Airplane on a treadmill

My goodness this thread is excruciating.

Its in the way an individual interprets a deliberately ambiguous hypothetical question.

The question is posed in AULRO and initially on the link in such a way as to highlight the way people think irrespective of the physics.
i.e some will think of a treadmill operating one direction while others consider in the opposite direction.

However, the key to the apparent question was answered many times and remains a law of aerodynamics.
No airspeed = no lift = no flight.

The concept may be better understood by considering an aircraft carrier.
Assume we are not bound by design limitations.
Sail along at 100kts which will provide a relative airflow of 100kts, with an aeroplane that flies at 100 kts or less and you have flight, though relative to the deck only the aircraft is stationary.

Now reverse this, the aircraft now has to provide the same nominal amount of thrust (and have an inconceivable deck length) to achieve a relative airflow of 0, which means no flight.however the inconceivably large deck is moving underneath the aircraft at 100kts.

, like some others i make my living maintaining aerofoils in suitable airflow.

Quote:

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Originally Posted by ramblingboy42

read back...

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I have done that several times even though I am beginning to suspect that you have not actually read mine or anyone else's.

Lets's take your posts one at a time to see where you went wrong.

Your first post said:

Quote:

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Originally Posted by ramblingboy42

I may be late into this but the aeroplane (not airplane) clearly wont fly in that situation.

It will remain completely stationary unless more engine power is applied or the speed of the conveyor changes.

If the speed of the conveyor matches the input of the aeroplane there will be zero airspeed.

The groundspeed will be high but no lift is being produced by the wings.....see.....the aeroplane is not moving through the air , only rolling on the conveyor using it's engine power to to keep up to the conveyor operator's input......or conversely the conveyor operator is keeping abreast of the pilot's input.

No argument. It won't fly.

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There it is! Your very first post shows why you keep repeating your error.

The conveyor simply cannot prevent the plane from gaining speed.

I will repeat that since it is the most important point that you seem to have missed.

The conveyor cannot prevent the plane from gaining speed.

I have explained several times and others have explained several times why the conveyor or treadmill cannot prevent the plane from moving forward.

You appear to be assuming that the treadmill can prevent the plane from moving forward.

It can't!

Please explain why you think it can prevent the plane moving forward.

Perhaps you did not read the original question carefully.

It does not say that the treadmill drags the plane back so that it doesn't move forward. It says that the treadmill attempts to match the speed of the plane.

The treadmill can attempt that all it likes, but it will fail.

The plane will move forward, gain airspeed and take off.

In view of the effort that I and others have put into trying to help you understand, it would be nice if you could put some effort into explaining exactly where you believe our thinking is incorrect. Just repeating that a plane needs airspeed to take off is not a useful comment. Everyone knows that.

Quote:

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Originally Posted by strangy

My goodness this thread is excruciating.

Its in the way an individual interprets a deliberately ambiguous hypothetical question.

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I'm assuming that people will read your post, so I won't quote all of it.

The question is not ambiguous. The question is not badly worded. It is not open to interpretation. The comparison with an aircraft carrier is quite unnecessary.

The question deliberately says that the pilot attempts to take off. It then says that the treadmill operator attempts to match the speed of the plane.

People who don't read the question carefully or are concentrating purely on the laws of aerodynamics will fail to grasp the fact that the treadmill can attempt all it likes, but will have no effect on the plane.

It is interesting that pilots on this forum seem to be the ones who have made the mistake that the question is deliberately and cleverly designed to encourage people to make.

It seems that pilots think only about what a plane needs to fly and are completely oblivious to the fact that the treadmill will have no effect.

The plane will fly!

Yep dumb ass pilots. what would they know right?
After all their understanding of phraseology and aerodynamics and application,, pfft.
I mean really who are they kidding
as I said excruciating.

If you are so sure that you are right and the rest of us are wrong, why have you never addressed the specific facts that we have presented?

Don't just tell us we are wrong.

Explain WHY we are wrong.

See my post at the beginning.

I asked a qualified pilot this question on sunday night. He is currently employed as a pilot. He said unequivically that the plane wont fly. "Its impossible for it to move", he said. I could have made another $100.00 of him but i didn't. Seems everyone thinks the propellor is connected to the wheels...

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

Rod, that adds weight to my claim that pilots are probably more likely to get the answer wrong than other people.
:)

I and several others are making a genuine attempt to help the pilots understand why they are wrong.

They are wrong because they are thinking too much about aerodynamics.

In an attempt to show where they are making their mistake, I offer the following analogy. Like most analogies, it isn't perfect, but might start people thinking in the right direction.

Remember that old joke that went something like this:
A plane from Queensland on its way to Victoria crashes in NSW. In which state would the survivors be buried?

Someone with a legal or aviation background might consider the legalities, federal v state laws, the ethical issues, and such things, but someone who reads the question carefully will realise that you don't bury the survivors.

This question is not about whether a plane can fly if it is held stationary.

The point is that it won't be held stationary.

https://www.aulro.com/afvb/images/im...016/11/351.jpg
:):)

Quote:

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Originally Posted by 67hardtop

See my post at the beginning.

I asked a qualified pilot this question on sunday night. He is currently employed as a pilot. He said unequivically that the plane wont fly. "Its impossible for it to move", he said. I could have made another $100.00 of him but i didn't. Seems everyone thinks the propellor is connected to the wheels...

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

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... the pilot is unequivocally correct...again