Circular airports: A new proposal for the airports of the future

At the beginning of 2017, was featured in the news that the Netherlands Aerospace Centre, with funding from the European Commission, was carrying out research on the design of a circular airport, or The Endless Runway as it is called, with the aim that it could become a reality towards the decade of 2040.

This type of airport, on which Dutch scientist Henk Hesselink has been working for years, is an attempt to put an end to one of the great fears of the pilots: crosswinds. Circular airports would allow aircraft to land against the wind regardless of the direction in which it was blowing. However, there are still many questions to be answered: such as how the curved trajectory of the runway affects control of the aircraft at low speeds on the ground, how it affects take-off and landing distances, or how the wear of the tires is affected as this would imply higher maintenance costs for airlines, amongst others. Flight simulators are currently being used to test this new model and trials with drones are expected in the coming years.

This airport runway model would also have an impact on actual airport design, with terminals, hangars and other airport facilities moving to the centre, the take-off and landing runway will run around the perimeter. This is perhaps the area where more work is still needed:  to find and develop an infrastructure which, in addition to adjusting to the runway design, is asefficient as some of today’ airports; the central access area also needs to be designed  in order to be safe and efficient.

How does a circular runway solve the problem of crosswinds?

When landing and taking off, a plane is better off doing so against a headwind which will help sustain it in the air. An excessively strong crosswind can result in runway closure (with the subsequent financial losses and inconvenience for passengers). In other cases, when crosswinds are borderline in strength, landing will require significant expertise from the pilots.

If instead of a straight runway there is a large 360º circular runway to choose from, you will theoretically be able to land against the wind whatever direction it’s blowing in. All directions are taking into account in in a circular shape, so it will always be possible to land against the wind.

Hans Hesselink was inspired by turbulent landings on videos such as this to develop his circular runway.

The curvature and bank angle of the circular airport

When we imagine this future circular airport, we could make the mistake of thinking of it as something small, with a sharply curved runway in which planes would have to land at an excessive turning angle. But this would not be the case according to designs at the Netherlands Aerospace Centre, where simulations of circular airports with a runway 3.5km in diameter and 11km in length are being considered.

To get an idea of the dimensions of this new runway, Madrid’s Barajas Airport has 15km of runway in total, if we were to string its four separate sections together one after the other. According to research and calculations made by Hesselink’s team, even though the length of the circular runway would be similar to that of three conventional runways, it would be able to handle the traffic flow of four.

According to Hesselink’s team, these 11km of circular runway would mean that the curvature radius would not be very pronounced, and thus the planes would only have to turn slightly on take-off and landing. They would also be helped by the upward incline of the runway towards the outside of the circle, called the camber or bank angle, which would counter the force pushing the plane towards the outside of the curve and help it stay on course.

This can be seen very clearly at velodromes, where cyclists use the steep bank angle to avoid flying out of the curve at high speeds.

This is therefore a truly innovative concept for airports which could provide advantages such as avoid accidents due to turbulence, or reductions in fuel consumption. It would also imply significant changes in the arrangement, layout and design of airport terminals, although research has not yet been carried out on whether this would improve airport management and operation. It would also require significant changes in the design of aircraft themselves, and possibly in training for crews. In short, it can certainly be considered a line of disruptive research that is worth paying attention to as if it does indeed come to live and prove the advantages involved, it could change the way we imagine airports.

More information on the project is available in the following video: