Circular runways proposal

[yorkie]

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

Could circular runways be the future of air travel? Aviation expert Henk Hesselink of the Netherlands Aerospace Centre believes so.

The circular runway is equivalent in length to 3 straight runways but the team calculate it can handle the work of 4 normal runways

What do the aviation experts/enthusiasts here think of this?

 

[D365]

As a mere passenger, I certainly don't like the sound of that

 

[Peter Mugridge]

That's going to put a lot of additional stress on the tyres for a start. Think of what going round a roundabout does to your car tyres. The curvature on these circular runways may not be that severe, but the speeds and masses involved are somewhat... high. On top of that there would be a high risk of going off the outside of the runway, especially when it rains.

 

[Hornet]

He is 50 years too late.

Popular Science Jun 1966 Pg76/77.

Coming:- Airports shaped like wheels.

https://books.google.es/books?id=2C...rcular runway in US military-aviation&f=false

The boys on PPRUNE are not too impressed.

 

[Domh245]

What a daft idea. Approach and then flare + roll to the right angle for the runway.
Would you have to approach it on a curved trajectory?
How would ILS and other approach systems work?
What about gusty conditions? You'd easily take the wings off.

 

[edwin_m]

All you have to do is tie a piece of string onto the relevant wing and attach the other end to a big hook in the centre.

 

[Tetchytyke]

April 1st is in a couple of weeks isn't it?

 

[AlterEgo]

This is an incredibly daft proposal. All of the problems are so obvious they don't even deserve to be pointed out!

 

[daikilo]

This is an incredibly daft proposal. All of the problems are so obvious they don't even deserve to be pointed out!

Well, might be good to get the BBC to point out that the guy presenting it wasn't being serious, or if he was he is naive!

For info, MLS can apparently do curved approaches as presumably could a GPS approach. Not that it appears to matter as his concept appears to be to fly straight until near touchdown.

 

[Spartacus]

It's not going to be much fun heading down the runway with an ever changing wind direction......

 

[button_boxer]

It's not going to be much fun heading down the runway with an ever changing wind direction......

Although presumably once you get used to it it means that takeoffs will be the same whatever way the wind is blowing, if you use whichever part of the circle takes you directly into the wind at the point of takeoff. No dealing with a different type of crosswind each time.

 

[Deepgreen]

That's going to put a lot of additional stress on the tyres for a start. Think of what going round a roundabout does to your car tyres. The curvature on these circular runways may not be that severe, but the speeds and masses involved are somewhat... high. On top of that there would be a high risk of going off the outside of the runway, especially when it rains.

As the runway would be canted rather like a car test track, the forces would not be lateral, but downwards as the aircraft gained speed and would be pressed down ever more strongly. All the other insurmountable problems aside, of course...

 

[Peter Mugridge]

You could say it is, quite literally, a loopy idea.

 

[shredder1]

Won`t the pilot get dizzy

 

[DynamicSpirit]

What a daft idea. Approach and then flare + roll to the right angle for the runway.

Well the story indicates that it's the work of a research team based at the Netherlands Aerospace Centre. I'm not an expert in that area, but the website looks like a reasonably legitimate organisation, which suggests that they would've done their research reasonably well, so perhaps the idea isn't that daft - although it certainly does raise a lot of questions.

Would you have to approach it on a curved trajectory?

Would it be a huge problem if you did?

But offhand I don't see any reason why the runway being curved would mean you'd need to approach on a curved trajectory. Presumably, you'd simply aim at the right bit of the runway and descend in a straight line to that point. The main issue I can see is that you'd have to be pretty accurate: Overshoot and you'd presumably have to abort the landing because the runway will have curved away from you. Ditto if you undershoot. With a straight runway, you clearly have a greater margin for error in that regard. But then I don't know how accurate landings are? Are modern aircraft/guidance systems sufficiently accurate in landing for that not to be an issue? Similarly for take-off, if you get the point of actually leaving the runway long, you'll end up taking off in (slightly) the wrong direction, though I'm guessing that's not really much of an issue - easy to correct once you're off the ground.

On the other hand, I don't know if the runway being canted would be an issue. Presumably the aircraft would have to be canted to match at the moment it touches down? (Would that be a reason for flying in on a curved trajectory after all?)

 

[DynamicSpirit]

As the runway would be canted rather like a car test track, the forces would not be lateral, but downwards as the aircraft gained speed and would be pressed down ever more strongly. All the other insurmountable problems aside, of course...

