The 'S' approach to LHR

Old Jun 29, 12, 1:59 am
  #1  
FlyerTalk Evangelist
Original Poster
 
Join Date: May 2007
Programs: BA Gold
Posts: 12,048
The 'S' approach to LHR

One thing I have noticed quite a few times now is that when we approach LHR from the east we circle once or twice over north-east London, then proceed due west, turn south east until due east of LHR and then turn west to approach LHR.

The whole thing looks a bit like an S, like this:

Code:
              \--------<------<----HOLDING PATTERN
                 \
                    \
                       \
LHR --<-------<---------
Why is this done? And does this type of approach have a name?
Sixth Freedom is offline  
Old Jun 29, 12, 2:12 am
  #2  
 
Join Date: Nov 2011
Location: LHR Air Traffic Control
Programs: BAEC Silver
Posts: 698
Scott can answer in more detail, but it's called a few things, usually 'tromboning'.

It is done for a few reasons:

Firstly, it keeps the aircraft within the lateral limits of the airspace designated for LHR inbounds.

Secondly, aircraft usually struggle to both descend and slow down at the same time. So even though it may be quiet and you leave Lambourne (The North-east holding stack) at 8000ft, there might not be enough distance if you turned straight for final approach to allow the aircraft to be on what we call a 'stable approach': It may not be able to get down to the required altitude quickly enough, or if it does it will be going too fast. So sometimes we add 'track miles' to an aircraft's route to allow it to maintain a constant and steady descent rate.

Thirdly, it is an efficient way of merging two streams of traffic. On your diagram, imagine another holding stack to the top left, and aircraft that leave that stack join the diagonal line in your diagram. And then imagine a mirror image of that scene to the south of LHR. Aircraft from both south and north need to be fitted into an arrival sequence, and so the northern sequence will have gaps for the south aircraft, and vice versa. Keeping the pattern similar allows an easier judgement of when to issue instructions to each aircraft to reduce speed, descend and turn to keep each aircraft in the correct position in the queue.
Heathrow Tower is offline  
Old Jun 29, 12, 2:18 am
  #3  
FlyerTalk Evangelist
Original Poster
 
Join Date: May 2007
Programs: BA Gold
Posts: 12,048
Thanks very much for that Heathrow Tower. ^

I suppose that I normally experience the north-east holding pattern because that is where I am coming from taking the great circle route (from BAH).
Sixth Freedom is offline  
Old Jun 29, 12, 2:30 am
  #4  
 
Join Date: Oct 2009
Location: Cambs
Programs: Mucci, BAEC Silver, Scandic 3rd Floor, PC Pleb, FB Off White, Tufty Club
Posts: 2,836
The vast majority of my approaches from OSL seem to follow that pattern too, except when the wind is blowing in the "wrong" direction It does afford some decent views if the cloud base is high enough. I have also noted that quite a lot of the time we seem to enter the Lambourne stack and be told by the captain/FO that we will have a 10 minute hold, only then seemingly to be cleared straight in (normally resulting in a rather hurried cabin readiness check).
FenLandK is offline  
Old Jun 29, 12, 2:43 am
  #5  
Moderator, Iberia Airlines, Airport Lounges, and Ambassador, British Airways Executive Club
 
Join Date: Feb 2010
Programs: BA Lifetime Gold; Flying Blue Life Platinum; LH Sen.; Hilton Diamond; Kemal Kebabs Prized Customer
Posts: 48,966
Originally Posted by Heathrow Tower View Post
Secondly, aircraft usually struggle to both descend and slow down at the same time. So even though it may be quiet and you leave Lambourne (The North-east holding stack) at 8000ft, there might not be enough distance if you turned straight for final approach to allow the aircraft to be on what we call a 'stable approach'.
Thank you for the interesting reply (as ever). So Lambourne is "my" main stack, which is just north of Watford. There are some other stacks that I've had the recent pleasure of exploring, what are their names? The two that come to mind are over Braintree in the north west, and over Chartwell in the south east. Do they have names too?
corporate-wage-slave is online now  
Old Jun 29, 12, 2:48 am
  #6  
FlyerTalk Evangelist
 
Join Date: Jan 2003
Location: somewhere north of London, UK
Programs: HH Gold, BA Silver, Accor Silver
Posts: 15,243
Funny, I can't recall this approach until the last time I flew into Heathrow from Zurich at the start of the month. We circled over Biggin Hill, then flew West, could see Gatwick immediately to the South, then turned right 180 degrees. Back towards Croydon then a 180 degree turn to the left to put us over Canary Wharf way.

