Airplane and Belt Conveyor

[Bob Denman]

:shocked: oops...
Good Point!
I stand corrected, and bow to your problem-solving skillset... :bowdown:

 

[PrairieSpyder]

A plane cannot fly without achieving a certain AIRSPEED. The contact with the ground and the speed at which it travels relative to the ground is irrelevant.

Consider a glider. After it is aloft, it gets lift by having air flow over it's wings. An engine is not required. Thrust comes from gravity.

 

[aeroshots]

Thanks

This is more enjoyable that I first thought, thanks.

So lets consider take off speed of a DC-9 is 140 Kts IAS for a given weight and atmospheric conditions. With zero wind and a normal runway (not one with a conveyer belt) its ground speed/(wheel speed if measured) will be 140 Kts GS for the given conditions. I know, there are other factors that relate to GS, but to keep it simple please humor me. In said example with the conveyer belt runway, the runway will correct for the speed of the "plane" (as I understand the riddle). One would need to ascertain if "plane" speed in this riddle is measured at the wheels or at the pitot tube (i.e. airspeed). If at the wheels then when the IAS reaches take off speed of 140 Kts the wheel speed would be 280 Kts because the runway would be matching the wheel speed thereby doubling it again and again to infinity. The airplane still takes off when it reaches 140 Kts IAS.

JMHO

OP what say you?:dontknow:

IAS = indicated airspeed
GS = Ground speed

 

[ARCTIC]

A plane cannot fly without achieving a certain AIRSPEED. The contact with the ground and the speed at which it travels relative to the ground is irrelevant.

Consider a glider. After it is aloft, it gets lift by having air flow over it's wings. An engine is not required. Thrust comes from gravity.

I wonder how many forums have had this very same question asked and how many hours have been devoted to arguing about it.


Here's the correct answer:

The wheels under a typical airplane are nothing more than nearly frictionless free spinning wheels. The airplane gets ZERO propulsion from the wheels. The airplane is drug through the air by the thrust created by the propeller. The airplane WILL TAKE OFF!!! If the wind was blowing hard enough an airplane could take off with no groundspeed whatsoever (think about that one for a while). It's all about the air movement NOTHING about the ground affects it.

Added thought here: The belt cannot overcome the forward motion of the airplane AND the conveyor moving in the opposite direction is going to cause a wind to assist in the plane's takeoff.

 

[jcthorne]

A plane cannot fly without achieving a certain AIRSPEED. The contact with the ground and the speed at which it travels relative to the ground is irrelevant.

Consider a glider. After it is aloft, it gets lift by having air flow over it's wings. An engine is not required. Thrust comes from gravity.

ehh, ok. The conveyor belt does not have any effect on airspeed either. Same point as I previously spoke. The plane achieves lift and forward speed in the normal manner. The conveyor belt is irrelevant.

 

[ThreeWheels]

This is more enjoyable that I first thought, thanks.

OP what say you?:dontknow:

I say, thank you, that's the purpose of this discussion.

As to the answer, some of you are correct, and others are not.
I won't end the thread prematurely.
If this thread remains active, the answer will be revealed at Spyder Quest in September of 2015.
Provided, of course, that I have enough beer......................................................

 

[Bob Denman]

This was a heckuva lot more fun, than I originally thought...

Thanks! :clap: hyea::yes:hyea:

 

[jcthorne]

I wonder how many forums have had this very same question asked and how many hours have been devoted to arguing about it.

It takes time to explain the laws of physics to those uneducated in the subject. They are not always easy concepts to understand. And this riddle tires to throw an irrelevant curve ball into the mix. Your answer may have explained it better than I did.

 

[Bob Denman]

But... Once in a while; the Pig DOES learn to whistle! :thumbup:

 

[vided]

 

[ARtraveler]

I hope this is technical enough for the Technicality Police. :roflblack::roflblack:

I will watch this one. Don't feel like math this morning. :yes:

 

[spydaman60]

I say, thank you, that's the purpose of this discussion.

As to the answer, some of you are correct, and others are not.
I won't end the thread prematurely.
If this thread remains active, the answer will be revealed at Spyder Quest in September of 2015.
Provided, of course, that I have enough beer......................................................

you and bridgett missed farkle bingo last year and that would be the perfect spot for the answer steve. ps. i won't ask where you and bridget were!:roflblack:
:roflblack::roflblack:

 

[aeroshots]

Yes and No

Not going to Spyderfest so I'll summarize my view and close with this.

Even if said plane requires forward motion to create lift, i.e. not VTO capable it will still take off. It will move forward due to its thrust being independent to its wheels. Again, the conveyer runway will match the rotation speed of the wheels into infinity or until the airplane reaches take off speed. Then airborne.:clap:

If the conveyer were successful in its attempt to keep the plane motionless, then grounded I say, GROUNDED. Unless of course the headwind were equal to the take off speed of said plane then the plane would hover above the conveyer and thumb its nose at said naughty conveyer runway for delaying its scheduled departure time and inconveniencing the passengers.

My personal conclusion is Yes and No.nojoke
I'm 100% confident in my conclusion. :roflblack:

 

[Yazz]

Arggg! Aeroshots, we posted at the same time, saying the same thing different ways. You said it better!

Leaving this in through...

Take a piece of lined paper and cut it in half lengthwise. Hold the paper under your lower lip and blow. That is the principle of lift which gets airplanes in the air and keeps them there.

 

[Bob Denman]

:yikes: Paper cut on my lower lip now... :banghead:
As I leak blood onto my collar; I'm left to ponder flight...

 

[ottawa-rider]

The plane will take off when its AIRSPEED reaches what the pilot call V2 or take-off speed.

The speed of the conveyor or its direction will not affect the plane's ability to reach that speed since it is not attached to the conveyor.

As has been said above, the only force acting on the plane is from the thrust of its prop or jet engine.

The only impact of the counter rotating conveyor will be a small amount of friction.

 

[ottawa-rider]

Seems like we are all tripping over each other trying to say the same thing.

 

[jonnysevel]

The counter direction conveyer has no effect once the engines are providing enough thrust to overcome rolling resistance of the wheels. It cannot 'counter' the forward acceleration that is the direct effect of the rearward acceleration of the air through the engines. This is nothing like a car that uses the wheels to generate the forward thrust.

:agree: Absolutely correct! not a case of relative motion.. If the wheels were providing the propulsion then that would be a different story

 

[jaherbst]

A plane is standing on a runway that can move (some sort of belt conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

NO

Jack

 

[bruiser]

The airline will charge passengers a fee for the conveyor.

The aircraft will become airborne as long as the engine(s) provide enough reaction force, thrust, to overcome aircraft weight, thrust to weight ratio, and forward speed to provide wing lift. The overall effect of the conveyor is nil.