Dear Joe,
here is my response to your 8 questions or should I say statements.
1) Robinson reliability. I have to admit that the flight control system is a picture of simplicity. The only problems I am aware of were some failures in the cyclic control system which may have resulted in the loss of several aircraft. It was traced to insufficient design strength. The parts were modified and no problems since. Although the system is simple the rigging procedure is not. Because of the rigging procedure the mechanic can inadvertently rig in too much pitch which could result in rotor stall (not to be confused with retreating blade stall). The rigging procedure can also set up binding of the swash plate and mechanical contact between control rods and fixed structure. The rigging procedure for the main and tail rotors are completely different from any other helicopter. Talk to the mechanics that service your aircraft.
2) No I am not. When I was in service many years ago I was a helicopter mechanic. The philosophy of the US Coast Guard at that time was if you fix it you must fly in it. The pilots on occasion would allow me to fly the helicopter. (HO4-S/ S-55, HO5-S/S-52, HO3-S/ S-51 and a Bell HTL-1. I could maintain course and altitude pretty well but I couldn't hover to save my ass.
3) Regarding fatigue failures what do you think causes the rotor mast to fracture. Whether the fatigue builds up over a long time or in an instant the fracture is still caused by fatigue. Fatigue played a part in the failure of the cyclic controls as mentioned above.
4) loss of rotor or rotor incursions on the airframe can be explained away by saying they were caused by pilot error. It could be that the pilots operated the helicopter outside of the restricted limits. The restricted limits relative to siseslip and out of trim were incorpoated in order to eliminate the extremely high flapping loads which resulted from the design of the rotor head.
5)I'm sorry for the loss of the pilots that experimented with low G recovery however, you haven't said what type of helicopter they were flying at the time. Regarding low rotor RPM I believe in a previous post it was stated that the rotor had a high rate of spool up due to the power available and the low inertia of the rotor system. Could it be that the rotor was placed in a stall condition due to too much pitch which increased the drag on the blades which prevented rapid spool up?
6)Regarding the Performance and efficiency that may have been true when the aircraft was first built but if you fly it according to the POH then the helicopter is like taking a Ferrari and replacing the engine with a Chevy (Holden) straight six. Sure you can still drive the Ferrari but how does its' performance compare to the original with the Ferrari engine installed.
7) Have you ever seen what the original 206 looked like when it was proposed to the US Army as a light observation helicopter. That helicopter lost in the competition to a Hughes 369 (H-500). Bell knew it had potential so they turned the design over to one of the top US industrial design firms and the rest is history.
8)Regarding compliance, the FARs and the AC 27-1 both require that the helicopter demonstrate Side slip at 90 degrees induced by hard input on the pedals both right and left. These documents also require demonstration of out of trim by 10 degrees left and right. Since the POH restricts the pilot from doing those things just Imagine if Frank Robinson went to the FAA and told them that he had just designed the R22 but they could not be side slipped or flown out of trim. The FAA would tell him to piss off.
Another point is that the FAA has a requirement that states any new and/or unusual design must be proved by dynamic testing as well as through an analytical process. The R22 rotor head met this criteria but the testing was never accomplished in accordance with the FAA procedure. Yet , the rotorhead was accepted. Could it be that Frank Robinson who was the FAA Designated Engineering Representative (DER) signed off the design. The fact that he was the DER violated the FAA regs which required that the DER not have a vested interest in the design or a financial relationship with the company producing the design.
Regarding fatigue and I'll add in wear please do the following: The next time you are in the repair shop and the mechanics have the rotorhead off the mast, have the mechanics check the mast for signs of wear or elongation of the holes that the teeter bolt fits into. Also, have them make the same check on the rotor head where the teeter bolt passes through. I saw two rotor heads that exhibited this wear and I attributed it to the tendency of the blades to lead and lag when they flap in relation to the rotor head. In order for this kind of wear to occur, the mast has to react the applied loads. This means that each blade leads and lags at the frequency of rotor RPM.
If the wear is evident on the holes in the mast and/or the rotor head the mast is under a cyclical fatigue that causes the mast to twist plus and minus at twice the speed of rotor RPM. Have them perform the check because if you and your buds fly the R22 the way you indicated there is a good chance that you are being set up for a fatigue failure. Another thing that the mechanics can do if you are allowed by your operating regs is to coat the mast with a product called stress coat. That will provide a visual check of the twisting of the mast.
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The Cat