Classic approaches I do recall are just big 180 degree turns normally from North London over to Canary Wharf, or coming over Wembley and making a 135 degree turn or so over central London.

Explanation greatly appreciated!

Last edited by Swiss Tony; Jun 29, 12 at 3:26 am
Swiss Tony is offline  
Old Jun 29, 12, 3:12 am
  #7  
 
Join Date: Jan 2009
Location: LUX
Programs: BA Gold GGL, Hilton Diamond, FB Grey, Amex MR, Trop Plus Gold
Posts: 851
The stacks are BIG (Biggin) over Biggin Hill, OCK (Ockham), and BNN (Bovingdon). LAM is NE arrivals, BIG SE, OCK SW and BNN NW
CloudGazer and george77300 like this.
Royce is offline  
Old Jun 29, 12, 3:24 am
  #8  
 
Join Date: Jan 2009
Location: LUX
Programs: BA Gold GGL, Hilton Diamond, FB Grey, Amex MR, Trop Plus Gold
Posts: 851
Originally Posted by Swiss Tony View Post
Funny, I can't recall this approach until the last time I flew into Heathrow from Zurich at the start of the month. We circled over Biggin Hill, then flew West, could see Gatwick immediately to the South, then turned right 180 degrees. Back towards Croydon then a 180 degree turn to the left to put us over Canary Wharf way.

Explanation greatly appreciated!
Seems like a reasonable routing from BIG into LHR. Over BIG, leave the hold heading 270, probably for sequencing with another a/c, rate 1 turn to the right, to take you beneath the stack (HeathrowTower: I guess this is deemed separation from those establishing on the LLZ?), then a left hand turn to where LAM and BIG streams merge. In from LUX we very regularly get this approach, even with no hold at BIG.

Edit: Here's something like what you did, probably spaced differently, as you would have been vectored. http://www.ead.eurocontrol.int/pamsl...2_EGLL_7-14_en
Royce is offline  
Old Jun 29, 12, 3:33 am
  #9  
 
Join Date: Jul 2005
Location: 64K or 2A
Programs: BA LT Gold, HH Diamond
Posts: 745
Originally Posted by corporate-wage-slave View Post
Thank you for the interesting reply (as ever). So Lambourne is "my" main stack, which is just north of Watford. There are some other stacks that I've had the recent pleasure of exploring, what are their names? The two that come to mind are over Braintree in the north west, and over Chartwell in the south east. Do they have names too?
If you're north of Watford, that's Bovingdon. Ex airfield now reduced to car boot market and prison (or similar)...
r22r44bell47 is offline  
Old Jun 29, 12, 3:45 am
  #10  
Ambassador, British Airways Executive Club
 
Join Date: Feb 2008
Location: UK
Programs: BA Gold, Mucci
Posts: 8,737
Interesting info there Heathrow Tower ^

I watched a documentary once on ATC and one of the ATC's who was being interviewed stated although you have all the flights in front of you they have to sort of 'think' in 3D to get a mental picture.

A stressful job at times I'd imgine and an awful lot of responsibilty and I think the vast majority of travellers don't appreciate how much you keep us all safe up there and on the ground. ^^^
PETER01 is offline  
Old Jun 29, 12, 4:44 am
  #11  
 
Join Date: Nov 2008
Location: London
Programs: BAEC
Posts: 912
You've only got to spend 5 minutes on flightradar24 to see what a amazing job ATC do getting everyone safely into LHR.

I have noticed there does seem to be some odd looking approach patterns some flights take. Example AA98 that's just arrived into LHR. It's done a couple of laps around South West London then flew over LHR to North London then come into land on what looks like 27R.



SIXTH FREEDOM

Think this is a perfect example of the S approach you describe.

Dover2Golf likes this.

