h a l f b a k e r yExpensive, difficult, slightly dangerous, not particularly effective... I'm on a roll.
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For silent takeoff:
Electic driven (silent) catapult device to launch plane where off-plane fuel is used (so airplane does not need the takeoff fuel on board) while running its own motor at low (and relatively quiet) speeds, or completely shut off.
For silent landing:
Airplanes coming in for landing
should idle their motors and open a parachute. If jet planes can use that kind of a system, why can't civil airliners?
Oh! and with modern systems for landing control, why do airplanes have to make those rotations over the cities, why can't there be a place above sea designated for waiting aircraft, invited in, only when almost sure that the airway is ready to take them in?
We gotcher landing right here.
http://spaceflightn.../n0211/22parachute/
[2 fries shy of a happy meal, May 16 2010]
Circular airport would also lead to "quieter" landings and takeoffs
Circular_20Airport
[ixnaum, May 17 2010]
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Annotation:
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So the catapult launches the jet about 100 feet off the end of the runway then it either throttles up its engines and makes noise, or crashes? As for landing do you mean a parachute to slow the plane down once it's landed? I don't see how this would make it quieter. |
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BTW not every airport is located right next to the ocean. |
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How about a gigantic set of lazy-tongs; the aeroplane is put on top, and then the tongs extend to 20,000 feet where the aeroplane starts its motors. |
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For landing, the men in the air traffic control tower can reach up with the lazy tongs and snatch the aeroplane from the sky. |
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You want the engine turning when you land in case you run our of runway and have to go around for another try. On top of that, a lot of planes need to reverse thrust on short runways.
I took thirty seconds to think about it, and thought of 17 better uses for an electromagnetic catapult strong enough to push an aircraft up to take-off speed. I admit, three of them were variations on "Sell it to the Navy" but no more than five directly involved people I don't like and only one directly involved masturbation; so, I think that's the same as being right.
You're right about the commercial jets though. I suppose they like to keep them close at hand so they can respond to changes in the takeoff and landing queues more quickly, but otherwise it's a good point. |
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The acceleration of a civil airliner is a mere gentle push compared to the giant boot-up-the-backside of a catapult launch, so you're talking about a very long catapult to reach VR plus substantial strengthening of the airframe. |
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Also, catapult-launched aircraft have the deck "pulled away from under them". A civil aircraft needs to "rotate" prior to the wheels lifting off. So the force needs to be applied evenly to the maingear; catapult launchers attach to the nosewheel. |
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To attain V2, the airliner is going to need its engines at 100% N1 as it climbs out of the ground effect. So the noise will still be there; you're just delaying spool-up a little way down the runway. |
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Handling pre-V1 aborts would be difficult because of the added inertia of the catapult traveller and linkage. |
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Marginally practical, complex and expensive, wouldn't achieve the desired result of sound reduction. |
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As to deploying a drogue, it's less efficient and more expensive than thrust reversers. And the engines are close to idle anyway during the glideslope and the flare. |
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I would first like to bun [victory]'s annotation. |
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As for the catapult launch, the advantage of the current
system is that, if the engines aren't working very well, you
tend to discover this while the ground is still under the
wheels. I'm sure there is a reason for this. |
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If the catapult were the length of the runway, then it
would certainly be possible to launch the planes with
same-as-current accelerations and less noise, and it might
well be possible to increase take-off weight. But on
balance I think it's a nogo. |
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Point taken about "stacking". On the other hand, I suspect
that most aircraft "stack" high enough that their noise is
not
significant compared to that of landing and offtaking
aircraft. |
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When first reading this, the aircraft carrier catapult
didn't come to mind - I thought of the medieval siege
catapult. Now, that would be worth bunning. |
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Right up to the point where the airframe went nose-first into the sod. |
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Have you by any chance noticed that all large civil airliners are built with tricycle undercarrages since about, oooh, 1950 ? It reduces their unfortunate tendency to "ground loop" .... |
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i gave this some thought. IF every plane was designed to make an unpowered controlled descent AND that descent could be made from the same pitch and general velocity that a powered launcher could deliver THEN you could rely on a catapult system of launching. In the event of an engine failure the plane would simply deploy the landing apparatus and land on a nearby co-linear landing strip or pad or whatever. Given that this is an entirely different way of looking at taking off and landing maybe we write it off too easily. In the case of a failure of the new slow descent gear the plane could make a conventional stall landing and the ability of the pilot to make a safe abort in case of takeoff engine failure could be enhanced. Hmmm. On the other hand a "gentle" descent might require an airfoil of impossible size and might also require the plane to slow to an unstable speed before being deployed. |
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Anyway, the catapult in this idea was not intended to push the plane along the runway, but rather to launch the plane high into the air, where it would then continue via a motor assisted down-glide, to fly out of the urban area. |
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C'mon, outside the urban area! The ocean was just an example. |
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My assumption, taken from experience of working nearby Lod Airport, was that most of the noise is from stacking at takeoff and thrust reverse at landing. But then again I may be wrong and most annos correct, that this is only a small portion of the noise, and the engines need to run. |
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OK, catapult points taken. (dangers, energy needed, body changes, G on passengers, stacking noise is not the issue, you'll still need stacking) |
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So how about a giant "hang glider" like system for noise reduction. Takeoff and landing would be slower but using much less energy. More planes could land and take off at the same time, because of the shorter runway! So you would reduce oil consumption for waiting planes, and perhaps enhance the airport capacity! (All while substantially reducing takeoff and landing noise) |
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woops, I thought "flag" was for giving a bun to the link. Read the help to check, and saw it means there's a problem with the link. Bun to you 2 fries! (+2u2fries) |
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