6 ms·

Engineer defends concept circular runway idea

2manyredirects 9y ago
> If someone one hundred years ago would have said that we would be transporting as many passengers in aircraft as we would in trains, people may have thought , "a steam engine would never fit in an aircraft made of wood and ropes". That's such an eloquent way of highlighting the need for conceptualisation in engineering but also the struggle to convince others (investors perhaps) that you're not a complete nutcase when you think outside the box.
- avar 9y ago
  If you're struggling to convince others it's best to leave the Galileo fallacy out of your arguments. Just because something was thought to be ridiculous in the past and now we know better, that doesn't mean that your seemingly ridiculous idea is just as misunderstood and underestimated as that other idea was at the time.
- mablap 9y ago
  The thing with thinking outside the box is that you never really know if you're doing it right unless you hit the "jackpot". I.e. an idea seems obvious to you, but not to your co-workers/friends/bosses/whatever and is usually met with serious resistance from them. Especially in a work setting where you have to convince "non-technical" people. Sometimes it takes more than nice words to get your message across.
- NikolaeVarius 9y ago
  But that's all with the benefit of hindsight and survivorship. Most outside the box ideas are nutcase ideas that fly in the face of basic physics and logic.
- astrodust 9y ago
  Engineers don't necessarily think in terms of today's equipment when writing out models that describe the problem. They think in terms of abstract concepts, like "power source" and "lift generator". We're already trying to build a space elevator when we don't even know what material can possibly withstand those forces. It's something over the horizon, but we're hopeful we'll find it. Likewise, powered flight was possible, the only problem was finding lighter, stronger materials for the airframe and a lighter, more powerful engine to fly it.
esemor 9y ago
As an airline pilot flying Boeing 757 and 767 I think this concept is really cool but it does overlook some fundamental principles of the unreliability of weather in order to be practical. This week I have landed in variable winds gusting up to 45 knots and then every inch of wingtip clerance counts, a drawback of this design. What if the aircraft makes a long landing (floats) and suddely faces a different wind component that subjects it to a tailwind. Also, the full circle would only be useable on zero wind days which makes me wonder about the economical reality of having a large part of the pavement be unusable most days.
- anotheryou 9y ago
  and conventional runways are ok with all wind? because the angle stays constant?
  - esemor 9y ago
    You never land with a tailwind and if the wind shifts the airport simply change the runway to the opposite one. If you use a circular runway and landing with a cross wind you would during your landing roll be subjected to a tailwind. Sure, you could stop using that part of the runway but then we're back at the practical economical argument for this design.
    - EliRivers 9y ago
      "Sure, you could stop using that part of the runway" Would you have to stop using that part of the runway, or stop using it within a certain height? That is to say, while landing, if at that part of the runway the aircraft was already solidly on the ground would it still be a problem? Likewise taking off; if the take off point was simply well before that part of the runway, would that be fine (have to think it would be, because after taking off the plane has no reason to follow the runway - it's already gone)? If that's fine, then would you actually have to stop using that part of the runway? Could you just rotate the landing/launch points so that nobody was landing/launching at that part?
      - 9y ago
srigi 9y ago
Under one of the original articles, in the comments section some military pilot pointed that lateral forces on big airliner on this runway would break the fuselage and gear of the plane. I'm disappointed that this argument wasn't addressed in todays article.
- nikcub 9y ago
  Given a radius of a curve and bank angle it is simple to calculate what the minimum required speed is to have 0 lateral force
  - rpmcmurphy 9y ago
    If only airplanes all landed and took off at the same speed. Actual take off and landing speeds will vary depending on the aircraft's characteristics, fuel/passenger load, wind conditions, and density altitude (which varies depending on temperature and humidity). So the idea that you could build a runway with a bank angle that produces 0 lateral force for all aircraft is just not possible. Sorry.
    - astrodust 9y ago
      It's not going to be as big a deal as, say, clipping a wing.
    - alejohausner 9y ago
      Why couldn't the runway adapt to these conditions? Why not arrange gigantic superfast hydraulic jacks all along the track, to vary the runway's tilt, according to the needs of the current aircraft? Oh and very flexible and strong runway materials to handle the change in circumference. As long as there were no power failures, this would be a piece of cake. Frankly, the circular design isn't ambitious enough, as initially proposed.
