grumpy wrote:No not automatically, just the way it is, speed is altitude, want to go up go faster, want to go down , go slower. Furthermore a plane cannot fly at full speed at sea level because the air is too thick, nor can it fly at higher speeds at ground level because of ground effects. If it were tried it would just lift off. Most jets take off at 165mph, trying to go faster and stay down just wont happen.
That's not really accurate.. There is a moving surface on the tail of the plane (horizontal stabilizer) called the elevator. It directs the plane up or down. Just as there is a moving surface on the horizontal stabilizer called a rudder. It directs the plane left or right. There are moving surfaces on the wings that move up on one side and down on the other they are called ailerons. They change the pitch of the plane..
Speed of the plane is needed to create lift with the wings. Air density does have an effect on speed but speed doesn't have a bearing on making the plane go up or down, that's the job of the horizontal stabilizer..
An airliner also has another moving surface on the wings called flaps. They mechanically extend on the trailing edge of the wing to increase the wing's surface area so it CAN take off and land at slow speeds such as 130 MPH. The flaps retract once its airborn so it can reach it's cruising speeds around 500 MPH. Otherwise it would need to reach over 200 mph to get off the ground
After re reading your post it would be accurate to say if you want to go faster, you need to go higher. If you want to go slower, you need to go lower.. Closer to the ground the air density is higher and more lift can be generated at slower speeds.. This works the other way too. IF a jet could stay in the air at 200 MPH with out stalling (no flaps) at 500 feet, It would need to maintain a higher speed at a higher altitude to maintain lift without stalling.. (stalling is when the wing can't produce enough lift to stay airborn and it simply falls out of the sky.)
Point an airplane at the ground and it will absolutely exceed its cruising speed of 500 mph no matter what altitude its at..
Sorry didn't mean for that to get so lengthy hahaha..