3 Runways on the same heading?

[doogle92]

Hi all,
question that's been pondering me for a while now and the LHR news today woke it up...there's probably a really simple answer to my question but.... Why do airports have several runways on the same heading. eg. Gatwick, Heathrow. Is this just to make landings/TOs simpler for busy airports or is there a better reason. Surely if theres a strong northerly wind, landing at LHR would be more awkward than if it head a north-ish heading runway...?
Could someone put an end to my ponders...?:confused:

[Coffin Corner]

I don't know exactly how they work out the initial runway QDMs when they first decide but obviously it must be based on some average wind direction over a given time, be that a year etc I don't know.
As for the 3rd runway at LHR why would you orientate it any differently? Because all you do here is have "conflicting" runways, so you will have to stagger the launch or landing of aircraft should the runways cross. If they are parallell then 1 shouldn't affect the other.

CC

[chiglet]

Historically, a/f runways were built into the "prevailing wind" direction. e.g.Manchester had 24/06 [southwesterly wind] Birmingham 33/15 [the prevailing wind comes via the Cheshire gap] Doncaster has 20/02...hope this helps

[philbky]

RAF airfields built from the 1920s often had a triangular runway pattern. Heathrow once had five runways - the pattern is still (just) discernable from the air.

Manchester, when under RAF control in WW2, was modified to the 3 runway pattern.

Runways are orientated to deal with the prevailing winds determined from historic data. There is a school of thought which says modern aircraft are better capable of handling cross winds than aircraft of 30 or more years ago but, outside of the UK, many airports have a number of runways with various headings and even use them at the same time (Boston, San Francisco, Dallas and Amsterdam immediately come to mind) and operations into wind are simpler and more comfortable than having to deal with crosswinds - especially if the winds are gusty.

[Rainboe]

We laughingly get told LHR is 'the busiest International Airport', but to see somewhere jaw droppingly busy, you need to stand at Chicago O'Hare on a nice evening and watch the planes all coming in for the 5 runways (I believe at the time), all being used at the same time. I think they have built one or two more since then. Then seeing at the United terminal the departures laid out as 2 @10.07, one at 10.08, 2 @10.09, 3 @ 10.10. That's busy! I once counted 25 aeroplanes visible from the ground in close proximity to the airport.

They lay out runways L, C and R. Better to have them parallel when you can so the departures and arrivals don't cross.
I don't know exactly how they work out the initial runway QDMs when they first decide but obviously it must be based on some average wind direction over a given time,
That is generally the first priority, but overriding this is the local topography and land available. This is the reason for that demented, long overdue for demolition, airport at Leeds-Bradford having a runway at 90 degrees to the prevailing wind! An airport built by civil servants to provide local jobs.......that has to be flown into by pilots (who didn't have any choice in the matter!). Ghastly place for an airport!

[DX Wombat]

Leeds-Bradford having a runway at 90 degrees to the prevailing wind! An airport built by civil servants to provide local jobs.......The runway at EGNM isn't at 90deg to the prevailing wind, the wind at Yeadon comes from multiple directions mainly from the Northwest down the Aire Valley and also down the Vale of York to the Northeast. The runway serving that direction has become a taxiway. The airport was used by AVRO to allow their locally manufactured aircraft to be flown to their military destinations during WW2.
Yeadon Airport (http://en.wikipedia.org/wiki/Leeds_Bradford_International_Airport#Early_history).

[Rainboe]

Funny the wind is almost always from the southwest....at 90 degrees to the runway!

A typical (http://uk.youtube.com/watch?v=LAljM7CaY10) Leeds landing. Whilst it is great fun for the pilots, as well as coping with a monstrous bulge in the runway and a downhill short stop, it's not really adequate for regular safe large aeroplane operations! One waits for the next overrun!

[harrogate]

The runway at EGNM isn't at 90deg to the prevailing wind, the wind at Yeadon comes from multiple directions mainly from the Northwest down the Aire Valley and also down the Vale of York to the Northeast. The runway serving that direction has become a taxiway. The airport was used by AVRO to allow their locally manufactured aircraft to be flown to their military destinations during WW2.
Yeadon Airport.

The old runway was the one used in the Avro days, and yes that was constructed specifically to accommodate the westerly prevailing wind. There is a localised airflow along the Aire Valley (as in any valley pretty much), but it's not the prevailing wind.

That said, the prevailing wind at Leeds is more westerly rather than the usual south westerly, but the current runway still doesn't accommodate this. The prevailing wind generally cuts the runway at about 60 degrees.

[Rainboe]

It makes for some 'sporting' approaches as in the video. What makes it harder is that you have to get it down on the numbers. If you float, the runway then falls down below you going steeply downhill, you're in trouble because if you then try and get it down, you are going to hit the runway hard when it goes flat again, so you try to make it gentle....which uses up runway, and then you are aware there's not an awful lot of it left. Doing all that whilst flying bizare drift in a howling crosswind. That video says it all! It's extraordinary- a triumph of council and civil servant decision making over practical considerations of 'is it actually sane to have an airport on top of a hill, in a valley, runway pointing at moors, wind always blowing across, and take-off to the NW and lose an engine- you've got a problem!

[K.Whyjelly]

I was told by some locals at LBA, many moons ago, that aircraft were built at the factory in WW11 dragged across the road to the field from whence they took off and were never seen again as they departed to their operational stations or MU's. They didn't care about the wind for landing in those days 'cos the aircraft weren't coming back........................standing by to be corrected/enlightened

[harrogate]

Ha.

Makes sense.

'cos the aircraft weren't coming back.................

The customer service function at Heathrow probably abides to the same principle*.

*Substitute 'aircraft' with 'customers'.