Chapter 2 - Aerodynamics of Flight
Forces in Flight
Like all aircraft, the four forces that affect PPC flight
are thrust, drag, lift, and weight. [Figure 2-10] In
steady PPC flight:
1. The sum of all upward forces equals the sum of
all downward forces.
2. The sum of all forward forces equals the sum of
all backward forces.
3. The sum of all moments equals zero.
THRUST – the forward force produced by a powerplant/
propeller as it forces a mass of air to the rear (usually
said to act parallel to the longitudinal axis).
DRAG – the aerodynamic force acting on the airfoil
lines and cart in the same plane and in the same direction
as the relative wind.
LIFT – the aerodynamic force caused by air flowing
over the wing that is perpendicular to the relative
WEIGHT – the force of gravity acting upon a body.