4 forces definition

[Ref. Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B Page 5-1, 5-6, 5-29]

The 4 forces definition :
the forward force produced by the powerplant/ propeller or rotor. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis. However, this is not always the case.
Thrust = (mass of air handled x slipstream velocity) – velocity of the aircraft.
Indeed, thrust in propeller-driven aircraft can be considered also in terms of the mass of air handled by the propeller. In these terms, thrust equals mass of air handled multiplied by slipstream velocity minus velocity of the aircraft.


a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.
(Also ref 5-6)
Drag is the force that resists movement of an aircraft through the air. There are two basic types: parasite drag and  induced drag. The  first  is called  parasite  because  it  in no way functions to aid flight, while the second, induced drag, is a result of an airfoil developing lift. (For More Click here!)


is a force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the centre of pressure (CP) AND perpendicular to the lateral axis. (For More Click here!)


the combined load of the aircraft itself,  the crew, the fuel, and the cargo or baggage. Weight is a force that pulls the aircraft downward because of the force of gravity. It opposes lift BUT acts vertically downward through the aircraft’s center of gravity (CG)


One more thing…
Don’t forget the Download on the tailplane – so 5 forces rightly…
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