"Because in making a turn, the momentum of the plane sets up a centrifugal force, acting horizontally outward. To counteract this, the force of lift must be inclined until it has a horizontal component equal to the centrifugal force. The machine is therefore tilted to one side, or banked, thus maintaining a state of equilibrium in which it will turn steadily. No turn can be made by the use of the rudder alone. The plane must be banked with ailerons before the rudder will have any turning effect.--Get me?"
"I get the last part. Guess I'll have to do some studying."
"Everybody has to do that. But I'll lend you some books, so you can bone up on the theory of flight. What I said just now amounts to this: if you don't bank enough you send your plane into a skid."
"Just like an automobile skids?"
"Yes. But of course the danger doesn't lie in hitting anything as in a car. A skidding plane loses her flying speed forward and drops into a spin. On the other hand, if you bank her too sharply, you go into a sideslip!"
"And the result in both cases is a crash?"
"Generally. But I think you've had enough instruction for today."
"Oh--but I want to know how you ended that turn. We're flying straight again now--and I was so interested in what you were saying, I forgot to watch what you did!"
"Well, after I had banked her sufficiently, I checked the wings with the ailerons and at the same time eased the pressure on the rudder. Then I maintained a constant bank and a constant pressure on the rudder pedal throughout the turn. To resume straight flight, I simply applied left aileron and left rudder: and when the wings were level again, I neutralized the ailerons and applied a normal amount of right rudder."
"My goodness!" exclaimed Dorothy--"and that is only one of the things I have to learn. I thought that flying a plane wouldn't be much more complicated than driving a car."