Upon completion of this chapter, the student will be able to construct a blade element
diagram, defining each of its components, and state their interrelationships. The student
will be able to identify the forces acting on the rotor system and their effects on the system.
Draw a blade element diagram.
Define the following terms: Airfoil, chord line, tip-path-plane, aerodynamic center,
rotor disk, pitch angle, linear flow, induced flow, angle of attack, lift, induced drag,
profile drag, thrust, and in-plane drag.
State the relationships between induced flow, linear flow, and relative wind;
between relative wind and angle of attack; between pitch angle and angle of attack.
Differentiate between and characterize the symmetrical and nonsymmetrical airfoils.
Define geometric twist and state why it is used in helicopter design.
Define geometric imbalance.
State how geometric imbalance affects horizontal blade movement (lead/lag).
Differentiate between and characterize the three types of rotor systems in use today.
State the method by which flapping is accomplished in each system.
State the method by which geometric imbalance is compensated for or eliminated in
THE ATMOSPHERE 1-1