Last edited by lancefan; Jun 29, 12 at 4:57 am
lancefan is offline  
Old Jun 29, 12, 7:41 am
  #12  
 
Join Date: Nov 2011
Location: LHR Air Traffic Control
Programs: BAEC Silver
Posts: 698
Lancefan

Sometimes it can be advantageous to take aircraft (in your case) from the south 'over the top' of LHR and then join the northern pattern. Especially if we landing on both runways at the same time (before 0700 local), so in this case your AAL98 may be planned to land on the northern runway. In such a scenario it is far better to have arrivals to the northern runway approach from the north, and vice versa, so if an particular aircraft is planned to land on the northern runway, but is in one of the southern stacks (BIG or OCK), it goes 'over the top' rather than having to cross over the other traffic out at 15 miles.

That being said, sometimes it just works out that that course of action is best. If you have a series of Heavy category aircraft inbound from the north stacks, and one Heavy to join in from the south. It might be better to take him over the top and join the back of the stream to the north.

At the end of the day, most of us ATCOs are lazy, so anything we do to lessen our workload is A Good Thing. ^
Heathrow Tower is offline  
Old Jun 29, 12, 11:17 am
  #13  
 
Join Date: Nov 2008
Location: London
Programs: BAEC
Posts: 912
Originally Posted by Heathrow Tower View Post
Lancefan

Sometimes it can be advantageous to take aircraft (in your case) from the south 'over the top' of LHR and then join the northern pattern. Especially if we landing on both runways at the same time (before 0700 local), so in this case your AAL98 may be planned to land on the northern runway. In such a scenario it is far better to have arrivals to the northern runway approach from the north, and vice versa, so if an particular aircraft is planned to land on the northern runway, but is in one of the southern stacks (BIG or OCK), it goes 'over the top' rather than having to cross over the other traffic out at 15 miles.

That being said, sometimes it just works out that that course of action is best. If you have a series of Heavy category aircraft inbound from the north stacks, and one Heavy to join in from the south. It might be better to take him over the top and join the back of the stream to the north.

At the end of the day, most of us ATCOs are lazy, so anything we do to lessen our workload is A Good Thing. ^
^ for the explanation.
lancefan is offline  
Old Jun 29, 12, 12:32 pm
  #14  
 
Join Date: Mar 2011
Posts: 384
Originally Posted by Heathrow Tower View Post

That being said, sometimes it just works out that that course of action is best. If you have a series of Heavy category aircraft inbound from the north stacks, and one Heavy to join in from the south. It might be better to take him over the top and join the back of the stream to the north.

At the end of the day, most of us ATCOs are lazy, so anything we do to lessen our workload is A Good Thing. ^
Taking an aircraft over the final approach to the other side actually increases the workload on approach as it requires a certain amount of co-ordination, both with your other approach colleagues and with the TMA. At least two extra phone calls, possibly more if there's conflicting traffic and a course of action needs to be agreed. It's not something that's done to reduce overall workload!

To be honest HT it wouldn't be done for the reason above. It's primarily done when there is a lot of traffic to come off in sequence in a row from the south stacks. The INT S Director doesn't have a lot of airspace to play with on westerlies and getting a number of aircraft from OCK and BIG into a sequence downwind can be challenging. That's when you might ask INT N if you can take one or two from OCK to the north side. It's done less frequently from north to south as INT N has more airspace to play with.

Doing it for TEAM reasons, yes possibly but not that routinely.

As for the 'S' turn. It would be possible on westerlies to feed straight in from LAM and BIG but it would require very accurate timing off the holds to have the aircraft in the right place at the right time to merge on to final. The aircraft aren't always where you want them in the hold either. The 'S' turn on westerlies allows that bit of flexibility in the timing off the stack by running traffic upwind first and then choosing the right time to turn downwind to fit in with the preceding traffic.
Scott Pilgrim is offline  
Old Jun 29, 12, 12:41 pm
  #15  
Suspended
 
Join Date: Jun 2006
Location: Earth
Programs: Proud owner of 3 Mucci's (yes, 3!) the latest being Chevaliere des Bains Chauds, BA Silver (6 yrs)
Posts: 10,985
The approach over Biggin Hill goes right over my house. I often look on Flight Radar 24 to see which flight it is.

See, even I have my geeky moments
HighwayToHEL likes this.
sunrisegirl is offline  

Thread Tools
Search this Thread
Search Engine: