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By Walter Müller
#26
The start of an airplane consumes a lot of energy and is very stressful to the tires. An airplane could be started (and landed) sitting on a magnetic driven carrier which is accelerated by a linear motor installed in the runway. This method will save fuel, tires and reduces noise at airfields dramatically.

Reward: A cleaner air for my planet.
By Dietmar Detering
#179
Sounds good, but I see a couple of practical problems:
1) the carrier will be very heavy itself. After accelerating the plane it has to be stopped again. Though the kinetic energy could be rescued, you need some more space.
2) the plane's engines have to run full speed when taking off in order to support the ascend. This takes some time (but could be coordinated with the acceleration contributed by the carrier, I guess). However, the ascend is probably the most important contribution to noise and energy use, but it won't be affected by the carrier.
3) When landing, do you want the plane to hit an accelerated platform (space and coordination with the plane) or a standing plattform (would fall apart when hit by the plane)?
In general, investment costs would be very high. The biggest problem, however, is in the implementation - Could the runways be used simultaneously the old and the new way? If not, how could the system change be coordinated within a heavily used infrastructure? Another question: How secure and reliable could be such a system?
By AaronAgassi
#848
A real and more practical innovation, for example, are breaks that store the energy from coming to a stop upon landing, to then use said taxiing on the runway.
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By Michael D. Grissom
#2233
A steam driven catapult like that used on aircraft carriers (only much slower) might work if the airplanes could be practically modified to take the stress. As for tires, the patent office is full of patents for tread designs that would spin up the tires before they hit the pavement. You're on the right track though because what they really want and need is engine noise cancelling devices.
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By FlatTop808
#2563
Why go to all that trouble? The same thing could be accomplished with inclined runways. Land on a level section that then slopes upward to the terminal, unload, reload, and head down the incline to take off. Build it tall enough and the planes could park on top of the treminal and reduce the size of the airport substantially.
All you're doing is storing some of the residual energy of the plane by making it coast uphill and regaining it by going back down the hill, all without resorting to silly, complicated, expensive catapaults and magnetic tracks.
This ideas is not a new one, I've seen it in technology magazines before, but as far as I know, no one has built an airport in this way.
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By Michael D. Grissom
#2570
Just curious FlatTop but, did you pick your name because of an aircraft carrier or your favorite hair cut,... or? I spent 3 years on a carrier.

Inclined runways make about as much sense as a perfect circle banked runway (race track) where you can always touch down directly into the wind (ie., PERFECT SENSE). I guess the perfect airport would have to be multiple opposing inclined parallel runways on an airport carousel always in line with the wind? What I would give to have the money to do that!

FlatTop,.. I hope you're not just passing through. Input and insight like yours is what this site is all about.
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By FlatTop808
#2590
FlatTop is a hair thing and 808 is my old motorcycle racing number. I'm a big transportation geek so that's why my posts have been in this part of the forum.
My "insight" may just be a flash in the pan but I'll stick around and see if I can find anything else to say.
What gets me about a lot of the posts I've read is that information about similar (or identical) ideas is readily available on the web. When I have a new idea, the first thing I do is Google it. Saves a lot of brain power when I know its already been done.
By aviator32
#3344
Hi-

Re: flattop808's reply about inclined runways:
2 problems:

first, if it's a fixed (non-movable runway), then you have a problem because it's not always facing into the wind. An aircraft's landing speed is reduced relative to the ground by landing into the wind. Because impact forces increase to the square of the velocity, landing as slow as possible is desirable.
Putting the terminal on the top of a hill with potential runways going in all directions might address that, but would be awfully expensive (you'd have to build the hill in most airports, which like flat open areas for obstacle clearance on landing and takeoff) and use a LOT of real estate.

Second: If it's a ramp of some sort - yikes! a ramp that could incline to accomodate an airliner would be a lot bigger and more expensive (and difficult to engineer) than an aircraft carrier style catapult.

What about some sort of magnetic device - magnets in aircraft landing gear and embedded in the runway (would it mess with the avionics in the aircraft though?) - with the effect of generating storable current like the magnets in an electric motor do - as aircraft land. Then that stored energy to launch the next one by reversing polarity (I'm no electrician. I don't know if that's workable - just an idea...)?

George
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By FlatTop808
#3384
I live about fifteen minutes from one of the world's busiest airports ( http://news.airwise.com/stories/2003/08/1060361148.html ) and guess what? None of its four runways are moveable. As a matter of fact, they're all parallel, running east-west. So much for landing into the wind all the time.
And how could inclined dirt cost more than a catapult? Granted, its well engineered dirt, but its still just dirt, at an angle. And how are you going build a catapult to launch a 747-400? It has a max takeoff weight of over 830,000 pounds. That's 425 tons. The Airbus A380 is supposed to be over a million pounds! For contrast, the F-14, pretty heavy for a fighter, weighs a paultry 72,000 pounds. The Airbus will weigh almost 14 times as much.
And we know that we have the technology to build bridges strong enough to support an airliner. Stapleton in Denver had one, Boeing in Seattle has one, and at Hartsfield the planes park at gates directly over the underground transportation system. Putting an entire terminal under the planes is not unreasonable.
By aviator32
#3385
It's true that in the real world you don't always get a direct headwind. Large airports, if they have a choice (not all have that choice), have several runways at different headings to give the pilots more options. And aircraft can, and do, land in crosswinds. But what if the wind is going in the same direction as the aircraft, so that they have to land downwind (ADD windspeed to aircraft's landing speed) in order to use the incline? Uphill/Downhill is a bigger deal than windspeed but most pilots would prefer to land into the wind, or at least a quartering headwind. Adding 25 mph to your landing speed is a really big deal, esp. if you are a heavy, fast airliner. No pilot likes to land downwind if he can help it. Plus, it would cost an awful lot of bucks to engineer dirt for an 8,000 foot runway. I'm not saying it's impossible, but debatable about it's cost efficiency.
I doubt that they would have parallel runways with opposite slopes. Runways are just too expensive, and at typicial major airports there is an aircraft landing every minute or so, often 24/7. Besides the cost of building, I'm sure airports wouldn't want a runway idled because the wind was running up the slope of the runway. A flat runway is more versatile because you can choose to land from direction or its opposite.
There are some airports that are built on slopes of varying degrees, esp. in mountainous areas, and you nearly always take off downhill and land uphill, regardless of wind. But it's a choice forced on them by the geography, and is regarded as far less than ideal. They'd rather have a flat runway so they have more choice when the wind comes from the opposite direction.
Built-up runways strong enough to support an airliner? What about strong enough to LAND an airliner? They don't always just settle dwn gently, esp. when it's turbulent. I've seen some pretty skanky landings.
I'm NOT suggesting a catapult, but some sort of magnetic induction system. You know how a generator/electric motor works: If YOU turn the motor, you generate current. If current is applied to the motor, IT turns. Why couldn't we do the same thing with an aircraft's landing gear, with electromagnets buried in the runway interacting with magnets fixed to the aircraft? Current would be generated by slowing down the aircraft, then the polarity reversed and used to accelerate outgoing aircraft. Besides, I'm just thinking of a helper for the orginal acceleration to reduce (not eliminate) energy requirements. You still need full power on the engines because the second you're off the ground, the "catapult" is of no further consequence.
That being said, I don't know what effect the magnetic stuff would have on the aircraft's instrumentation, or even if such a helper would be practical enough to make a difference. But as a pilot I don't see ramps as a practical option.
By jabberwock359
#8020
Michaels msg about patent offices stuffed full of ideas for tread that would speed tyres up is interesting.
Why cant the wheels be powered in some way to match ground speed?
Sureley that would save heaps on tire replacement and incidentally provide smoother landings. I dont understandwhy they havent done this already
By Rishi
#8038
FlatTop808 wrote:
Why go to all that trouble? The same thing could be accomplished with inclined runways. Land on a level section that then slopes upward to the terminal, unload, reload, and head down the incline to take off. Build it tall enough and the planes could park on top of the treminal and reduce the size of the airport substantially.
All you're doing is storing some of the residual energy of the plane by making it coast uphill and regaining it by going back down the hill, all without resorting to silly, complicated, expensive catapaults and magnetic tracks.
This ideas is not a new one, I've seen it in technology magazines before, but as far as I know, no one has built an airport in this way.

*******
Theoretically there does not seem to be anything repugnant in the idea as the lawyers love to say. However, if all the kinetic energy (minus friction and wind drag) is recovered as potential energy the rise required for the runway may be pretty steep (not punny).

At a 150 mph landing speed, this could be about 1500 feet. This would translate as a 6 mile long runway even with a steep 1 in 20 slope. The bonus is that you can have a great 1500 feet tall building under the run way.
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