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Dutch Scientist Proposes Circular Runways For Airport Efficiency (curbed.com)
An anonymous reader quotes a report from Fast Company: While airport terminal architecture has a solid history of style and innovation, rarely is a proposal put forth to utterly redesign the runway. But that's precisely the aim of Henk Hesselink, a Dutch scientist working with the Netherlands Aerospace Center. Dubbed the "endless runway," Hesselink's brainchild is a 360-degree landing strip measuring more than two miles in diameter. Since airplanes would be able to approach and take off from any direction around the proposed circle, they wouldn't have to fight against crosswinds. And three planes would be able to take off or land at the same time. Hesselink's team uses flight simulators and computerized calculations to test the unconventional design, and have determined that round airports would be more efficient than existing layouts. With a central terminal, the airport would only use about a third of the land of the typical airport with the same airplane capacity. And there's an added benefit to those living near airports: Flight paths could be more distributed, and thereby making plane noise more tolerable. BBC produced a video detailing Hesselink's circular runway concept. The concept is fascinating but there are many questions the video does not answer. Phil Derner Jr. from NYC Aviation writes via Business Insider about some of those unanswered questions in his article titled "Why the circular runway concept wouldn't work." The fundamental issues discussed in his report include banked runway issues, curved runway issues, navigation issues, and airspace issues. What do you think of Hesselink's concept? Do you think it is preposterous or shows promise?
A computer doesn't give a shit if the runway is straight or curved, because it can handle a little more left (or whatever) while it's managing dozens of other things. But a human can't do that. You want to make pilots have to account for bank and curvature in addition to everything else? That's obviously a shit idea.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
... just make it octagonal or some other n-agon.
One of the major issues seems to be what happens when a plane comes in too fast. Straight runways handle that well. It is hard to handle that with circular runways. There are a lot of other safety advantages of the standard setup.
I love how he places his drawning in the middle of nowhere with no roads or train tracks, or even neighby restraints on the layout of the land. Sure you can pull all that underground, but he seems to just ignore it.
My first thought was: how the heck are you going to keep this runway clear of snow? You've gone from a single (or dual) short strip to a (pi*2mi)= 6.28 mile loop. That's a lot of runway to plow.
Then there's the long taxi time from the outside to the terminal in the center. That's a 1 mile radius taxi. Lots of wasted time.
Then there's the poor saps living around the airport. Instead of a well-defined small number of houses with noise pollution, you've spread it all over a huge area. Lots more people to complain. I doubt people want to build houses *inside* that 2 mile loop of land, so the footprint of this beast will be impractical for an airport near anything existing at all.
And if there's a consistent level of wind (from any direction), that "3 at the some time" argument goes away, and you're back to a small strip of usable runway, at least until the wind dies down.
Why are 'scientists' designing airports? Lets let engineers and designers do that, and the scientists can stick to science.
It wouldn't cost much to model this in a simulator, and let a couple dozen pilots try it out. We'd find out pretty quick how easy or hard it really is. It would be an interesting semester project for some students at Embry-Riddle.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
This idea was studied in the 1940's, and was rejected then, it's still a bad idea.
The video is pretty funny, they say you can always take off and land into the wind, but then state you can take off or land 3 planes at once at different places along the circle, but that would require one of those planes to land in a 60 degree crosswind, and the other to land in a 60 degree quartering tailwind, unless you had the planes on crossing approach paths (a really, really bad idea). A rejected landing would either put the plane right into another's approach/departure path or put wake turbulence right into short final approach of another aircraft. Wake turbulence from a heavy plane can flip a smaller plane, an A380 flipped a business jet 3 times flying 1000 feet below it last week*, the business jet landed, but the airframe is totalled. Another one also nearly flipped a 737 about the same distance away**. Ignoring it is idiotic, wake turbulence is at it's worst with heavy planes at low speeds, and drifts downwards and outwards. 3 simultaneous take offs still has the problem that if one plane takes off directly into the wind, the other 2 have to take off with a 60 degree crosswind & 30 degree tailwind unless you cross departure paths, at the other extreme it's a 30 degree crosswind into the wind, 90 degree crosswind, and a 30 degree crosswind/60 degree tailwind. You also put wake turbulence into the approach path of the next runway. You really can only use 2 runways on the circle if you account for the wind. Maybe I'm missing something, but I've made a bunch of diagrams and haven't found a solution that actually works for using 3 runways and accounting for the wind with non-crossing flight paths.
