Steady-State Flight—A condition when an aircraft is in straight-and-level, unaccelerated flight, and all forces are in balance.
 

THRUST
Thrust, like lift, is generated by the rotation of the main rotor system. In a helicopter, thrust can be forward, rearward, sideward, or vertical. The resultant of lift and thrust determines the direction of movement of the helicopter.
The solidity ratio is the ratio of the total rotor blade area, which is the combined area of all the main rotor blades, to the total rotor disc area. This ratio provides a means to measure the potential for a rotor system to provide thrust.
The tail rotor also produces thrust. The amount of thrust is variable through the use of the antitorque pedals and is used to control the helicopter’s yaw.
 
 

DRAG
The force that resists the movement of a helicopter through the air and is produced when lift is developed is called drag. Drag always acts parallel to the relative wind. Total drag is composed of three types of drag: profile, induced, and parasite.
PROFILE DRAG
Profile drag develops from the frictional resistance of the blades passing through the air. It does not change significantly with the airfoil’s angle of attack, but increases moderately when airspeed increases. Profile drag is composed of form drag and skin friction.