Why are runways flat? Surely running up the side of a mountain the 250 vertical metres needed to stop the plane, then turning around and going back down to get to take off speed using gravity offers some efficiencies. On a slope of say 1:1 the runway is a hell of a lot shorter, even with a 500 metre flat bit before the slope. Yes, of course it needs to have one side with no mountain so that landings can abort.
-- thorpie, Feb 27 2004

O68 http://www.airnav.com/airport/O68
Doesn't look so long up there, does it? You'll use up most of that for landing. [Klaatu, Oct 04 2004]

Soldier Bar Airport http://www.airnav.com/airport/85U
Check out the picture, this is only a 4 degree slope. [added] Your "500 metre" flat bit is just about as long as the entire runway. [Klaatu, Oct 04 2004]

You are at an airport in the not-too-distant future http://cem.colorado...s/su2000/clara.html
[duroncrush, Oct 04 2004]

A 'Green Airport' http://www.earthisl...ID=232&journalID=48
This airport is inclined to reduce pollution [duroncrush, Oct 04 2004]

Accelerated Runway http://www.ascho.wp...uildings/runway.HTM
[duroncrush, Oct 04 2004]

Let's see...you are dropping at a rate of 500FPM...the ground is coming up to meet you...not a good scenario.

As I pilot, I can tell you that sloped runways are the shits to land on. And, if you have to go-around for any reason, you have a mountain in front of you. And, since we are up in the mountains, how about the effect of density altitude upon the performance of the aircraft? This would be a disaster waiting to happen.

Try flying into O68 (Mariposa, California). The slope is only 21 feet from one end of the runway to the other end. Landing "downhill" (runway 8) is hard because the ground keeps going away from you and you land long. Landing on the "uphill" (runway 26) is hard on your landing gear and you risk a prop-strike.

As far as your "flat bit", go out to any airport and see how many pilots can set it "on the numbers"

Fishbone from a pilot.
-- Klaatu, Feb 28 2004


Baked The inclined runway idea was tested during WWII and discontinued. A new concept has been proposed and shows promise but needs to be proven before cities will take the risk to build an airport based on inclined runways. NASA should build a test strip and get some good data before this idea is boned to death.
-- duroncrush, Feb 28 2004


// Why are runways flat? //

So airplanes don't crash into them.
-- waugsqueke, Mar 01 2004


This whole idea reminds of a scene from Air America...

[Unabubba] drive around the Dales in Yorkshire, there's a fair few short stretches of 1 in 4 road dotted about, although I've yet to see one longer than 300yds, they tend to have sharp 90 and 180 degree bends on them as well. You're right about the road surface sliding, it's quite common so see tarmac creep on steepest parts- the inside of sharp bends. The only thing that confuses me is how they lay it...

I think that if you were landing on an upward slope you'd have to maintain a higher approach speed so thet your descent angle stayed the same as normal relative to the surface of the runway so that could negate the effect of it. It would be possible to have a runway with a 200m, 300m or whatever length flat bit graded into a steep upward slope to slow the planes down; this would be no harder to land on (unless you're inclined to seriously overshoot the keyboard) and would have the same advantage. Pilots would then have the choice of gunning the engine and parking at the top or taxiing back down the slope to the level bit at the bottom.
-- squigbobble, May 11 2005



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