View Full Version : LHR delays
spotwind
3rd Sep 2006, 17:53
Guys,
Quick question for the london ATC'ers.
Lots of delays this morning operating into LHR, slots, EAT's whilst holding etc.
The code for the slots was weather related. However, it appeared ok , maybe just a bit breezy (15- 20 knots ish)
How does this affect the flow rate when the separation looked to be the normal 3 miles?
The 3,000ft wind this morning was 270/45ish knots ergo traffic going down the approach would have had a slower groundspeed than in lighter wind conditions and so it takes a longer time to get from say 15nm on final to touchdown.
If it takes longer for each aircraft to go down the approach then you'll get less of them down in any one hour period and so if the demand is significantly greater than the landing rate being achieved flow will need to be put on to regulate said demand. Does that make sense?
Strong headwinds at altitude kill the landing rate.
HEATHROW DIRECTOR
3rd Sep 2006, 18:55
Groundspeed!
There's an echo in here...
Talkdownman
3rd Sep 2006, 19:22
As HD will love to remember, in the old days on LHR 23 (before SMF ;) and vortex wake separations) we used to pack 'em in 2 miles apart, otherwise we'd be there all day. And we could still cross tow-ers on the dual taxiways and shoot the gaps with landers on 28L. Fabulous fun! The separation of arrivals using time separation is long overdue. When are we going to be provided with the technology to be able to tell 'number 2' to 'follow the one ahead by two minutes' ? Follow my leader', pearls on a string, we can just click 'em with a mouse and just sit back and watch...........:hmm:
spotwind
3rd Sep 2006, 19:28
Thanks for that chaps... seems so obvious now you mention it !
Perhaps we should have offered 200 to 4D ;)
throw a dyce
3rd Sep 2006, 22:07
Wrong kind of wind is it?;)
HEATHROW DIRECTOR
4th Sep 2006, 06:43
Throw a dyce... Yes, but you wouldn't believe the number of airline pilots and airfield managers who simply cannot comprehend that simple fact. They rush about like headless chickens: "What's the reason for the delays?" "Why are we only landing 35 an hour?" "Can't you pack them tighter?" When a two-second glance at the anemometer (or FMS!) would answer the question.
TopBunk
4th Sep 2006, 06:53
HD
I think you'll find that most pilots think that it's ATC who aren't flexible enough on days such as yesterday. I was asked for 160kts from about 12 miles yesterday luchtime. WTF?
Why not 180 to say 6 miles then reduce to finals speed. As you say, a distance separation will give you slower flow rate UNLESS you keep the speed up to generate an equivalent groundspeed - so why do ATC slow you down earlier?
TB.....maybe you were following an AFR?:ugh:
It is not done willy nilly mate. Maybe it was a trainee.
One things for sure, it was done for a reason!
throw a dyce
4th Sep 2006, 07:50
HD,
It's a pity some of the vortex separations couldn't be reduced when it's windy,to recover some of the lost space with slow groundspeeds.The odd few miles saved could help reduce delays.The vortices may disperse quicker in rougher conditions.Just a thought but feel free to shoot me down.:)
TopBunk
4th Sep 2006, 08:01
Alan
I accept that it was obviously done with a reason - if we hadn't been slowed down we would have got to about 3 miles (ilo 2.5nm) behind a medium (not AFR) - and we were a heavy :rolleyes: .
If I'm following an AFR or IB or AZ I always get that extra twitch factor re spacing and their 160 kts to 4nm being somehow diffferent to everyone elses. This was not the case yesterday.
My general point is that ATC seem very rigid in their application of speed reduction points which in strong headwind/low groundspeed conditions does result in lower than possible flow rates. Don't get me wrong here, LHR and LGW are the best around, but it could be better with a little science applied.
Topofthestack
4th Sep 2006, 08:14
We HAVE to provide standard vortex separation WHATEVER the wind! It would be nice to have time-based separation just for those windy days but the regulators won't allow us to use it, or even define what would be acceptable. On a very windy day we could squeeze it very tight, as we used to do on RWY23, but I'm sure that some of the fly boys would be screaming about being too close. The next problem is just how do you achieve that separation, they've tried several approach sequencing tools for 'normal' weather but none of them have worked so far, so what chance is there for 'windy' days?
Gary Lager
4th Sep 2006, 08:39
I'm sure that some of the fly boys would be screaming about being too close
Nah, we'd probably just use the TCAS Traffic display to reduce speed without the need to bother ATC...
:ugh: :mad:
Yeah, 'cos that doesn't happen now! :E
Talkdownman
4th Sep 2006, 10:30
OK, well lets just get the TCAS to hold 80 seconds timing from the one ahead to achieve a rate of 45. It should be fine with types of same wake category....
throw a dyce
4th Sep 2006, 10:48
Topofthestack,
Remind me which part of the Mats part 1 vortex separation rules allows 2.5 nm spacing.I thought it was 3nm minimum.So LL reduce vortex minima already to suit themselves?:rolleyes:
Dycey..... so two "lights" need three miles VORTEX in Scotland?
