Circular Airport - Endless Runway

The “circular airport” concept is not going round in circles

Reiner Hertl
3 pictures
4 minutes

Endless runway, never-ending story? There were controversial and heated arguments when the Dutch engineer Henk Hesselink presented his progressive runway design, although discussions about the circular runway calmed down again post-2017. Its feasibility is about to be tested on a Dutch “Vliegkamp” – with drones for now.

Designed for 2050

Perhaps even operational by 2040 – although estimates about its progress vary. A novel airport design, such as this, requires a massive leap of faith and originally the concept was not expected to become a reality before the middle of the century. But time is of the essence – and airport capacity is becoming a serious issue. Passenger numbers are growing year on year and it is proving difficult to keep pace with the increasing density of aircraft in the air and on the ground. Hence airports are constantly seeking to optimise their capacity: a structurally novel approach, such as the “circular airport”, would potentially provide much-needed relief. The smart thinking behind the endless runway theoretically offers up many opportunities. In practice, the concept configuration is set to enter a new test phase following extensive simulations.

Close Europe-wide cooperation for the vision

The collaboration partners on the “Endless Runway” research project, headed up by the Royal Netherlands Aerospace Centre NLR, are the German Centre for Air and Space Flight DLR, the French National Aerospace Lab ONERA, the official Spanish National Institute of Aerospace Technology INTA and the Polish Institute of Aviation ILOT. FP7, the last but one European Research Framework Programme, also brought the airport volte-face one step closer.

Freight drones are set to sound out a smaller scale application

Hesselink, the spiritual father of the “circular runway” wants to commence trials with delivery drones on the Valkenburg Navy Base in southern Holland. In many respects, these fixed-wing aircraft behave in the same way as passenger aircraft and these UAV trials could continue to advance the benefits of the idea and expose potential problems. After all, there have been objections a-plenty from experts from the outset. But let’s briefly take a look at the idea of the circular runway that the NLR has been working on since 2012 against this backdrop:

Banked like a special car race track – just “not a roller-coaster”

The concept circular runway would be approximately 3.5 kilometres in diameter and 10 to 11 kilometres in length. Three aircraft would be able take off and land on it simultaneously, hence it would equate to the length of some four conventional runways. The circular runway would be wider, at some 140 metres, and would be banked inwards, looking rather like the former race track in Monza or the Indianapolis oval circuit. The centrifugal forces caused by the banking would aid the aircraft when taking off or landing. According to Hesselink, passengers and pilots would not feel like they were “on a roller-coaster” and would only experience g forces of around 1.2.

Hesselink summarises in this video why no one would be thrown out of the bend.

The 360° circular runway: the solution to the airport of the future?

The anticipated benefits would naturally be the clinching factors: up to two-thirds less land needed for an airport and increased airport capacity. It would allow takeoffs and landings to be made into a direct headwind every time and, overall, would reduce aircraft noise, emissions and aviation fuel. The concept aims to allow aircraft to take off from any point, hence the ideal point, on any runway. It would also make landings independent of standard approach routes and side winds. In all, the circular runway would present massive benefits, but the unanswered questions and aspects nonetheless represent more than minor obstacles.

The obstacles will hold back the ‘circular airport’ for some time to come

As with many utopian projects, the cost initially represents a crucial opposing factor: its greater width, unique design and construction demands could mean that the circular runway is up to 50 per cent more expensive than conventional runways. Safety factors also present major challenges – particularly in adverse weather and in the event of multiple simultaneous takeoffs and landings. Not to mention the problems caused by an aborted takeoff. And ultimately the location is a critical factor – a circular runway requires land unimpeded by buildings or mountains in its direct vicinity and also no other neighbouring airports, as would be the case in major cities.

Further research and new technologies offer gradual progress

Aircraft designed to land on a curve, pilots trained to do so and IT technology capable of regulating simultaneous takeoffs and landings in a circular pattern: the research projects on the circular runway concept are ongoing, and the real test environment with drones might just be around the corner. And the future might be witness to something that evolved from a futuristic concept but is becoming increasingly necessary in the ever-increasing demand for flights: a new airport of the future.

Images are used courtesy of NLR – Royal Netherlands Aerospace Centre.

by Reiner Hertl

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