they waypoint.
For more infomation on this have a look at the following link
http://www.pprune.org/ubb/NonCGI/For...ML/000823.html
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willadvise, thanks for the information you gave in response to Wiley's query. I think most of us can understand how the maths quite correctly gives a theoretical increase in the probability of collision with the wider crossing window that offsetting causes at airways intersections. I can also see that this wider window throws the current formulae you use to calculate clearances for crossing traffic out the window. What I’m trying to get across is that maybe someone at the top should use some lateral thinking and accept that maybe they need to accept these wider tolerances and re-calculate the formulae to allow for a (preferably embedded) offset. Crossing traffic doesn’t scare me nearly as much as opposite direction traffic on the same airway. To hit crossing traffic, you’ve got to be really unlucky in having both aircraft crossing the same three dimensional spot at exactly the same time. With opposite direction traffic, many aircraft occupy exactly the same line in azimuth for up to eight or more hours.
Even if the decision I’ve been asking for was made tomorrow by ICAO, it would still be years before an embedded offset was a part of even one, let alone every FMS in the world. This is why I believe we simply have to allow the manual offset to be made a legal option – and preferably, a requirement – for all aircrew, ASAP. I don’t like the 0.1NM argument put forward by some ATC people. This will not prevent a TCAS Resolution Alert in the event of a mistake - and recent events within my own airline have proven that when surprised pilots receive an unexpected (and in this case, genuine) RA, they sometimes react not exactly as per the TCAS instructions. I want to avoid pilots having to manoeuvre to avoid whenever possible in a TCAS encounter and 0.1NM offset won’t achieve this. Anyone who doesn’t believe me, get clearance from ATC for 1.0NM right of track the next time you have traffic approaching 2000’ above or below you and take a look how close that is. Imagine 0.1NM and you’ll see that it simply isn’t enough.
Even if the decision I’ve been asking for was made tomorrow by ICAO, it would still be years before an embedded offset was a part of even one, let alone every FMS in the world. This is why I believe we simply have to allow the manual offset to be made a legal option – and preferably, a requirement – for all aircrew, ASAP. I don’t like the 0.1NM argument put forward by some ATC people. This will not prevent a TCAS Resolution Alert in the event of a mistake - and recent events within my own airline have proven that when surprised pilots receive an unexpected (and in this case, genuine) RA, they sometimes react not exactly as per the TCAS instructions. I want to avoid pilots having to manoeuvre to avoid whenever possible in a TCAS encounter and 0.1NM offset won’t achieve this. Anyone who doesn’t believe me, get clearance from ATC for 1.0NM right of track the next time you have traffic approaching 2000’ above or below you and take a look how close that is. Imagine 0.1NM and you’ll see that it simply isn’t enough.
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I don't see any need to increase the tolerances for the calculations to account for a 1nm offset. In oceanic airspace in Aus. you are considered to have a cross track tolerance of 50nm(yes thats 50nm left and right), in RNP10 airspace its 25, and over land it is 14nm. With current navigation systems a 1nm offsett can easily be asborbed into these tolerances. I would like to see it reduced to 25nm over the ocean and 10nm over land.
I don't see any need to increase the tolerances for the calculations to account for a 1nm offset. In oceanic airspace in Aus. you are considered to have a cross track tolerance of 50nm(yes thats 50nm left and right), in RNP10 airspace its 25, and over land it is 14nm. With current navigation systems a 1nm offsett can easily be asborbed into these tolerances. I would like to see it reduced to 25nm over the ocean and 10nm over land.
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willadvise, to clear up a (very small) point of apparent contention: I don't believe anyone in his right mind would suggest pilots should stick in an offset if being radar vectored. (Your original post >>" The controller is expecting you to fly a particular track and makes judgements based on your predicted track only to find you a mile or so closer to that other aircraft that you were going to slide nicely 5nm past."<< )
Is there anywhere except a terminal area where you allow an aircraft to get within 5NM of other traffic? Even in Europe, where I've had same level cruising traffic quite close, I can't remember seeing any only 5NM away. I don't think anyone is suggesting that we as pilots should build in our own bugger factor over a controller's vectors.
