Helicopter Aerodynamics

Question 1

Induced Flow

Answer 1

Caused by relative wind created by rotating blades

Question 2

Transverse Flow

Answer 2

As forward speed increases, induced flow in the front decreases while induced flow in the back increases. Front rotor flaps up while rear flaps down. Vibrations occur. Helicopter pitches up and left. This occurs around 20 knots.

Question 3

Retreating Blade Stall

HHHLST

Answer 3

Reaches critical angle of attach:
High forward airspeed
High density altitude
High gross weight
Low RPM
Steep/Abrupt turns
Turbulence
Vibration/pitch up/roll to retreating blade
Slow down/lower power to correct

Question 4

Corriolus

Answer 4

Blades spin faster when closer to axis of rotation