How can Heathrow so many movements?
 

Hello,
I'm working on my diploma thesis dealing about the modelling of runway capacities. At the moment I'm trying to validate my simulation results with the declared capacities. Unfortunately regarding London-Heathrow, there is a rather big gap between my results and the "real life values".
When I'm right, Heathrow operates in segregated mode like ,for example, Airport Manchester as well. But how is Heathrow able to handle much more traffic (~85 in contrast to ~65 movements per hour)? Does Heathrow use speacial operations or reduced (radar/wake vortex) separations? Many thanks for your help!

One obvious difference, which you will no doubt have noticed, is that Heathrow's runways are 1400m apart, whereas there is less than 400m between those at Manchester.

if you look at the AIP they have some stuff on the special air qualities around LHR to do with wake turbulence

And you have to be an ATCO at least as cool as John Cusack or Billy Bob Thornton ;)

On a serious note, I suspect Heathrow Director or Gonzo will be along shortly to help you :ok:

As well as walking on water and feeding thousands with a few fish and a loaf, Heathrow controllers can compress time into what is know as the "Heathrow Minute".

Oh yes.... 31 seconds!

Spitfire,
notwitstanding the fact that the southerly runway at Manchester is hardly ever open these days, bear in mind the following:-

On westerly operations at manchester, all departures have to cross the landing runway to get to the departure runway.
On easterlies, all landed traffic has to taxi across the runway being used for departures.
This is not ideal and inevitably slows the movement rate down. It does not happen at Heathrow, but some crossings do occur there due to the terminal geography.

Prior to the introduction of the second runway at Manch, 54-58 movements per hour was often achieved. i believe the record stood at 60 for some time.

That was a fun hour. 28 arrivals and 32 departures IIRC. :cool:

Adding the second runway did not bring forth as many advantages in moving aircraft as you would imagine. Nearly all departures from 24L followed the same initial route (due noise abatement) and so there was little use made of the "Manchester minute" which for some reason had to be 60 seconds. The "Manchester 2 minutes" was used a lot though, and it, unsurprisingly had to be 120 seconds. 117 seconds was apparently not enough.:rolleyes:

Without wishing to get all defensive:eek:, the so-called Heathrow minute is just the use of Reduced Separation in the vicinity for departing aircraft which any airfield can do depending upon the tracks of those aircraft. For example, on easterlies a MID followed by a DVR is 2 minutes as specified in the MATS Part 2, but yesterday were being launched 'wheels up' which if they're both Medium category aircraft can be as little as 45 seconds. Visually separated until 3nm apart and diverging.

Thanks for your informative replies!

I have two additional questions:
How are the arrivals separated under VMC?
Does Heathrow use the usual 2,5/3nm radar and the wake vortex separations?

<<Does Heathrow use the usual 2,5/3nm radar and the wake vortex separations?>>

Yes but weather conditions can play a part in the final approach separations. VMC separations cannot be used in Class A airspace. Occasionally, under certain prescribed conditions, both runways may be used for landing. If the weather is good, reduced separation may be used when pilots can see other aircraft on final approach.

The arrivals are separated by either the required wake turbulence minima, or if no wake turbulence applies then the usual spacing for arrivals is 3nm applied to 4DME, which is about 2.5nm at touchdown. If we have a decent headwind, and good visibility, we apply 2.5nm radar sep to 4DME which means 2nm at touchdown visually separated.

Heathrow is not unique, Copenhagen handles in the region of 80-90 movements per hour using two runways separated by not much more than 600 m (but significantly staggered). There are three runways in total, but the crosswind is only used when it's REALLY windy.

EbonyGrove. When I worked at Kidlington in 1970 we achieved very high movement rates, far in excess of Heathrow. But there is a great deal of difference between a sky full of VFR clockwork mice and a sky full of IFR commercial jets!

Spit, Good on you - I wish you success with your thesis.

Other posters: please feel free to shoot me down - I don't want to give a young lad/lass a bum steer, and there are plenty out there with a damned sight more knowledge than me. But, for what it's worth, and in my experience, as follows:

In a 'standard' environment, an airfield with one runway handling a normal mix of traffic; turbos, medium jets and heavies can safely accommodate 40 movements per hour.

That's a real basic stat Spit, but holds true in my experience.

We then have the added levels of complexity, as alluded to by some of the brains on this thread - parallel runways, distance between runways, high-speed turn-offs, noise abatement; the list goes on. Some of these factors contribute to increased capacity, others hinder it.

The problem in 'modelling runway capacities' is that there are so many variables. And don't discount the political as regards noise abatement, which includes the politicians insisting on 'noise-sharing' that inhibits the ability of the coalface (the controllers) to move more traffic than they actually can.

Writing a thesis on this stuff, Spit, is a real challenge. Where to start and not tie yourself up in knots? How does one write a tight paper that is logical and flows?

My advice is to start with the basic stat (40 movements per hour for a single runway), then discuss variable by variable the factors that influence capacity - parallel runways etc. That will give you some structure and a starting point. You can then identify section by section those factors that increase and decrease capacity. Even then, the variables will overlap - it's a complex environment and there are no absolutes.

To the brotherhood reading this, I am prepared for incoming and have retreated with a Merlot.

Good luck Spit!

Gonzo
 

Does 'C' Watch's record total of 98 in one hour (followed by 90 and 89 in the next two hours), achieved in Summer '99 still stand?

Ask Suzy and Mike nicely and they'll tell you all about it!

Nothing compared with 60/hr single runway eh' Manch'?

I just wondered if movements may also become limited due to high cross-winds and the fact that the old 23/05 runway(s) is/are no longer available? I realise 23/05 was only used very infrequently but can an excessive cross-wind affect the movements per hour?

Not just crosswind, but headwind!

Picture an aircraft flying 160 kt to 4 nm. In an hour there could be 160 nm of arrivals spaced at 3 nm giving approx. 53 arrivals in an hour if spacing is accurate and no wake turbulence requirement exists. Now put in a mere 10 kt headwind component (at 2000 ft) gives a ground speed of 150 kt and only 50 arrivals. 30 kt headwind aloft would suggest fewer than 44 per hour!

Throw in variations of spacing and a few A380s an hour and you can see why they "only" achieve scheduling of forty something and hour.

A single runway operation can reduce delays in wind by reducing the (non-vortex) spacing to take account of the extra time between arrivals: nil wind and 7 nm required between arrivals to facilitate a departure you should manage 23 arrivals and 23 departures. If the wind increases the space required reduces so the same runway utilisation could be achieved in a 35 kt wind and 5.5 nm spacing.

Spitfire 01234
 

Don't concentrate too much on Heathrow....have a look at Gatwick who are the absolute masters of single runway operations. A comparison of peak Gatwick performance on a single runway far exceeds Heathrow's two runway equivalent. Airport design has a big impact on movement efficiency. Do some reading to brief yourself.....look at the UK AIP [google...then open IAIP]...find London Heathrow and look at the layout.....look at London Gatwick. Buy an anorak and go and watch how it all works. Don't laugh....that's how I started in the job.

In addition to the runway crossings mentioned by Zooker in Post 7 Manchester's departure routes, for environmental reasons, are not particularly good for capacity with many consecutive departures requiring longer separation intervals. Also the taxiway and stand infrastrucure could not cope with capacity levels achieved at Heathrow without getting totally clogged up. So to achieve the best capacity out of two runways you need the whole airport infrastructure and ATC procedures to be designed to match it.