      - htwillie 9y ago
        Yeah - make a huge rotating disc of a runway that rotates at a constant speed, so the pilot can stick the landing at whatever radius has an angular velocity equal to groundspeed. Then slow down the disk enough to allow taxiing toward the center exit drain.
jenhsun 9y ago
Opposite Opinion: REALITY CHECK: CIRCULAR RUNWAYS http://theavion.com/reality-check-circular-runways/ http://theavion.com/reality-check-circular-runways/
- EliRivers 9y ago
  Not to disagree with anyone, but just thinking out loud, some of those arguments seem valid only because the current means of flying assumes straight runways. Like the ones about how existing instrument systems and procedures, made for straight runways, will be inapplicable to circular runways.
mrfusion 9y ago
Im still suggesting my rho shape variant of this idea. You have a straight runway with enough distance to land but then have the circle for slowing down once landed.
- Arizhel 9y ago
  That won't work. Normal small airports that only have one runway use the runway in both directions, depending on wind direction. You never land with a tailwind, and you never take off with one either. A rho shape wouldn't work here because the circle is only at one end, preventing bidirectional use.
  - mrfusion 9y ago
    But for larger airports it would.
    - Arizhel 9y ago
      I don't see how. I don't see how this would result in better land utilization at all. You could have a big circle around the airport (like in the original circular runway idea), with a bunch of straight "stems" protruding in all directions, which can then be chosen based on prevailing winds. Then airplanes can land on these stems and then enter the circle after their speed has greatly dropped, so it's really like a big circular taxiway of sorts. And departing planes can accelerate in the circle some, then proceed onto the appropriate stem and increase to take-off speed and take off. This might actually increase throughput, I dunno. However the land usage would be atrocious, because you probably aren't going to have any productive use of all that land between the stems, and the overall area used when you account for the maximum extent of the stems is going to be enormous. The traditional layout of having a number of parallel runways really makes more sense as far as land-use efficiency.
  - CodeWriter23 9y ago
    Two straight sections of runway that intersect with the circle 180 degrees opposite of each other.
mrfusion 9y ago
I'm thinking if we ever figure out a way to reduce airport foot prints it could drastically drop housing costs. There are hundreds? Of acres of prime urbanish land. Look at Boston for example. I wonder if they take the opportunity cost of having an airport there into the cost of flying? That land could be worth 100 billion??
- matt4077 9y ago
  It's a drop in the bucket if you look at the percentage it would add to total available land, and also considering that the ground isn't usually the most expensive part of construction, and that most airports are outside the cities they serve. One interesting data point in that regard is Berlin's Tempelhof Airport (which you might remember from Indiana Jones 3). It's extremely central because it was one of the first commercial airports and was shut down a few years ago. It's a park now and will probably remain–the plan to build even a few houses was killed by a referendum. It's also a really fascinating place, because it feels entirely unlike a normal park. There are very few trees, so it's much more open. The runways remain unchanged, and it's quite an experience to jog there, with all the history that place has seen always on your mind. (https://www.google.de/maps/@52.4760745,13.3994616,3a,75y,279.09h,101.14t/data=!3m8!1e1!3m6!1s-JSQQRTZZliQ%2FVgVCFvx_gYI%2FAAAAAAAABVs%2F5u0jXkkv8qQ3cr2XinPhV6iuJBez0G4vQCJkC!2e4!3e11!6s%2F%2Flh4.googleusercontent.com%2F-JSQQRTZZliQ%2FVgVCFvx_gYI%2FAAAAAAAABVs%2F5u0jXkkv8qQ3cr2XinPhV6iuJBez0G4vQCJkC%2Fw203-h100-k-no-pi-0-ya110.74613-ro-0-fo100%2F!7i8704!8i4352?hl=en https://www.google.de/maps/@52.4760745,13.3994616,3a,75y,279...)
- astrodust 9y ago
  If one day VTOL aircraft are more practical, even cheaper than conventional planes, the size of the airport can shrink dramatically. It's too early to tell if experiments like Lilium are successful (http://www.theverge.com/2017/4/20/15369850/lilium-jet-flying-car-first-flight-vtol-aviation-munich http://www.theverge.com/2017/4/20/15369850/lilium-jet-flying...) but that could completely upend the entire aviation industry if proven more cost-effective.
- Scarblac 9y ago
  I think this will happen naturally, as we will have to limit the number of flights due to CO2 constraints.
htwillie 9y ago
For any given approach, with a circular runway there's exactly one point tangent to the runway to land. Landing short or long isn't an option. Things are conventional because they tend to work well. And part of working well is being resilient to errors and non-optimal situations.

