GENERAL AERODYNAMICS Flashcards
Forces Acting On The Aircraft
Lift, Weight, Thrust, and Drag.
Lift
Opposes the downward force of weight.
Weight
Force of gravity.
Drag
Opposes thrust and acts rearward parallel to the relative win.
Airfoil Terms & Definitions
Chord- the length of the chord line from leading edge to trailing edge.
Chord Line- a straight line intersecting leading and trailing edges of the airfoil.
Mean Camber Line- a line drawn halfway between the upper and lower surfaces of the airfoil.
Leading Edge- front edge of an airfoil.
Trailing Edge- the rearmost edge of an airfoil.
Flightpath Velocity- the speed and direction of the airfoil passing through the air.
Relative Wind
Induced Flow
Resultant Relative Wind
Angle of Attack(AOA)
Angle of Incidence
Center of Pressure- It’s where all the air forces on a blade seem to meet.
Blade Span- the length of the rotor blade from center of rotation to the tip.
Airfoil Types
Symmetrical and Non-symmetrical.
Blade Twist
Helps helicopter blades push air evenly.
Relative Wind
Airflow relative to an airfoil and is created by movement of an airfoil through the air.
Rotational Relative Wind
The air hitting the blade head-on.
Resultant Relative Wind
Relative wind modified by induced flow.
Induced Flow
Downwash.
Angle o Incidence (AOI)
Angle between the chord line of a blade and rotor hub.
Angle of Attack (AOA)
angle measured between the resultant relative wind and chord line.
Hovering Flight
Most challenging because of constant control adjusting.
Translating Tendency
Helicopter tends to drift in the direction of tail rotor thrust.
Pendular Action
Fuselage is suspended from a single point, it is free to oscillate either longitudinally or laterally.
Coning
centrifugal force acting outward and lift acting upward, blades assuming a conical path.
Coriolis Effect
Rotating mass moves closer to the axis of the rotation it will increase in speed, further away speed will decrease.
Gyroscopic Precession
When force is applied to a spinning object that force will be felt 90 degrees later. Robinson’s 72 degrees.
Dissymmetry of Lift
Differential lift between advancing and retreating halves of the rotor disk caused by the different wind flow velocity across each half.
Translational Lift
When transitioning from hover to forward flight the efficiency of the rotor disk producing lift is increased.
Effective Translational Lift
Rotor blades become more efficient as forward airspeed increases.
Transverse Flow Effect
Differences in lift between the fore and aft portions of the rotor disk.
Autorotation (Forward)
State of flight where air is moving up through rotor disk.
Thrust
Force produced by the rotors.
Airfoil
Any surface producing more lift than drag.
