10min. long. sep
10min. long. sep
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Well, it's a few years since I did totally procedural control, but I'm with you. You have ten minutes separation until the second (faster) aircraft reports at xyz (assuming both report on-time).
(edit for punctuation!!!)
[This message has been edited by Numpo-Nigit (edited 17 December 2000).]
(edit for punctuation!!!)
[This message has been edited by Numpo-Nigit (edited 17 December 2000).]
Guest
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At 1210, you have minimum separation. Therefore, if the following aircraft is faster, you lose separation immediately after 1210.
Or - looking at it another way - if you wait until 1220, how far ahead of the faster aircraft is the slower one? Certainly not 10 minutes flying time for the faster aircraft!!
Or - looking at it another way - if you wait until 1220, how far ahead of the faster aircraft is the slower one? Certainly not 10 minutes flying time for the faster aircraft!!
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2 sheds
Agree with the sentiment, but not fully with what you say. Remember we're talking time here and not distance. So at 1210, the faster aircraft IS 10 minutes flying time from the slower aircraft and will remain so until 1220. After that the separation will erode, but not before.
We use a sliding Mach number technique to cater for such situations over the Atlantic. By applying a relevant time interval based on the aircraft's speeds, you should have the standard 10 minutes separation when the second aircraft pops out the other side of the pond.
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10 West
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Agree with the sentiment, but not fully with what you say. Remember we're talking time here and not distance. So at 1210, the faster aircraft IS 10 minutes flying time from the slower aircraft and will remain so until 1220. After that the separation will erode, but not before.
We use a sliding Mach number technique to cater for such situations over the Atlantic. By applying a relevant time interval based on the aircraft's speeds, you should have the standard 10 minutes separation when the second aircraft pops out the other side of the pond.
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10 West
UK ATC'er
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just a small point, is it not based on GS rather than TAS?
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"The views expressed here are a personal rant and rave and in no way reflect the views of my employer/s, not even by coincidence I should imagine "
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Yeg, Numpo and 10W
It would be of interest to know if you are employing an element of radar separation / monitoring in the equation at the time the second aircraft passes the fix - either UK environment or US side of the Atlantic - which might make what you describe acceptable to the receiving authority. However, if we are talking application of the basic purely procedural 10 min longitudinal (or 15 min in some parts of the world), then I stick by the previous post (Good on yer, Karrank).
To expand the point, consider the aircraft at FL 80, a Cherokee (groundspeed 1 mile per minute) followed by a TriStar (groundspeed 8 miles per minute) - same estimates. Are you seriously suggesting that separation exists until 1220 when the Tristar passes the fix???
It would be of interest to know if you are employing an element of radar separation / monitoring in the equation at the time the second aircraft passes the fix - either UK environment or US side of the Atlantic - which might make what you describe acceptable to the receiving authority. However, if we are talking application of the basic purely procedural 10 min longitudinal (or 15 min in some parts of the world), then I stick by the previous post (Good on yer, Karrank).
To expand the point, consider the aircraft at FL 80, a Cherokee (groundspeed 1 mile per minute) followed by a TriStar (groundspeed 8 miles per minute) - same estimates. Are you seriously suggesting that separation exists until 1220 when the Tristar passes the fix???
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LoLevel
Nope. it's TAS based, since G/S is a constantly moving feast. And for a minimum of 10 minutes, no speed differential is specified.
2 Sheds
Yes, it's radar derived as they enter the Atlantic, HOWEVER, procedural separation could be based on aircraft reports alone, for example in domestic procedural separation. In fact, mid Atlantic, that's exactly what we use for obvious reasons
On your second point, strictly speaking, yes the PA28 and TriStar ARE separated, ICAO decrees they are separated up till the point where 10 minutes no longer exists. For aircraft at the same level and on the same track, the MINIMUM separation is 10 minutes. If you have the MINIMUM, then you're legal until that is lost. Not sure that anyone would be silly enough to apply it though without a different plan in the case you quote. !!
Otherwise, if you think about it, a prop departing from Europe for Iceland has immediately lost separation with the B763 departing the Middle East for the USA at the same level on the same route because the B763 will eventually catch it in about 4 hours time !! I think not
You're trying to link distance into a longitudinal time separation, which is totally irrelavant. Two PA28's @ 120 Kts and 10 minutes apart (20NM in still air) are actually just as separated as a PA28 and an L1011 10 minutes apart in terms of time, even although there is 80NM between the second pair.
