Frans,
The forces are as illustrated in my first posting.
If you throttle back the engine, all properly designed and built aircraft
automatically pitches down to gain speed. The pitch-down is of course the
result of the stabilizer's design and angle of incidence vs. the wings' .
Why gain speed: To give required lift.
To get enough speed to give the required lift, the pulling force must be
kept up. Lost propeller thrust must be compensated by something. As lift
CANNOT give force in the direction of flight (remember, BY DEFINTION it is
perpendicular to the direction of flight, thus it has no forwards nor
backwards component flight-direction-wise).
What is this "something" force that compensates for engine power? Look at
the bottom illustration in my first posting: To create a forward force
(forward meaning in the direction of flight) to maintain speed to maintain
lift, the only possible force available is the gravity's flight-direction
component. The steeper the pitch-down, the larger this force becomes, and
the faster down you fly. This creates more lift (perpendicular to the
flight direction), of course, but the vertical component of the lift remains
the same - equal to the weight of the aircraft plus the vertical component
of the downward stab. force.
The gravity component acts on every atom in the structure's molecules, but
we commonly consider them all grouped together at what we refer to as the
center of gravity (CG), and uses this as point as the one common point where
the total pulling force acts. Neither the fuselage nor the wings pull the
aircraft forward, good ol' gravity does it all by itself!
Do this, Frans: Shake off all your conceptions. Look ONLY at my
illustrations. The global airplane forces are actually this simple.
Alan,
Right on!
Regards,
Svein
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