Separation between arrival and departure aircraft
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Separation between arrival and departure aircraft
Hi everybody:
I have a question about the separation between arrival and departure aircraft,one aircraft is on final approach while another departure aircraft is holding short of runway, at what distance for the landing one from touchdown can the tower controller authorise the departure one to get onto the runway for take off, and in this scenario, what separation standard shall the tower controller use?
Thank for any replies!
I have a question about the separation between arrival and departure aircraft,one aircraft is on final approach while another departure aircraft is holding short of runway, at what distance for the landing one from touchdown can the tower controller authorise the departure one to get onto the runway for take off, and in this scenario, what separation standard shall the tower controller use?
Thank for any replies!
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Any distance that the controller thinks that he can safely get the departure airborne, as a general rule of thumb, where I work, if the arrival is outside 3.5 miles (depending on wind conditions, weather, departing aircraft type {not a heavy} ) then it is possible to depart an aircraft ahead.
If the gap is tight then I am using reduced separation in the vicinity of an aerodrome. Some units have deemed separations between arrivals and departures in tight gaps (providing the departing aircraft is xxxx metres along the runway when the arrival reaches the threshold then they are deemed separated and a "land after the departing" clearance can be issued)
If the gap is tight then I am using reduced separation in the vicinity of an aerodrome. Some units have deemed separations between arrivals and departures in tight gaps (providing the departing aircraft is xxxx metres along the runway when the arrival reaches the threshold then they are deemed separated and a "land after the departing" clearance can be issued)
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Another question, according to ICAO, a landing aircraft cann't be directed to cross the threshold of the runway until the preceding departure one has crossed the end of runway. How to apply this rule?
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Thats what we are paid for, its basically down to judgement and experience of a/c types, wind, how confident the pilot sounds etc. And as mentioned some units don't have to worry about this as there are local procedures which allow, when certain criteria/distances are met, two a/c to be on the runway at the same time.
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according to ICAO, a landing aircraft cann't be directed to cross the threshold of the runway until the preceding departure one has crossed the end of runway. How to apply this rule?
,had such possibilities.
I can't now give you more precise answer but glimpse at new version of document and you will see it. also it is clear stated that such procedures(reduced separation between dep/arr and other combinations) must be approved by appropriate ATS authority .
Practically it means there is no reduction in separation in many countries around the world. As you may know DCAs and similar institutions aren't usually informed about problems and possibly solutions
Also I believe that set of technical devices should be employed for such procedures and that means:new procedures,tenders,corruptions, approvals....
It wouldn't work....
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Don't get confused between IFR separation (e.g. reduced separation in the vicinity of an aerodrome) and what might be called general aerodrome control, which is not quite so clearly defined.
As to the original question - local procedures may refine any rules of thumb, but the tower controller should not line up a departure unless there is sufficient time to get it away (and, technically, past the upwind end of the runway) before the inbound reaches the landing threshold. Amongst the other factors already mentioned that will affect the minimum range of the inbound I would include the location and distance from the runway of the holding point. And then add a bit for comfort incase the inbound goes around.
But as BigBoeing points out, it's largely what a controller gets paid for.
If the inbound goes around, technically it's essentially an Approach problem! Having said that, use of a reduced separation in the vicinity of the aerodrome may become very useful in such circumstances - which is why the decision whether or not there is room to get a departure away is affected by weather.
On the second question - just as you have to judge whether there is room to get the departure airborne before the inbound gets to the runway you can add a bit to let the departure get past the upwind end too. In practice though, certainly at busy airports, it seems common practice to be happy if the wheels of the departure are off the ground by the time the inbound crosses the threshold. But this means that there always has to be a plan for the go around!
As to the original question - local procedures may refine any rules of thumb, but the tower controller should not line up a departure unless there is sufficient time to get it away (and, technically, past the upwind end of the runway) before the inbound reaches the landing threshold. Amongst the other factors already mentioned that will affect the minimum range of the inbound I would include the location and distance from the runway of the holding point. And then add a bit for comfort incase the inbound goes around.
But as BigBoeing points out, it's largely what a controller gets paid for.
If the inbound goes around, technically it's essentially an Approach problem! Having said that, use of a reduced separation in the vicinity of the aerodrome may become very useful in such circumstances - which is why the decision whether or not there is room to get a departure away is affected by weather.
