Lining up more than one aircraft for take-off on the same runway
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Lining up more than one aircraft for take-off on the same runway
There is a lot of pressure these days to squeeze every movement that is possible out of a runway. Even at airports that sometimes are not considered to be busy the peak periods now see delays caused by limited runway capacity. In some cirumstances one way to increase runway capacity - if the runway and taxiways are suitably configured - is to line up more than one aircraft on the runway.
The UK Manual of Air Traffic Services permits this - the relevant text is below:
Line-up instructions may be issued to more than one aircraft at different points on the same or crossing runways provided that:
a) it is during daylight hours;
b) all aircraft are continuously visible to the aerodrome controller;
c) all aircraft are on the same RTF frequency;
d) pilots are advised of the number of aircraft ahead in the departure sequence, and the position/runway from which these aircraft will depart;
e) the physical characteristics of the runway do not render preceding aircraft in the departure sequence invisible to succeeding aircraft on the same runway.
There is no guidance about how far apart the aircraft have to be when a preceeding aircraft in the sequence rolls. The rolling aircraft will generate propwash or jet eflux straight at an aircraft lined up behind. There is the risk also that debris etc. will be picked up and blown toward the aircraft behind.
Pilots I have spoken to do not have a consistent view on whether they are happy with such a line-up clearance. Some have said that there is no way that they would accept the line-up regardless of the distances involved whilst others don't see a problem and there are views in-between depending on the exact circumstances.
Just wondered whether anyone has additional guidance or experience that might help to clear up whatever safety issues there are in the procedure?
What is interesting is that it is difficult to question the wisdom of doing this without additional guidance or safety assessment - to use the current buzzwords - when Eurocontrol appears to be advocating doing it without any apparent limitations - take a look at the videos on the page. One view I've heard after viewing the videos is that if Eurocontrol says it's OK, then it must be safe.
Any other views?
The UK Manual of Air Traffic Services permits this - the relevant text is below:
Line-up instructions may be issued to more than one aircraft at different points on the same or crossing runways provided that:
a) it is during daylight hours;
b) all aircraft are continuously visible to the aerodrome controller;
c) all aircraft are on the same RTF frequency;
d) pilots are advised of the number of aircraft ahead in the departure sequence, and the position/runway from which these aircraft will depart;
e) the physical characteristics of the runway do not render preceding aircraft in the departure sequence invisible to succeeding aircraft on the same runway.
There is no guidance about how far apart the aircraft have to be when a preceeding aircraft in the sequence rolls. The rolling aircraft will generate propwash or jet eflux straight at an aircraft lined up behind. There is the risk also that debris etc. will be picked up and blown toward the aircraft behind.
Pilots I have spoken to do not have a consistent view on whether they are happy with such a line-up clearance. Some have said that there is no way that they would accept the line-up regardless of the distances involved whilst others don't see a problem and there are views in-between depending on the exact circumstances.
Just wondered whether anyone has additional guidance or experience that might help to clear up whatever safety issues there are in the procedure?
What is interesting is that it is difficult to question the wisdom of doing this without additional guidance or safety assessment - to use the current buzzwords - when Eurocontrol appears to be advocating doing it without any apparent limitations - take a look at the videos on the page. One view I've heard after viewing the videos is that if Eurocontrol says it's OK, then it must be safe.
Any other views?
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I, and my colleagues at Heathrow, used multiple line-ups without any problems. I've certainly had 4 lined up on 09R - a pretty common occurrence and it's the only real way to get traffic moving at a busy airport. I don't know what the current rules are but we could only do it by day when I was there.
aceatco, retired
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Do it often within our limited ability (Luton) with so many now willing to take the intersections and the ability to use 1 min splits. Or light acft/helicopters from the mid point.
Not counting the Red Arrows (nine lined up) I've had a line up sequence of:
One Mig 29, followed by an ATP, followed by 4 Vampires and a Venom; the latter 5 needed to line up on concrete hence the sequence; if they'd held on tarmac it would have melted!
