Changing Ends

[rich_g85]

I was up at Leeds Bradford today and the active runway was changed from 14 to 32. All I saw was the green threshold wing bars on 14 go out and aircraft start landing on 32.

The question I'm asking is: What's actually involved 'behind the scenes' once the decision is taken to switch runways? I presume the lights need re-jigging, ATIS needs changing - what else? Who actually makes that decision (I assume the decision is made 'for' that person by the wind - but who?

One other question - a Jet2 aircraft specifically requested runway 14 (instead 32) for 'performance reasons' - Why might that be?

Thanks,
Rich

[HEATHROW DIRECTOR]

Usually its the Tower Supervisor who makes the decision based on the actual and forecast wind. For noise abatement reasons, some airfields have preferential runway directions so they will continue to use the runway under certain conditions even if the wind has "gone round".

What actually happens varies depending on the airfield. At a small airfield outside controlled airspace it may just mean ATC telephoning a few agencies, such as the AFS, and sdvising them of a runway change. Signals square (if the airfield has one) would be changed and airfield lights switched (a 2 minute job). At a major airport the change could take half an hour witj many agencies needing to be advised and liaised with. Major routes around the terminal area need to be changed, etc, etc. However, it usually runs pretty smoothly!!

[Nicholas49]

HD - this question may just be too involved to provide a brief explanation so I'll try to phrase as succinctly as possible.

When there is a runway switch at LHR, how do you prevent aircraft making their way to final approach for the 'wrong' (no longer in use) runway? Do you have to hold everyone in the holding stacks while the last landings 'filter out'? Or is it possible to synchronise the change-over while aircraft continue to leave the stacks?

Since the airport has a departure/arrival every minute or so, is there any sort of delay while the switch-over happens?

Appreciate this may be complex but very grateful for any explanation you can offer!

Nick

[HEATHROW DIRECTOR]

<<how do you prevent aircraft making their way to final approach for the 'wrong' (no longer in use) runway>>

Hi Nick. All aircraft flying into Heathrow - and the majority of other UK airports - are under radar control from take-off to touch-down so they do not make their own way to the runway. They are given instructions on altitude, speed and headings to fly to produce a landing sequence which results in a very high landing rate, even in poor weather conditions.

When a runway change is decided at Heathrow a specific time is promulgated for the change and various agencies advised. All being well that time will be the last landing in one direction followed very soon by the first landing from the other direction. The radar controllers who are directing the inbound traffic are told well in advance - maybe 30 minutes or so - of the time of the change so they can calculate which aircraft will be the last lander before the switch over. Meanwhile, they have already directed traffic off the stacks for the opposite landing direction.

The radar controllers are in constant contact with the Tower controllers and will be advised of, say, the last 4-5 departures. As the departures follow specific routes the approach radar controllers can liaise with the departure radar controllers to ensure adequate separation between the "first landers" and the "last departures". It may sound complex but it usually works quite smoothly.

There is usually a short delay during the change-round but rarely is it significant.

[WHBM]

It is not always the case that runway direction is all one way, or all the other. Here at London City it is common that sometimes crews will request a departure in the opposite direction to the standard in use; there are a range of issues that can lead to this (the "performance reasons" request described above), from the aircraft being marginal in performance in the opposite direction due to weight and temperature (the main issue being obstacle clearance minimas on climbout), through to just wanting a shorter route.

It is very dependent on there being no inbounds nearby, and the aircraft still being within any headwind limits, so a still summer day is most likely, but if they can be accomodated it will happen.

[Kestrel_Stu]

a Jet2 aircraft specifically requested runway 14 (instead 32) for 'performance reasons' - Why might that be?

This is typical at Leeds, it's all to do with them bl**dy great hills to the NW (wheras there are no obstacles to the SE as the ground falls away towards Leeds). We need to ensure a minimum climb gradient in the event of an engine failure, to clear all obstacles by a designated margin.

For our A320s with CFM engines we are restricted to around 72,600kg take-off weight from runway 32 (assuming dry, nil wind, 15 degrees).

From runway 14 however we can lift our full maximum take-off weight of 77,000kg, even with a 5 knot tailwind.

Makes all the difference when trying to get to the Canaries non-stop.

[zetland76]

But the elevation at the east end of the main runway (14-32) is about 200 metres and after 3miles the elevation drops to 60 metres in the Wharfe valley at Otley. Following the valley for another 8 miles to Ilkley it only rises to 80 metres.
About 6 miles from the runway at 280 degrees Ilkley Moor rises to 402 metres and about 10 miles at 310 degrees Beamsley Beacon rises to 400 metres.
However flying off the end of 14 takes the plane directly over the new “skyscrapers” in Leeds city centre.
I would have thought that “risk assessment” would dictate that flying off 32 and having an engine failure would be potentially less grave than flying off 14.

[captain_flynn]

Speaking of runway changes I noticed LHR has been landing planes on 27L all day today. Anyone know why the 3pm change over didnt happen?

[plumponpies]

As Kestral stu said, its about minimum climb gradients you MUST acheive in certain segments of the takeoff, particularly in the event of an engine failure. And the Chevin is right slap bang in the middle of one of those segments. Hence Rwy 32 becomes restrictive.

Aircraft Performance is a science and to explain it to a layperson, (forgive the term) would take more than a couple of paragraphs.

[HEATHROW DIRECTOR]

Captain Flynn. I don't know the answer, but possibilities are: ILS on 27R u/s, problem with lights on 27R, work in the undershoot of 27R, loss of a major runway turn-off on 27R, under certain wind conditions turbulence from the hangars can cause problems on 27R, etc, etc.... But it was probably none of those!!

[Gonzo]

under certain wind conditions turbulence from the hangars can cause problems on 27R,

Ding!..........

[captain_flynn]

Cheers guys! I was hoping one of you ATC fellas would respond. Much appreciated. :ok:

[HEATHROW DIRECTOR]

Gonzo is your actual ATC fellah... I just sit around on a rubber ring drinking Horlicks!!

[captain_flynn]

Oh sorry! Heathrow Director, I thought you was ATC at some point. :}
Thanks though guys, I appreciate the answer.