> If someone one hundred years ago would have said that we would be transporting as many passengers in aircraft as we would in trains, people may have thought , "a steam engine would never fit in an aircraft made of wood and ropes". That's such an eloquent way of highlighting the need for conceptualisation in engineering but also the struggle to convince others (investors perhaps) that you're not a complete nutcase when you think outside the box.

avar 9y ago
If you're struggling to convince others it's best to leave the Galileo fallacy out of your arguments. Just because something was thought to be ridiculous in the past and now we know better, that doesn't mean that your seemingly ridiculous idea is just as misunderstood and underestimated as that other idea was at the time.
mablap 9y ago
The thing with thinking outside the box is that you never really know if you're doing it right unless you hit the "jackpot". I.e. an idea seems obvious to you, but not to your co-workers/friends/bosses/whatever and is usually met with serious resistance from them. Especially in a work setting where you have to convince "non-technical" people. Sometimes it takes more than nice words to get your message across.
NikolaeVarius 9y ago
But that's all with the benefit of hindsight and survivorship. Most outside the box ideas are nutcase ideas that fly in the face of basic physics and logic.
astrodust 9y ago
Engineers don't necessarily think in terms of today's equipment when writing out models that describe the problem. They think in terms of abstract concepts, like "power source" and "lift generator". We're already trying to build a space elevator when we don't even know what material can possibly withstand those forces. It's something over the horizon, but we're hopeful we'll find it. Likewise, powered flight was possible, the only problem was finding lighter, stronger materials for the airframe and a lighter, more powerful engine to fly it.

esemor 9y ago

As an airline pilot flying Boeing 757 and 767 I think this concept is really cool but it does overlook some fundamental principles of the unreliability of weather in order to be practical. This week I have landed in variable winds gusting up to 45 knots and then every inch of wingtip clerance counts, a drawback of this design. What if the aircraft makes a long landing (floats) and suddely faces a different wind component that subjects it to a tailwind. Also, the full circle would only be useable on zero wind days which makes me wonder about the economical reality of having a large part of the pavement be unusable most days.

anotheryou 9y ago
and conventional runways are ok with all wind? because the angle stays constant?
- esemor 9y ago
  You never land with a tailwind and if the wind shifts the airport simply change the runway to the opposite one. If you use a circular runway and landing with a cross wind you would during your landing roll be subjected to a tailwind. Sure, you could stop using that part of the runway but then we're back at the practical economical argument for this design.
  - EliRivers 9y ago
    "Sure, you could stop using that part of the runway" Would you have to stop using that part of the runway, or stop using it within a certain height? That is to say, while landing, if at that part of the runway the aircraft was already solidly on the ground would it still be a problem? Likewise taking off; if the take off point was simply well before that part of the runway, would that be fine (have to think it would be, because after taking off the plane has no reason to follow the runway - it's already gone)? If that's fine, then would you actually have to stop using that part of the runway? Could you just rotate the landing/launch points so that nobody was landing/launching at that part?
    - 9y ago

srigi 9y ago

Under one of the original articles, in the comments section some military pilot pointed that lateral forces on big airliner on this runway would break the fuselage and gear of the plane. I'm disappointed that this argument wasn't addressed in todays article.

nikcub 9y ago
Given a radius of a curve and bank angle it is simple to calculate what the minimum required speed is to have 0 lateral force
- rpmcmurphy 9y ago
  If only airplanes all landed and took off at the same speed. Actual take off and landing speeds will vary depending on the aircraft's characteristics, fuel/passenger load, wind conditions, and density altitude (which varies depending on temperature and humidity). So the idea that you could build a runway with a bank angle that produces 0 lateral force for all aircraft is just not possible. Sorry.
  - astrodust 9y ago
    It's not going to be as big a deal as, say, clipping a wing.
  - alejohausner 9y ago
    Why couldn't the runway adapt to these conditions? Why not arrange gigantic superfast hydraulic jacks all along the track, to vary the runway's tilt, according to the needs of the current aircraft? Oh and very flexible and strong runway materials to handle the change in circumference. As long as there were no power failures, this would be a piece of cake. Frankly, the circular design isn't ambitious enough, as initially proposed.
    - htwillie 9y ago
      Yeah - make a huge rotating disc of a runway that rotates at a constant speed, so the pilot can stick the landing at whatever radius has an angular velocity equal to groundspeed. Then slow down the disk enough to allow taxiing toward the center exit drain.

