and when was that, when you googled this mess 30 seconds ago and ran across a cool new acronym? ground speed and air speed are both valid and important parameters to an aircraft's flight. obviously airspeed is more relevant to whether there's enough airflow over the wings to create enough lift, but both are used and both are usually measured in knots.

10/28/2007 7:33:17 PM

no

acutally ive known that for about 8 years

i did some heavy reading in hs because i was leaning towards getting my pilots license...didnt have the cash to do it

the only speed that you need to be concerned with at take off is KIAS, because then you dont have to compensate for wind speed and direction for things like v1, v2, stall speed, etc

10/28/2007 7:46:32 PM

the plane does not take off.


the wheels fail and the plane falls over and blows up



[/thread[]

10/28/2007 7:48:01 PM

10/28/2007 7:52:21 PM

Quote :

"acutally ive known that for about 8 years i did some heavy reading in hs because i was leaning towards getting my pilots license...didnt have the cash to do it the only speed that you need to be concerned with at take off is KIAS, because then you dont have to compensate for wind speed and direction for things like v1, v2, stall speed, etc"

fair enough. your post came off as kindof douchey so I felt I needed to say something. i was in the same boat...when I was 14 I started taking lessons, got ~25 hours or so but couldnt come up with the money or time to finish. Still regret that

10/28/2007 7:55:56 PM

Quote :

"obviously airspeed is more relevant to whether there's enough airflow over the wings to create enough lift, but both are used and both are usually measured in knots."

Yes. Ground speed is used only to calculate the amount of ground covered while in the air, which is why it has absolutely nothing to do with a plane taking off.

Look at it this way.

If a plane is just sitting on the ground directly opposing the wind (i.e. a headwind) the ground speed it takes off at will be the approx the airspeed it normally takes off minus the velocity of the headwind. Therefore if the headwind was say 100 kts and that is the airspeed at which the aircraft normally becomes airborne, it will take off with a groundspeed of 0 kts.

10/28/2007 8:04:33 PM

for page 3

10/28/2007 8:55:48 PM

Quote :

"air or ground it doesn't matter. lets talk about the speed with respect to the ground. which in this example (no wind) is the same as the air. i'm not talking about any silly airspeed measurements to determine lift, i'm talking about the speed of the aircraft to the ground, to make the question simple. (for those people who obviously need it spelled out for them.)"

to be truly correct, you want to consider the speed of the aircraft relative to the surrounding air. Neglecting wind, this is the same as ground speed.

Quote :

"well last time i checked, aircraft speed was measured in KIAS (knots indicated air speed) which is the only speed that matters"

aircraft speed can be measured in KIAS (knots indicated airspeed), ktas (knots true air speed), kcas (knots calibrated airspeed), or you can account for the wind and use ground speed (ktas +/- wind). It depends on what you're trying to do.

For considering takeoff, stall speed, etc, you are concerned with KIAS, because that's what the airplane "feels" (i.e., varying on density altitude, etc).

10/28/2007 9:01:47 PM

Quote :

"what in the original question says the plane can't have forward motion relative to the ground?"

what in the original question says the plane has forward motion relative to the ground? The question says "takeoff speed on a conveyor belt. It seems logical to me to assume that the question is saying that the plane is moving relative to the belt surface in that instance. Otherwise, it would have said "takeoff speed relative to the ground." As such, the plane isn't moving relative to the ground, so there is no lift. end of thread

10/28/2007 9:07:21 PM

^lift isn't determined by speed relative to ground...
in a high wind a plane can maintain altitude without moving forward at all relative to the ground.

10/28/2007 9:09:54 PM

^ absolutely true, but the question mentions nothing about a headwind, so it is fair to assume that such a thing is irrelevant.

10/28/2007 9:10:50 PM

There aren't enough carl faces to express my feelings on seeing this thread again.

10/28/2007 9:37:41 PM

burr0 there's no way you're actually that dense. i concede to the fact that your trolling has gotten the best of me.

10/28/2007 10:49:26 PM

are people still arguing that the plane will take off?

lol

10/28/2007 11:03:32 PM

^ ahaha are you serious, you too???

10/28/2007 11:52:25 PM

Engine thrust FTW.

10/28/2007 11:58:51 PM

If the plane is traveling at 100 mph equivalent of thrust and the conveyor belt is going 100 mph it will take off. I think what people are misunderstanding is that this: say that a take off speed is 100 mph (i dont know about planes). If a conveyor is moving underneath the wheels of a plane in neutral at 100 mph, the plane does not move back at 100 miles per hour. Thus, the thrust of the engines will overcome the friction of the conveyor and propel the plane.

People are thinking that as the plane increases it thrust, then conveyor increases its speed to a greater extent to compensate. For the conveyor to slow the wind thrust of 100 mph, then the conveyor's ground speed must be much higher.

10/29/2007 12:26:51 AM

if you don't understand what's going on here, definitely disregard the post above this one, because I don't even know what the fuck he means by about half of that.

10/29/2007 12:36:44 AM

^ I think he's indicating that if the plane and the conveyor are traveling at the same speed, the plane will take off. If the conveyor is traveling much faster than the plane, the plane will not take off.

^^ Is that what you mean?

10/29/2007 12:41:47 AM

it doesn't make any difference how fast the conveyor is traveling, unless it's moving so fast that it generates enough friction in the wheel bearings to overcome the thrust of the engine. i'll bet that 99% of the time, the bearing or the tire would fail before that even happened...and we're talking about a conveyor going really, really fast.

10/29/2007 12:53:14 AM

The speed of the conveyor has absolutely no bearing. The conveyor could be moving forward even, and it wouldn't affect the dynamics of the situation (inertia anyone?). If the planes engines are on and functioning properly, it will move (unless of course something is physically blocking it). It's that simple.

