Circular runways are the answer! ?

[Jaded]

http://www.bbc.co.uk/news/magazine-39284294

A circular runway 3.5km in diameter will do the work of 4 conventional eunsways and make sure everyone living nearby gets the sane amount of noise,

[robgul]

I saw that - and wondered about the need for planes to take off into the wind to gain  lift from the aerofoil effect of the wing shape - but then I think that nowadays jets take off by use of brute force from the engines and create their own adequate lift.

Interesting concept though - probably going to go the way of the Maplin Sands airport idea.

... and if the project failed the runway would make a great velodrome

Rob

[Cudzoziemiec]

http://www.bbc.co.uk/news/magazine-39284294

A circular runway 3.5km in diameter will do the work of 4 conventional eunsways and make sure everyone living nearby gets the sane amount of noise,

The sane amount of noise is a mad idea!  I look forward to flying from Brooklands.

[mrcharly-YHT]

I wonder about the need to have defined 'paths' for aircraft after they take off. Different planes have different takeoff distances, so that's going to result in planes coming out at various tangents. What happens then? Bit of an air traffic control nightmare I would have thought.

[Andrij]

The Endless Runway Project

[Jaded]

mrc: I thought the Air traffic would be interesting!

Cudzo:

[Polar Bear]

I would imagine in reality that the runway would be segmented and various points of the runway would be fixed for navigation purposes.   Therefore it would be a 'relatively' easy task to plan an atc map based upon say 12 segments as oppose to two or three runways, each bi-directional.

With a greater variety of approach angles I would imagine that in fact there would be more distribution of the noise of take off and landing.   Some would be happier, others less so.

[Pingu]

I wonder how difficult that would be to land on.

[Torslanda]

Would it totally eliminate crosswind landings?

[Polar Bear]

I would imagine so given that you can approach it from any angle.   The interesting bit would be in countries like the UK where the wind changes direction frequently.   Would the atc systems be able to be flexible enough to move with the wind?

[ElyDave]

This is not far off an old idea from the 20s/30s, to have an elevated set of runways above King's Cross/St Pancras.  There were 3 or 4 radial runways to get around the idea of taking off into a headwing (or near as dammit) with a circular taxiway - sort of spoke and hoop idea.

That would have given a city centre airport.  For some reason the idea of planes landing over a populated area never took off (pun intended), despite what we now see with Singapore etc

[mrcharly-YHT]

"It eliminates landing with a crosswind"

How? So you approach into the wind, part way round the merry go-round your headwind is now a crosswind. Ditto on takeoff. Doesn't sound very easy for pilots to cope with.

So the runway is 3.5km in diameter. That is *MASSIVE*.

Heathrow is, what, about 2.5x1km plus some waste ground. About 2.5 sqrkm.  This proposed circular airport is 9.6sqrkm!

[mattc]

I was asumming that your landing approach is a straight-line (a tangent in this case). So you choose that direction according to wind.

But the thing is banked. Do they turn just before touchdown? Landing on anything non-flat sounds dicey to this layman, but how would I know?!

Maybe they do approach on a "merry-go-round" heading!


3.5km does seem huge - and seems to wipe out a lot of the "advantages" being claimed for this arrangement.

Still, it's always fun to see new ideas - especially ones clearly dreamed up by dutch architects high on their local produce.

[LittleWheelsandBig]

Most large expanses of asphalt or concrete in an airport have a 1% crossfall for drainage.

[ElyDave]

but that's hardly a "banking" is it, more a camber as you'd find on roads

[LittleWheelsandBig]

Normal straight road crossfall/ camber is about 2.5%

What sort of banking is being proposed for this runway?

[Cudzoziemiec]

Significant enough to call it a banking rather than a camber? The idea must be that the banking reduces the need for steering after touchdown, kind of like a wall of death.

I'm just wondering whether they'll go clockwise or anticlockwise and whether they'll actually be able to have multiple planes using the runway at the same time.