On the second question - just as you have to judge whether there is room to get the departure airborne before the inbound gets to the runway you can add a bit to let the departure get past the upwind end too. In practice though, certainly at busy airports, it seems common practice to be happy if the wheels of the departure are off the ground by the time the inbound crosses the threshold. But this means that there always has to be a plan for the go around!
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One mile <> one mile, you have to watch for speed on final. Also scenarios are different depending on a/c types - as Spitoon says, usually you're happy with the departing one getting its wheels up, so surely you have to judge how long a given a/c type takes to start its roll, how long will it go down the runway etc. Also, if the arriving a/c is slower (e.g. 737 departing, ATR arriving), a possible go around scenario gets easier, as it has small chance of catching up with the preceeding.
And, if we're talking about speeds, then wind comes into consideration. I did line up and depart an a/c with 767 on 2 miles, but it was doing 80kts GS due to headwind
And, if we're talking about speeds, then wind comes into consideration. I did line up and depart an a/c with 767 on 2 miles, but it was doing 80kts GS due to headwind
No passing the buck here!!
If the inbound goes around, technically it's essentially an Approach problem!
I beg to differ but if there's a go-around the tower controller has blown it and has to ensure that there is either:
- visual separation between the departing aircraft and the one going around or
- a continuing radar separation standard or
--in a non radar environment a procedural standard can be established ie the aircraft departing has left a level on climb such that there is an available level for the aircraft going around to be assigned
I beg to differ but if there's a go-around the tower controller has blown it and has to ensure that there is either:
- visual separation between the departing aircraft and the one going around or
- a continuing radar separation standard or
--in a non radar environment a procedural standard can be established ie the aircraft departing has left a level on climb such that there is an available level for the aircraft going around to be assigned
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As far as you take
The DOC4444, clearly states as per 7 10.1 Separation of landing aircraft and preceding landing and departing aircraft using the same runway
]Except as provided in 7.11 and Chapter 5, Section 5.8, a landing aircraft will not normally be permitted to cross the runway threshold on its final approach until the preceding departing aircraft has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway-in-use[/I][/B]
It depends on your skill and experience how far can you go.
]Except as provided in 7.11 and Chapter 5, Section 5.8, a landing aircraft will not normally be permitted to cross the runway threshold on its final approach until the preceding departing aircraft has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway-in-use[/I][/B]
It depends on your skill and experience how far can you go.
Last edited by Jat Jet; 16th Sep 2008 at 10:09.
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Can you get an departure A/C wheels off the ground while an landing A/C just crossing the threshold of the runway? If you do so, it turns out that you must have issued "cleared to land" to the landing one when the departure one was just on the runway, as i know, you can't issue landing clearance until the runway is clear of any traffic, and you also can't issue landing clearance as late as 2 miles from threshold, so the key point is when to issue landing clearance so that the minimum separation between depture A/C and landing A/C can be met.
There is a separation standard to be applied- check your Manual.
How that separation standard is accomplished is based on numerous factors which will determine the "runway occupany time" of the departing aircraft.
- the aircraft types concerned (speed down final and departing clias
- aircraft weight (long haul etc)
- the weather conditions (headwind, cloud base, visibility)
Taking all these into account, not only is the prescribed separation standard required at the moment of takeoff/landing of the two aircraft but the ADC must ensure that, in the event of a go around, a separation standard can be applied
eg firing a C182 with a lear on a 3 mile final might be OK in VMC because, not only will you have the prescribed standard when the Lear touches down but the C182 should be far enough out that in the event of the Lear going around instuctions can be issued to maintain visual separation. Try this in IMC and immediately the Lear has nowhere to go and the controller can't maintain separation ie
- can't maintain visual separation
- won't have 3nm radar separation (or may have but very quickly won't have)
- in a non radar environment the C182 won't be through a level which would give you an IMC assignable level to the Lear
In a nutshell then you can clear the departing aircraft for takeoff any time you like- there is no absolute cut-off. What comes with training is the judgement to know, taking into account the factors above, that the departing aircraft will land with the appropriate runway separation standard and that, in the event of a go-around, you'll be able to apply another standard between the two.
I might be teaching people how to suck eggs here, just that the original question seems to be fairly basic and I'm trying to give a fairly basic answer.
