Rocky Mountain Club B5

Discussion Forums => Off-Topic => Topic started by: jayryan on July 06, 2007, 02:23:21 AM

Title: This is being debated on another thread
Post by: jayryan on July 06, 2007, 02:23:21 AM
A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

Title: Re: This is being debated on another thread
Post by: 03Indigo on July 06, 2007, 05:01:04 AM
no, if the plane ends up being stationary, due to the belt moving in the opposite direction, there is no wind speed, and that wind speed, air moving over the wings, is what gives a plane lift.

Title: Re: This is being debated on another thread
Post by: SweetVW on July 06, 2007, 05:09:06 AM
I agree with Jon and it sounds like all you did was put the plane on a giant dyno (my minds picutre).
Title: Re: This is being debated on another thread
Post by: 03Indigo on July 06, 2007, 06:05:19 AM
then again, a plane gets thrust from the air, and the wheels spin freely.  So, as long as the plane can roll, it pushes thrust into the air, and the wheel speed will essentially be twice that of the plane since the ground is moving underneith.

On a dyno, the vehicle is tied down, if the plane is not tied down, and has free movement, and can thrust through the air, it should take off as the wheels provide no forward motion.....meaning the belt does nothing.
Title: Re: This is being debated on another thread
Post by: gragravar on July 06, 2007, 07:02:13 AM
one, I declare massive repost - as we debated this about a year and a half ago.

see here:
http://www.rmcb5.com/forums/index.php/topic,3763.0.html

second, the plane will take off.  as jon so kindly points out, the plane gets its thrust from the air, not through turning the wheels.

if you put a car on a conveyor and tried to power the car via the wheels it wouldnt gp anywhere, but if you hook that same car up to a wall with a winch, then pull the car forward, it will move - the wheels might go 2x as fast as they would have otherwise, but it will move.  same with the plane.  once the plane moves, it gets air under the wings and it will take off.
Title: Re: This is being debated on another thread
Post by: Spicoli on July 06, 2007, 07:13:40 AM
The plane will take off.

The engines of a plane create air speed... The speed a plane needs to take off is related to wind, not speed relative to the ground.

Even though there is a conveyer belt, the plane will still reach the proper lift to take off... but the ground speed would be twice that what is needed. 

If a plane needs to go 60mph to take off, and there was a 60mph head wind, the plane could just take off straight up like a helicopter.
Title: Re: This is being debated on another thread
Post by: 92UrS4 on July 06, 2007, 07:18:32 AM
Haha, nice Andrew, I was like, this seems really familiar, I think it's a repost...it is!
Title: Re: This is being debated on another thread
Post by: SweetVW on July 06, 2007, 07:33:28 AM
I never was very good at word problems.  But after reading the comments, I can understand what is being asked.  I mentioned the dyno visual just because I was not taking in acocunt the engines providing the thrust.  I am having a serious blonde hangover day.   ??? ::)
Title: Re: This is being debated on another thread
Post by: jayryan on July 06, 2007, 11:13:14 AM
Man, Andrew, how do you have a memory like that? LOL. I must've missed it last time, sorry guys.
Title: Re: This is being debated on another thread
Post by: gragravar on July 06, 2007, 01:06:05 PM
Man, Andrew, how do you have a memory like that? LOL. I must've missed it last time, sorry guys.

meh.  I was the one that posted it last time, so it was easier for me to remember.
Title: Re: This is being debated on another thread
Post by: hotani on July 06, 2007, 01:42:22 PM
wasn't this on AWOT? I think the thread was fookin' ginormous. The 'won't-take-off' people were really sticking to their guns!
Title: Re: This is being debated on another thread
Post by: gragravar on July 06, 2007, 01:49:42 PM
wasn't this on AWOT? I think the thread was fookin' ginormous. The 'won't-take-off' people were really sticking to their guns!

yep, it was there the day I got frustrated with those morons and posted it over here.
Title: Re: This is being debated on another thread
Post by: PasSoup on July 06, 2007, 05:30:26 PM
I originally stole it from here and posted it on PW.
Title: Re: This is being debated on another thread
Post by: English on July 07, 2007, 09:01:22 PM
So i figured that the answer was no.....but as with all these type of questions it's the opposite of what you would think.

For what it's worth...we just got a new guy at work who "fly's Ultralights" (what ever the heck one of those is?) and he is positive that "there is no way the plane will ever take off"

...correct me if i'm wrong but i'm sure someone smarter than me, ie Einstein, said "a little knowledge is a dangerous tool"

I like being stupid!?!
Title: Re: This is being debated on another thread
Post by: hotani on July 08, 2007, 12:41:50 AM
Ultralights are hang-gliders with a seat and small engine/prop attached. They don't take an engineering degree (or pilot's license) to fly.