All the other potential benefits mentioned ignore the wind as a factor. It also later ups the capacity to doing the work 4 runways without explaining why. But let's ignore all the flaws in the concept itself and think about building one anyway.
11,480 foot runways would fit inside of the space of the circle, and you could build 3 at the same width for less concrete that the circle would use. But the circular runway looks a bit wider then needed, so you probably can get 4 standard runways out of the same area of concrete, probably a lot more since you don't need 50 taxiways. Even if that's not the case, 4 normal runways would use less land, and would not require building an enormous banking underneath the concrete, or the reinforced tunnels under the runways for passengers, cargo and equipment. The banking doesn't sound expensive until you realize that there's about 7 miles of it. The tunnels would need to be able to withstand a fully loaded A380 doing repeated hard touchdowns on it (remember, they can land anywhere on the circle) plus a safety factor, and be large enough for everything the airport needs. There would need to be enough land to build it near a large enough city to require an airport this size, which usually don't have large areas of inexpensive land available. And where are the cars parking?
6 runways - 3 pairs in a triangular format, with terminals and parking, uses far less land than the circular format, and is much easier to expand. The 3.5km runway idea mentioned earlier would use 5.3 km^2 or area for the triangular runways, where as a circular 3.5km diameter runway would require 9.6 km^2 of land, and in the picture much more than half of that area is for the runway and taxiways. You can fit a lot of terminals and parking in the 4.3km^2 you have left over with the triangular runways (and that does not include the area in the center of the triangle). And why would you want the terminal in the middle? It makes ingress/egress more difficult, for little to no benefit. On days with any wind (which is the vast majority of them), you'd only be using one pair of runways/2 upwind paths on the circle.
A complete, well thought out presentation of a bad idea is still a bad idea. They use the wind to justify one "benefit", but then pretend the wind doesn't exist as it is a massive problem to nearly
...they wouldn't have to fight against crosswinds. And three planes would be able to take off or land at the same time...
If three are landing at the same time, I'd say that at least one is fighting cross-winds.
Instead of a loop, we should make the runway a Möbius strip! That way, planes can taxi along both sides of the tarmac, allowing it to last twice as long!!
Centripital force is
F = mv^2/r
or a = v^2/r
At a typical takeoff speed of 150 knots, the lateral acceleration needed to keep the plane centered on a round runway with a 1.5km radius is 3.97 m/s^2, or 0.40g. On a freeway you'd just tilt the roadway based on the expected transit speed (about 24 degrees for 0.40g). But with a circular runway, planes are going to be traversing every part of it at all speeds from 0 to 150 knots, so there's no single tilt which will eliminate the problem. Likewise, during the takeoff roll the required lateral force will increase with velocity. So you can't just tilt the wheel/joystick at a certain angle and hold it there while taking off. You have to constantly adjust it as your velocity increases.
If a plane has to make a no-flaps emergency landing at 200 knots (which also happened to be about the regular takeoff speed of Concorde), now you're talking a lateral force of 7.06 m/s^2, or 0.72g. Which brings us to why runways are straight in the first place. It's not because it's easier to design and build. It's because it's a stable travel path. If for whatever reason during takeoff or landing the plane's controls stop working, the plane will want to go straight. Making the runway straight means the plane naturally (and with a little luck) will stay on the runway. Making the runway round means if you lose that lateral force being applied by your control surfaces for whatever reason, the plane is guaranteed to depart the runway at speed.
Aircraft landing gear are designed to land in a straight line, they are not designed to handle side loads.
It doesn't take much side load for that gear to fold up under the airplane.
Not to mention instrument approaches... I'd love to see a precision instrument approach chart to a circular runway.
Most large airports have several parallel runways. LAX for example has 4 parallel runways, normally all in simultaneous use - 2 are used for departures, and 2 for arrivals. This gets a lot of airplanes in and out at the same time.
If the runway was a circle, you might be able use on side for arrivals and the other for departures at the same time, but that's it.
Circular runways remains a stupid idea.
Disclaimer: I'm also a pilot.
Scientists do science (hypothesis, theory, test, publish repeat). Engineers apply science and business.
That's the old fashioned way.
The new way is:
1) Do a study with lots of measurements
2) Crunch the numbers looking for an interesting trend
3) Create a plausible explanation for the trend
4) Publish!