One Mig 29, followed by an ATP, followed by 4 Vampires and a Venom; the latter 5 needed to line up on concrete hence the sequence; if they'd held on tarmac it would have melted!
niknak
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Responsibilities of Aerodrome Control are to provide a SAFE, EXPIDITOUS and ORDERLY flow of air traffic.
We use it all the time, often it's the only way to keep things sane and orderly but not at the expense of safety.
We use it all the time, often it's the only way to keep things sane and orderly but not at the expense of safety.
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Yes, also use this all the time to good effect. A very handy tool. Some points from your original post:
Our MATS2 does provide some guidance regarding whether certain entry points are too close to allow 2 aircraft to enter and line up at the same time. This however is as much to do with separation as they enter rather than jetwash.
Of course. A degree of common sense on the part of the controller and the use of experience necessary. I don't believe anyone would clear (for example) a 777 for take off with an ATR a hundred metres behind. I wonder what other experience ATCOs here have of mixing aircraft types in this way? I've only ever been taught to use my common sense and never seen any official guidance.
I suppose this is feasible. However I would be concerned if there was debris (of any shape or size) on the runway - since this may be the least of our worries.
There is no guidance about how far apart the aircraft have to be when a preceeding aircraft in the sequence rolls.
The rolling aircraft will generate propwash or jet eflux straight at an aircraft lined up behind.
There is the risk also that debris etc. will be picked up and blown toward the aircraft behind.
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Jetblast
Where a RWY is under constant visual surveilance, and (in Australia at least) inspected two or three times a day (since the concorde crash) Jet Blast collecting debris on a sealed RWY is a very minimal risk. If a pilot is not happy with a clearance then I believe the onus is on him to decline it and request an alternative.
I can clear a turbo-prop for immediate take-off, and line up an A340 at the full lenght concurrently and the Heavy will usually still roll without delay. Is a Dash 8 really going to blow FOD into an A340 that is lining up 500m behind it? Unlikely. The risk is acceptable (i.e., once in a thousand years) vs the economy achieve (the possibility of getting two away in a gap vs only one when it's marginal).
Our Manual (MATS) only requires us to pass traffic. There is a mention in another part of the document that advises against issuing an immediate take off clearance to a B747 with a lighter ACFT behind as the Jet Blast can extend as far as 600m behind.
I can clear a turbo-prop for immediate take-off, and line up an A340 at the full lenght concurrently and the Heavy will usually still roll without delay. Is a Dash 8 really going to blow FOD into an A340 that is lining up 500m behind it? Unlikely. The risk is acceptable (i.e., once in a thousand years) vs the economy achieve (the possibility of getting two away in a gap vs only one when it's marginal).
Our Manual (MATS) only requires us to pass traffic. There is a mention in another part of the document that advises against issuing an immediate take off clearance to a B747 with a lighter ACFT behind as the Jet Blast can extend as far as 600m behind.
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I think that there is a very significant difference in the runway operating mode and allowing this to occur. If the runway is departure-only, then this might be acceptable practice. If the runway is mixed mode, then it is unlikely to be acceptable. This is because you might forget at night, and then land one on approach on top of the second departure. Same applies for leaving a departing aircraft on an arrivals runway other than giving a take-off clearance in the line-up clearance.
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This is because you might forget at night,
The UK Manual of Air Traffic Services permits this - the relevant text is below:
Line-up instructions may be issued to more than one aircraft at different points on the same or crossing runways provided that:
a) it is during daylight hours;
Line-up instructions may be issued to more than one aircraft at different points on the same or crossing runways provided that:
a) it is during daylight hours;
Just wondered whether anyone has additional guidance or experience that might help to clear up whatever safety issues there are in the procedure?
Having read the above CDG Shorts fatality, it is interesting to note the recommendation 4.1.4 that a conditional clearance should be used to enhance situational awareness. This at the same time as trials are ongoing to remove use of conditional clearances from runway instructions. 