Warped Factor
4th Sep 2006, 10:58
HD
I think you'll find that most pilots think that it's ATC who aren't flexible enough on days such as yesterday. I was asked for 160kts from about 12 miles yesterday luchtime. WTF?
Why not 180 to say 6 miles then reduce to finals speed. As you say, a distance separation will give you slower flow rate UNLESS you keep the speed up to generate an equivalent groundspeed - so why do ATC slow you down earlier?
The 180 to 160 speed reduction is used to fine tune the spacing.
You sometimes need that small overtake just to reduce the spacing a touch, especially if doing 2.5nm (which the weather wasn't officially suitable for the other day, cloud too low).
If you wanted to do 180 to 4 then we'd probably need to be turning you on at 200 so that we still have that 20kt differential. But whatever speed you do down final it's important that everyone does exactly the same otherwise more capacity is wasted as distance has to be provided for someone wanting to go fast behind somone wanting to go slow.
We are pretty flexible at getting the maximum number of a/c down the approach, years of experience have taught us what will work and what will not.
Time based spacing is on the back burner. The algorithms that ran FAST are still around and I believe could be adapted to provide guidance in tis respect. Be careful what you wish for...
WF.
throw a dyce
4th Sep 2006, 11:42
Alan M,
Don't remember too many Cessna's doing VFR circuits at LL.:p It would seem that 2.5nm vortex is the norm,in Southern Englandshire,between non lights on a nice day.OR is it?;)
Dyce,
Not sure of your point.
What vortex separation should we be applying between mediums? Or Heavies following Mediums?
2.5 mile vortex is not the norm. 2.5 mile spacing however, is.
Dycey boy. No - there aren't many C172 at LHR, but there are HS25s/C550etc etc.
Gonzo has given you a clue.
Re-read what you are writing before you lose any more street cred (and then surrender yourself to your LCE!!!)
:ugh: :D :bored:
Married a Canadian
4th Sep 2006, 14:33
How about allowing visual approaches into Heathrow..then asking the pilots if they are happy to follow the heavy visually with reduced separation....they can stay above the vortex and land long.
Reduces the space...increases the flow...and everyone goes home happy.:D
For our major customer, at least, landing long will get you a meeting with the boss, tea but no bicuits......
Del Prado
4th Sep 2006, 15:47
My general point is that ATC seem very rigid in their application of speed reduction points which in strong headwind/low groundspeed conditions does result in lower than possible flow rates. Don't get me wrong here, LHR and LGW are the best around, but it could be better with a little science applied.
I think it's been answered but just to clarify, the speed reduction 'point' is when you are the correct spacing behind the preceeding, it's nothing to do with geography!
HEATHROW DIRECTOR
4th Sep 2006, 15:48
Married a Canadian... Great.. best bit of humour that's been on here for a while.
A/c can fly visual approaches to Heathrow any time the weather is good enough, which isn't often!! It's OK having one follow one, but try it with 25 and watch the result.. The radar controllers can beat any "machine" so far so I don't have to say how well they could beat lots of pilots doing their own thing.
HEATHROW DIRECTOR
4th Sep 2006, 15:54
Del Prado... What do you think the ATC service does? Pilots often have clever ideas for running ATC... I showed a bunch of BA Command Course guys round Heathrow Tower once... one of them asked "Couldn't you get us to reduce speed slightly over the Atlantic to avoid holding?" And he meant it! Then there was the bloke who asked if he could see the computer that dished out all the headings we gave aircraft. I pointed to my head... but he just didn;t get it!
The "system" is based on what the majority of airlines and pilots want. If you have a better idea then you should submit it to NATS. When Concorde started some clever F/O made a barrowload of cash by coming up with "Standard approaches" so they did their own thing and avoided radar vectors. It only worked for a few weeks before they gave up and did it our way thereafter.
No HD, now they reduce speed over the Atlantic so they don't b:mad:r up the T4 parking plan! :ugh:
TopBunk
4th Sep 2006, 16:39
..which the weather wasn't officially suitable for the other day, cloud too low
SCT at 3000' when I made my approach....suitable I believe?
Be careful what you wish for...
I spent over 4 years on the Airbus at LHR and never had to go-around at LHR - I accepted/asked for quite a few 'land afters' when happy, and am (generally) happy with 2.5nm separation.
My point is that if you have a minimum spacing requirement of 2.5nm, then you can get a greater number of aircraft over that point at a greater speed in a given time.
If you have a 10kt headwind @ 160kts IAS giving a groundspeed of 150kts at 8nm finals you will get 1 aircraft per minute.
If you have a 30kt headwind @ 160kts IAS giving a groundspeed of 130kts at 8nm finals you will get 1 aircraft every 70 seconds
That is a reduction of over 15% aircraft movements per hour [given same aircraft categories all the time].
