To: Dave Jackson
Regarding your comment about the rapid adding of an additional 10-degrees of cyclic the disc will tilt the additional 10-degrees within one revolution. Ask any one that learned to fly in a Bell and they will recount stories about how difficult it is to hover because of the slow reaction of the rotor to control input. In most cases the new pilot will over control by adding more cyclic because the rotor has not yet responded. Based on demonstrated fact the disc will not respond in one revolution.
Quote: “If there happened to be 45º of delta-3 then every degree of flap will remove one degree of pitch. This means that none (i.e. 0%) of the change in cyclic stick pitch gets through to the blades.”
This could only exist in a theoretical situation and it would require changing the pitch horn. On the Bell there is in effect a delta hinge effect but it requires that the pitch link / pitch horn interface be above the teeter hinge. In an Ideal situation if you could maintain this alignment in flight there would be no pitch flap coupling. The same applies to a fully articulated rotor system. On the Sikorsky system (maybe not on the S-76) there is an offset of 45-degrees between the blade and the pitch horn / pitch link interface and, these blades have pitch flap coupling.
Quote: “If the phase lag angle is reduce by 20º, from 90º to 70º, then the location of lowest and highest teetering will be 20º further around the mast. There will still be 180º of increased pitch and 180º of decreased”.
Are you describing what occurs on the Robinson if you are, just change the numbers to 18-degrees and 72-degrees. If you are, are you saying that the disc will tilt down 20-degrees (18-degrees) beyond the mast in the direction of rotation.
I’ll add more when what you have stated fully sinks in or you further explain what you said using mechanic or non engineer speak.
