Mart,
The subject of delta3 is taking this thread off topic. In addition, a lot has been previously been posted on this subject; on PPRuNe threads and on this
copy of another forum's thread
A couple of hundred hours have been spent studying delta3, plus even more time has been spent attempting to understand the Robinson rotorhead. I believe that my understanding of delta3 is correct. However, being a cynical engineering type I have never been totally comfortable with Frank Robinson's association between delta3 and phase lag.
Chuck Beaty's comment [in your posting], may have been the appropriate response to Frank Robinson's
"This is a highly technical subject which can only be fully explained using very technical engineering terms."
If there is any desire to continue this topic, perhaps it should be done as a continuation of an earlier related thread.
Dave