That's roughly true, but I see a problem. The lateral force only vanishes at a particular speed. Since aircraft accelerate and decelerate considerably on the runway, you'd therefore only have no lateral force for a brief moment (presumably, you'd design the runway so that moment occurs about halfway through take-off/landing - which would mean that maximum lateral force experienced during take-off/landing is still considerably less than it would've been without a cant.)

If my algebra is correct, the speed for no lateral force is v= sqrt(g * r * tan theta), where g is the acceleration due to gravity, r is the radius of the runway circle, and theta is the angle of the cant from the horizontal.

 

[daikilo]

That's roughly true, but I see a problem. The lateral force only vanishes at a particular speed. Since aircraft accelerate and decelerate considerably on the runway, you'd therefore only have no lateral force for a brief moment (presumably, you'd design the runway so that moment occurs about halfway through take-off/landing - which would mean that maximum lateral force experienced during take-off/landing is still considerably less than it would've been without a cant.)

If my algebra is correct, the speed for no lateral force is v= sqrt(g * r * tan theta), where g is the acceleration due to gravity, r is the radius of the runway circle, and theta is the angle of the cant from the horizontal.

And to complicate matters, lift-off and touch-down speeds are variable for a given aircraft, for a given weight and between aircraft. In addition, as happens on car tracks the banking is in fact a curve in the vertical dimension, you progressively accelerate up the banking / decelerate down it so the runway "width" would be impressive.

 

[edwin_m]

If an aircraft is banked it will naturally turn in that direction, because the lift force from the wings is acting at an angle rather than straight up. It has to be counteracted (by rudder I think) if the aircraft is to fly banked but in a straight line, which suggests that takeoff and landing would be curved.

The lift force being non-vertical also means that the total lift force would have to be greater to counteract the weight of the plane, so take-off and landing speeds would be greater leading to higher fuel consumption. I think it would have to be designed so the planes took off and landed close to the equilibrium speed for the banking.

 

[jon0844]

How good is such a design for a plane needing to make an emergency landing? It would seem, to a non expert like me, that it would make things a lot more complicated and potentially dangerous.

Looking on the BBC, plenty of people think it's a great idea and are saying that those who slag the idea off are probably like those who once said planes couldn't fly.

 

[daikilo]

How good is such a design for a plane needing to make an emergency landing? It would seem, to a non expert like me, that it would make things a lot more complicated and potentially dangerous.

Looking on the BBC, plenty of people think it's a great idea and are saying that those who slag the idea off are probably like those who once said planes couldn't fly.

Technically, it can probably be done, in what I might call a perfect world, but probably not with the gains suggested.

Practically, we know what the issues are and we don't have simple solutions. The issue is whether alternative solutions may be better.

 

[Deepgreen]

Well the story indicates that it's the work of a research team based at the Netherlands Aerospace Centre. I'm not an expert in that area, but the website looks like a reasonably legitimate organisation, which suggests that they would've done their research reasonably well, so perhaps the idea isn't that daft - although it certainly does raise a lot of questions.



Would it be a huge problem if you did?

But offhand I don't see any reason why the runway being curved would mean you'd need to approach on a curved trajectory. Presumably, you'd simply aim at the right bit of the runway and descend in a straight line to that point. The main issue I can see is that you'd have to be pretty accurate: Overshoot and you'd presumably have to abort the landing because the runway will have curved away from you. Ditto if you undershoot. With a straight runway, you clearly have a greater margin for error in that regard. But then I don't know how accurate landings are? Are modern aircraft/guidance systems sufficiently accurate in landing for that not to be an issue? Similarly for take-off, if you get the point of actually leaving the runway long, you'll end up taking off in (slightly) the wrong direction, though I'm guessing that's not really much of an issue - easy to correct once you're off the ground.

On the other hand, I don't know if the runway being canted would be an issue. Presumably the aircraft would have to be canted to match at the moment it touches down? (Would that be a reason for flying in on a curved trajectory after all?)

Yes, which is very tricky, not least because of the huge increase in vulnerability to cross winds grabbing the wings and slamming you into the ground. The approach could be curved or straight but there would have to be last minute turn/cant to align in the horizontal and vertical axes with the runway. The whole basis of flying into the wind when landing or taking off would be lost in any case - it's not a runner.

 

[D365]

Looking on the BBC, plenty of people think it's a great idea and are saying that those who slag the idea off are probably like those who once said planes couldn't fly.

But some ideas are more implausible than others. That's a rather poor notion.

 

[edwin_m]

Could we have a circular runway at Heathrow as a lasting monument to British transport policy?

 

[rebmcr]

Could we have a circular runway at Heathrow as a lasting monument to British transport policy?

Ha!