All I am saying is that we need to try to be more proactive on both sides (ATC and pilots) to try to keep the flow rates up. This is achieved by (1)varying ATC speed targets at a given range as a function of groundspeed and (2) pilots flying the required speed aaccurately.
At LHR there are certain operators who don't, but the home based guys and the regulars from KLM, Lufty, Aer Lingus, SAS do seem to cause less problems than some others:rolleyes: . I am suggesting an intelligent approach and further education where necessary to maximise the utilisation of a scarce resource until political intelligence provides extra capacity [fatchance/]
throw a dyce
4th Sep 2006, 20:47
Gonzo and Alan M,
Thanks boys point taken you're quite correct.Just in a rush to get to work.Didn't engage brain at all there.:ugh: Yes you don't need vortex behind lights and with heavies following.I also checked the AIP about your 2.5nm SPACING and it can be used where there's no vortex requirement.I thought you guys used it between mediums.:oops :ouch:
The thing I was curious is how can you use 2.5nm SPACING,when it seems the minimum radar is 3nm across the UK.Here if I used 2.5nm,after no vortex requirement,it would be certain tea and biscuits in the spanking room.Does the following a/c have to have the first visual.
Dyce,
No problem!:ok:
We can use 2.5 spacing (in fact it's still officially a trial...has been ever since I've been at LL, that's 7 and a half years) when certain conditions are met (day, dry runway, good braking action, 10kt mean headwind etc etc.). However, we are also drawing up an SI which will legitimise 2.5 separation (ICAO already does, AFAIK) outwith the conditions; when you aim for 3 miles, you'll always get the odd 2.5 miler. Obviously there will be conditions on that too, Tower will have to see them both inside 6.5DME.
Hang on, why would you rush to work??? :E
Well done mate.
It is a reduced separation standard.... like you getting the tower to say they are visual to a VFR crosser when you have IFRs in and out - as in Reduced Separatoin in the Vicinity of an Aerodrome.
You can apply to ATSSD for any relaxation of rules, as is done to allow free flow in the LHR zone during Royal Ascot, whereupon the traffic that is normally all SVFR and kept 3 miles apart flies into the zone from the boundary 4 miles away only calling Ascot Tower! (A rule 21 exemption I believe)
Interestingly, the MATS pt2 gives some criteria for it's use, namely that it is only applied to 4dme..... but then let the tower separate them! (that said, it is not just imposedon Arrivals)
I am with Gonzo; getting a piece of the good book wrong is one thing... but rushing to work?? UNFORGIVEABLE
cheers
it is not just imposedon Arrivals
cough cough :yuk: cough cough.....
throw a dyce
4th Sep 2006, 21:24
Thanks for that.Interesting.Yeah I know it's a crime to rush to work,but then we have the delights of going through BAA security on to airside.I think you guys will have that joy to come,once your new tower opens.Takes forever at the moment.Cheers
MancBoy
4th Sep 2006, 22:14
Fellas, don't jest about slowing stuff down when they are a couple of hundred miles out.
I've heard it mentioned recently of a possible solution to BA's problems of arriving too early at the hold and wasting fuel flying round in circles.
MancBoy,
Believe me, I wasn't joking.
HEATHROW DIRECTOR
5th Sep 2006, 06:42
<<I've heard it mentioned recently of a possible solution to BA's problems of arriving too early at the hold and wasting fuel flying round in circles.>>
One of the major problems in the past was good old BA asking to take up the hold when there was no delay!! They'd often go round for 15-20 mins for no reason except that "the stand isn't quite ready". As totally unbelieveable as it sounds, that is fact! I trust it doesn't happen nowadays.....
The stand still isnt ready, they just do the holding on the acres of ground space we have :ugh:
Del Prado
5th Sep 2006, 10:56
Del Prado... What do you think the ATC service does?
I think I know Bren, been doing it longer than you've been retired;) (not sure I understand your question though friend)
Top Bunk, thanks for explaining the problem, not sure you're close to a solution though.
Firstly, the point you need the 2.5mile spacing is when the first passes 4dme, your plan for higher speed approaches won't work because of the variety of aircraft we get and the inability of some (many) of those to do 180 to four miles. The different types also reduce speed at different rates, how do you suggest resolving that?
Secondly, while I have no doubt you are a very good pilot, eager to accept high speed/late landings and other clearances to expedite the traffic there are many that won't. Not just Air France but even your own airline.
Thirdly, we need to provide 3 mile radar separation on base leg then 2.5 mile spacing on finals. The timing of the turn has to be perfect, R/t discipline is just not good enough to allow us to do that anywhere near as consistently as we'd like.
Your plan might almost work if all we had were A320's from Midland, BA, Shamrock, Scandi and Lufthansa (provided they didn't start asking for 4 miles behind a 321) but there's in no way, with todays R/t standards and adherence to speed control I can see us reducing the spacing any more.
As an aside, what we achieve at the moment is pretty incredible and often done 'beyond' the rules using the vast amount of experience in the Heathrow team. I can't see that continuing if our pension continues to come under threat. The goodwill just isn't there.