Just imagine a sea plane or a snow plane. It doesn't matter that they don't have wheels, it's the engines that are pushing the plane, not the wheels.



[Edited on October 29, 2007 at 1:36 AM. Reason : ]

10/29/2007 1:24:46 AM

At first I thought the conveyor could keep the plane stationary, and if it could then there would be no air moving over the wing for lift (right?). After some brief thought however I don't think it's possible for the conveyor to counteract the airplane's speed at all, so it will accelerate and get lift etc. etc.

Am I dumb or not?

10/29/2007 2:15:40 AM

^ Correct. Because:

Quote :

"it's the engines that are pushing the plane, not the wheels."

FTW

I used to think the plane wouldn't take off either. It does. The wheels don't matter. The engines will push the plane forward no matter what.

10/29/2007 4:04:56 AM

Quote :

"to be truly correct, you want to consider the speed of the aircraft relative to the surrounding air. Neglecting wind, this is the same as ground speed."

of course.

but the situation arronburro is describing the airplane would have no airspeed, no ground speed, no speed measurable by GPS, or any other speed. all that is happening is the treadmill is moving harmlessly underneath the airplane, while it's inertia keeps it still (in a frictionless world)

I'm just trying to simplify the problem for people who can't comprehend it.

10/29/2007 10:08:50 AM

well technically it wouldn't take off because the wings would break when they hit the front of the treadmill

10/29/2007 10:24:11 AM

OK HOW ABOUT A NEW QUESTION...

if the plane had spinners, which way would they spin.

AND WOULD THEY STOP?

10/29/2007 10:28:14 AM

yes i think the problem is people think of the plane like its a car

if it was a car, it wouldnt go anywhere, because the wheels push the car and the treadmill would oppose the wheels

in the case of the planes the spin of the wheels is independent of the plane speed, the speed of the plane is dependent on the propellers. So if the plane moves 1 mile an hour forward, the treamil moves 1 mile an hour backwards the wheels would move 2 miles per hour.

10/29/2007 10:29:06 AM

if there were zero friction, and we started with a wheel rotation of 0, then no, the spinners would not spin.

10/29/2007 10:29:24 AM

they would spin counter clockwise because the engines are propelling the plane and the wheels are free spinning

10/29/2007 10:29:29 AM

so you are telling me i cannot do burnouts with an airplane....

10/29/2007 10:59:48 AM

lollerz at this thread.

I think my fav is when someone posts their flawed argument and end it with "I WIN. YOU HAVE BEEN PWNED. END OF THREAD!"

10/29/2007 11:07:01 AM

The plane will not take off until you Tokyo Drift that biatchhhh!

10/29/2007 12:39:06 PM

Some people are having a hard time visualizing the force needed to overcome the running treadmill.

imagine this:

You place a bike on a threadmill. You, standing on the ground, hold the bike as the treadmill speeds up to its maximum speed. Imagine the force required to keep the bike in place (not much). Imagine the force needed to push the bike forward a little on the treadmill (not much). Now imagine the same thing with a jet, with 10,000+ pounds of thrust. It will gain airspace and lift.

[Edited on October 29, 2007 at 12:51 PM. Reason : .]

10/29/2007 12:50:42 PM

^ and i feel sorry for them and their pitifully small minds

10/29/2007 1:01:57 PM

Quote :

"Now imagine the same thing with a jet, with 10,000+ pounds of thrust. It will gain airspace and lift. "

Uhhm, no. Planes gain lift by wind moving over the wings. All the treadmill is doing is moving the wheels.

[Edited on October 29, 2007 at 1:18 PM. Reason : a]

10/29/2007 1:18:12 PM

^ you misread or misinterpreted what he was saying

10/29/2007 1:21:34 PM

http://www.youtube.com/watch?v=peLD2vlxRM0

10/29/2007 1:27:39 PM

http://www.youtube.com/watch?v=Xg1oszADX04

10/29/2007 1:44:24 PM

what if the wheels were square?

10/29/2007 1:46:11 PM

"Uhhm, no. Planes gain lift by wind moving over the wings. All the treadmill is doing is moving the wheels."

No, seriously? I guess I had no idea what got the airplane I own in the air.

You misunderstood what I was trying to say. I am saying that the plane will be able to easily gain momentum and accelerate across the moving treadmill, creating airflow over the wings and thus lift.





[Edited on October 29, 2007 at 2:07 PM. Reason : .]

10/29/2007 2:04:47 PM

I think the real question here is whether or not Bear Grylls or Les Stroud is the pilot of the plane. Also, Bear/Les will probably be eating some BBQ while trying to take off... what type of BBQ would you guys say is the best for such a case?

10/29/2007 2:39:33 PM

10/29/2007 2:42:58 PM

nm

[Edited on October 29, 2007 at 2:50 PM. Reason : /]

10/29/2007 2:43:43 PM

the best kind of bbq will ALWAYS be eastern nc vinegar based pork!

10/29/2007 3:03:06 PM

bttwat

11/7/2007 9:14:14 AM

what if the speed of the treadmill was equal to the amount of thrust from the airplane's engines.
would it still go up? or does the speed of the treadmill not matter, but the amount of thrust from the engines?

11/7/2007 9:40:21 AM

if it were a brick wall, then maybe.
what if the speed of the internet matched the speed of the treadmill?

11/7/2007 9:45:18 AM

^^Speed of the treadmill doesn't matter. It could be going 0.9999*speed of light and just as long as the wheels could handle spinning that fast it would still take off.

11/7/2007 10:07:52 AM

bttt

11/7/2007 10:40:36 PM

⇒

11/7/2007 10:42:51 PM