FAA Helicopter Flying Handbook Practice Test

The concept being tested is the path the rotor blade tips trace as they rotate. That path lies in the tip-path plane—the imaginary plane along which the blade tips move during rotation. In a typical helicopter, this plane is nearly horizontal, but factors like blade flapping and coning can tilt it a bit relative to the rotor mast.

The rotor disk, by contrast, is the circular area swept out by the blades as they rotate, not the actual path of the tips. The other terms, such as azimuth plane and chord plane, refer to different ideas: azimuth relates to angular position around the rotor, while the chord plane is the blade’s cross-sectional plane along its length, not the motion of the tips.