Is it just me or are people fucking thick?

[kalmar]

Fair enough, but you are then adding more assumptions about the length of the runway. Most passenger planes take off using less than half of the available runway. But yes, a bit more drag (and we're only talking about tiny amounts) will require a bit more time / few more feet to reach the take-off speed, correct, but it'll still take off if you ask me

[piku]

We need more snakes...

[Mir Nyet]

Planes do have a max thrust, if the rolling road provided enough of a dampening force to tip that balance (if the plane takes off at max thrust) then surely it does not matter how long the runway is, as the planes thrust is no longer enough to get it into the air (because it cannot attain take off speed)?

[kalmar]

Planes do have a max thrust, if the rolling road provided enough of a dampening force to tip that balance (if the plane takes off at max thrust) then surely it does not matter how long the runway is, as the planes thrust is no longer enough to get it into the air?

But then you are assuming that the rolling road (via, remember, very small frictional losses in the tyres and axles) is able to oppose a large percentage of the engines output. As explained, this is impossible as the ludicrously high rolling-road speed that you would need would be way beyond what any tyre (or wheel, or bearing for that matter) can stand. So it's pointless to make that assumption. Especially as it's not what the article is specifying.
But if you do make the assumption, then yes, the plane wouldn't take off - but this has been already stated / admitted several times during this thread

Let's see, a 747's engines can produce about 100,000 pound-foot of force. That's about 500,000N. (round numbers here). So if it takes 1 second to cover 1 meter (full thrust, only just rolling), you'd need to absorb HALF A MEGAWATT somewhere to prevent the plane accelerating. That's a lot of power. It'll melt bits of plane.

Now, I know you'll come back with "but surely it would only take a little fraction more drag so that it would never reach take-off speed". But that's not the case. You need to account for about the remaining half of the engine power that isn't accelerating the plane. It's still a lot. It's still not a workable assumption.

[tufty]

Planes do have a max thrust, if the rolling road provided enough of a dampening force to tip that balance (if the plane takes off at max thrust) then surely it does not matter how long the runway is, as the planes thrust is no longer enough to get it into the air (because it cannot attain take off speed)?

Planes never *require* full thrust to take off. There are civil (and military) aviation rules that cover this. The margins for error are *very* large, mainly due to the amount of damage to both property and public opinion that several hundred tonnes of airliner can cause if it falls out of the sky.

http://www.aerospaceweb.org/question/pe ... 0088.shtml might give some idea of the variables involved just with takeoff speeds.

Simon

[disciple]

And yet people are arguing quite vehemently that of course it'll take off, you idiots.

Am I missing something?

Wow 10 pages!

But yeah you've misread the question.

The answer is of course it fucking takes off.

But I'm sure this has been said repeatedly over 10 pages hasn't it.

[fred_zen]

Let's see, a 747's engines can produce about 100,000 pound-foot of force. That's about 500,000N. (round numbers here).

Next: what's the speed (relative to air) of a 747 taking off? According to [url=http://www.aerospaceweb.org/question/performance/q0088.shtml]this site|/url], there are actually a number of answers (if you want the plane to safely take off, you need more speed than just what's needed to generate enough lift). Let's say 250 km/h (we just want the plane to stand a chance of taking off, not to take off safely).
How much drag does a 747 take from air when taking off at 250 km/h?

[Guru-Meditation]

We need more snakes...

So if the plane is full of snakes it will be too heavy to take off?

[kalmar]

How much drag does a 747 take from air when taking off at 250 km/h?

Probably easier to find out what the fuel consumption is in level flight at that speed and work it back from there. Can't be arsed though.

[tufty]

Let's see, a 747's engines can produce about 100,000 pound-foot of force. That's about 500,000N. (round numbers here).

Next: what's the speed (relative to air) of a 747 taking off? According to [url=http://www.aerospaceweb.org/question/pe ... 0088.shtml]this site|/url], there are actually a number of answers (if you want the plane to safely take off, you need more speed than just what's needed to generate enough lift). Let's say 250 km/h (we just want the plane to stand a chance of taking off, not to take off safely).
How much drag does a 747 take from air when taking off at 250 km/h?

Wikipedia says Cd for a 747 is 0.031; you can work out the rest, more or less, from http://en.wikipedia.org/wiki/Drag_equation if you can find its frontal area.

Simon

[Nutty]

I think it would take off.. The engines thrust is not applied to the road, its applied to the air to propel the plane forward, so I'm sure whatever happens under the wheels is irrelevant..

For a car of course, it would be stationary, because the drive is applied to the surface that is moving to counter it.

So I reckon the plane would accelerate and take off.

[kalmar]

I think it would take off.. The engines thrust is not applied to the road, its applied to the air to propel the plane forward, so I'm sure whatever happens under the wheels is irrelevant..

For a car of course, it would be stationary, because the drive is applied to the surface that is moving to counter it.

So I reckon the plane would accelerate and take off.

You are teh correct0r. You win a prize of some kind.

[piku]

We need more snakes...

So if the plane is full of snakes it will be too heavy to take off?

No, because Bruce Willis will shoot the terrorists on the ground who've taken over the guidance system. This will cause the government agent on the plane who bears a resemblance to Tom Cruise to kick the fat people off the plane first.

Thus preventing cruelty to animals which always rates higher than personal safety in films.

[sponge]

You are all a bunch of thick, soft twats.

Due to friction, the plane will actually begin to move BACKWARDS.

Now, think about that one.

[piku]

You are all a bunch of thick, soft twats.

Due to friction, the plane will actually begin to move BACKWARDS.

Now, think about that one.

Does that mean the plane will try to fly into the ground? Plane wings don't work in reverse, they're the wrong shape.