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Thanks for all the comments. My original question was not about whether it could be done - the rules quite clearly permit it subject to certain conditions - but rather whether anyone is aware of additional guidance about when not to do it. As niknak says "We use it all the time, often it's the only way to keep things sane and orderly but not at the expense of safety." but my interest is knowing when we start eating into the margins of safety.
To my simple mind there are two hazards...
First is the risk of debris causing damage to aircraft sitting behind another at take-off power. Despite regular runway inspections - and let's face it, two or three times a day is not very often, there could easily be 200 movements between inspections - small bits and pieces inevitably find their way onto a runway along with grit and grass cuttings etc. which can pebble-dash another aircraft. Maybe not a big problem but there's a small risk of something more substantial being on the runway.
The second risk is of the following aircraft being physically damaged as a result of the jet or prop wash. Ozzie ATCO asks is a Dash 8 really going to blow FOD into an A340 that is lining up 500m behind it? The answer is probably no, but it was the reverse situation that I had in mind. As hangten says, a degree of common sense on the part of the controller and the use of experience necessary. hangten also says that he/she doesn't believe anyone would clear a B777 for take off with an ATR a hundred metres behind. But the rules/guidance permit it.
But would anyone line up a C172 120m behind a B757 (a situation that is quite feasible in a number of places that I can think of)? I presume and hope that any controller will say "no, that would just be silly" but when does it stop being silly? Is that ATR Ok if it's 200m behind the B777? If you're not happy with that, how about a B737 250m behind an A330?
I am all in favour of us controllers using their common sense / training / experience to make these judgements. But I can't help feeling that some local guidance might be necessary to protect a controller that has limited experience or is just having a day when common sense is not their strong suit against the excesses of some operations managers that are pushing for every movement possible to be squeezed out of the runway.
discountinvestigator, provided the controllers are properly trained and apply it correctly there is nothing wrong with this procedure. Are we to proscribe every procedure that could possibly fail because of human error? Heavens to betsy, we'll have to stop vectoring aircraft around the sky just in case we forget to turn one before it hits another! This is why risk management is a good idea - to find out how things can fail and to do things to stop them going wrong in a catastrophic fashion.
bookworm, yes, runways are dangerous places but, with respect, of the contributors to the CDG accident I don't think that the line-up clearance was a principal factor. Of course, had the controller not given the line-up clearance in that way the chain of events leading to the accident would have been broken on that night. But then, had the controller identified the position of the aircraft before issuing the line-up clearance..... Had the controller specified the runway access point.... Had a Rapid EXIT taxiway not been used to enter the runway.... And so on. And whilst I'm almost loathe to say it, if the UK procedures had been applied in that situation I suspect that the accident would have been prevented.
To my simple mind there are two hazards...
First is the risk of debris causing damage to aircraft sitting behind another at take-off power. Despite regular runway inspections - and let's face it, two or three times a day is not very often, there could easily be 200 movements between inspections - small bits and pieces inevitably find their way onto a runway along with grit and grass cuttings etc. which can pebble-dash another aircraft. Maybe not a big problem but there's a small risk of something more substantial being on the runway.
The second risk is of the following aircraft being physically damaged as a result of the jet or prop wash. Ozzie ATCO asks is a Dash 8 really going to blow FOD into an A340 that is lining up 500m behind it? The answer is probably no, but it was the reverse situation that I had in mind. As hangten says, a degree of common sense on the part of the controller and the use of experience necessary. hangten also says that he/she doesn't believe anyone would clear a B777 for take off with an ATR a hundred metres behind. But the rules/guidance permit it.
But would anyone line up a C172 120m behind a B757 (a situation that is quite feasible in a number of places that I can think of)? I presume and hope that any controller will say "no, that would just be silly" but when does it stop being silly? Is that ATR Ok if it's 200m behind the B777? If you're not happy with that, how about a B737 250m behind an A330?