Every time I throw the "automatic embedded offset above 10,000 feet" argument forward the same argument is put forth: "There are airfields above 10,000'". Not too many, particularly if capable of taking jet aircraft, but this apparent problem can be overcome with existing technology. As soon as any current FMC-equipped aircraft enters a STAR (and until it exits a SID), the offsetting facility is not enabled. The same feature would fix the problem for any airfield above 10,000'.
Could someone give me a list of such airfields? Maybe in the Andes or Nepal? I've landed above 10,000' in New Guinea, but it wasn't at an airfield - and it's not an experience I'm in any hurry to repeat. Thin, thin air and a very dramatic demonstration of how TAS is the overriding factor over IAS that far above sea level...
Is there anywhere except a terminal area where you allow an aircraft to get within 5NM of other traffic? Even in Europe, where I've had same level cruising traffic quite close, I can't remember seeing any only 5NM away. I don't think anyone is suggesting that we as pilots should build in our own bugger factor over a controller's vectors.
Every time I throw the "automatic embedded offset above 10,000 feet" argument forward the same argument is put forth: "There are airfields above 10,000'". Not too many, particularly if capable of taking jet aircraft, but this apparent problem can be overcome with existing technology. As soon as any current FMC-equipped aircraft enters a STAR (and until it exits a SID), the offsetting facility is not enabled. The same feature would fix the problem for any airfield above 10,000'.
Could someone give me a list of such airfields? Maybe in the Andes or Nepal? I've landed above 10,000' in New Guinea, but it wasn't at an airfield - and it's not an experience I'm in any hurry to repeat. Thin, thin air and a very dramatic demonstration of how TAS is the overriding factor over IAS that far above sea level...
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I suggest that if you decided to offset a mile in any airspace, excepting on approach, it's unlikely anyone would notice, or if they did the assumption would be the poor pilot is having trouble navigating (not suggesting for 1 minute that pilots navigate poorly 
)
In a/space with bi-directional routes it seems sensible to offset and keep your transponder and TCAS on!
Ratboy.....NZ runs a fair portion of the Pacific Ocean and Tasman Sea with 'OCS'- (oceanic control system), using the technology you mention. It appears to work well, the major advantage the system has over Ozzy's TAATS or any of the other current systems is the 'conflict probe' software. RVSM and Flexi tracks are becoming the norm, ie: Free flight (more or less) so it wont matter how far you off set because your traffic may well be tracking on a random route too!! So.....offset anyway, keep your transponder and TCAS on and keep a sharp lookout skipper
[This message has been edited by TinPusher (edited 03 December 2000).]
[This message has been edited by TinPusher (edited 03 December 2000).]
[This message has been edited by TinPusher (edited 03 December 2000).]
)In a/space with bi-directional routes it seems sensible to offset and keep your transponder and TCAS on!
Ratboy.....NZ runs a fair portion of the Pacific Ocean and Tasman Sea with 'OCS'- (oceanic control system), using the technology you mention. It appears to work well, the major advantage the system has over Ozzy's TAATS or any of the other current systems is the 'conflict probe' software. RVSM and Flexi tracks are becoming the norm, ie: Free flight (more or less) so it wont matter how far you off set because your traffic may well be tracking on a random route too!! So.....offset anyway, keep your transponder and TCAS on and keep a sharp lookout skipper
[This message has been edited by TinPusher (edited 03 December 2000).]
[This message has been edited by TinPusher (edited 03 December 2000).]
[This message has been edited by TinPusher (edited 03 December 2000).]
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To clarify my original point.
: I don't believe anyone in his right mind would suggest pilots should stick in an offset if being radar vectored.
