about the separation between departing aircraft and the following landing aircraft

[mxwbuaa]

in chapter 8 of ICAO doc 4444 -ATS surveillance services, the separation between the departing aircraft and following arrival aircraft is not specified, so, when can the controller in tower can instruct an aircraft to take off based on the position of arrival aircraft on final ? and what's the logic behind it?

and in this article: "Two minutes are required between take-offs when the preceding aircraft is 74 km/h (40 kt) or more faster than the following aircraft and both aircraft will follow the same track" what kind of speed does it mean ? cruising speed or the actual speed in the phase of departure?
thanks!

[jmmoric]

in chapter 8 of ICAO doc 4444 -ATS surveillance services, the separation between the departing aircraft and following arrival aircraft is not specified, so, when can the controller in tower can instruct an aircraft to take off based on the position of arrival aircraft on final ? and what's the logic behind it?

and in this article: "Two minutes are required between take-offs when the preceding aircraft is 74 km/h (40 kt) or more faster than the following aircraft and both aircraft will follow the same track" what kind of speed does it mean ? cruising speed or the actual speed in the phase of departure?
thanks!

The standard surveillance separation is 5 nm, or any other depending on the minimum separation the unit has. And that is the surveillance separation between arrivals and departures as well.

What most approach controllers do, is either by standard agreement between TWR and APP, or individually, release aircraft with reference to arriving aircraft. Then the TWR controller can apply "reduced separation in vicinity of an airport", hence see both aircraft and determine there is no risk of collision, and thereby get well below normal surveillance separation.

On days with bad weather, where the "vicinity separation" also known as TWR-separation, cannot be used, there are a few "procedural separations", like the departure has to depart before the arrival reaches 5 NM final etc. Most TWR controllers will gladly accept releases with reference to arriving aircraft, and apply whatever separation is available depending on weather.

40 kts? It says 40 kts.... so the speed difference has to be 40 kts... if you take the TAS from their flightplan, I'd say you need to have a chat with your OJTI again.... But that could vary from place to place... but the way I was taught was we consider actual speed of the aircraft. (I've seen TAS from the flightplan used during basic training, just for the students to get a feel for it, and not "overburden" them)

[chevvron]

Aircraft are deemed to be separated if the distance between them is constant or increasing thus as a departure is accelerating and an arrival is decelerating, it's up to the tower controller to decide the departure separation.

[2 sheds]

Aircraft are deemed to be separated if the distance between them is constant or increasing thus as a departure is accelerating and an arrival is decelerating, it's up to the tower controller to decide the departure separation.
And your reference for that sweeping statement?

2 s

[Red Dragon]

In an ICAO environment the departing aircraft needs to have crossed the upwind end of the runway prior to the arriving aircraft crossing the landing threshold. This assumes no reduced runway separation (RRSM) is being used. How the tower controller achieves it is usually based on experience, but will be dependent on weather conditions also i.e. VMC/IMC.

[terrain safe]

In an ICAO environment the departing aircraft needs to have crossed the upwind end of the runway prior to the arriving aircraft crossing the landing threshold. This assumes no reduced runway separation (RRSM) is being used. How the tower controller achieves it is usually based on experience, but will be dependent on weather conditions also i.e. VMC/IMC.

Or on a nice sunny day: Wheels up before Wheels down! :O

[Red Dragon]

Or on a nice sunny day: Wheels up before Wheels down! :O

In the UK yes, but ICAO runway separation requires the departing to have crossed the upwind end of the runway - irrespective of the weather conditions. Quite restrictive when you've got a 4500m runway!

[Gonzo]

In the UK yes, but ICAO runway separation requires the departing to have crossed the upwind end of the runway - irrespective of the weather conditions. Quite restrictive when you've got a 4500m runway!

....as does the forthcoming EASA Part.ATS...

[jmmoric]

....as does the forthcoming EASA Part.ATS...

