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Aerodynamics

Basic Propeller Principles (Part One)

Aerodynamics

The aircraft propeller consists of two or more blades and a central hub to which the blades are attached. Each blade of an aircraft propeller is essentially a rotating wing. As a result of their construction, the propeller blades are like airfoils and produce forces that create the thrust to pull, or push, the aircraft […]

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Stalls (Part Three)

Aerodynamics

Airfoil shape and degradation of that shape must also be considered in a discussion of stalls. For example, if ice, snow, and frost are allowed to accumulate on the surface of an aircraft, the smooth airflow over the wing is disrupted. This causes the boundary layer to separate at an AOA lower than that of […]

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Stalls (Part Two)

Aerodynamics

There are three flight situations in which the critical AOA can be exceeded: low speed, high speed, and turning. The aircraft can be stalled in straight-and-level flight by flying too slowly. As the airspeed decreases, the AOA must be increased to retain the lift required for maintaining altitude. The lower the airspeed becomes, the more […]

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Stalls (Part One)

Aerodynamics

An aircraft stall results from a rapid decrease in lift caused by the separation of airflow from the wing’s surface brought on by exceeding the critical AOA. A stall can occur at any pitch attitude or airspeed. Stalls are one of the most misunderstood areas of aerodynamics because pilots often believe an airfoil stops producing […]

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Aerodynamic Forces in Flight Maneuvers (Part Three) – Forces in Descents

Aerodynamics

As in climbs, the forces which act on the aircraft go through definite changes when a descent is entered from straight-and-level flight. For the following example, the aircraft is descending at the same power as used in straight-and-level flight. As forward pressure is applied to the control yoke to initiate the descent, the AOA is […]

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Aerodynamic Forces in Flight Maneuvers (Part Two) – Forces in Climbs

Aerodynamics

For all practical purposes, the wing’s lift in a steady state normal climb is the same as it is in a steady level flight at the same airspeed. Although the aircraft’s flightpath changed when the climb was established, the AOA of the wing with respect to the inclined flightpath reverts to practically the same values, […]

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Aerodynamic Forces in Flight Maneuvers (Part One) – Forces in Turns

Aerodynamics

If an aircraft were viewed in straight-and-level flight from the front [Figure 4-28], and if the forces acting on the aircraft could be seen, lift and weight would be apparent: two forces. If the aircraft were in a bank it would be apparent that lift did not act directly opposite to the weight, rather it […]

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Aircraft Design Characteristics (Part Six) – Spiral Instability

Aerodynamics

Spiral instability exists when the static directional stability of the aircraft is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium. When the lateral equilibrium of the aircraft is disturbed by a gust of air and a sideslip is introduced, the strong directional stability tends to yaw the nose into […]

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Aircraft Design Characteristics (Part Five) – Free Directional Oscillations (Dutch Roll)

Aerodynamics

Dutch roll is a coupled lateral/directional oscillation that is usually dynamically stable but is unsafe in an aircraft because of the oscillatory nature. The damping of the oscillatory mode may be weak or strong depending on the properties of the particular aircraft. If the aircraft has a right wing pushed down, the positive sideslip angle […]

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