The following posting was pilfered from rec.aviation.rotorcraft.
It is posted here for its informational value and, more importantly, it's posted in the hope of provoking thought, or, better yet, just provoking; like the good old days.
Lu,
This subject is directly related to your concerns. Your comments will be appreciated.
Posting by Steve Waltner, on rec.aviation.rotorcraft
I sent an e-mail the their [Robinson] customer service address and received this response:
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First, let's ensure everyone understands that the R22/R44 MR hub has one central teeter hinge and two coning hinges (one per blade). Teetering (a specific type of flapping) occurs primarily about the teeter hinge while coning occurs about the coning hinges. At the root-end of each main rotor blade is a spindle bearing assembly, about which the MR blade changes pitch (feathers) and which in turn connects the blade to the hub via the coning hinge.
When there is insufficient centrifugal force to keep the rotor disc flat, the blades will droop. To prevent the blades from drooping so low as to chop off the tailcone, aluminum droop stops affixed to the main rotor driveshaft are contacted by stainless-steel spindle tusks extending inboard of the coning hinge. Both the droop stop and spindle tusk can be seen thru the window on either side of the hub. Do not confuse the aluminum droop stops with the amber-colored urethane teeter stops also affixed to the driveshaft.
The arm between the droop stop and coning hinge (the fulcrum) is very short, while the arm between the droop stop and blade tip is quite long (on the R22 the ratio is about 75:1). This ratio accounts for the "Never Pull Down - Push Up Opposite Blade" sticker on the underside of the blade tip. Even when the blades are stopped, the droop stops are reacting a large amount of force, which in turn creates friction between the droop stop/spindle tusk surfaces. This friction is important in reducing rotor teetering at low rpm when there is little centrifugal force stiffening (and minimizing flexing of) the MR blades. Raising the collective (don't do it!) during shut down increases the blade angle of attack and generates enough blade lift to unload the droop stops, which removes the friction that is retarding rotor teetering. Any cyclic inputs, or wind, causes teetering which reduces clearances and allows the now-flexible MR blades to contact the tailcone (and your disembarking passengers).
Fly (and shut down) safely!
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I also asked for clarification on using the tail rotor to slow down the pitch, which received the following response:
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RHC will not recommend using the pedals to slow down main rotor. We
have an elastomeric bearing on the tail rotor assembly that will flap
and may strike the tailcone and or cause unnecessary wear.
Slow down drive system by using the rotor brake.
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Steve