[Jaded]

Three at the same time 

Oops.. what about cross winds... 

[Cudzoziemiec]

Yeah I know they say three at the same time but I'm just wondering how it'll work if one of them lands a bit too late or takes up more than their share of slowing-down runway. Still, I guess atm it works ok with landing on straight runways while the previous plane's still at the far end.

[Greenbank]

Three at the same time 

Oops.. what about cross winds... 

With a gentle wind you can have 3 (or even 4 they say) landings at the same time, gentle cross winds aren't a problem.

With a strong wind you have to effectively cut the capacity to 2 simultaneous landings/take-offs so that one has roughly a headwind and one a tailwind upon approach. You'd line up so that you're about 10-20deg off the wind direction and so by the time you land you'd have turned a maximum of 20-40 deg and so you'd still avoid the bulk of the crosswind. By the time you've turned meaningfully into the crosswind you'd be moving slowly enough on the ground for it not to matter.

[Diver300]

I saw that - and wondered about the need for planes to take off into the wind to gain  lift from the aerofoil effect of the wing shape - but then I think that nowadays jets take off by use of brute force from the engines and create their own adequate lift.

Interesting concept though - probably going to go the way of the Maplin Sands airport idea.

... and if the project failed the runway would make a great velodrome

Rob

Tim may be along to refine my answer, but on all but stupidly powerful military planes, just about all the lift comes from wing area, angle of attack and speed though the air.  Wing cross-sectional shape adds a bit, and makes them more efficient but isn't a big effect. If it was, paper planes wouldn't fly.

Speed though the air is always important. Taking off and landing into the wind means the over-the-ground speed is reduced by the speed of the wind. The faster the plane, the smaller the fraction of take-off speed that is gained with any particular head wind, but it is always there.

A circular runway would always be used so that take-off and landing was at the point that was into the wind, if the wind speed was any significant fraction of the take-off speed. Take off and landing speeds would have to be slightly faster as some of the lift would go to cornering the plane. However, especially when the wind is light enough not to matter, having an infinite runway would take quite a bit of pressure off difficult landings and take offs.

https://www.youtube.com/watch?v=TSVC2eWO_nw

and this is what happens if you have to stop without reverse thrust, anti-lock brakes or any possibility of taking off again:-


With a circular runway, you just circle on the tarmac until dizzy you stop.

[LittleWheelsandBig]

Takeoff velocity of commercial jets is around 150 knots (77 m/s) and the radius of the circular runway is 1750m. According to https://mathtab.com/app_id=75 the required banking angle (assuming zero lateral friction) seems to be 0.33 degrees which is about 0.6%. Seeing as that is less than the normal 1% drainage crossfall, I wouldn't be too concerned about the banking. Feel free to point out where I've dropped a decimal.

Increase the banking to 1% (i.e. normal straight runway crossfall) and the runway radius can be reduced to 1000m. Given the allowable operational crosswind envelope of existing airliners, I don't think that this would be a major problem.

[caerau]

So the runway is 3.5km in diameter. That is *MASSIVE*.

And there lieth the architects' and civil engineers' wet dream

[mark]

"It eliminates landing with a crosswind"


So the runway is 3.5km in diameter. That is *MASSIVE*.

Heathrow is, what, about 2.5x1km plus some waste ground. About 2.5 sqrkm.  This proposed circular airport is 9.6sqrkm!

Looking at Google Maps, Heathrow appears to be more like 2.5 x 1, miles so 2.5 sq miles/6.5 sq km, and the owners feel the need for another runway. The closest airport to me (Denver International Airport) takes up about 4 x 5 miles, so 20 sq miles/51 sq km. Granted, efficient use of space wasn't a priority when DIA was built, but DIA is probably a better example of how much room the aviation industry feel is necessary to move lots of people efficiently.

[clarion]

Seems mad to me, but I await TimC's sage words