NIFE Aerodynamics 2-2-1 Latest Update 100% Pass

NIFE Aerodynamics 2-2-1 Latest Update 100% Pass Total drag eqn (Not EO) Dt = Dp + Di Define Parasite drag and its components Drag that does not aid flight. Has two basic elements: form drag and friction drag. Dp = qf Form drag Results from the disruption of the streamline flow; and the resistance of skin friction. Caused by laminar airflow separation from a surface creating a low pressure wake behind an object. The pressure differential between the front and rear creates suction that retards forward motion. Friction drag Drag generated by more turbulent flow. Rough surfaces increase the thickness of the boundary layer and create greater skin friction. Helps prevent boundary layer separation Describe induced drag Occurs at the wingtip. Inherent to a wing producing lift. Air curls up over the wing tip and combines with the down wash to form vortices at the wing tips. The downwash creates a new average relative wind that hits the wing at a lower AOA that the actual relative wind. Rotates lift vector aft, creating an effective lift (Leff) and an induced drag component. Higher AOAs have a lower Ps which creates stronger wingtip vortices, which then increases induced drag. Describe factors affecting induced drag, given the induced drag equation, and changes in lift, weight, density, velocity, and wingspan + Lift increases > induced drag increases + Weight increase > Induced drag increases + Density increase > Induced drag decreases + Velocity increase > Induced drag decreases + Wingspan increase > Induced drag decreases List prevention methods of induced drag 1. Wingtip Devices: Helps inhibit airflow around the wingtip 2. Ground effect: Reduces full rotation cycles of wingtip vortices Define total drag Sum of induced drag and parasite drag Describe the effects of changes in velocity on total drag Parasite drag increases as the square of airspeed, and induced drag varies inversely as the square of the airspeed. As speed decreases to near stall speed, the total drag increases due to the sharp rise in induced drag. As speed reaches terminal velocity, the total drag increases due to parasite drag. Explain the importance of L/D max - The lowest total drag is also the greatest ratio of lift to drag. - Produces min total drag, where parasite and induced drag are equal. - L/Dmax AOA is the most efficient AOA - Any movement away from L/Dmax will increase drag Define the boundary layer The layer of airflow over a surface that demonstrates local airflow retardation due to viscosity. Usually 1mm