You don't neccesarily to have to be radar vectored for the controller to consider your track. Some examples. You have just departed via a SID. The SID is designed to keep you away from the corresponding STAR. You offset 1nm right. The guy opposite to you on the STAR offsets 1nm right and you find yourself 2nm closer to each other (depending on how the SID/STAR routes are designed).
You depart on a SID there is only one bit other bit off trafic you conflict with. The controller leaves you on the SID for a while (intending to give you direct once there is sufficent separation with the other aircraft) and sees that you are going to slide 5nm past the other aircraft, now you are passing through 10000ft and so you put your offset in. Oh sh!t not going to pass after all.
You depart on a SID there is no other traffic so it is cancelled and you are given direct to your first enroute waypoint. Do you offset?
Tin Pusher comments that he wouldn't notice 1nm offsets and may assume pilots are having trouble navigating. I disagree. I can see what nav equipment you are carrying in your flight plan. If you don't have GPS/IRS then I will cut you some more slack, but if you do a 1nm offset will be obvious. on radar.
You ask if less than 5nm is used anywhere else other than in the terminal area. Apart from visual separation I can give one other instance. This is going to be a little difficult to explain but I will give it my best shot.
Aicraft 1 is tracking north bound. Acft 2 south bound. They are tracking via a VOR at A. There is 15degrees between their nominal tracks. According to lateral separation prinicipals these aircraft are considered to be separated at 15nm from VOR A. At which point the two aircraft will nominally be 3.9nm from each other. Now assuming you are both offsetting 1nm to the right you will now pass 1.9nm from each other. Do you still want to offset over land when I am going to be making decisions like this.
Like I have said before. I don't really have a problem with you offsetting over the ocean but please consider what I have said above before you do it in radar coverage or over land.
Cheers
WA
fixed image link.
[This message has been edited by willadvise (edited 05 December 2000).]
To clarify my original point.
: I don't believe anyone in his right mind would suggest pilots should stick in an offset if being radar vectored.
You don't neccesarily to have to be radar vectored for the controller to consider your track. Some examples. You have just departed via a SID. The SID is designed to keep you away from the corresponding STAR. You offset 1nm right. The guy opposite to you on the STAR offsets 1nm right and you find yourself 2nm closer to each other (depending on how the SID/STAR routes are designed).
You depart on a SID there is only one bit other bit off trafic you conflict with. The controller leaves you on the SID for a while (intending to give you direct once there is sufficent separation with the other aircraft) and sees that you are going to slide 5nm past the other aircraft, now you are passing through 10000ft and so you put your offset in. Oh sh!t not going to pass after all.
You depart on a SID there is no other traffic so it is cancelled and you are given direct to your first enroute waypoint. Do you offset?
Tin Pusher comments that he wouldn't notice 1nm offsets and may assume pilots are having trouble navigating. I disagree. I can see what nav equipment you are carrying in your flight plan. If you don't have GPS/IRS then I will cut you some more slack, but if you do a 1nm offset will be obvious. on radar.
You ask if less than 5nm is used anywhere else other than in the terminal area. Apart from visual separation I can give one other instance. This is going to be a little difficult to explain but I will give it my best shot.
Aicraft 1 is tracking north bound. Acft 2 south bound. They are tracking via a VOR at A. There is 15degrees between their nominal tracks. According to lateral separation prinicipals these aircraft are considered to be separated at 15nm from VOR A. At which point the two aircraft will nominally be 3.9nm from each other. Now assuming you are both offsetting 1nm to the right you will now pass 1.9nm from each other. Do you still want to offset over land when I am going to be making decisions like this.
Like I have said before. I don't really have a problem with you offsetting over the ocean but please consider what I have said above before you do it in radar coverage or over land.
Cheers
WA
fixed image link.
[This message has been edited by willadvise (edited 05 December 2000).]
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willadvise, I can well understand the concerns you express in your examples. However, they illustrate very clearly why line pilots, ATC and the regulators haven’t been able to get together and solve this problem to date. Put simply, it is ignorance of each other’s problems and concerns and a lack of will so far by those in a position to do something constructive towards addressing them.
