Debate: Will this plane take off?

[Kreeper X]

ARGH! I admit defeat... I get it now... I'm a complete idiot here, so please forgive me.

Seriously, I sat down and did some critical thinking and came to the realization that the wheels are going to move as fast as they need to in order to allow the forward motion... I'm seriously red faced here as to how I didn't recognize it... Time for a physics refresher course me thinks...

At least I'm not the only one...

[GRRWingNut]

It's okay, Kreeper!

We will forgive you.....as long as you don't design any airplanes, or runways, or airports, or for that matter, conveyor belts....

Don't feel too bad, I said before there are airline pilots with many many hours in the cockpit, and many many hours studying aviation and flying, who have spent their whole lives dedicated to aircraft, that still think that the plane won't take off. Some of the pilots that work at my company believe it won't....

The kicker for most people comes when they realize that airspeed makes an aircraft fly, not groundspeed.

And yes, the conveyor seems to negate any forward motion, but in reality, it can only negate groundspeed. Since the thrust is acting not on the ground but on the air around the aircraft, there is no way for the conveyor to stop the thrust, and therefore airspeed.

jj

[mobey]

How the hell did I miss that. The "runway" moving in oposite direction of the planes' travel will actually cause the weels to move in a forward motion. DOH!!!
I was picturing it backwards, I surrender

I am so smart
I am so smart
S.M.R.T.
I mean S.M.A.R.T.
Homer Simpson

[Elemental]

kreeperx said:

Now on the other hand, the moving treadmill IS going to generate a flow of air below the wing since it is moving at a rapid speed, so as the plane isn't moving, the air above the wing is going to be moving slower than the air below the wing by default which COULD generate lift.

The would not generate lift. In fact that would suck the plane to the ground. Remember, air has to be moving faster OVER the wing than air moving under it. Air that moves faster over a surface applies less pressure, which in turn sucks the wing up.


Well, I haven't read all the posts, but I will make some points. First, if the wheels are frictionless, then they should not play a role in the problem. Think about it. It would be like something just floating over the ground, but instead it makes contact with the ground (only there is no friction). This means that the key is in the fact that the belt matches the plane's speed, no that of the wheels.

I really don't wan to think about this seeing as how I just took an Honors Physics exam, but I want to know the answer.

[GRRWingNut]

Is it vain to quote yourself???

Elemental, the short answer is yes, and good luck on your physics eam!!

grrwingnut said:

Okay, guys, here we go...

If a paintball is sitting in the breech, and the barrel is a conveyor belt that was somehow set up to move opposite the direction of the paintball, when you pull the trigger, would the paintball leave the barrel?

The propeller(or turbine) is the thing that provides the thrust for the aircraft. This source of thrust acts on the air around the aircraft, not the runway, like a car.

Therefore, the wheels have no effect on the acceleration of said aircraft.

Therefore, the conveyor would have no effect on the acceleration of said aircraft.

Groundspeed does not matter, only airspeed.

Let's say that this aircraft needs to achieve 100 mph before it can lift off.

Let's pretend that this aircraft is taking off into a headwind of 50 mph. It will still take off at 100 mph airspeed. But because it started with a 50 mph headwind, it only needs another 50 mph airspeed to be at 100 mph. Therefore, the aircraft can take off with a groundspeed of 50 mph

This same airplane, again lifting off at 100 mph, takes off again, this time into a tailwind of 50 mph. This time, it needs to accelerate to 50 mph to get an airspeed of 0, and then accelerate more to an airspeed of 100, making it's groundspeed 150 mph.

So if this aircraft was on some sort of conveyor, this conveyor would only affect groundspeed. Airspeed is a direct result of thrust, and therefore not affected by groundspeed.

jj

Hope this helped....again!!

jj