The "runway separation" is the only directly defined separation for us TWR controllers... technically we just have to ensure that separation.... and that goes for IFR and VFR. Though there's the either "passed the upwind, or have started a turn out", which is really helpfull when squeezing in those VFR departures.

(Other than that, we fall under the "safe, orderly and expeditious flow" and "prevent collision". But that "runway separation" is ofcourse not something approach can use as a separation (where I've worked at least), they only have the option of having tower help with the "reducing separation in vicinity of airport" for them.)

[mxwbuaa]

The standard surveillance separation is 5 nm, or any other depending on the minimum separation the unit has. And that is the surveillance separation between arrivals and departures as well.

What most approach controllers do, is either by standard agreement between TWR and APP, or individually, release aircraft with reference to arriving aircraft. Then the TWR controller can apply "reduced separation in vicinity of an airport", hence see both aircraft and determine there is no risk of collision, and thereby get well below normal surveillance separation.

On days with bad weather, where the "vicinity separation" also known as TWR-separation, cannot be used, there are a few "procedural separations", like the departure has to depart before the arrival reaches 5 NM final etc. Most TWR controllers will gladly accept releases with reference to arriving aircraft, and apply whatever separation is available depending on weather.

40 kts? It says 40 kts.... so the speed difference has to be 40 kts... if you take the TAS from their flightplan, I'd say you need to have a chat with your OJTI again.... But that could vary from place to place... but the way I was taught was we consider actual speed of the aircraft. (I've seen TAS from the flightplan used during basic training, just for the students to get a feel for it, and not "overburden" them)


but in non-radar environment or just procedural control environment , how can you know in real time the actual speed of a departing aircraft the speed of which is increasing ?

[whowhenwhy]

....as does the forthcoming EASA Part.ATS...

AltMoC can be developed to address this at those aerodromes where it might be an issue

[jmmoric]

Ask the pilot.

Thank you...

I was just about to say the same...

[Red Dragon]

Ask the pilot.

If you can't judge it visually then yes, although I've never felt the need to do that to an arrival inside 4nm or so. A knowledge of aircraft performance is usually enough and if you're fortunate enough to have radar in the tower then reference to ground speed/Mode S usually does the trick.

[chevvron]

I gave clearance for take off when arriving traffic was not less then 2.5 miles before RW (VMC). I did it for 42 years as a Tower controller.
NATS controllers at Gatwick did it at a shorter range than that; I was on the flight deck of a '737 and from 4 mile final, 3 aircraft were cleared for departure before we got landing clearance.

[2 sheds]

NATS controllers at Gatwick did it at a shorter range than that; I was on the flight deck of a '737 and from 4 mile final, 3 aircraft were cleared for departure before we got landing clearance.
All of which illustrates that Gatwick is (or was, prior to current traffic reduction) an incident waiting to happen, but does not address the OP's query.

2 s

[Del Prado]

All of which illustrates that Gatwick is (or was, prior to current traffic reduction) an incident waiting to happen, but does not address the OP's query.

2 s

thats quite a statement!

others might describe Gatwick as the worldwide standard bearer for efficient single runway operations.

[jmmoric]

4 miles final and 3 departures? That’s 3 departures in less than 2 minutes.... if your 737 is doing 120 on final, and the departures use 40 seconds to get airborne... it’s barely doable.

I’d personally believe in 2 departures.... unless something small you can get out of the way fast.

[LookingForAJob]

Radar screen: https://yadi.sk/i/bavSJqLSzXQ63A
Interesting display! What do you do with it?

[spekesoftly]

NATS controllers at Gatwick did it at a shorter range than that; I was on the flight deck of a '737 and from 4 mile final, 3 aircraft were cleared for departure before we got landing clearance.

But only two departures on this occasion? ..........

Coming back to Gatwick on a fam flight once in a 737, we were a 4 miles on 08 and they still had time to launch 2 before we got landing clearance.

