Movement Capacity LHR

[Mäx Reverse]

Could any of the LHR ATCOs please advise me of the number of movements (if possible divided in DEPs and ARRs) which are used for regulation purposes at LHR airport.

I'm flying for Lufthansa and passing through LHR at least 2-3 times a month and I'm always amazed how easy the traffic is flowing given all the local restriction and the incredible amount of traffic.

Now we're in a discussion with ATC at my home Airport MUC which also has two independent, paralles RWYs which are alwasy used BOTH for DEPs and ARRs (mixed mode) which in my view gives less overall capacity than LHRs segregated mode.

Any comments appreciated.

Cheers, MAX

[Gonzo]

I'm not sure, but I believe the declared capacity is 45 deps per hour, and 42 arrivals. However, we regularly exceed that...I think our 'record' hour for runway movements is 99.

[Mäx Reverse]

Thanx a lot!

Regards, MAX

[uhb129b]

My question is somewhat related to what Mäx Reverse is asking.

I am reading that the introduction of mixed mode at LHR would increase the current annual capacity of 470,000 movements to 550,000.

What would be the source of this increase?

One would think that the capacity should be higher in segregated mode, as the traffic flow is less complex.

[Del Prado]

One would think that the capacity should be higher in segregated mode, as the traffic flow is less complex

The most efficient use of the runway is for aircraft arriving and departing on one runway.
Compare Gatwick's hourly rate of well above 50 compared to Heathrow's 40-45 per runway. However the complexity of integrating traffic at Heathrow will give a movement rate somewhere between the present 87 and below the theoretical maximum of 112 per hour.

[uhb129b]

The most efficient use of the runway is for aircraft arriving and departing on one runway.

Is this explained somewhere in detail?

I see the numbers, hear the opinions from people smarter than me, I am just unable to understand why is this like that? :confused:

[choclit runway]

Because you are utilising the tarmac when, for example, a five or six mile vortex gap is required between arriving a/c by inserting a departure:D

CR

[JustaFew]

Having the procedure of 'land after the departing' helps to some extent.

[120.4]

Choclit runway has it. And at Heathrow about 30% of traffic is heavy, creating a large number of vortex gaps.

One other characteristic of mixed-mode is its resiliance to strong headwind. As the headwind increases the time interval between traffic spaced 3nm apart increases and therefore fewer aircraft per hour cross the landing threshold. As 3nm is the minimum radar separation there is noting one can legally do about it.

However, in mixed mode the longitudinal separation on final approach is well above radar minimum and so provided there is no vortex element required, the physical spacing can be legally and safely reduced with increasing wind in order to preserve an acceptable time interval (time based spacing). A mixed-mode runway does not therefore suffer in strong headwind as a segregated runway does.

.4

[A7700]

"As 3nm is the minimum radar separation "
I think Heathrow ATC is allowed until 2,5 NM on the last 10 NM leg
ICAO allows 2 NM if a local safety case demonstrate the feasibility (Need of high speed exit taxiways, radar integrity etc..)
"As the headwind increases the time interval between traffic spaced 3nm apart .."
For the annualy few days of real strong headwind, just ask the crews to keep higher indicated airspeed than as long as theA/C can do it and the difference is peanuts...The difficulty is more on the radar vectoring side when, with high wind gradients ( in force and direction) the accuracy of the sequencing from downwind to ILS interception is decreased
"in order to preserve an acceptable time interval (time based spacing.."
The last EUROCONTROL real time simulation have not proven the efficiency of the so called "time based separation"

[Del Prado]

One other characteristic of mixed-mode is its resiliance to strong headwind


The major airlines have a big problem with the robustness of landing rate at Heathrow in strong winds. Mixed mode is seen as the holy grail of maintaining a constant movement rate. However at Gatwick, when the wind is strong the movement rate goes up by maybe 10%. When mixed mode is introduced should we endevour to provide a consistent movement rate or an expeditious one?

[120.4]

A7700

3nm is the nominal standard minimum radar separation, variable under certain conditions. At Heathrow, 2.5 is the absolute minimum.

I am not aware of an ICAO approval to 2nm to the same runway and I'd be grateful for a reference on that.

"for the annualy few days of real strong headwind, just ask the crews to keep higher indicated airspeed than as long as theA/C can do it and the difference is peanuts...The difficulty is more on the radar vectoring side when, with high wind gradients ( in force and direction) the accuracy of the sequencing from downwind to ILS interception is decreased"

That is just the point. The different speed requirements between types does not permit that and there is a big debate going on about this. A BA B757 will not do 170 to 4DME. Mode S indicates they insist on slowing from 160IAS at about 5DME so that they can be stable by 1000' DH. On the other hand, the Airbuses have this Ground speed, wind-shear protection thing that stops them slowing in very strong wind.

