Powered Parachute Flying Handbook

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 wind.


WEIGHT – the force of gravity acting upon a body.

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