Helicopter Dynamics: Phase Angle
Thread Starter
Joined: Nov 2000
Posts: 452
Likes: 0
From: Vancouver, BC, Canada
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.
__________________
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.