jenhsun 9y ago

Opposite Opinion: REALITY CHECK: CIRCULAR RUNWAYS http://theavion.com/reality-check-circular-runways/ http://theavion.com/reality-check-circular-runways/

EliRivers 9y ago
Not to disagree with anyone, but just thinking out loud, some of those arguments seem valid only because the current means of flying assumes straight runways. Like the ones about how existing instrument systems and procedures, made for straight runways, will be inapplicable to circular runways.

mrfusion 9y ago

Im still suggesting my rho shape variant of this idea. You have a straight runway with enough distance to land but then have the circle for slowing down once landed.

Arizhel 9y ago
That won't work. Normal small airports that only have one runway use the runway in both directions, depending on wind direction. You never land with a tailwind, and you never take off with one either. A rho shape wouldn't work here because the circle is only at one end, preventing bidirectional use.
- mrfusion 9y ago
  But for larger airports it would.
  - Arizhel 9y ago
    I don't see how. I don't see how this would result in better land utilization at all. You could have a big circle around the airport (like in the original circular runway idea), with a bunch of straight "stems" protruding in all directions, which can then be chosen based on prevailing winds. Then airplanes can land on these stems and then enter the circle after their speed has greatly dropped, so it's really like a big circular taxiway of sorts. And departing planes can accelerate in the circle some, then proceed onto the appropriate stem and increase to take-off speed and take off. This might actually increase throughput, I dunno. However the land usage would be atrocious, because you probably aren't going to have any productive use of all that land between the stems, and the overall area used when you account for the maximum extent of the stems is going to be enormous. The traditional layout of having a number of parallel runways really makes more sense as far as land-use efficiency.
- CodeWriter23 9y ago
  Two straight sections of runway that intersect with the circle 180 degrees opposite of each other.

mrfusion 9y ago

I'm thinking if we ever figure out a way to reduce airport foot prints it could drastically drop housing costs. There are hundreds? Of acres of prime urbanish land. Look at Boston for example. I wonder if they take the opportunity cost of having an airport there into the cost of flying? That land could be worth 100 billion??

matt4077 9y ago
It's a drop in the bucket if you look at the percentage it would add to total available land, and also considering that the ground isn't usually the most expensive part of construction, and that most airports are outside the cities they serve. One interesting data point in that regard is Berlin's Tempelhof Airport (which you might remember from Indiana Jones 3). It's extremely central because it was one of the first commercial airports and was shut down a few years ago. It's a park now and will probably remain–the plan to build even a few houses was killed by a referendum. It's also a really fascinating place, because it feels entirely unlike a normal park. There are very few trees, so it's much more open. The runways remain unchanged, and it's quite an experience to jog there, with all the history that place has seen always on your mind. (https://www.google.de/maps/@52.4760745,13.3994616,3a,75y,279.09h,101.14t/data=!3m8!1e1!3m6!1s-JSQQRTZZliQ%2FVgVCFvx_gYI%2FAAAAAAAABVs%2F5u0jXkkv8qQ3cr2XinPhV6iuJBez0G4vQCJkC!2e4!3e11!6s%2F%2Flh4.googleusercontent.com%2F-JSQQRTZZliQ%2FVgVCFvx_gYI%2FAAAAAAAABVs%2F5u0jXkkv8qQ3cr2XinPhV6iuJBez0G4vQCJkC%2Fw203-h100-k-no-pi-0-ya110.74613-ro-0-fo100%2F!7i8704!8i4352?hl=en https://www.google.de/maps/@52.4760745,13.3994616,3a,75y,279...)
astrodust 9y ago
If one day VTOL aircraft are more practical, even cheaper than conventional planes, the size of the airport can shrink dramatically. It's too early to tell if experiments like Lilium are successful (http://www.theverge.com/2017/4/20/15369850/lilium-jet-flying-car-first-flight-vtol-aviation-munich http://www.theverge.com/2017/4/20/15369850/lilium-jet-flying...) but that could completely upend the entire aviation industry if proven more cost-effective.
Scarblac 9y ago
I think this will happen naturally, as we will have to limit the number of flights due to CO2 constraints.

htwillie 9y ago

For any given approach, with a circular runway there's exactly one point tangent to the runway to land. Landing short or long isn't an option. Things are conventional because they tend to work well. And part of working well is being resilient to errors and non-optimal situations.