The designers of the most commonly used Flight Management Systems foresaw your objection as you detailed in your examples. Offsetting isn’t possible in a STAR or a SID. The feature is not selectable until the SID had been completed and if an offset is still in place on descent, it is automatically deleted at the beginning of the STAR.
To repeat the main thrust of my argument: as line pilots, we don’t perceive a big problem in an ATC environment where a controller is actively vectoring aircraft on radar, particularly in a ‘first world’ environment. The arousal level of all concerned in these phases of flight is usually high enough to have at least one set of eyes sufficiently on the big picture to prevent glaring mistakes being made. (I have to say there are exceptions even to this, and ‘Murphy’ is always lurking in the shadows ready to catch even the sharpest controller or pilot out, as seems to have been illustrated by the recent very near miss between the loosely formating F15 with the Britannia 757 over the UK late last month. If initial explanations of this incident prove to be true, is there anyone out there who still places his total trust in TCAS to provide separation?)
It is the other ten hours of a long haul flight, (or the forty minutes of a short haul flight), where arousal levels are not quite so high, where co-ordination between ATC agencies may be poor or non-existent, (between semi-warring agencies for example, like Larnaca and Ankara), where we want to see something done. There have been more than a few incidents already attributable to the super accuracy of modern nav systems, some of them in so-called ‘first world’ countries, even the U.S.A. In Africa, offsetting’s been recognised as an easily-achievable and much-needed fix. Do we have to wait until hundreds more die in one more single catastrophe before we slam the proverbial stale door and adopt it elsewhere in the world? It’s not as though it hasn’t happened on a large scale already – it has, but so far, ‘out of the Western media’s eye’ in places like India or Africa. So far in the West, thankfully it’s only been commuter or charter aircraft involved, like the accident over the Grand Canyon in the U.S. If it ever happens to two widebodies full of Western tourists or businessmen, you can bet the media and the lawyers! will be screaming “Why didn’t you as an industry do something to prevent this when you knew the problem existed?”
We’re not in any way accusing you as Air Traffic Controllers of being sub-standard in the performance of your jobs. We’re just acknowledging that we are all human. It’s all too possible for a pilot to misread a clearance or acknowledge a climb or descent instruction for another aircraft with a similar callsign. It’s just as easy for a harried controller to miss or misread the information passed to him on an aircraft entering his airspace. It happened off the east coast of Africa a couple of years ago and the crew and passengers of two jet aircraft paid the ultimate price.
Murphy' Law says that if such an error does occur, the errant aircraft will almost certainly be in conflict with some other aircraft. Twenty years ago, such an error might have gone unnoticed except in some pilot’s or controller’s annual fitness report. Today, thanks to the extremely accurate nav systems most of us use, that same small error could have catastrophic consequences. Offsetting in the cruise phase of flight (when not under radar vectors) would put in place a ‘bugger factor’ that might help prevent one small mistake leading to a catastrophe.
If we could just talk, (and maybe more importantly, listen) to each other, as we’re doing on this thread, we might get around the misunderstandings that could give an outside observer the impression that we’re all too busy defending our individual pieces of turf to do what’s best for all of us.
Somebody on another thread mentioned the 'Titanic' principle of management - where each department is perfctly happy so long as its deck chairs are all neatly arranged. Meanwile the overall 'ship' is sliding gracefully under the waves. The same might be said of this argument.
Edited for typos.
[This message has been edited by 410 (edited 05 December 2000).]
The designers of the most commonly used Flight Management Systems foresaw your objection as you detailed in your examples. Offsetting isn’t possible in a STAR or a SID. The feature is not selectable until the SID had been completed and if an offset is still in place on descent, it is automatically deleted at the beginning of the STAR.
