cenrtifugal force on plane

[stranger12]

Hi All,

Can someone please explain this to me as I am struggling to understand it

One, the vertical component, continues to act perpendicular to the earth and opposes gravity. The other, the horizontal component, acts parallel to the earth's surface and opposes centrifugal force caused by the turn.

it is from here

Turns (http://avstop.com/ac/flighttrainghandbook/turns.html)

[ArcticChiller]

http://i47.photobucket.com/albums/f182/leftieman/Aircraft%20Physics%20Discussion%20Images/forces_during_turn.gif

Think of it as force vectors, remember physics class? :) Equilibrium of forces. Maybe that helps. Sometimes the force opposed to the centrifugal force is reffered to as centripetal force.

[Shaggy Sheep Driver]

Just think where your pencil would go if you drop it.

Straight and level - It'd fall to the floor

Sustained inverted - it'd fall to the canopy top, or roof if you have one. Or be lost forever if open cockpit.

Balanced erect turn at any angle of bank - it'd fall to the floor

In the top of a loop while inverted - it'd fall to the floor

[Top West 50]

Try "Mechanics of Flight" by AC Kermode (ISBN 0-582-42254-X)

[Pilot DAR]

Decades ago, I was a wet behind the ears "know it all", who worked for an airline. The Chief Pilot, Bill, had dreamed up a "give away" for the kids on our flights. It was an 8 inch or so circle of that thin white styrofoam which eggs and hamburgers used to come in. It was nicely printed with the airline logo, and all kinds of pretties. It was punched such that an arc of the circle could be folded up to form an arch crossing the center of the circle. From the center of that arch, hung a little plastic pointer. This pointer swung over marks printed in the center of the circle, which would indicate a turn, if the pointer were displaced to one side.

Foolishly, in a room populated with my seniors (certainly not my peers!) I asked: "Bill, do all your pilot rudder their turns?".

After a couple of moments of silent consideration, the arch was folded back down, the whole thing placed in the drawer, and never seen again. Probably, I came closer than I was aware to a very similar fate, but in any case, I was not too welcomed in flight ops for a while....

I figured out that my knowledge of the physics of flight were not too bad, but my corporate ladder skills were terrible....

[nonsense]

Are you having difficulty with the distinction between centrifugal force (http://en.wikipedia.org/wiki/Centrifugal_force) (the apparent force outwards experienced within a frame of reference which is accelerating toward the centre of the turn, eg: inside the turning vehicle) and centripetal force (http://en.wikipedia.org/wiki/Centripetal_force), (the real force exerted by the wings on an aircraft, tyres on a ground vehicle, the rope on a bucket swung about your head, etc, which actually makes the subject vehicle or bucket turn)?

[Heston]

Indeed. Forget about centrifugal force since it is entirely fictitious. Understand what is really going on in a turning aircraft and why.

[worrab]

The key to this is that any moving object will continue to move in a straight line at constant speed unless some force is applied.

In straight flight, a flying aircraft will fall because of the force of gravity unless we do something to keep it up. We generate lift from the wing to oppose gravity and keep the aeroplane in the sky.

And now you'd like to turn a corner. You need a force to turn the aircraft. You could use the rudder to yaw the plane and let the engine pull you round the corner. This will work, but it's slow and not very comfortable. A better way is to tilt the plane so that lift from the wing is pushing the plane round the turn. The more you bank, the more lift is turning the plane.

Of course, if you use some of your lift to turn, you have less to fight gravity and the plane will descend. You counter this by pulling back on the stick a little to maintain height.

(No mention of centrifugal force? That's because it doesn't really exist. Anything that's turning is accelerating and the force you apply to make the turn goes to accelerate the plane onto its new vector)

W

[cockney steve]

think of it as a bike,or motorbike of the sky ......
for a given speed, the tighter the turn, the more you "lean" it in.:}

[wiggy]

As other have said ignore "centrifugal force" - it doesn't exist as a "real" force in the Physical world and it can produce much confusion.

As far as turns go - the aircraft is banked the aircraft, the lift vector now has a horizontal component ('cos it's tipped over) - that horizontal component provides the centripetal/sideways force which causes the aircraft to describe a curved path.

I agree you will feel that you are being pushed down into your seat - this is simply because your body would like to continue travelling in a straight line (Newton's Laws), so whatever you don't draw it on the vector diagram as a force acting to oppose the turn because it isn't.

One, the vertical component, continues to act perpendicular to the earth and opposes gravity. The other, the horizontal component, acts parallel to the earth's surface and opposes centrifugal force caused by the turn.