[LastStandards]

Wake turbulence is an increasing threat in the training world - at one airfield in particular with a low to medium flow rate I/my student has been well inside 4nm (Light) when a departure (Medium or greater) has been released. Marginal but manageable, except we're planned/announced to go around not to land. And a reasonable headwind, putting the ensuing wake turbulence neatly in our climbout lane. Individual tower controllers vary with awareness and negotiation on this - some are excellent once the issue has been recognised by offering alternatives, others are perhaps not as aware from the training or organisational background.

Training is complex for all, but the majority of instrument training does need the full approach to be truly valid - particularly on a test where to complete an approach for my candidate they need the opportunity to fly it to procedure minima. On the flip side, while training traffic may be a little slower to respond to calls/not perfectly accurate at times, all IFR training is done with a suitably qualified adult observing/commanding, which ought to control the risk level a bit.

Really very happy to discuss this with ATCOs/arrange liaison flights once easily possibly to try and foster understanding on all sides, since ultimately we're all working towards the same aim of minimum paperwork/maximum achievement!

[mike current]

Really very happy to discuss this with ATCOs/arrange liaison flights once easily possibly to try and foster understanding on all sides, since ultimately we're all working towards the same aim of minimum paperwork/maximum achievement!

The situation you describe is just poor controlling. Wake turbulence is not optional and in real life is an MOR matter, whilst on a training course is pass/fail sort of stuff.
If controllers at your airport can't apply safe wake turbulence separation, then they need retrained!

[Gonzo]

Wake turbulence is an increasing threat in the training world - at one airfield in particular with a low to medium flow rate I/my student has been well inside 4nm (Light) when a departure (Medium or greater) has been released. Marginal but manageable, except we're planned/announced to go around not to land. And a reasonable headwind, putting the ensuing wake turbulence neatly in our climbout lane. Individual tower controllers vary with awareness and negotiation on this - some are excellent once the issue has been recognised by offering alternatives, others are perhaps not as aware from the training or organisational background.

Training is complex for all, but the majority of instrument training does need the full approach to be truly valid - particularly on a test where to complete an approach for my candidate they need the opportunity to fly it to procedure minima. On the flip side, while training traffic may be a little slower to respond to calls/not perfectly accurate at times, all IFR training is done with a suitably qualified adult observing/commanding, which ought to control the risk level a bit.

Really very happy to discuss this with ATCOs/arrange liaison flights once easily possibly to try and foster understanding on all sides, since ultimately we're all working towards the same aim of minimum paperwork/maximum achievement!

I’d recommend getting in touch with the ATC unit concerned here, to raise your concerns about wake separation between a departure and a subsequent go around.

[parishiltons]

Wake turbulence is an increasing threat in the training world - at one airfield in particular with a low to medium flow rate I/my student has been well inside 4nm (Light) when a departure (Medium or greater) has been released. Marginal but manageable, except we're planned/announced to go around not to land. And a reasonable headwind, putting the ensuing wake turbulence neatly in our climbout lane. Individual tower controllers vary with awareness and negotiation on this - some are excellent once the issue has been recognised by offering alternatives, others are perhaps not as aware from the training or organisational background.

Training is complex for all, but the majority of instrument training does need the full approach to be truly valid - particularly on a test where to complete an approach for my candidate they need the opportunity to fly it to procedure minima. On the flip side, while training traffic may be a little slower to respond to calls/not perfectly accurate at times, all IFR training is done with a suitably qualified adult observing/commanding, which ought to control the risk level a bit.

Really very happy to discuss this with ATCOs/arrange liaison flights once easily possibly to try and foster understanding on all sides, since ultimately we're all working towards the same aim of minimum paperwork/maximum achievement!
So in the second para it mentions that the scenario is IFR training. In that case, the 'go around' would be initiated no later than the MAPT, so the training aircraft should be above the departing aircraft - given that wake turbulence sinks, there should be no problem. If you are finding that departing flights have a significantly greater RoC than the training aircraft such that they are climbing through your level, then yes, some liaison with local ATC would be warranted and they could treat your flight as a departing light behind a medium > 25000kg and apply the appropriate WT standard (in my ICAO compliant country 2min or 5NM - MATS 10.6.2.1 applies).