To repeat the main thrust of my argument: as line pilots, we don’t perceive a big problem in an ATC environment where a controller is actively vectoring aircraft on radar, particularly in a ‘first world’ environment. The arousal level of all concerned in these phases of flight is usually high enough to have at least one set of eyes sufficiently on the big picture to prevent glaring mistakes being made. (I have to say there are exceptions even to this, and ‘Murphy’ is always lurking in the shadows ready to catch even the sharpest controller or pilot out, as seems to have been illustrated by the recent very near miss between the loosely formating F15 with the Britannia 757 over the UK late last month. If initial explanations of this incident prove to be true, is there anyone out there who still places his total trust in TCAS to provide separation?)
It is the other ten hours of a long haul flight, (or the forty minutes of a short haul flight), where arousal levels are not quite so high, where co-ordination between ATC agencies may be poor or non-existent, (between semi-warring agencies for example, like Larnaca and Ankara), where we want to see something done. There have been more than a few incidents already attributable to the super accuracy of modern nav systems, some of them in so-called ‘first world’ countries, even the U.S.A. In Africa, offsetting’s been recognised as an easily-achievable and much-needed fix. Do we have to wait until hundreds more die in one more single catastrophe before we slam the proverbial stale door and adopt it elsewhere in the world? It’s not as though it hasn’t happened on a large scale already – it has, but so far, ‘out of the Western media’s eye’ in places like India or Africa. So far in the West, thankfully it’s only been commuter or charter aircraft involved, like the accident over the Grand Canyon in the U.S. If it ever happens to two widebodies full of Western tourists or businessmen, you can bet the media and the lawyers! will be screaming “Why didn’t you as an industry do something to prevent this when you knew the problem existed?”
We’re not in any way accusing you as Air Traffic Controllers of being sub-standard in the performance of your jobs. We’re just acknowledging that we are all human. It’s all too possible for a pilot to misread a clearance or acknowledge a climb or descent instruction for another aircraft with a similar callsign. It’s just as easy for a harried controller to miss or misread the information passed to him on an aircraft entering his airspace. It happened off the east coast of Africa a couple of years ago and the crew and passengers of two jet aircraft paid the ultimate price.
Murphy' Law says that if such an error does occur, the errant aircraft will almost certainly be in conflict with some other aircraft. Twenty years ago, such an error might have gone unnoticed except in some pilot’s or controller’s annual fitness report. Today, thanks to the extremely accurate nav systems most of us use, that same small error could have catastrophic consequences. Offsetting in the cruise phase of flight (when not under radar vectors) would put in place a ‘bugger factor’ that might help prevent one small mistake leading to a catastrophe.
If we could just talk, (and maybe more importantly, listen) to each other, as we’re doing on this thread, we might get around the misunderstandings that could give an outside observer the impression that we’re all too busy defending our individual pieces of turf to do what’s best for all of us.
Somebody on another thread mentioned the 'Titanic' principle of management - where each department is perfctly happy so long as its deck chairs are all neatly arranged. Meanwile the overall 'ship' is sliding gracefully under the waves. The same might be said of this argument.
Edited for typos.
[This message has been edited by 410 (edited 05 December 2000).]
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Willadvise
Excellent graphics. I work radar TMA airspace where, if aircraft are anywhere near each other at the same FL (in your example both aircraft are within the area of conflict, I assume they are at different levels) they will be locked on headings and know about each other.
Procedural sep's are designed with a fudge factor, perhaps someone with a penchant for ICAO Doc's and the like could advise if 1nm off track within an airway, (assuming that nav is without reference to VOR or other ground based nav aids), is within tolerance or not??
I still maintain that on bi-directional routes (even if in radar coverage) it would be prudent to offset, if only 1/2nm, especially in RVSM airspace.
410
I would be happy to fly with you on the condition you get me to destination 'unbuggered' and if that includes offsetting then go for it!!
Excellent graphics. I work radar TMA airspace where, if aircraft are anywhere near each other at the same FL (in your example both aircraft are within the area of conflict, I assume they are at different levels) they will be locked on headings and know about each other.
Procedural sep's are designed with a fudge factor, perhaps someone with a penchant for ICAO Doc's and the like could advise if 1nm off track within an airway, (assuming that nav is without reference to VOR or other ground based nav aids), is within tolerance or not??
