Adrian_

You're partially right, didn't wanted to go that deep Bernoulli's principle explains the flight itself, but not the take-off in modern aircraft. The supplementary ascensional force needed to lift the plane from the ground comes from the force given by the air flying under the wing and pushing in the various accesories extended downwards at take-off



The P51 thing iss perfectly natural, since no fixed propellor airplane is capable of taking off from the spot.

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1979 Euro

pasa

The tail lifted because the propeller was in effect providing airflow over the rear wing.

blown 87

But a Maule M5 can come damn close to that.

RicerSchnitzzle

The answer is yes if the engine can provide enough pull. All of the propeller blades are wings themselves. Rather than airflow creating a low and high pressure zone over the wing, the props (Foils) move through the air creating the same differential of pressure "lifting" the plane forward. The wing moves through the air rather than the air over the wing. When the plane moves forward and runs out of rope it will pull taught bringing the plane up in the air. But only if the engine can create enough forward thrust to overcome the plane's weight. If you have enough engine it can be done.

This can be proved simply. Get a balsawood rubber band airplane. Attach the tail to a string and then hold the other end of the string. Have a friend (If you have any) pre-load the rubber band to what we used to call "TRIPLE KNOTTED" as kids. That dangerous zone where you either got the most exciting flight of your childhood or the rubber band broke leaving you walking home early... Let go of the plane and see what happens. At max thrust when you first let go the plane will indeed go straight out. However it will quickly loose enough thrust and start dropping, keep the string taught until verticle facing the ground.

Adrian_

That's why I'd put my money on the Dornier's Do 335 push-pull propellor configuration if we were to bet which real-life propellor airplane can do this .

blown 87

There has not been one flown since right after WW2, IIRC there are only three left in the world.

Adrian_

True, but still, it's a real airplane. What's more important for our subject is the concept of a push-pull propellor aircraft.


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1979 Euro

mark kibort

Yep, its all about thrust and force vectors. Holding a plane by its tail by a stong enough string, it will lift off given the proper force and thrust vectors

mk

RicerSchnitzzle

What if you put a mustang RR engine in a 928 so this thread doesn't get moved? With a heavy duty chain attached to the rear bumper would it still make it around the N-ring?

GlenL

This is ridiculous.

The answer is no.

Picture how long the wings are and the take off speed. Then look at the area behind the propeller. Divide the lengths and multiply by the speed. You'd need supersonic flow behind the prop to begin to get the lift. And that flow is turbulent and the flow is supersonic. It's not going to work. Never.

Or how about engines placed prop tip to prop tip? The thing will be too heavy to fly.

blown 87

I can tell you that a C150 will fly while trying to get it tied down in a strong wind, not far and not under control, but it did become airborne with zero ground speed and no engine thrust.

Tony

No it wont..if the airplane is held in spot by the said string how does the wing move through air to generate LIFT and get the airplane airborne?.

A HarrierJet in hover does NOT create any lift over its wings as it sits supended in the air. It is kept in the air by the thrust vector..not a lift vector. It flies but does not generate lift. The Staurn V flys the same way...no lift...just lots of thrust.

So your answer is right...but also wrong.

The saying is...Given enough thrust a brick will fly


Tony...adding to the topic reply count

mark kibort

an air foil is a thrust vectoring device to a certain extent. air flow generated ONLY by the propeller, routed over the air foil could generate enough lift to lift an aircraft, if the tail was tied by a rope, cable of some sorts. There is a force vector due to lift, and that is what im referring to. Now, couple those forces to the leverage of the tail section which would allow the prop to also vector a downward force/thrust vector, and suddenly you can see how even a cessna with enough thrust , tied to a pole, could levitate. It might even be able to point straight up like a helecoper. Now if we are talking a level angle of attack of the wings, and using only the pressure differntial of the thrust and air flow of the prop over the wing, that would depend on the weight of the aircraft and the shape of the wing. but, in concept, it could levitate.

This is funny, i was having the same conversation with someone on the racing forum. I was on the other side, saying that it was impossible for a plane to be flying (cessna) at 0 indicated air speed. (porpoising on a landing approach). In a head wind yes, but not with no head wind, no indicated air speed and only thrust from the engine alone. The reason is not that it is in concept, impossible, its because a cessna has too little power to generate enough lift (vectored lift) on its own.

Mk

docmirror

Oye vey.

jon928se

Wings largely irrelevant. (the airflow over the wings induced by the prop will induce some lift)

Simple forces and vectors. so long as the plane remains horizontal (or at least points at a less down angle than the string points down) there will be a net resultant force upwards. given enough thrust from the prop the plane will lift off the ground. It's not flying in the accepted meaning of flying.

There must be a number of planes that can do this as I have seen aerobatics/stunt planes that can prop hang (vertical speed = 0) then accelerate upwards again.