Originally Posted by
helispotter
I thought some of you might be interested to see how John S Fay described rotor phase lag in his 1954 book "The Helicopter and how it flies". He then goes on to indicate that "some rotors can therefore be said to behave like a gyroscope in that their phase lag is 90-degrees". So that association has been around a long time. Relevant pages as follows:
“Some rotors can therefore be said to behave like a gyroscope in that their phase-lag is 90 degrees.”
FWIW, I believe the reference is to the Bell-Hiller rotor system, although not explicitly stated.