I still maintain that on bi-directional routes (even if in radar coverage) it would be prudent to offset, if only 1/2nm, especially in RVSM airspace.
410
I would be happy to fly with you on the condition you get me to destination 'unbuggered' and if that includes offsetting then go for it!!
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In the enroute case where using the least accurate means of navigation combinations, and a procedural standard is achieved, isn't the basic lateral separation still only 1nm (worst case)?
Therefore if each ACFT throws in it's own offset, this lateral sep point must be looking pretty shaky! (case is assuming no ADS/RADAR)
Therefore if each ACFT throws in it's own offset, this lateral sep point must be looking pretty shaky! (case is assuming no ADS/RADAR)
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Concerning RVSM over the atlantic: wouldn't it be much safer, and would capacity not be greatly increased if the NAT's would be separated by 30nm laterally (instead of the current 1 degree lattitude = 60nm) than by reducing the vertical separation to 1000 feet (1/6 nm)?
I have never understood this. But please correct me if I overlook something here.
I have never understood this. But please correct me if I overlook something here.
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UK investigators worry about RVSM after Atlantic airprox
David Morrow, London (07Jun01, 14:56 GMT, 536 words)
UK accident investigators are urging regulators to review operating procedures in reduced vertical separation minima (RVSM) airspace after a clear air turbulence encounter caused a serious airprox incident over the North Atlantic last year.
Shortly after hitting the turbulence a New York-bound THY Turkish Airlines Airbus A340-300, cruising at FL360, suddenly pitched up and climbed rapidly to FL384. The uncommanded manoeuvre resulted in the A340 passing through FL370, an altitude assigned to a Canada 3000 Airbus A330-200 which had been above the THY jet and overtaking it slightly to one side at the time.
UK accident investigators probing the incident are warning that there is no formal procedure in place for avoiding the risk of collision in such circumstances. The accuracy of modern navigation systems, says the Air Accidents Investigation Branch report into the 2 October incident, is such that there is a greater chance that overtaking aircraft will be separated only vertically and, in RVSM airspace, by just 1,000ft.
It stresses that the speed of the A340’s climb – initiated by the aircraft’s automatic protection systems after it hit the turbulence – was so sudden that the A330 crew might not have been able to initiate evasive action. The report describes the event as a “serious loss of separation” and says the A340 pilot estimated the aircraft to be horizontally separated by 1nm (1.8km).
This has disturbing implications for the RVSM safety case, says the report: “If the intruder aircraft continues its climb there can be no guarantee that an aircraft directly above it could respond in sufficient time to avoid a collision.”
It adds: “It is not clear whether the European or Oceanic [RVSM] safety case studies and models have taken account of the risks of clear air turbulence coupled to the response of sophisticated flight-control systems such as those fitted to the Airbus fly-by-wire aircraft series.”
There is no formal procedure listed in the North Atlantic Minimum Navigation Performance Specifications Airspace operations manual for limiting the risks while overtaking at RVSM altitudes. The report states that lateral offset flying should be considered as a way of providing an effective safety barrier.
“The collision risk could have been reduced if the commander of the overtaking aircraft had been permitted (and expected) to temporarily increase the lateral separation between the two aircraft before they reached the line-abreast position,” it says.
It points out that simulations have indicated that a lateral separation of 1.5nm (2.8km) would be enough to prevent an aircraft’s traffic collision-avoidance system (TCAS) from generating a resolution advisory to the crew, and adds that flying a 2nm lateral offset is already an approved procedure used to mitigate wake turbulence problems.
“There would appear to be a safety case for extending this contingency procedure to overtaking, particularly in regions where turbulence of any kind is evident or forecast.”
Recommendations made in late November last year urged the CAA to request a review of overtaking procedures in RVSM airspace as well as suggest the development of a standardised lateral offset procedure. A spokesman for the CAA says: “We have put forward these recommendations to the appropriate international authorities. It’s really out of our hands now and we can’t say how or when the issues will be addressed.”