Frankly having had a look at the link and seen that comment I'd suggest you invest in a better book/look for a better website.

[Above The Clouds]

Think of the centripetal force as an acceleration, now relate it to a fast accelerating car, you get pushed rearwards into the seat.

Now apply that logic in the horizontal plane because the aircraft is banked, but this time you get pushed downwards into the seat, i.e. "G" force an acceleration.

[john_tullamarine]

One, the vertical component, continues to act perpendicular to the earth and opposes gravity. The other, the horizontal component, acts parallel to the earth's surface and opposes centrifugal force caused by the turn.

It may help if you think about the forces which are capable of causing changes in motion and reactions which are resulting from those forces.

During the turn, for level flight, lift and gravity are forces which happen to balance out. If, however, you arrange things so this is not the case the difference provides a net force which moves the aircraft either up or down.

The force in the turning plane is that which is causing the turn .. ie inwards toward the centre of the turn. Usually this is referred to as centripetal force with a resulting centripetal acceleration .. doesn't matter at all what you call it .. but it is what is turning the aeroplane.

The resulting reaction from the centripetal force is the reaction ascribed to Mr Newton. Sometimes folk call it a psuedo force but it really is a consequence of the centripetal force and acceleration. No different to swinging a mass on the end of a string about your head .. the force is your pulling on the string to make it accelerate towards the centre of the turn .. the pull on your hand is the reaction. Often this is called centrifugal (as in from centrifuge) reaction.

Forget worrying too much about the terms .. think of what can make the mass accelerate and in which direction.

[stranger12]

thanks very much for this.

I am going over it few times to make a sense of it and will post back if I have further questions

[India Four Two]

stranger12,

I was going to post much along the same lines as most of the other responses here, particularly when I saw the diagram posted by ArcticChiller.

My physics teacher, Doc Strawbridge, would be turning in his grave - "Class, there is no such thing as centrifugal force!"

If you mentally modify ArcticChiller's picture by removing the Centrifugal Force vector and the Resultant Load vector, then you have the actual forces acting on an aircraft in a turn. As mentioned above, the Lift vector has to be larger, so that the Vertical component still equals the Weight and the Horizontal component provides the force necessary to turn the aircraft. In order to increase the Lift, you have to increase the angle of attack, by pulling back on the stick.

The aircraft in the picture could not turn if the forces were as shown, because they are in equilibrium.

[keith williams]

"Class, there is no such thing as centrifugal force!"

That type of statement is the cause of the widespread misunderstanding regarding the subject of forces.

The fact that some forces are classified as "Real Force", does not mean that the other types of forces do not exist in the real world.

A simple internet search for "Real force and inertial forces" will reveal a lot of material on this subject.

Albert Einstein (not generally known to be an intellectual slouch) argued that Gravity is not a real force, but is an Inertial Force. So anyone who wishes to argue that centrifugal force does not exist because it is not a real force, must also logically argue that gravity does not exist.

The diagrams in post 2 represent the situation in an accelerating reference frame. To achieve constant acceleration in a give direction in such a frame requires the applied forces and opposing inertial forces in that direction to be equal and opposite. The diagrams show this correctly.

[bookworm]

http://imgs.xkcd.com/comics/centrifugal_force.png
XKCD (http://xkcd.com/123/)

[Heston]

Now try explaining what an accelerating reference frame is to your average PPL student...

[India Four Two]

keith williams,


I appreciate your point and I should say that I fully understand the concept of inertial forces and frames of reference.


However, as Heston so succinctly put it, using an accelerating frame of reference is not going to help the average PPL student understand the forces acting on an aeroplane in a turn. Explaining turning as the interaction of Lift and Weight is much more readily understood.


As an aside, the cartoon posted by bookworm is one of my favourites. Lots more great cartoons where that came from:
xkcd: Centrifugal Force (http://xkcd.com/123/)


PS I see bookworm also posted the link, but I missed it. It obviously wasn't in my frame of reference!

[wiggy]

Please lets not turn this into a p'ing contest, I suspect many of us here are aware of Mr Einstein's works, perhaps in some detail....fundamentally as India Four Two said:

using an accelerating frame of reference is not going to help the average PPL student understand the forces acting on an aeroplane in a turn.

:ok:


Wiggy

[keith williams]

I have never argued that the use of an accelerated frame of reference is the best method of teaching this subject to the average PPL student. I have simply pointed out that the diagram in post 2 is correct, but one must realize what it represents.