To: The Nr Fairy
According to the R-22 POH the maximum allowable rotor and engine speed is 104%. You indicated that you experienced an overspeed beyond that point however you did not indicate the actual rotational speed other than to state that the gages went off the scale. Any excedence of the allowable speed would necessitate some type of inspection, which you indicated was done. However if the overspeed drove the instruments off the scale there is no way of telling exactly how fast both the engine and rotor were turning. If this is the case, I would think that the helicopter should have been grounded and an engineering (not LAME engineering) examination should have been performed to determine if excessive stresses were experienced due to “Centrifugal forces" on the main and tail rotor blades and the two rotorheads as well as other rotating parts of the drive line. Also the engine should have been torn down to determine if any of the moving parts had been overstressed or possibly stretched.
Not knowing the CAA regs. I would think that there would be a requirement to enter the overspeed occurrence in the aircraft log with further indication of what inspections were performed to clear the helicopter for further flight. Otherwise your inadvertent overspeed may manifest itself at some later date causing harm to the unaware pilots.
