PPRuNe Forums - View Single Post - Helicopter Dynamics: Phase Angle
View Single Post
Old 13th August 2001 | 06:09
  #1 (permalink)  
Dave Jackson
 
Joined: Nov 2000
Posts: 452
Likes: 0
From: Vancouver, BC, Canada
Post Helicopter Dynamics: Phase Angle

Lu; The following bits of information may answer your concern about phase lag.
__________________

The phase lag "stems from the two components ...... one aerodynamic due to the distribution of airloads from the angular motion, the other from the gyroscopic flapping motion." ~ Padfield, [my bold]

Prouty, (I think it was him) has stated that when the control plane (swashplate) is changed by cyclic input the tip-path-plane will realign itself with the control-plane within 1/2 of a rotor's revolution.

"For blades freely articulated at the center of rotation, or teetering rotors, the response is lagged by exactly 90-degrees in hover; for hingeless rotors, such as the Lynx and Bo105, the phase angle is about 75 to 80-degrees."

It has been stated that the conventional swashplate is an ideal control mechanism for rotors with a 90-phase angle, but it is not ideal for rotors with a phase angle less than 90.
___________________

To me it appears that Lynx's 75 to 80-degree phase angle is a compromise between the gyroscopic precession's 90-degrees and the aerodynamics' < 75-degrees.
Dave Jackson is offline