Thread: Airplane on a treadmill

Originally Posted by vnx205

They all fail to realise that the treadmill can't stop the plane moving forward.

UNSW school of physics response. To stop the plane moving forward need one or more of:

a) conveyor running at supersonic speeds.
b) pilot applying wheel breaks.
c) pilot not revving engine creating less than normal thrust.
d) a conveyor so huge and fast it moves the surrounding atmosphere with it.

Of course it all been covered before and I know from previous experience it's pointless but anyhow...

UNSW School of Physics:- The plane on the conveyor belt

I think some of the responses from the people on here with aeronautical qualifications suggests that they might be quite knowledgeable about things that are covered in their training and things that they have experienced.

However, when it comes to something they were not taught or have not discovered through experience, they are not necessarily more expert than the rest of us.

Flight training doesn't cover planes on treadmills, so our resident aeronautical experts are obviously quite out of their depth on that subject.

At the moment, I think they are the only ones who are still answering the question incorrectly.

The treadmill is like a politician - it's all smoke and mirrors...

Ask a Pilot how they make a aircraft take off - they will answer correctly every time..

The only time any link to the landing gear has impact on taking flight is on the deck of an Aircraft carrier (the catapult)

I have a theory about why so many pilots get this wrong. I'm starting with the assumption that they are generally intelligent people (although some can be particularly stubborn).

As soon as they hear a question about aircraft, their mind goes straight to their understanding of aerodynamics. That is hardly surprising since that is a subject they know about and a place where they feel comfortable.

Because they focus on aerodynamics, they assume the question says that the plane tries to take off and the spinning treadmill holds it stationary. Their answers are then based on that mistake.

If they thought a little more about treadmills and a little less about aeroplanes, they would realise that the question couldn't possibly say that because it would be a physical impossibility. The treadmill has no effect.

The question is correctly and carefully worded. The pilot tries to take off and the treadmill operator tries (and fails) to hold the plane stationary.

The pilots aren't answering the question that was asked, they are answering a different meaningless question.

It is because they know about planes that they leap to the wrong conclusion.

Since it is quite understandable that they would see the question as something about planes, it is appropriate that we have all been more tolerant in dealing with their recalcitrance than we might have been for less aeronautically qualified people.

Well Though Ive found this thread excruciating I can also admit being incorrect.
All of us are at one time or another.

So why do Pilots seem to have the most difficulty with this?

Heres why.

Firstly lift (and this not the universally correct terminology for all aerofoils however in the case of this fixed wing aeroplane will do) only comes from airflow which is one of the facts mentioned by myself and others.
So all pilots are looking for airflow to create lift which requires a fwd speed.
Obviously this is generated by whatever motive system is fitted.
Any perception of an action contrary to this instinctively leads to negative answer.
Particularly where in any case thrust is required for the aircraft to remain stationary relative to position on the conveyer.

Next. All manner of ground inhibits the generation of that fwd speed and therefore lift.
Ill stay on takeoff and ignore landing.
The takeoff run required for a given day i.e wind-temp-weight-altitude and surface, varies considerably and on a marginal rwy, is the difference between a happy day and turning the multimillion $ ship into ball with you in it.

The above is what I had to subconsciously hurdle.
Pilots dont theorise about landing surfaces such as the one posed. We work with data and factual numbers generated by actual operation on the surfaces encountered augmented by lessons learnt from failures and success over the history of aviation.
Which results in typically systematic, procedurally driven process coupled with a dextrous skillset.

Considering surface for takeoff capability.
eg. A long grass rwy can provide enough friction to prevent gaining enough airspeed for takeoff.
A tailwind increases the distance for take off (and landing) as more length of rwy is required to overcome the tailwind and generate fwd airspeed.
The practical use of these facts on daily basis causes an instinctive view that any surface which appears counter intuitive to the desired outcome as preventing or inhibiting takeoff.

Wheels: They are not frictionless marvels and breakaway thrust is needed to get a machine moving from standing.
Therfore if on a conveyer the aircraft is going backwards unless thrust is applied to breakaway from the initial wheel contact patch to get it rolling.
Because we all work with a calculated actual numerical distance required for takeoff run subconsciously we again discount the hypothetical.
Now subconsciously these and other experienced and mandatory initial factors are building a "no" position.
Add to this that all the above are always finite quantities which if disregarded end badly for any flight.
However
need to be disregarded in the hypothetical question eg. the absurdity of the conveyer in the first instance.
Now..
It is because of the above (very simply stated) factors to be considered for take off that some of us have put practical application and dismissal of hypothetical absurdity rather than pursue the final outcome.

If you were able to place any pilot who thought the plane woulndt fly, onto said conveyer, the initial response when the airspeed increased would be that the conveyer wasnt able to keep up with the plane. I reckon most would get it as soon as the thing left the ground.

So, this may help it may not. I certainly dont feel silly.
In fact Im going to use this thread as an example in Human Factors refresher courses to highlight how we can be conditioned to exclude or accept information based on our exposure to highly specific and demanding roles.

Originally Posted by strangy

If you were able to place any pilot who thought the plane woulndt fly, onto said conveyer, the initial response when the airspeed increased would be that the conveyer wasnt able to keep up with the plane. I reckon most would get it as soon as the thing left the ground.

The pilot in the mythbusters video was equally surprised when he took off. The question being tested by mythbusters was, I think, worded slightly differently to the one originally posed here though the mythbuster video nonetheless demonstrates the basics of it.

https://www.youtube.com/watch?v=0ul_5DtMLhc

Ah yes. In the OP Vlad (whom I suspect is a great red herring tosser) poses the question and shares a link. In the link a blogger named Chris gives us said question and some variants, then he predicts exactly what will happen on any forum it's posted on and carries on to tell us why the aircraft will take off.
He got it right, or should I say wright?

What if, instead of an aeroplane on the treadmill, there was a.....


















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