Operating the Endless Runway
Wind direction, wind speed, and visibility conditions are the major factors in the decision of air traffic control to use a certain runway configuration. Limits on tailwind and crosswind components determine whether runways can be used or not and low visibility limits the use of dependent runways. Direction of the runways results in a dependency to the wind direction and that aircraft have the use the same approach path, resulting in the need for wake turbulence separation. The Endless Runway operates a concept consisting of a circular runway that will allow take-off in any direction and landing from any direction.
The fundamental principle of The Endless Runway is that the aircraft take-off and land on a large circular structure. This will allow for the unique characteristic that the runway can be used in any wind direction, thus making the runway independent of the direction of the wind and therefore also the airport capacity independent of the wind direction. Three different situations can be identified for aircraft landing on the circular runway: strong wind, low wind, and changing wind directions.
a) In strong wind conditions, the aircraft will fly in sequence towards the Endless Runway to allow for landing at the touchdown point where dependency from the wind is at a minimum (exactly headwind). This is no difference from today, with the exception that an optimum touchdown point always exists where for a conventional runway a certain crosswind will need to be accepted; hence the Endless Runway reaches a sustainable maximum capacity under every wind condition with every wind direction.
b) In low wind conditions, no meteorological restrictions exist for the aircraft to land towards any direction, enabling the possibility of shorter landing intervals. The aircraft can be sequenced such that consecutive aircraft originate from different directions and do not have to be spaced according to wake turbulence categories, see figure 1.
c) With changing wind, the aircraft sequence can gradually “move” with the wind direction. No break in the sequence occurs which is the case with conventional runway configurations. No costly operations for tactical runway changes or changing runway directions during operations will be necessary.
From a capacity point of view, The Endless Runway seems to be advantageous compared with a classical runway system. The Endless Runway project will assess capacity of the newly proposed runway, but also take into consideration the additional developments it involves (ATC new tools and procedures), and the trade-offs (from an environmental standpoint, etc.).