Aeroplane question (not a conveyor belt)

[tybalt]

The people at work have suggested an alternative plane takeoff problem.

All velocities relative to ground

Plane on ground (not conveyor belt)
Big fan behind plane (on a truck following behind if you like), blowing at plane
Velocity of air from fan is equal to airplane velocity

Maybe they should try that on mythbusters (with a model).

[davido140]

I'll wade in with a guess first then, plane wont take off, the air blowing from behind will cancel-out or at the very least bugger up the lift generated by the wings.

[John MacK]

Plane will take off no problem.










If it's a Harrier.

[Papoo]

Aircraft needs air flowing over the wings from front to rear to generate lift. Therefore, if an aicraft takes off at 100mph in still air, if it had a 20mph tailwind, it would need a groundspeed of 120mph to induce the necessary airflow to take off.

So, yes, if the big fan blew air at 100mph, the take off speed would be 100mph higher than the aircrafts normal take off speed.

I like fans, and planes, so I would also like to see the mythbusters take on it.

[Eric Mc]

tybalt said:

The people at work have suggested an alternative plane takeoff problem.

All velocities relative to ground

Plane on ground (not conveyor belt)
Big fan behind plane (on a truck following behind if you like), blowing at plane
Velocity of air from fan is equal to airplane velocity

Maybe they should try that on mythbusters (with a model).

Do they know how a plane works?

[Bluetoo]

obviously not, I guess you could create some kind of hovering plane in the airstream the fan creates but not sure what the practical use would be?

[williamp]

[monty python]

We build a large rabbit, and then leave it outside the gates. And...

[/monty python]

[Eric Mc]

Bluetoo said:

obviously not, I guess you could create some kind of hovering plane in the airstream the fan creates but not sure what the practical use would be?

You've just reinvented the wind tunnel.

[Papoo]

Eric Mc said:

Bluetoo said:

obviously not, I guess you could create some kind of hovering plane in the airstream the fan creates but not sure what the practical use would be?

You've just reinvented the wind tunnel.

Respect.

[davido140]

Eric Mc said:

tybalt said:

The people at work have suggested an alternative plane takeoff problem.

All velocities relative to ground

Plane on ground (not conveyor belt)
Big fan behind plane (on a truck following behind if you like), blowing at plane
Velocity of air from fan is equal to airplane velocity

Maybe they should try that on mythbusters (with a model).

Do they know how a plane works?

It's magic isnt it?

[SlipStream77]

I use an RC simulation called Aerofly Pro, it's quite fun to turn up the wind speed and then try taking off in a large scale prop 'plane.

Facing the wind, you have to give it some revs to stop going backwards but when the aircraft is stationary with sufficient revs, gently pulling back on the stick makes it take off. It's really quite odd seeing an aircraft do this, the attitude is the same as a normal take off, but the ground speed is zero.

[MartG]

SlipStream77 said:

I use an RC simulation called Aerofly Pro, it's quite fun to turn up the wind speed and then try taking off in a large scale prop 'plane.

Facing the wind, you have to give it some revs to stop going backwards but when the aircraft is stationary with sufficient revs, gently pulling back on the stick makes it take off. It's really quite odd seeing an aircraft do this, the attitude is the same as a normal take off, but the ground speed is zero.

IIRC this used to happen for real, back when biplanes took off from aircraft carriers steaming into the wind - the wind over deck often got very close to the planes takeoff airspeed

[strudel]

MartG said:

SlipStream77 said:

I use an RC simulation called Aerofly Pro, it's quite fun to turn up the wind speed and then try taking off in a large scale prop 'plane.

Facing the wind, you have to give it some revs to stop going backwards but when the aircraft is stationary with sufficient revs, gently pulling back on the stick makes it take off. It's really quite odd seeing an aircraft do this, the attitude is the same as a normal take off, but the ground speed is zero.

IIRC this used to happen for real, back when biplanes took off from aircraft carriers steaming into the wind - the wind over deck often got very close to the planes takeoff airspeed

Similar Example

Edited by strudel on Monday 10th August 19:28

[dr_gn]

SlipStream77 said:

I use an RC simulation called Aerofly Pro, it's quite fun to turn up the wind speed and then try taking off in a large scale prop 'plane.

Facing the wind, you have to give it some revs to stop going backwards but when the aircraft is stationary with sufficient revs, gently pulling back on the stick makes it take off. It's really quite odd seeing an aircraft do this, the attitude is the same as a normal take off, but the ground speed is zero.

I do it every time I fly my slope soarer gliders - if the wind's right, just push the nose down enough and it will 'hover' with zero ground speed all day long. In fact this is the best way to land them: point into wind while still in the lift band and push the nose down gently with zero ground speed. You can just as easily fly 'backwards' by putting in enough up elevator.

[tybalt]

Eric Mc said:

Do they know how a plane works?

Yes. It was a suggestion for a workable stupid method for stopping things taking off.