Aerodynamics Flashcards
Profile drag is composed of:
Form drag and skin friction
Profile drag is caused by:
The frictional resistance of the blade passing through the air
Induced drag associated with:
The production of lift.
Parasite drag is associated with:
Non-lifting surfaces.
Profile drag _______ ________ with an increase in airspeed. (Increases/decreases)(gradually/exponentially)
Increases gradually
Parasite drag _______ _______ as airspeed increases. (Increases/decreases)(gradually/exponentially)
Increases exponentially.
Induced drag _______ _______ as airspeed increases.
Decreases exponentially
_____________ is the term used to describe the left-drifting tendency of the helicopter in a hover. What causes this?
Translating tendency. Caused by left pull of tail rotor to counteract the counterclockwise yaw created by the main rotor. (Need to pull the nose right, tail drifts left.)
Due to the helicopter hovering with the CG located beneath the rotation axis (rotor hub), __________ causes the aircraft to “swing through” any accelerative changes.
Pendular action
As centrifugal force pulls the rotors straight away from the hub and weight simultaneously acts on the hub, ______ occurs to the rotor arc. This increases/decreases with weight or blade loading.
Coning: increases.
The accelerative increase and decrease in rotation as the blades flap is a phenomenon known as ________.
The Coriolis Effect
Ground effect occurs within _______ of the surface and results in _______.
One rotor diameter of the surface
Results in an increase in rotor efficiency due to a decrease in induced flow.
___________ causes forces acting on the rotor to be “felt” 90 degrees later. Unless counteracted by smoothly applying forward cyclic, this will result in _______.
Gyroscopic Precession.
Blowback.
Translational lift causes an increase in rotor efficiency at approximately _______ KIAS.
16-24 KIAS
As you pass through ETL, airflow over the vertical stabilizer becomes less turbulent, resulting in increased lift across the tail. Combined with the increase of main rotor efficiency, this causes a resultant _________ motion and must be compensated for with _________.
Right yaw.
Must be compensated for with an increase in left pedal.
The change in relative speed as the blade rotates through the air in forward flight results in _________ and would cause the aircraft to tumble immediately if not corrected for by _________.
Dissymmetry of Lift.
Flapping.
Factors that contribute to ULY:
WE MAY LOSE LEFT CONTROL PHLLL Weathercock stability Main rotor/tail rotor interaction Loss of translational lift Left crosswinds Collective induced high yaw rates
Flights regimes susceptible to ULY are:
PHLLL
Pilot induced high yaw rates Hovering pedal turns, tail through the wind line Low pedal margin maneuvers Low speed left downwind turns Left sideward flight
Regarding the blade element diagram, _________ acts perpendicular to relative wind.
Total lift
Regarding the blade element diagram, the angle formed by the chord line and the tip path plane or reference plane is known as the __________.
Pitch angle.
The angle of attack is the angle formed by the _________ and the _________.
Relative wind and the chord line.
The three types of drag are:
Profile
Induced
Parasite
