Why are most runways east to west ?

[PompeyPaul]

Ok, I don't get this. I've now got some more experience, I've done some more land aways, and I've now flown in the USA \ Canada and Europe.

There seems a real tendency to have runways roughly located east to west. They are always 24/06 or 27/09 type layouts.

Yes I know there are north \ south or north east \ south west runways out there but it seems where ever I fly in the northern hemisphere runways are almost always *roughly* east west. Why is this ?

I was wondering if it were due to the earth rotating to the east so we were being pushed into an eastery wind. The thing is, I always seem to spend more time flying 2* runways than 0* runways.

Maybe it doesn't mean anything and it just so happens that I've flown a LOT of 2*/0* runways. I can't help feeling though, there are far far far more 2*/0* runways than anything else so what is causing this phenomena ?

[S-Works]

Global climatology and coriolis effect.

[Cusco]

The prevailing winds in UK are mainly westerly: many single strip airfields are orientated E/W.

The classic A layout of wartime airfields was to always ensure an into wind runway and always to be able to takeoff into wind, a pretty essential requirement for fully laden bombers.

Cusco.

[Lister Noble]

An advantage for the aircraft carrier.

Also I undrstand that many early grass fields were any direction.
Lister

[pulse1]

The prevailing winds in UK are mainly westerly

While that used to be true, I am convinced that, in the last year or so, we have had more northerly or southerly winds than westerly. This is probably due to the fact that depressions which used to pass mainly to the north of the UK, now seem to travel much more south. I understood that this because the jetstreams are pushing more to the south than normal.

Or maybe I just think it is because I now fly a more limited crosswind type which is based at a field with a east/west r/w.

[172driver]

Simple answer - prevailing winds. In fact you will find that in most of western Europe the vast majority of runways is oriented roughly west-east. There are, of course, local exceptions, mostly to do with morphological features (mountains).

[n5296s]

Come to the Bay Area. Nearly everything is within 20 degrees of 12/30. Prevailing wind as the air blows in/out of the Golden Gate (and other gaps in the hills, e.g. west of Hollister).

n5296s

[youarealoooser]

Prevailing wind is fine for inland airfields. See breezes often determine the direction of runways near the coast. Best built at 90 degrees to the coast line.

[scooter boy]

Other factors like local topography have a bearing too.
Look at the runway direction at Plymouth - it is 13/31 (06/24 rarely used although I departed 06 yesterday).
Both 13 and 31 approaches are clear from the looming peaks and tors of Dartmoor which lies North East. The instrument procedures also reflect this.

Digressing slightly, it always amazes me how much our ancestors understood the weather (without recourse to the gadgetry we currently have available). You just have to consider the way farmhouses were orientated and their surrounding barns. The barns were usually planned to be wind and rain breaks and were on the "weather" side of the property - usually the South and West sides (in Cornwall).

SB

[youarealoooser]

Doesn't always follow. 3 letters..... BHX !

[betterfromabove]

Interesting exceptions in Switzerland (often orientated along valley) & Rhone Valley of France (N-S to cope with Mistral).

What's scary is how many fewer N-S runways there are than say 25 years ago in the UK. Some were inherited from the old generous WW2 fields, sure, but can anyone think of a major x-wind runway being built in the Uk since then?!?

I can think of plenty that have closed....Heathrow, Bournemouth, Norwich.

[betterfromabove]

Southampton

Actually, can anyone explain why Southampton's runway is orientated N-S?!?

Am presuming it was already pinned in by Eastleigh & the railway line when it was first built...

Anyone experience of operating a 757 in there? Looks very "interesting"!

[cats_five]

I have a feeling BHX is more N/S than E/W.

[bookworm]

Here is graphical analysis ("wind rose") of 10 years of hourly wind data for a busy international airport in Scotland.

Trust you to cloud the debate with real data, PKPF68-77.

Is there a local topographical reason for the 060 peak at the "busy international airport in Scotland" or is that a general trend?

[TheOddOne]

When planning a new runway, it used to be a reuqirement to furnish decades of 'prevailing wind' data to determine runway direction, when crosswind component was more important to commercial aircraft. however, my experiences of nearly 2 decades at a large aerodrome in the South-East with a currently 08/26 orientation was that this 'prevailing wind' idea is no longer relevant. A North-South orientation would have been much better at LGW, because whilst all the current a/c using it would have been easily able to cope with 260/10-15 winds, almost invariably the Winter lows brought surface winds of 180/30G45, a real challenge on 26L, especially coming out of the lee of 'Laker's Revenge' or Hangar 6 as it used to be called.

Generally the operational split between 26 & 08 ops at LGW was/is around 70/30 respectively. The results for LHR are slightly skewed as they operate a Westerly preference i.e. will accept up to a 5kt tailwind on 27L/R - easily accommodated by the length of the runways. The recent closure of 23 at LHR was I suppose a demonstration of the cross-wind tolerance of many modern large aircraft(05 closed many moons ago). STN's runway 05/23 remains the best dirty-weather runway in the South-East.

Of course non of the above helps us types flying a/c with a demonstrated crosswind performance of only 17kt!

TheOddOne

[Slopey]

@PKPF68-77

I'd be interested to see a wind rose for Aberdeen if you have one - every single time I've flown in and out of there in the trusty 172, there seems to be a 10kt xw.

[Slopey]

Interesting many thanks

[gasax]

Given that you have Brimmond, Elrick and Tyrebagger hills arranged along the western and south western sides of the airfield at Dyce that directionality is as expected.

However take for instance Shetland where there is precious little shelter from anything and the good old SW predominate. (As they do down along the Angus coast)

[wrecker]

I always thought it was so one could fly off into the sunset on the vernal and autumnal equinox

[deltayankee]

In north Italy, too, many strips are N-S because the prevailing wind is not wind, except for a few days in the year when it blows from the North. In the alps to the north they follow the sensible practice of aligning the strips with the valleys.