How that separation standard is accomplished is based on numerous factors which will determine the "runway occupany time" of the departing aircraft.
- the aircraft types concerned (speed down final and departing clias
- aircraft weight (long haul etc)
- the weather conditions (headwind, cloud base, visibility)
Taking all these into account, not only is the prescribed separation standard required at the moment of takeoff/landing of the two aircraft but the ADC must ensure that, in the event of a go around, a separation standard can be applied
eg firing a C182 with a lear on a 3 mile final might be OK in VMC because, not only will you have the prescribed standard when the Lear touches down but the C182 should be far enough out that in the event of the Lear going around instuctions can be issued to maintain visual separation. Try this in IMC and immediately the Lear has nowhere to go and the controller can't maintain separation ie
- can't maintain visual separation
- won't have 3nm radar separation (or may have but very quickly won't have)
- in a non radar environment the C182 won't be through a level which would give you an IMC assignable level to the Lear
In a nutshell then you can clear the departing aircraft for takeoff any time you like- there is no absolute cut-off. What comes with training is the judgement to know, taking into account the factors above, that the departing aircraft will land with the appropriate runway separation standard and that, in the event of a go-around, you'll be able to apply another standard between the two.
I might be teaching people how to suck eggs here, just that the original question seems to be fairly basic and I'm trying to give a fairly basic answer.
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Interestng response, yarra. Do you really have prescriberd separations in Oz? It may just be semantics but in the UK the books talk about separation between IFR flights and spacing for other requirements - although the only ones that come to mind are wake vortex. I mentioned earlier in this thread that 'general aerodrome control' is not well defined. ICAO Doc 4444 says
No mention of separation - just keeping it safe, orderly and expeditious. How the controller does that is largely a judgement thing.
To set out minimum requirements for all aircraft/flights seems to take half the fun out of it!
ericliu, in the UK, except in LVOs, the distance from touchdown by which a landing clearance should be issued is usually guidance. In the extreme case, as long as the clearance is issued before the wheels touch down all is OK. Of course, in normal operations landing clearances are issued before that but, again, it's a judgement thing.
7.1.1.1 Aerodrome control towers shall issue information and clearances to aircraft under their control to achieve a safe, orderly and expeditious flow of air traffic on and in the vicinity of an aerodrome with the object of preventing collision(s) between:
a) aircraft flying within the designated area of responsibility of the control tower, including the aerodrome traffic circuits;
b) aircraft operating on the manoeuvring area;
c) aircraft landing and taking off;
d) aircraft and vehicles operating on the manoeuvring area;
e) aircraft on the manoeuvring area and obstructions on that area.
a) aircraft flying within the designated area of responsibility of the control tower, including the aerodrome traffic circuits;
b) aircraft operating on the manoeuvring area;
c) aircraft landing and taking off;
d) aircraft and vehicles operating on the manoeuvring area;
e) aircraft on the manoeuvring area and obstructions on that area.
To set out minimum requirements for all aircraft/flights seems to take half the fun out of it!
ericliu, in the UK, except in LVOs, the distance from touchdown by which a landing clearance should be issued is usually guidance. In the extreme case, as long as the clearance is issued before the wheels touch down all is OK. Of course, in normal operations landing clearances are issued before that but, again, it's a judgement thing.
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you also can't issue landing clearance as late as 2 miles from threshold
Yarra, in procedural control you won't have separation even if its lear departing cessna landing...
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In the case other than reduced runway separation, twr can't issue landing clearance to the arriving A/C until the preceding departure one has lift off the ground, but what if the gap is too tight, the landing pilot decided to go around for the absent of landing clearance, what do you do to deal with this situation?
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... what if the gap is too tight, the landing pilot decided to go around for the absent of landing clearance, what do you do to deal with this situation?
As to what to do. Well, if the weather is nice and you can tell one to turn left and the other to turn right and separate them visually it's not too much of a problem - assuming they're not one above the other! In poorer weather when you can't do visual separation you may need to co-ordinate something with approach (remember, plan ahead) in case it happens. Pass traffic information to both the aircraft so that the pilots know as much as possible about the intentions of the other - again, do it when it's begining to look like it's not going to work, not as the aircraft goes around.
