Pilots question

[Firestar]

A plane is standing on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes' speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction).


The question is:

Will the plane take off or not? Will it be able to run up and take off?

 

[tommays]

Re: Pilots question

No

Tommays

 

[Bondo]

Re: Pilots question

Planes Don't Care how fast the Ground Speed is,..........

It's all about Air Speed........

Replace your Conveyor with a BIG Fan,+ the plane Could lift Off.........

 

[aspeck]

Re: Pilots question

Absolutly not. Need the air flow over the wings to create lift. It is not the speed, but the lift. Speed is only needed to create lift. If the plane is standing still, no lift.

Now if the conveyor belt was propelling the plane forward, the plane would not need to "run up", the conveyor could get it up to speed for take off.

 

[JB]

Re: Pilots question

What Bondo said.

Example: A light plane takes off from the deck of a nuke carrier running into a 20 knot breeze at 30 knots. Air speed is 50 knots and the plane rises from a fixed spot on the deck.

In your example you seem to assume that wheel speed cancels air speed. Aircraft care not about wheel speed, they move relative to the air, not the ground.

 

[QC]

Re: Pilots question

Yes it will take off. Unless the brakes are set, the plane does not care what speed the conveyor is running, it will still propel itself forward as it's propulsion acts on the surrounding air, not the surface . . . Theoretically the only additional load affecting the equation is that created by the wheel bearings spinning faster than they would normally have to.

 

[QC]

Re: Pilots question

Ooops. New mouse with those fliipin' side buttons :| I keep hitting the "back" button by mistake. Should help the post count until I get used to it.

 

[Firestar]

Re: Pilots question

Ooops. New mouse with those fliipin' side buttons :| I keep hitting the "back" button by mistake. Should help the post count until I get used to it.

d:^d

 

[jtexas]

Re: Pilots question

It might take off. it's more likely to hit a barricade or berm or highway or whatever when it runs off the conveyor.

good answer, QC - hey let's try it with the brakes on and see if it burns up the conveyor motor...........

 

[tommays]

Re: Pilots question

If the belt is moveing at a matched speed to the PLANE its not going any place

the tires might wear out


Tommays

 

[Haut Medoc]

Re: Pilots question

Would it take off once the tires wore out? :}

 

[crunch]

Re: Pilots question

Yup, backwards.

 

[QC]

Re: Pilots question

You guys are missing it. Why does the plane care how fast it's wheels are spinning?

 

[crunch]

Re: Pilots question

It doesn't.... until they blow and it rips the undercarriage off. Then, if the conveyor is still running at say, 160 MPH, that puppy will take off backwards.

 

[tommays]

Re: Pilots question

When i run on a treadmill there is just never a breeze

Gotta use a fan to move the air


Tommays

 

[QC]

Re: Pilots question

tommays,

Mount that fan to your nose and add 100 bhp . . . You still on the treadmill?

 

[jtexas]

Re: Pilots question

try this:

1. Position a treadmill with its back against a wall.
2. Put a skateboard on the treadmill. Stand on the skateboard.
3. Turn the treadmill on.
4. Push against the wall with your hands.

As the treadmill accelerates, do you have to push harder to keep from smashing into the wall? If you lean against the wall with your feet on the skateboard, can the treadmill go fast enough to keep you from falling on your arse?

Gravity is holding the aircraft to the moving runway. And friction. It will start to move backwards. If the treadmill is moving the plane backwards at, say 250 knots, its airspeed is -250. To achieve a ground speed of zero would require enough thrust to achieve an air speed of 250. But once it reaches 250 knots relative to the runway, it'll be holding at airspeed of 0, while producing 250 knots worth of thrust. How can it not move forward?

 

[technostingray]

Re: Pilots question

"if you don't speak the language, you become subservient to those who do."

 

[technostingray]

Re: Pilots question

Now what did I do with that whistling emoticon I stole from xtraham? 8)

 

[tommays]

Re: Pilots question

(This conveyor has a control system that tracks the planes' speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction).

As described the plane will never be moveing and the wings will not have air flow


Tommays