To: Dave Jackson
“I'm happy to drop the term 'gyroscopic'. It is a good one for holding a spinning bicycle wheel in your hand and saying "Wow". It is also a valid analogy for describing a basic teetering rotor head, which is used in conjunction with a 90-degree offset pitch horn and a swashplate”.
Response:
Why do you feel that a Bell rotor system emulates the qualities of a gyroscope just because it has a 90-degree pitch horn? Yet you totally discount the Sikorsky and all of the other multi blade helicopters which have a precession angle of 90-degrees. The Bell is a two-blade system and it is designed with a 90-degree lead on the pitch horn. The Robinson has a 72-degree lead on the pitch horn and it too is a two-blade system. The reason it has a 72-degree lead is because the pitch horn can’t cross the cone hinge. If it did, it would have severe pitch flap coupling to such an extent that it would be uncontrollable. That is why I feel so strongly about the R-44 as on it the pitch horn has crossed the cone hinge causing a reversal to the normal pitch flap coupling.
If you remember in past posts I acknowledged aerodynamic precession as an alternate theory to gyroscopic precession but whether you think aerodynamic or gyroscopic precession the precession or phase angle is 90-degrees. How in engineering or plane talk do you prove aerodynamics over gyroscopic precession when the resultant to the pilots input takes place 90-degrees later in the direction? What law in aerodynamics or blade theory dictates that from an aerodynamic standpoint the blade will respond in 90-degrees?
[ 21 November 2001: Message edited by: Lu Zuckerman ]