Dig out the Doc 4444 guys !!
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10 West
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Nope. it's TAS based, since G/S is a constantly moving feast. And for a minimum of 10 minutes, no speed differential is specified.
2 Sheds
Yes, it's radar derived as they enter the Atlantic, HOWEVER, procedural separation could be based on aircraft reports alone, for example in domestic procedural separation. In fact, mid Atlantic, that's exactly what we use for obvious reasons
On your second point, strictly speaking, yes the PA28 and TriStar ARE separated, ICAO decrees they are separated up till the point where 10 minutes no longer exists. For aircraft at the same level and on the same track, the MINIMUM separation is 10 minutes. If you have the MINIMUM, then you're legal until that is lost. Not sure that anyone would be silly enough to apply it though without a different plan in the case you quote. !!
Otherwise, if you think about it, a prop departing from Europe for Iceland has immediately lost separation with the B763 departing the Middle East for the USA at the same level on the same route because the B763 will eventually catch it in about 4 hours time !! I think not
You're trying to link distance into a longitudinal time separation, which is totally irrelavant. Two PA28's @ 120 Kts and 10 minutes apart (20NM in still air) are actually just as separated as a PA28 and an L1011 10 minutes apart in terms of time, even although there is 80NM between the second pair.
Dig out the Doc 4444 guys !!
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10 West
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ICAO DOC4444 8.1.1 Longitudinal separation shall be applied so that the spacing between the estimated positions of the aircraft being separated is never less than a prescribed minimum.
At 1210 there is 10 minutes spacing between the positions of the aircraft.
At 1220 the positions of the aircraft have moved by distance based on their GROUNDSPEED. Assuming the GROUNDSPEED is closing like the TAS (and it might not be) the positions of the aircraft will be closer together. You have had less than 10 minutes spacing since 1210, how much less depends on their GROUNDSPEED.
10W, your prop & B763 (they have airports in Iceland?) have 10 minutes until the spacing between the positions of the aircraft is less than 10 minutes.
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I am not an animal, I am an ATC.
At 1210 there is 10 minutes spacing between the positions of the aircraft.
At 1220 the positions of the aircraft have moved by distance based on their GROUNDSPEED. Assuming the GROUNDSPEED is closing like the TAS (and it might not be) the positions of the aircraft will be closer together. You have had less than 10 minutes spacing since 1210, how much less depends on their GROUNDSPEED.
10W, your prop & B763 (they have airports in Iceland?) have 10 minutes until the spacing between the positions of the aircraft is less than 10 minutes.
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This is getting technical !!! As I said before, I am not currently employing totally procedural separation. However, are there not other factors which could apply?
1. If, after the fix xyz (I'll assume a VOR), the aircraft tracks diverge by 45 degrees or more, those aircraft will remain separated.
2. If the second aircraft has been instructed to hold at xyz, then the ten minutes will not be infringed.
3. Otherwise, if the two aircraft will continue on the same route, I still believe that procedural separation exists up until the instant that the second aircraft reports at xyz. By then, of course, it is too late to do anything and a loss of separation is inevitable. But, if the second aircraft had been cleared to achieve vertical separation by xyz, then we're safe.
Right, I hope I've dredged that accurately from the depths of my memory. If I got it wrong, rest assured that I will not be putting anybody's life "on the line" in this way. In fact, SRG WILL NOT PERMIT anything but the simplest (ten minutes, same speed) procedural separation to be employed at LATCC in the event of a radar failure. Their view is that, as it's not a skill regularly practiced, it should either be a part of the annual ECT refresher process or not permissable.
1. If, after the fix xyz (I'll assume a VOR), the aircraft tracks diverge by 45 degrees or more, those aircraft will remain separated.
2. If the second aircraft has been instructed to hold at xyz, then the ten minutes will not be infringed.
3. Otherwise, if the two aircraft will continue on the same route, I still believe that procedural separation exists up until the instant that the second aircraft reports at xyz. By then, of course, it is too late to do anything and a loss of separation is inevitable. But, if the second aircraft had been cleared to achieve vertical separation by xyz, then we're safe.
