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Separation SID's with same initial segment

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Separation SID's with same initial segment

Old 4th Sep 2019, 20:36
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Separation SID's with same initial segment

Hi all,

Not new here, but now with an account . I have a question regarding the minimum departure separation is used by different ANSP's. How do you guys sequence and separate the following;

What if some of the SIDs for a specific runway have the same 'initial segment' before turning towards their specific basic indicator. Do you use the same time separation as considered for the same SIDs flown by aircraft behind each other in the departure sequence? For instance;

SID A1B: after departure climb straight ahead, at 2 'XXX' DME 2 turn left to track 045 and intercept 'ZZZ' R-180 proceed to 'QQQ' and proceed to 'GGG'.
SID B1B: after departure climb straight ahead, at 2 'XXX' DME 2 turn left to track 045 and intercept 'ZZZ' R-180 proceed to 'QQQ' and proceed to 'LLL'.

Initial segment is exactly the same, but they are considered as 'different' SIDs. How are those separated? 1 or 2 minutes? And to be sure I am NOT talking about wake turbulence minima.

Thanks all for the information and reply
ATCOEHAM is offline  
Old 5th Sep 2019, 20:18
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More than likely same track and therefore at least 2 minutes but what is the runway layout for the A1B and B1B SIDs? It also depends on speeds, in the UK for instance, the time for successive departures depends on speed, some countries are less concerned by this and rely on Radar separation very soon after departure.
Rwy1234 is offline  
Old 5th Sep 2019, 20:51
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Departure separations are usually laid down in the local orders.
HEATHROW DIRECTOR is offline  
Old 6th Sep 2019, 06:30
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Very much dependent on runway config. Most airports that share the runways for arrivals and departures will rarely have to wait to launch another departure.

Unless A380s are involved, the arrival sequence will usually allow the Tower to depart one aircraft in between successive arrivals. This creates a natural gap of 2 mins/5nm that are utilised at many capitol city airports.
Maggie Island is offline  
Old 6th Sep 2019, 07:32
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Cool, thanks!! And what is your way of working with different SIDs on the same rwy turning left and right but only the initial climb out track X DME from the field is the same? Do you also consider that as 2 minutes? Suggest me that if so you are almost never allowed to separate only 1 minute, only when sending them left or right after departure or to apply level separation.
ATCOEHAM is offline  
Old 6th Sep 2019, 08:12
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Join Date: Jul 2018
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'Diverging' SIDs usually separate within the first couple of miles. Your example, where they both go to "QQQ" before separating, sound like they share the same track for quite a few miles. The airport would probably consider them the same SID, so a common time separation would be 2 minutes (for similar performance aircraft).
flightcatcher is offline  
Old 6th Sep 2019, 09:00
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Assuming you have a radar environment wouldn't you be using that? 3/5nm until they diverge?

Guess it all depends on how far they would fly on the same track.
Gonzo is offline  
Old 7th Sep 2019, 08:40
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Thank you all! Useful information
ATCOEHAM is offline  
Old 8th Sep 2019, 01:12
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Even though most of our SIDs are RNAV, the turn off the initial heading is controller initiated at 3600' (noise) or later. Tower will provide 3nm between successive departures unless a following departure is either turned immediately or is using pilot applied visual separation. Visual separations can be spectacularly small in some cases! The only timed separations we use are those required when following an A380.
cossack is offline  

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