Are Circular Runways The Next Big Thing?

Circular Runway

Round airports have been around since the early days of aviation, because that layout allowed the flighty planes of the day to land directly into the wind no matter which direction it was blowing. Every bit of turf within that circular landing area was potential runway.

But circular runways are another thing altogether. And while the idea might seem totally crazy at first blush, there's some serious research being done to see if circular runways could achieve increased airspace system capacity, which absolutely is limited by the number of available runway ends. With a circular runway, there would be, theoretically, an unlimited number of runway "ends" at any given airport.

The Idea

With a circular runway, planes could approach to land from many different angles, so you could have multiple planes on approach simultaneously. And you could have planes taking off and landing at the same time as well. Great, in theory.

But in order for planes to be able to navigate the turn, the runway would need to be banked, as an oval racetrack is. Planes would approach to land and then turn into the curve as they landed, touching down and continuing to turn with the runway---there's no going straight with round runways.

Once the plane landed and decelerated, it would turn off on one of numerous high-speed taxiways toward the terminal, located by necessity in the center of the whole setup.

Easy as pie.

The Problems

The infrastructure would be enormously expensive to change. If we're talking about the financial feasibility of the idea, we could stop the conversation right here. Can you imagine DFW scraping its seven runways and building a giant circular replacement? Even if the circular runway were able to do what its proponents claim it could, the increased capacity wouldn't cover the rebuilding of an airport that's larger than the island of Manhattan. Plus, think of all the tunnels you'd have to build to get ground vehicular traffic into and back out of the terminal area. And if you ever needed to expand operations, how would you do that?
The physics and aerodynamics of it are concerning. Planes landing on a circular banked surface, given there was sufficient wing clearance over the surface, isn't too hard an idea to accommodate. Just think about landing a small plane on a banked race track. Think you could pull it off? Yeah, me too. But what about if it rained, or got icy, or if there was a mechanical issue on landing? An object in motion wants to go straight. That's the beauty of a straight runway. If we want to turn, we need to do something to make that happen, either with the landing gear and brakes or aerodynamically, through control surfaces. It's not undoable, but it's harder than going straight, that's for sure. Finally, and there are many more concerns than these, balked landings would be problematic, airplanes of different speeds would inescapably come into conflict on the runway, crosswinds would accompany every landing, at least at some point, and at some point you'd be landing downwind, too.
The ILS approach wouldn't work at such an airport, though one could imagine having multiple straight-in approaches to different points along the circle, and WAAS-based approaches could be established for curved paths.

The Verdict

With any kind of proposal, there are two ways to approach testing the idea, virtually and physically. The Air Force tested the idea in the 1960s but quickly abandoned it for all the reasons stated and more. More recently, aviation think tanks in the Netherlands and the UK have run computer simulations, which seemed to confirm some benefits. But even the chief proponents of round runways give away the weakness of the idea when they admit the runways would have to be heated to prevent catastrophic runway contamination and computers would have to be used to route traffic of varying speeds to the runway to realize the efficiencies hoped for. And that's not even getting into the multi-trillion-dollar infrastructure spend that would be necessary for widespread adoption of the idea. But that said, is this idea really as crazy as it sounds? Actually, yes, yes, it is.

Plane & PilotStaff