Right, I hope I've dredged that accurately from the depths of my memory. If I got it wrong, rest assured that I will not be putting anybody's life "on the line" in this way. In fact, SRG WILL NOT PERMIT anything but the simplest (ten minutes, same speed) procedural separation to be employed at LATCC in the event of a radar failure. Their view is that, as it's not a skill regularly practiced, it should either be a part of the annual ECT refresher process or not permissable.
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Spodman
Well said. ICAO does promote this confusion, I think, by putting a double arrow on the illustrations in 4444.
Numpo
Your f'rinstances:
1. No. At the time the first passes the VOR, you have already lost separation, although I grant you, you might be able to regain it very quickly depending on particular tracks and whether DME used.
2. No. As No 1 - even if the second aircraft has been instructed to hold, you have lost 10 min longitudinal, and you can't claim 5 min from the holding pattern because the second aircraft ain't yet in the hold -he's thundering along in the same direction and eating up the space between.
3. No - see my example. You have lost separation at 1210 unless another form of separation, usually vertical, is established by that time. At 1220, the aircraft are 1½ min from collision. In the original example posed by Yeg, the situation might not be so hazardous but the principle is the same.
The variations suggested by some correspondents might seem reasonable, might be quite safe, but are not necessarily application of provable separation minima.
Well said. ICAO does promote this confusion, I think, by putting a double arrow on the illustrations in 4444.
Numpo
Your f'rinstances:
1. No. At the time the first passes the VOR, you have already lost separation, although I grant you, you might be able to regain it very quickly depending on particular tracks and whether DME used.
2. No. As No 1 - even if the second aircraft has been instructed to hold, you have lost 10 min longitudinal, and you can't claim 5 min from the holding pattern because the second aircraft ain't yet in the hold -he's thundering along in the same direction and eating up the space between.
3. No - see my example. You have lost separation at 1210 unless another form of separation, usually vertical, is established by that time. At 1220, the aircraft are 1½ min from collision. In the original example posed by Yeg, the situation might not be so hazardous but the principle is the same.
The variations suggested by some correspondents might seem reasonable, might be quite safe, but are not necessarily application of provable separation minima.
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OK 2 sheds, I concede. As I said, I'm not really up-to-speed with totally procedural control these days, and I suspect that you are much hotter on MATS Part 1 than I am. Before I slink away though, I will make a final point to reassure any visitors to this thread. It is a fact that we can always contrive, for discussion, scenarios which are potentially unsafe and yet meet the legal criteria of procedural separation. However, none of us would ever support an attempt to actually use them "for real". The bottom line is that everything is a minimum separation and we all use more whenever there is a hint of a doubt.
(edited to remove a double negative!!!)
[This message has been edited by Numpo-Nigit (edited 19 December 2000).]
(edited to remove a double negative!!!)
[This message has been edited by Numpo-Nigit (edited 19 December 2000).]
PPRuNe Bashaholic
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In YEG's example there is plenty of time to prevent a collision
At 1220, aircraft A has been flying for 10 minutes beyond the VOR (5.9 miles a minute in still air, or 59NM).
To make up that distance, aircraft B flying at 8 miles a minute is going to take 28 minutes to catch up with aircraft A.
So in the 28 minutes after B passes the VOR, aircraft A will fly a further 165NM (+ the original 59NM) taking it to 224NM from the VOR. Aircraft B will fly 224NM also.
Thank God for radar and ADS !!
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10 West
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At 1220, aircraft A has been flying for 10 minutes beyond the VOR (5.9 miles a minute in still air, or 59NM).
To make up that distance, aircraft B flying at 8 miles a minute is going to take 28 minutes to catch up with aircraft A.
So in the 28 minutes after B passes the VOR, aircraft A will fly a further 165NM (+ the original 59NM) taking it to 224NM from the VOR. Aircraft B will fly 224NM also.
Thank God for radar and ADS !!
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10 West
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Well put 2 sheds, but you are right about those arrows. I love these exchanges, really challenges your preconceptions.
Sorry Smurfjet, we have it on our "internal" internet, but I can't link you to it.
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I am not an animal, I am an ATC.
Sorry Smurfjet, we have it on our "internal" internet, but I can't link you to it.
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I am not an animal, I am an ATC.