[LastStandards]

So in the second para it mentions that the scenario is IFR training. In that case, the 'go around' would be initiated no later than the MAPT, so the training aircraft should be above the departing aircraft - given that wake turbulence sinks, there should be no problem. If you are finding that departing flights have a significantly greater RoC than the training aircraft such that they are climbing through your level, then yes, some liaison with local ATC would be warranted and they could treat your flight as a departing light behind a medium > 25000kg and apply the appropriate WT standard (in my ICAO compliant country 2min or 5NM - MATS 10.6.2.1 applies).

Indeed, that is probably the controller's expectation, not least with our slower groundspeed. The reality is that training aircraft at this particular airport (not my home base, but does have based MEP operators) are often climbing with significantly reduced performance while simulating engine failures - another discussion topic perhaps. Decent headwind days put us far closer to potential wake from 737/A320 departures cleared to an initial level 3-4000' above our cleared level.

Thanks to all agreeing that there is a potential issue here. Quiet discussions are ongoing but I would far rather educate and liaise than regulate, not least to find out what we can do better to communicate potential issues. It's not a constant issue at the airport in question but is notable because it's the only airfield I use regularly where I've had to consider negotiating an early turn etc 4 times in the last 2 years - statistically insignificant, but more exciting for us. Also worth noting that tower ATCOs have recognised the issue every time at a late stage, so awareness does exist, but indicative of complexities when mixing medium, heavy, light, and training traffic in reasonably close proximity. Worst case would be for the airfield to stop accepting training traffic due to workload/risk!

[Lissart]

Great post from LastStandards - and yes, there IS an issue here. A big one..... There is no excuse for any controller not having a grasp of the risks involved with wake turbulence, even if the exact scenario is not quite as described in MATS1.

While I would acknowledge that if able, then the training scenario to which the instructor is working should be respected and granted. If for no other reason than simple politeness. If able... But training flights are a lesser flight priority than Normal Flights. That is a fact and should be borne in mind by both parties. At my last station, this was not the case and scheduled traffic would be held on the rwy - sometimes for up to 5 minutes - waiting for a release from radar while a trainer went around not below 700', asymetric, standard missed etc. Really got me irritated as not expeditious. No attempt being made to come up with a solution to limit the delay. (Plenty of options!)

I also recall at a beloved former station, when as a relatively newly validated tower controller it really started to kick off. I forget the exact details, apart from the fact that in the middle of all this chaos going on on the ground with departures etc. there was a DA42 bimbling down the approach. EXAM callsign, IFR check-out. Whatever and why ever, he was getting closer and closer to his go around. In the end - when I finally got around to it! - he got the "Cleared to land, land only" call. This was a piece of phraseology we used, maybe not frequently, but when wake turbulence was obviously an issue. In this case it clearly was. The examiner came back - and no doubt trying to help me out as it was obvious I was really busy - said he was happy to accept and early left, visual, and to apply his own wake turbulence separation. Unfortunately, WT is NOT at the discretion of ATC (or instructors...) so he got a negative. The student performed a perfect landing, taxied round and departed again in total safety.

The point of my post is thus that while we should all try and accommodate all requests it is not always possible. Training flights have to accept this - and their lower priority - and I'd suggest that there is excellent training value to be gained from being prepared as much as possible for ALL eventualities. Go-arounds when the mind-set is to land, landings when the mind-set is for the go-around. (What, prey, happens when on applying GA power, splutter, splutter - engine dies? !!) And all variations in between.

And before anyone chips in and reminds me, I am well aware that EXAM callsigns are the same priority as normal flights! But my example is offered to illustrate real life.

I phoned the flight school later and spoke to the examiner. The student passed with flying colours, he being particulary impressed with how he handled something unforeseen being thrown at him!!!!!!!!