Source: Air Transport Intelligence news
David Morrow, London (07Jun01, 14:56 GMT, 536 words)
UK accident investigators are urging regulators to review operating procedures in reduced vertical separation minima (RVSM) airspace after a clear air turbulence encounter caused a serious airprox incident over the North Atlantic last year.
Shortly after hitting the turbulence a New York-bound THY Turkish Airlines Airbus A340-300, cruising at FL360, suddenly pitched up and climbed rapidly to FL384. The uncommanded manoeuvre resulted in the A340 passing through FL370, an altitude assigned to a Canada 3000 Airbus A330-200 which had been above the THY jet and overtaking it slightly to one side at the time.
UK accident investigators probing the incident are warning that there is no formal procedure in place for avoiding the risk of collision in such circumstances. The accuracy of modern navigation systems, says the Air Accidents Investigation Branch report into the 2 October incident, is such that there is a greater chance that overtaking aircraft will be separated only vertically and, in RVSM airspace, by just 1,000ft.
It stresses that the speed of the A340’s climb – initiated by the aircraft’s automatic protection systems after it hit the turbulence – was so sudden that the A330 crew might not have been able to initiate evasive action. The report describes the event as a “serious loss of separation” and says the A340 pilot estimated the aircraft to be horizontally separated by 1nm (1.8km).
This has disturbing implications for the RVSM safety case, says the report: “If the intruder aircraft continues its climb there can be no guarantee that an aircraft directly above it could respond in sufficient time to avoid a collision.”
It adds: “It is not clear whether the European or Oceanic [RVSM] safety case studies and models have taken account of the risks of clear air turbulence coupled to the response of sophisticated flight-control systems such as those fitted to the Airbus fly-by-wire aircraft series.”
There is no formal procedure listed in the North Atlantic Minimum Navigation Performance Specifications Airspace operations manual for limiting the risks while overtaking at RVSM altitudes. The report states that lateral offset flying should be considered as a way of providing an effective safety barrier.
“The collision risk could have been reduced if the commander of the overtaking aircraft had been permitted (and expected) to temporarily increase the lateral separation between the two aircraft before they reached the line-abreast position,” it says.
It points out that simulations have indicated that a lateral separation of 1.5nm (2.8km) would be enough to prevent an aircraft’s traffic collision-avoidance system (TCAS) from generating a resolution advisory to the crew, and adds that flying a 2nm lateral offset is already an approved procedure used to mitigate wake turbulence problems.
“There would appear to be a safety case for extending this contingency procedure to overtaking, particularly in regions where turbulence of any kind is evident or forecast.”
Recommendations made in late November last year urged the CAA to request a review of overtaking procedures in RVSM airspace as well as suggest the development of a standardised lateral offset procedure. A spokesman for the CAA says: “We have put forward these recommendations to the appropriate international authorities. It’s really out of our hands now and we can’t say how or when the issues will be addressed.”
Source: Air Transport Intelligence news
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...and as elected representative for the 232 of us sitting directly behind you, we had a quick vote after the meal and have decided we would also like you to fly offset
(sorry to bring a layman pax into your fascinating, superbly written and highly informative thread.)
(sorry to bring a layman pax into your fascinating, superbly written and highly informative thread.)
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I don't think anybody would be thinking of offsets below at least FL100 and my personal suggestion, FL200.
However, the smart folks at ICAO don't sit up night after night watching opposite direction traffic passing PRECISELY head-on time after time after time after time after time after time.......you get the message.
All the talk about pilot tolerances, equipment tolerances, the need to recalculate safety heights for the offset route, the need to recalculate latsep points fot ATC sounds just great. It ignores one thing, GPS equiped a/c today ARE EXACTLY ON TRACK!!! And they WILL hit head-on if someone makes a mistake.
The boffins, to use that American expression, need to get out more. So do the ICAO and IFALPA folks who sit around pontificating while the rest of the world wonders.