Sound technique should overcome sequencing difficulties. E.g.
1. The use of vertical fseparation until established takes care of significant opposing base leg GS differentials; it means you can turn in tight without fear and then let the GS differential open up the gap.

2. Long final length gives up to about 3 minutes (say between 18nm and 8nm) over which 20kts speed differential can be used to tighten spacing. (That is a full mile of catchup - if you've missed by more than a mile then something may be wrong with basic technique.)

NATS' data investigations show that Gatwick is a little more resilient to strong winds than Heathrow because, operating in mixed-mode, it can reduce spacing to preserve a time interval - Heathrow cannot (legally).

Point 4

[120.4]

DP. Sorry didn't see your post

Of course, one wishes to maximise the landing rate to reduce delays. Trouble is, we've done that for years and so now the bean counters take it for granted and schedule a load more. This uses up all the spare capacity (which is a safety/service buffer) putting Heathrow in the position it is. If a service/safety buffer had been insisted upon over the years, the third runway decision would have had to have been made 15 years ago. Spare capacity is not waste - it keeps the operation robust in difficult times and that serves everybody, airlines, ATC, and Pax.

For this reason, the capacity gains of mixed-mode will not all be given to scheduling. At peak times the majority will go to reducing delays but greater increases in scheduling will be permitted off peak; the airlines have bought into this principle (for now at least).
.4

[uhb129b]

Thank you all for the answers!

I am no expert in this, and it was a novelty for me that the vortexes distinguish between arriving and departing aircraft. :-)

[120.4]

uhb12b

The reason for that is that vortex is generated as a result of lift and that ceases at the moment the nose wheel touches the ground. Under normal circumstances this will occur well before the point at which the next departing aircraft will become airborne and therefore vortex separation is not applicable. It follows that a B737 can depart as soon as a preceding, landing B747 has vacated the runway. Whereas, if they were both departures or arrivals, 2 minutes would be required.

.4

[SINGAPURCANAC]

.I think our 'record' hour for runway movements is 99.

You mean 99 operation per day/week!
Once I had 0 operation during 4 shifts( 12 hours each) and I received salary on time.
Who is better LHR ATCOs or me?

P.S. Best regards for LHR ATCOs.

[zessee]

Mr. 120.4, what is the minimum and optimum spacing between 2 arrivals currently in use by U guys to permit a departure in a mixed mode operations. Tks.

[Gonzo]

It all depends on the wind, and which runway we're using.

I've got two departures away in a 6 mile gap on 27L with a 15kt headwind

I've also decided not to go for even one departure in a 7 mile gap on 09R with no wind.

[120.4]

Zessee

Gonzo has it.

It very much depends on the wind, the aircraft types involved and, I have to say, the operators too. If the next landing aircraft is a B757 or BA146 (very slow inside 4DME) and all the operators are Heathrow based, and the wind is such that the landers are routinely making the optimum turn off, 4nm would be the absolute minimum that I would even consider; but it would very much depend on the day. At Gatwick, 2 B737s in a 6nm gap used to be routine. (I once managed 4 heavies in a 12nm gap).

The legal requirement is that the next landing aircraft doesn not cross the landing threshold unless the preceding departure is 2,000m down the runway if airborne or, 2,500m if it is still on the runway and rolling.

.4

[TopBunk]

I am now on the 744, but was previously on the 319/320/321 fleet at LHR for a local operator (so that makes me BA!).

I frequently offered to take a 'land after' clearance if the circumstances were appropriate (and ATC were usually happy enough to grant it) when (and because) I was happy with the separation, I knew performance of the aircraft I was flying, it obviated the lack of landing clearance due comms/blocked freq
etc.

I hope that this process helped both me and ATC to operate efficiently.

Translating this process to places I now fly on the 744, after a 11 hour shift, at less familiar airports, is more difficult, and the company concensus is to request vectors to an ILS.

I do not disagree. LH and SH are different due both familiarity and practice and body clock.

[zessee]

Tks 120.4 & Gonzo,

My absolute minimum is 5 NM spacing (mainly for local pilots) as our 2 rapid exits not at optimum locations. If preceding medium arrival, we are comfortable with 6-7 NM spacing but preceding heavy we are comfortable with 7-8 spacing. Of course, speed of following arrival is another major factor.

We have not implement land/depart after ... , so we are not that much off from one of the busiest airport.