Originally Posted by
SASless
The Title is "Sikorsky Helicopter Flight Theory For Pilots And Mechanics". I highly recommend it for use by those wishing to learn more about the subject ...
I agree. Many of the diagrams in my class notes, that then found their way into AP3456, had their inspiration there.
They are not cheap as they are scarce.
You can look at a copy at
https://archive.org/details/sikorsky...-and-mechanics