I am all in favour of us controllers using their common sense / training / experience to make these judgements. But I can't help feeling that some local guidance might be necessary to protect a controller that has limited experience or is just having a day when common sense is not their strong suit against the excesses of some operations managers that are pushing for every movement possible to be squeezed out of the runway.
discountinvestigator, provided the controllers are properly trained and apply it correctly there is nothing wrong with this procedure. Are we to proscribe every procedure that could possibly fail because of human error? Heavens to betsy, we'll have to stop vectoring aircraft around the sky just in case we forget to turn one before it hits another! This is why risk management is a good idea - to find out how things can fail and to do things to stop them going wrong in a catastrophic fashion.
bookworm, yes, runways are dangerous places but, with respect, of the contributors to the CDG accident I don't think that the line-up clearance was a principal factor. Of course, had the controller not given the line-up clearance in that way the chain of events leading to the accident would have been broken on that night. But then, had the controller identified the position of the aircraft before issuing the line-up clearance..... Had the controller specified the runway access point.... Had a Rapid EXIT taxiway not been used to enter the runway.... And so on. And whilst I'm almost loathe to say it, if the UK procedures had been applied in that situation I suspect that the accident would have been prevented.
bookworm, yes, runways are dangerous places but, with respect, of the contributors to the CDG accident I don't think that the line-up clearance was a principal factor.
I'm not suggesting that lining up more than one on the runway is to be avoided entirely -- there are inevitable trade-offs between safety and expediency. But the accident at CDG shows that it can go horribly wrong.
That, of course, doesn't really answer your question Spitoon, which was focused on minimum spacing for jet/prop wash.
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You give me line-up clearance behind another aircraft; as the aircraft commander I'll deem whether I consider it safe and I'll either accept your kind invitation or politely refuse it - simple, ain't it?
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judge11, you do not always have that option. On a runway used both for take-off and landing, with a threshold departure and an intersection departure holding, I recently had the situation where the aircraft at the threshold was given a "line up and wait" as soon as the landing a/c had passed his position, to be followed, a few seconds later, by a "line up and wait" to the aircraft holding for the intersection departure.
I was the R2160 on the intersection, and a B737 was on the threshold. I don't think my propwash did any damage to the 737, some 300 meters behind. But my point here is that both of us did not know what departure order ATC had in mind until we both had received our instructions and by then it would have been too late for the 737 to "politely refuse" - as they were already lining up.
I have read this thread with interest and am surprised that there are no guidelines for something like a "sterile area" behind various types of aircraft where the propwash or jet blast may be dangerous. And it's not just the case with being lined up on the runway. Equally, how close behind a 737 should/can I taxi in my R2160?
I was the R2160 on the intersection, and a B737 was on the threshold. I don't think my propwash did any damage to the 737, some 300 meters behind. But my point here is that both of us did not know what departure order ATC had in mind until we both had received our instructions and by then it would have been too late for the 737 to "politely refuse" - as they were already lining up.
I have read this thread with interest and am surprised that there are no guidelines for something like a "sterile area" behind various types of aircraft where the propwash or jet blast may be dangerous. And it's not just the case with being lined up on the runway. Equally, how close behind a 737 should/can I taxi in my R2160?
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Bookworm
I don't think you have picked a very good example here. Although the line up clearance to the Short 330 was not good at all ('Line up no.2'), the fact that the take-off instruction to the Air Liberte was in French probably meant that the Short crew had no situational awareness whatsoever. I think I am right in thinking from the PPRuNe thread at the time that neither spoke French.
You can do a lot with conditional/multiple line up clearances so long as you choose you words carefully and make sure everyone is in the loop.
I don't think you have picked a very good example here. Although the line up clearance to the Short 330 was not good at all ('Line up no.2'), the fact that the take-off instruction to the Air Liberte was in French probably meant that the Short crew had no situational awareness whatsoever. I think I am right in thinking from the PPRuNe thread at the time that neither spoke French.
You can do a lot with conditional/multiple line up clearances so long as you choose you words carefully and make sure everyone is in the loop.
the fact that the take-off instruction to the Air Liberte was in French probably meant that the Short crew had no situational awareness whatsoever
You can do a lot with conditional/multiple line up clearances so long as you choose you words carefully and make sure everyone is in the loop.