But most of all, don't get into that situation. Make a decision in good time - don't let it run on until you are no longer controlling events. Easy to say, and even with years of experience you can get suckered in! But as soon as you start feeling uncomfortable be ready to use plan B.
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Whenever you are controlling you have to have a way to handle things not going as you expected - in the case of arriving aircraft, always know what you will do if it goes around.
[...]
But most of all, don't get into that situation.
[...]
But most of all, don't get into that situation.
. BTW - at my place the aviation authority suggested training in re-establishing separation after it was lost. Management decided its not a good idea, as it would teach ATCo's how to circumvent separation minimaSituation from today - single runway ops, Ajet lining up with Bjet and Cjet on final. Cld for take-off (immediate), steady after 40 secs, Bjet too close, cancelled take-off and go around. Bjet turned early to allow Ajet to depart on rwy hdg before Cjet, but Ajet now deciding he needs 1 minute to prepare his departure after reclearance
, and Cjet also going around... So, to reiterate - do not line up if NOT ready (almost fully does not fit here ).
Australian Separation Standards
Yep- we have them. I thought everyone did??
Australian MATS:
Runway Separation Standards -
Take-off
10-55-410
Behind a preceding departing aircraft
Apply the 'take-off behind a preceding departing aircraft' standard to fixed wing aircraft, provided that you do not permit a departing aircraft to commence take-off unless the preceding departing aircraft:
a. has crossed the up-wind end of the runway-in-use; or
b. has commenced a turn; or
c. is airborne and has reached a point at least 1800 M (6000 FT) ahead of the following aircraft, provided the runway is longer than 1800 M (6000 FT) and the distance can be readily determined; or
d. is airborne and has reached a point at least 600 M (2000 FT) ahead of the following aircraft provided the :
1. preceding aircraft has an MTOW of 7000 KG or less
2. following aircraft has an MTOW of less than 2000 KG; and
3. following aircraft is slower than the preceding aircraft; or
e. is airborne and has reached a point at least 600 M (2000 FT) ahead of the following aircraft, provided both aircraft have an MTOW of less than 2000 KG.
Given my example of the Lear Vs C182 it's certainly possible, if the situation is reversed ie C182 on final with the Lear to go, that, in the event of the C182 going around, there would be a procedural separation standard available. Given the performance of the Lear there's a good chance it would be through A040 quickly enough to give you A030 for the C182. In a radar environment the speed differential would probably give you your required 3nm separation.
Once again the controller's judgement determines the timing of when the departing aircraft is cleared for take-off. This is where appropriate training and experience is all part of not boxing yourself into a corner with no way out. After all there's normally an easy way and a hard way to do it. Hopefully you can have a long and happy career by doing it the easy way.
Australian MATS:
Runway Separation Standards -
Take-off
10-55-410
Behind a preceding departing aircraft
Apply the 'take-off behind a preceding departing aircraft' standard to fixed wing aircraft, provided that you do not permit a departing aircraft to commence take-off unless the preceding departing aircraft:
a. has crossed the up-wind end of the runway-in-use; or
b. has commenced a turn; or
c. is airborne and has reached a point at least 1800 M (6000 FT) ahead of the following aircraft, provided the runway is longer than 1800 M (6000 FT) and the distance can be readily determined; or
d. is airborne and has reached a point at least 600 M (2000 FT) ahead of the following aircraft provided the :
1. preceding aircraft has an MTOW of 7000 KG or less
2. following aircraft has an MTOW of less than 2000 KG; and
3. following aircraft is slower than the preceding aircraft; or
e. is airborne and has reached a point at least 600 M (2000 FT) ahead of the following aircraft, provided both aircraft have an MTOW of less than 2000 KG.
Given my example of the Lear Vs C182 it's certainly possible, if the situation is reversed ie C182 on final with the Lear to go, that, in the event of the C182 going around, there would be a procedural separation standard available. Given the performance of the Lear there's a good chance it would be through A040 quickly enough to give you A030 for the C182. In a radar environment the speed differential would probably give you your required 3nm separation.
Once again the controller's judgement determines the timing of when the departing aircraft is cleared for take-off. This is where appropriate training and experience is all part of not boxing yourself into a corner with no way out. After all there's normally an easy way and a hard way to do it. Hopefully you can have a long and happy career by doing it the easy way.