[parishiltons]

Indeed, that is probably the controller's expectation, not least with our slower groundspeed. The reality is that training aircraft at this particular airport (not my home base, but does have based MEP operators) are often climbing with significantly reduced performance while simulating engine failures - another discussion topic perhaps. Decent headwind days put us far closer to potential wake from 737/A320 departures cleared to an initial level 3-4000' above our cleared level.

Thanks to all agreeing that there is a potential issue here. Quiet discussions are ongoing but I would far rather educate and liaise than regulate, not least to find out what we can do better to communicate potential issues. It's not a constant issue at the airport in question but is notable because it's the only airfield I use regularly where I've had to consider negotiating an early turn etc 4 times in the last 2 years - statistically insignificant, but more exciting for us. Also worth noting that tower ATCOs have recognised the issue every time at a late stage, so awareness does exist, but indicative of complexities when mixing medium, heavy, light, and training traffic in reasonably close proximity. Worst case would be for the airfield to stop accepting training traffic due to workload/risk!
Absolutely - communication is way better than quoting the rules to each other at 10 paces. Suggest you set up a meeting between your organisation (and any other training organisations that conduct similar operations), and the local ATC check and standardisation people and operations supervisors. The outcome could a a letter of agreement or something similar that puts parameters around how your operations are interfaced with other traffic. The alternative is to risk having training operations restricted. Hope it works out for you.

[chevvron]

4 miles final and 3 departures? That’s 3 departures in less than 2 minutes.... if your 737 is doing 120 on final, and the departures use 40 seconds to get airborne... it’s barely doable.

I’d personally believe in 2 departures.... unless something small you can get out of the way fast.
All 3 departures were 737s, the first was rolling as we hit 4nm; the second was cleared as soon as the first was airborne and I was pretty amazed when the third was then cleared, however we still got landing clearance by about 1.5nm; don't ask me what departure separations were used as I don't know however my crew said similar situations were not unknown.
I'd call it good runway utilisation.
On another fam flight departing 08R in a 737, the captain wound it up to about 50% before we even turned onto the runway so maybe these guys were doing the same.

[ILS27]

All 3 departures were 737s, the first was rolling as we hit 4nm; the second was cleared as soon as the first was airborne and I was pretty amazed when the third was then cleared, however we still got landing clearance by about 1.5nm; don't ask me what departure separations were used as I don't know however my crew said similar situations were not unknown.
I'd call it good runway utilisation.
On another fam flight departing 08R in a 737, the captain wound it up to about 50% before we even turned onto the runway so maybe these guys were doing the same.

I 'd call it mass murder awaiting to happen.
unless you had Huracan Katrina on your nose on final approach, and even then ....

[alfaman]

I 'd call it mass murder awaiting to happen.<br />unless you had Huracan Katrina on your nose on final approach, and even then ....<br />A bit of an exaggeration: if it's within the unit safety case, then it's safe to use. If it isn't, there'll be safety reports to explain why it happened, &amp; how to avoid it happening again. Unless you know the unit &amp; the requirements, you're not really in any position to judge...<br />

[ILS27]

<br />A bit of an exaggeration: if it's within the unit safety case, then it's safe to use. If it isn't, there'll be safety reports to explain why it happened, &amp; how to avoid it happening again. Unless you know the unit &amp; the requirements, you're not really in any position to judge...<br />

eeeehhh, no....sorry ....I don't think so.

As a matter of fact I AM in a position to judge.

At 4 NM and even with a VERY strong headwind component on a B737 on final app you are talking of aprox. 2-3 MINS to the threshold. AND EVEN if that's the case you are looking for trouble, as you are relying on 3 pilots, 3 planes and a lot of other factors with no surprises.

And any safety management system, or manual for ATS operation, or safety case, that tells you is OK to launch THREE a/c when a jet a/c l is at 4NM on finals should be brought to a court of room straight away charged with attempted mass murder, and convicted to be hanged by their covers...

And good luck trying to find one that states such an insanity.