Why are there delays in fog?

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Old Aug 18, 18, 8:02 pm   -   Wikipost
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This thread captures a lot of insights about some of the background factors behind delays at LHR and other airports. Here are some hyperlinks to key posts:

Why are there delays in fog? (Post 1)
Why are there delays in wind? (Post 84)
Why does it take so long to get airborne? (Post 90)
Related to the above, how is decided who gets delayed or diverted? (Post 52)
What are the different ATC roles for arrival and departure? (Post 63)
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Old Aug 19, 18, 3:42 am
  #91  
 
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Thank you for that great explanation.

I was just wondering last night how slots/timing etc all worked across so many sectors and airports.

Given CTOT works for Europe ... does it auto link into something similar for the US and AsiaPac?
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Old Aug 19, 18, 3:48 am
  #92  
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Originally Posted by Heathrow Tower View Post
The following is a simplified description. Flow control (sometimes referred to by its acronym as ATFM or ATFCM -Air Traffic Flow (Control) Measures) which forms part of the overall Network Management, is an incredibly complex beast.
By way of a housekeeping note, the above valuable insight started life in the main EC261 thread but it's probably best placed here as well. It's not specifically fog related, of course, but I think it does explain the background to what can be very tedious delays in departing European airports. Many thanks to HT for writing this up.

Edit: I've put a wiki on this thread to provide a roadmap to key posts.

Last edited by corporate-wage-slave; Aug 19, 18 at 4:07 am Reason: Mention Wiki
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Old Aug 19, 18, 3:57 am
  #93  
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Originally Posted by NoTiersForMe View Post
I was querying the other thread about impact on takeoffs during fog. You introduce concept of "free flow" in takeoff procedure at post #63 with the discussion of handover between ATC and radar in regular ops and how that might affect control of when you next give takeoff clearance to next aircraft. But in fog are we more likely to have go arounds of inbound aircraft and so that knocks on to when you handover for some [in this case] southbound departures crossing 27L. I guess I'm curious about any other fog/weather issues for takeoff. Or, simply, the delay of the inbound aircraft is biggest influence of the delay of the same plane making up the corresponding rotation outbound.
Hi NoTiersForMe.

Apologies, I've only just seen this post. If you ever get to see this then I apologise for missing it.

When controlling the departure runway, we always assume an arrival will go around. It's all part of defensive controlling, much like defensive driving: Plan for the worst.

The weather conditions don't really make a difference to this. Let's consider departures from the northern runway, taking off towards Windsor. If the departure is turning right to the north, we generally wait until hte departure is turning right, and assuming we have ther correct separation between this aircraft any any other departing aircraft, ahead or behind, then we transfer it.

For aircraft turning left (especailly those going via Dover which is quite an early left turn all the way around to head SE, we have to be a bit more cicumspect given the possibility of a missed approach from the southern runway.

For the departure, we either keep the aircraft on the tower frequency until it's well to the SW of LHR, possibily even almost directly S of us. Our radar display gives us the altitude readout of the aircraft via its transponder (Mode C for the techies!), but we need to ensure this is accurate, so a technique is to ask hte departure to report its altitude, which enables us to check the accracy of the radar for its altitude. In this case, if it's at 2000ft and climbing, and there is a missed approach, I can tell the arrivals ruwnay controller, who's sat next to me, that s/he can climb the missed approach aircraft to 2000ft. If the aircraft is climbing quickly (think A320 type rather than A380!), I can probably transfer it at that 2000ft point (once the altitude is checked). If it's a slow climbing aircraft, I might well keep it with me for a few more seconds.

I am also constantly checking the position of the possibly conflicting arrival. If there is one aircraft jsut about to touch down, and the next one is 4 miles out, then as soon as the first one lands and isn't going to go up again(!), I'll transfer the southbound as there's no a confliction will occur. It's very dynamic and there are lots of factors to think about, so it's difficult to describe on paper.

Hope that helps.

Last edited by Heathrow Tower; Aug 19, 18 at 4:05 am
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Old Aug 19, 18, 4:03 am
  #94  
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Originally Posted by MPH1980 View Post
Thank you for that great explanation.

I was just wondering last night how slots/timing etc all worked across so many sectors and airports.

Given CTOT works for Europe ... does it auto link into something similar for the US and AsiaPac?
No, not really. The flights that originate outside of the European region are considered 'out of area'. In terms of network management there is a small amount of cooperation, mainly between Europe and the USA, and Europe and the Middle East. It's growing, but it's not yet to the extent that occurs within Europe. For example, the different dates of clock changes between Europe and the USA is a usual issues, causing eastbound flights to arrive in Europe an hour earlier for a week every year, etc. City/airports pairs are also looking to cooperate more closely, for example, LHR and JFK do talk to eachother to try and mutually work out any issues between the traffic flow between those airports.
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