If lift can occur at any angle, Why don't Cessna 152's flip over in flight?

Question

The main wing has a curved surface on top of the wing, the horizontal stabilizer has a curve on the bottom. Since lift is generated from both surfaces, why does the planes tail not get flipped downward?

Answer 1

I'm not sure I completely understand what you're asking, but I'll give give it a shot and try to keep it simple.  The tail produces lift, but it's not the same lift that the wing produces.  It is lift in the downward direction.  This is because, like you said, the tail is shaped like an upside-down wing.  This produces what's called a tail-down force.

Without a tail-down force, the lift produced by the wings would cause the aircraft to nose over (like others have said, the center of gravity or "pivot point" of the airplane is in front of the center of lift of the wing).  The downward lift created by the horizontal stabilizer balances this out.

Answer 2

The answer is simply because the force exerted by the horizontal stabilizer counterbalances the force exerted by the wing. Center of gravity and center of pressure are important considerations, but the bottom line is that you have two devices, each with a unique inherant motion, and these motions balance each other out.  Here's a very basic layman's explanation,

On a conventional aircraft design, the reason that a horizontal stabilizer is required in the first place has to do with Newtons Third Law of Motion: For every action, there is an equal and opposite reaction. Since air moving over the upper surface of a wing is ultimately being displaced downward to the rear in a curved motion due to the shape of the airfoil,  the wing (according to Newton's law) naturally wants to pitch over in the opposite direction. The horizontal stabilizer is there creating it's own force that counteracts that motion. The distance the stabilizer is placed from the wing basically determines what size it must be to counteract the pitching motion of the wing.

As you point out, a wing produces lift in any attitude (if you have the power and / or momentum to hold it there), but so does the horizontal stabilizer, in roughly the proportion required to counteract the pitching moment of the wing, no matter what the speed as long as it is above the stall. The elevator is there so that the pilot may vary the effect of the stabilizer, thereby precisely controlling the motion of the airplane about the lateral axis, or pitch axis as it is sometimes referred to.

<EDIT> p.s. to the person who gave the thumbs down. I answer questions on here, not for points (which are meaningless) but to give accurate understandable information. I challenge you to disprove what I've said here, so I'm all ears and will gladly respond to private email.

Answer 3

flaps

Answer 4

Simplest answer incoming!

The plane doesn't flip because the aircraft is designed to be heaviest at the front.  The engine is up there for a reason.  The purpose of the tail is to add a counterbalance to the weight of the engine and push the tail down, thereby raising the nose.

Think of a perfectly balanced teeter-totter.  That is an airplane in flight.

Answer 5

To understand this you need to be familiar with two terms, center of gravity and center of pressure (lift).  Think of the center of gravity as being the fulcrum on a scale... the balance point of the airplane.  The center of pressure is the total sum of all the lift produced by the main wing, which happens in a specific point along the wings surface.

In normal situations, the center of gravity lies ahead of the center of pressure.  Thinking about this on a balance beam, you can see how the plane would rotate forward unless the tail surface was producing downforce.  The amount of downforce can be controlled by the elevator or stabilizer position.  If the aircraft is loaded towards it's aft limit (think bricks in the back baggage area), the center of gravity and center of pressure may coincide at one point.  In this situation the tail may not need to create any downforce at all to 'balance' the airplane.  

Taking it done step further, you can now see why a plane will fly faster if it is loaded with an aft CG... because the tail is producing less downforce and consequently less induced  drag.

Answer 6

I agree flaps and aerodynamics are at play here.

Answer 7

center of gravity is rather towards the front

the control surfaces will exert whatever counter force is necessary , especially trim tabs.

the difference in lift the wings and the tailplane generate are extremely different.

the lift generated by the horizontal stab is minimal. It is used to give the aircraft a positive attitude. this means when the stick is released, the plane will tend to return to straight and more or less level flight.

as a side note, there are planes with neutral or even negative attitude; requiring a computer to assist the pilot fly in a controlled manner.

Answer 8

the lift is increased with speed. If the plane was going any faster this may happen.

with model rc planes if you get too big an engine on a plane it will only go up, you can't fly straight and level.