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Separation

Old 9th Oct 2020, 14:42
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Join Date: Jun 2008
Location: uk
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Separation

Just a quick one, if you take away reduced separation in the vicinity, how is an arriving aircraft (with less than prescribed Radar separation) deemed separated from departing traffic?
Example During a period of low cloud inbound >2nm (not visible) and departure just airbourne, how are they deemed separated? We seem to do this all the time in the UK at many airports but where is anything written down?
broken headset is offline  
Old 17th Oct 2020, 00:14
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Join Date: Dec 2005
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Don't know about the UK, but in En Zed when the aerodrome controller is unable to provide reduced separation (due cloud/viz/whatever) we use a table of distances under delegation from the approach unit. The distances are tailored to a particular performance group, so fast on final vs slower to depart, the distance is considerably larger than the vice versa. Typically at my unit the distances range from 4nm up to 8nm, or more for a particularly low performance departure. This is supposed to guarantee radar separation in the event the arriving aircraft makes a missed approach.
When the weather is above IFR circuit minimas for the category of aircraft, and the aerodrome controller is able to provide visual separation, everything speeds up considerably.

The procedures are aerodrome-specific.

In your situation, with a departure airborne and an arrival on 2 mile final, you're probably looking at about 3 miles between them. I don't have any idea what separation is being applied, and it would seem you don't, either.
Your unit standards officer or senior controller, or the parent approach unit should be able to answer questions around this.
One would hope.
Tarq57 is offline  
Old 17th Oct 2020, 11:48
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Join Date: Jun 2002
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In the old days I would have argued that I was applying Geographic Separation - Constant or Increasing ( speed on take off faster than approach ) and then Vertical after levels are crossed possibly followed by diverging tracks
Geographic separation used to be in our book.
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Old 17th Oct 2020, 13:12
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Join Date: Apr 2018
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There is no answer to this. It's just accepted as an ATC dogma. 😂😂 Applying the separation minima at all times would be too impractical.
The minute the inbound goes around and the departure has just taken off, you have a loss of separation. If they land, you don't.
No one knows why. It's the way it's always been and shall remain enshrined in mythology. 😂😂
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Old 17th Oct 2020, 16:20
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Not so much dogma as, in the case of the UK, the CAA never reproducing in the UK MATS the ICAO departure/arrival runway separations (applicable unless "reduced separation in the vicinity..." applies) - and then bringing them up to date for a radar/ATM environment. Historically, one reason may be that they are expressed so clumsily.

2 s
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Old 17th Oct 2020, 17:16
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Originally Posted by 2 sheds View Post
Not so much dogma as, in the case of the UK, the CAA never reproducing in the UK MATS the ICAO departure/arrival runway separations (applicable unless "reduced separation in the vicinity..." applies) - and then bringing them up to date for a radar/ATM environment. Historically, one reason may be that they are expressed so clumsily.

2 s
Is that the "landing aircraft will not be permitted to cross the runway threshold until the departing aircraft has crossed the end of the runway" bit?
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Old 17th Oct 2020, 21:07
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Originally Posted by mike current View Post
Is that the "landing aircraft will not be permitted to cross the runway threshold until the departing aircraft has crossed the end of the runway" bit?
I think you actually mean this:- "Unless specific procedures have been approved by the CAA, a landing aircraft shall not be permitted to cross the beginning of the runway on its final approach until a preceding aircraft, departing from the same runway, is airborne."

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Old 17th Oct 2020, 22:10
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Originally Posted by terrain safe View Post
I think you actually mean this:- "Unless specific procedures have been approved by the CAA, a landing aircraft shall not be permitted to cross the beginning of the runway on its final approach until a preceding aircraft, departing from the same runway, is airborne."
Yep, I was referring to the ICAO version. The one you quote (CAP 493) looks like the CAA's interpretation of the ICAO Doc 4444.
Still doesn't answer the separation question though.
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Old 18th Oct 2020, 11:12
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Is that the "landing aircraft will not be permitted to cross the runway threshold until the departing aircraft has crossed the end of the runway" bit?
No, I had in mind...
5.7 SEPARATION OF DEPARTING AIRCRAFT FROM ARRIVING AIRCRAFT

2 s
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Old 19th Oct 2020, 06:03
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Join Date: Aug 2003
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In the good old days, I trained CAA/NATS in 1980's it was always 90 deg line mid point runway and arrival sector and departing sector! I.e geographic separation. This exists fine until a go-around then we earn our ATC pay! Obviously as weather conditions go down then possible go-around needs to be factored in and this seems to change with the unit.
Plus units with multiple runways have their own separation standards. My last unit, I retired last week, a non UK unit with two staggered vortex dependant runways we operated 'segregated' in VMC i.e. normal gaps down to 3nm or less with visual separation. Then in IMC they became 'dependant' and min distance between arrivals became 5nm more normally 4nm. In LVO's this went to 8-10nm.
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Old 26th Oct 2020, 14:58
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The rules, if not using radar, is described in PANS-ATM 5.7.

The one we use is the departure may take off in a direction which is different by at least 45 degrees from the reciprocal of the direction of approach of the arriving aircraf before the arriving aircraft passes a fix, which in our case is located 5 NM from the threshold.

Rest are for us either not relevant, are downright stupid, or simply not usable.
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