Will The Plane Fly? - Page 2

Cork Rib · 22 November 2007, 13:22

Quote:

Originally Posted by kitten

you said it

Ok kitten, instead of throwing bombs, why don.t you give us the wisdom of your brain?

Cookee · 22 November 2007, 13:26

Quote:

Originally Posted by Cork Rib

Only if the speed created by the thrust EXCEEDS the reverse speed of the treadmill. The aircraft will then be moving forward and creating lift under the wings. It would then give a shorter take off run. Conversly, if the thrust is less the aircraft would reverse on the treadmill. Remember in the original question there was no mention of any simulated wind speed.

OK let me have a go at explaining it - if it was a car it would stay stationary as the wheels are turning against the treadmill. The thrust of the plane is acting against the air not the treadmill, therefore the plane will behave completely normally but the wheels will be going faster - that's all.

Cork Rib · 22 November 2007, 13:43

Cookee, i accept your explanation. it made sense when you used the car / plane analogy. thats the beauty of an online arguement. We get there in the end

Nos4r2 · 22 November 2007, 14:15

Quote:

Originally Posted by Cookee

OK let me have a go at explaining it - if it was a car it would stay stationary as the wheels are turning against the treadmill. The thrust of the plane is acting against the air not the treadmill, therefore the plane will behave completely normally but the wheels will be going faster - that's all.

Time for pedant's corner

You're assuming the wheelbearings and tyres are completely frictionless and that there's no gravity-so the plane is in fact providing a force that's acting on the conveyer-ie the engines aren't just acting against air.

In reality the wheel bearings and tyres would probably die before it got off the ground.

Cookee · 22 November 2007, 14:42

Quote:

Originally Posted by Nos4r2

Time for pedant's corner

In reality the wheel bearings and tyres would probably die before it got off the ground.

I'm not sure we're talking about reality here - what about the bearings in the conveyor - while we're at it what about the conveyor itself!

Besides if the plane is capable of the sort of rough landings I've experienced over the years I think one double speed take off would be possible!

yoyo · 22 November 2007, 15:09

No airflow across the wings...No take off. This and that end of chat.....

Cookee · 22 November 2007, 15:10

Quote:

Originally Posted by yoyo

No airflow across the wings...No take off. This and that end of chat.....

Have you read post number 22?

jwalker · 22 November 2007, 15:27

Quote:

Originally Posted by Cookee

Have you read post number 22?

Did you read this part of the original question?

Quote:

The conveyor belt is designed to match the speed of the plane exactly but moves in the opposite direction.

Cookee · 22 November 2007, 15:38

Quote:

Originally Posted by jwalker

Did you read this part of the original question?

Yes - I'm interested as to what effect you think that has!

Watchemrocks! · 22 November 2007, 15:52

Quote:

Originally Posted by yoyo

No airflow across the wings...No take off. This and that end of chat.....

I agree! If you don't, please explain where the relative wind would come from that produces a negative pressure above the wings that exceeds the weight of the airplane.

Andy Moore · 22 November 2007, 15:54

Quote:

Originally Posted by Nick Hearne

But the wheels do not propel the plain it is the thrust from the engines, so it will take of as normal moving forward through the air creating lift under the wing!

But it will not be moving forward in relation to the surrouding air because the conveyor is running backwards at an equal velocity to the engines take off velocity. So, the plane appears to be stationary as far as air flow is concerned.

Poly · 22 November 2007, 16:28

If the engines are off and the plane sits on a moving conveyor which direction does the plane go?

if there is "zero friction" in the tyres/bearings then they just spin and the plane remains stationary.

If friction is considered the plane moves at the same speed (and direction) as the conveyor (as it would with the brakes on) then why with the engines on providing forward thrust is there no longer a thrust in the opposite direction from the conveyor"?.

Anyone going to try it with a model at the local gym?

Cookee · 22 November 2007, 16:28

Quote:

Originally Posted by Andy Moore

But it will not be moving forward in relation to the surrouding air because the conveyor is running backwards at an equal velocity to the engines take off velocity. So, the plane appears to be stationary as far as air flow is concerned.

Can you explain how the conveyor has an effect on the thrust of the engines? The engines do not propel the wheels, they push against the air, therefore the plane will go forwards in relation to the air and the surrounding ground, and at double the speed in relation to the conveyor.

The conveyor velocity does not equal the engines velocity as they are not connected!

Andy Moore · 22 November 2007, 16:50

Quote:

Originally Posted by Cookee

The conveyor velocity does not equal the engines velocity as they are not connected!

Correct. The conveyor velocity is equal-and-opposite to the potential take-off velocity of the plain.

Therefore, the plane will effectively be stationary in its air space, Yes, the wheels will be going twice as fast but this is irrelevant.

J S · 22 November 2007, 17:02

Quote:

Originally Posted by Polwart

If the engines are off and the plane sits on a moving conveyor which direction does the plane go?

if there is "zero friction" in the tyres/bearings then they just spin and the plane remains stationary.

If friction is considered the plane moves at the same speed (and direction) as the conveyor (as it would with the brakes on) then why with the engines on providing forward thrust is there no longer a thrust in the opposite direction from the conveyor"?.

Anyone going to try it with a model at the local gym?

As i said i have had a very simlar situation with my model planes.

James