For mine, an official 1nm offset above FLxxx can't come soon enough!
G'day
However, the smart folks at ICAO don't sit up night after night watching opposite direction traffic passing PRECISELY head-on time after time after time after time after time after time.......you get the message.
All the talk about pilot tolerances, equipment tolerances, the need to recalculate safety heights for the offset route, the need to recalculate latsep points fot ATC sounds just great. It ignores one thing, GPS equiped a/c today ARE EXACTLY ON TRACK!!! And they WILL hit head-on if someone makes a mistake.
The boffins, to use that American expression, need to get out more. So do the ICAO and IFALPA folks who sit around pontificating while the rest of the world wonders.
For mine, an official 1nm offset above FLxxx can't come soon enough!
G'day
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As a non-oceanic controller it does seem strange to me that separation in the vertical can be reduced by 50% to 1000 feet, but the lateral still remains at 60 miles or 10 minutes in trail which is about 80 miles.
I know its a procedural environment and commnication is difficult but surely modern aircraft are more likely to deviate vertically than laterally.
Have any studies been carried out on the advantages of reducing the lateral (track) separation by 50% to 30 miles (an awful long way even allowing for offsets)?
You could use the RVSM produced levels (300, 320, 340 etc) on the intermediate tracks so that vertical separation on the same track became 2000 feet again.
Just a thought...
I know its a procedural environment and commnication is difficult but surely modern aircraft are more likely to deviate vertically than laterally.
Have any studies been carried out on the advantages of reducing the lateral (track) separation by 50% to 30 miles (an awful long way even allowing for offsets)?
You could use the RVSM produced levels (300, 320, 340 etc) on the intermediate tracks so that vertical separation on the same track became 2000 feet again.
Just a thought...
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I been reading this thread quite closely, good instructive and informative comments from both sides of the fence so to speak.
With regard to whether we (the ATC's) can see if you are off track, here in the Middle East we certainly can. The new kit we have is pretty good, we can see to within 0.1nm if we feel like it.
Having said that, I do see many aircraft sitting comfortably 1-2nm off track on a regular basis. I personally have no problem with it unless I'm RADAR vectoring, then it would be impossible for the pilot to offset anyway wouldn't it?
Having heard of many opposite direction near misses (and same direction come to think of it) coming out of the airspace to the east of us...I am more than happy to see the offset happening.
BTW willadvise...I haven't been in Oz for a few years now...are you guys now using the ICAO 15 degrees 15 miles now? I have always felt that 3.75nm is not really enough...if we are using radar, we need 5 (usually)so I can't see that 3.75 is safer.
BTW someone asked about lateral separation...it's 1nm between the POSSIBLE positions of two aircraft (that takes into account the xcross track errors and adds one for mum).
Keep the good gen coming, I feel it is of benefit to both sides especially with the possible implementation of RVSM in most places of the world.
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turn the plane! turn the plane!
With regard to whether we (the ATC's) can see if you are off track, here in the Middle East we certainly can. The new kit we have is pretty good, we can see to within 0.1nm if we feel like it.
Having said that, I do see many aircraft sitting comfortably 1-2nm off track on a regular basis. I personally have no problem with it unless I'm RADAR vectoring, then it would be impossible for the pilot to offset anyway wouldn't it?
Having heard of many opposite direction near misses (and same direction come to think of it) coming out of the airspace to the east of us...I am more than happy to see the offset happening.
BTW willadvise...I haven't been in Oz for a few years now...are you guys now using the ICAO 15 degrees 15 miles now? I have always felt that 3.75nm is not really enough...if we are using radar, we need 5 (usually)so I can't see that 3.75 is safer.
BTW someone asked about lateral separation...it's 1nm between the POSSIBLE positions of two aircraft (that takes into account the xcross track errors and adds one for mum).
Keep the good gen coming, I feel it is of benefit to both sides especially with the possible implementation of RVSM in most places of the world.
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turn the plane! turn the plane!