Flight Instructor for Rotorcraft Category Helicopter Rating › II. Technical Subject Areas › Task D. Principles of Flight

HI.II.D.K8

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Dissymmetry of lift.

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Get a short, cited explanation of this element written from the FAA handbooks: the core idea, the numbers that matter, common test traps, and a quick self-check.

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Helicopter Flying Handbook p. 2-19
Chapter 2: Aerodynamics of Flight › Forward Flight › Dissymmetry of Lift
Retreating Blade As relative wind speed of the retreating blade decreases, the blade loses lift and begins to flap down. It reaches its maximum downflap velocity at the 9 o’clock position, where wind velocity is the least. This downflap ... vertical vector to the relative wind which increases the AOA. Figure 2-35. Airflow in forward flight. Dissymmetry of Lift Dissymmetry of lift is the differential (unequal) lift between advancing and retreating halves of the rotor disk caused…
Helicopter Flying Handbook p. 2-14
Chapter 2: Aerodynamics of Flight › Airflow and Reactions in the Rotor Disk › Angle of Attack
control rearward tilt of the rotor (blowback) caused by flapping action and (along with blade flapping) counteract dissymmetry of lift (discussed in chapter 3). Cyclic feathering causes attitude of the rotor disk to change but does not change the amount ... path plane is perpendicular to the mast. The flapping action alone, or along with cyclic feathering, controls dissymmetry of lift. Flapping is the primary means of compensating for dissymmetry of lift. Pilots adjust AOA through normal control manipulation…
Aviation Maintenance Technician Handbook - Airframe p. 2-23
Chapter 2: Aerodynamics, Aircraft Assembly, & Rigging › Forward Flight › Dissymmetry of Lift
Dissymmetry of Lift Dissymmetry of lift is the differential (unequal) lift between advancing and retreating halves of the rotor disc caused by the different wind flow velocity across each half. This difference in lift would cause the helicopter…