Page 477 - engelsk

Principles of flight

If the above is fulfilled, we have an ideal situation where the 4 forces all act at

the same point: the center of pressure for lift (the red plus sign in the figure on

the previous page) which in this case is equal to the center of gravity.

And here we do not need to use the elevator

On the other hand, if the

center of gravity is moved,

for example if a person

moves from the front seat

to the back seat, we must
correct for the changed

center of gravity by using

the elevator if we want to continue flying horizontally.

If we do not do this, the machine will become heavier behind the center of
gravity in the above-mentioned case, thereby pitching up the nose and climbing.

To counteract this, we must trim the tailplane or apply downward elevator

deflection.

A prerequisite for horizontal flight at constant speed is:

- that lift is equal to weight

- that thrust is equal to drag

- that the negatively acting moments of thrust and drag are equal to the

positive moment of lift

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 477