Powered Parachute Flying Handbook

Chapter 2 - Aerodynamics of Flight


Weight is a measure of the force of gravity acting upon the mass of the PPC. It is the force that opposes lift, and acts vertically downward through the aircraft’s center of gravity. Weight consists of everything directly associated with the powered parachute in flight: the combined load of the total PPC (wing, risers, engine, cart, fuel, oil, etc.), people (clothing, helmets, etc.), and baggage (charts, books, checklists, pencils, handheld GPS, spare clothes, suitcase, etc.). In stabilized level flight, when the vertical component of lift is equal to the weight force, the PPC is in a state of equilibrium and neither gains nor loses altitude.

Because the trim angle is set at the factory, the PPC airspeed is predetermined, before takeoff, by the weight of the aircraft and the wing design. The more weight, the more forward airspeed is generated. Therefore, gravity is the primary force for creating forward speed — pulling the wing through the relative wind while airborne. The forces in gliding flight are very similar to those for an airplane or gliding sailplane. [Figure 2-15] Specific numbers presented in this chapter are examples to serve as a basis to understand the concepts. Each PPC has unique flying characteristics and these numbers will be different, but can be compared to your PPC to provide a greater understanding of your unique performance. Note the component of weight acting along the flight path. This component of weight is called thrust by some but is more accurately the weight component providing the forward force.


Compared to an airplane, as discussed in Chapter 3 of the Pilot’s Handbook of Aeronautical Knowledge, thrust serves different purposes in the PPC: (1) it is used to accelerate the PPC to flying speed while inflating the wing (2) it is used to climb when at high thrust, cruise level at medium thrust, and descend at lower thrust. Variations in thrust have negligible effect on PPC airspeed which remains relatively constant whether climbing, descending, or in level flight.

When enough thrust is added to produce level flight, the relative wind stream becomes horizontal with the earth; the angle of attack and speed remain about the same. Just as described in the Pilot’s Handbook of Aeronautical Knowledge for the airplane, thrust equals total drag for level flight. [Figure 2-16]

When in straight-and-level unaccelerated flight:


When excess thrust is added to produce climbing flight, the relative air stream becomes an inclined plane leading upward, while angle of attack and speed remain about the same. Just as described in the Pilot’s Handbook of Aeronautical Knowledge for the airplane, the excess thrust determines the climb rate and climb angle of the flight path. [Figure 2-17]

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