Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Robinson Helicopter Company (Robinson) Model R22 helicopters, that currently requires installing a low-rotor RPM caution light and resetting the low-RPM warning unit to activate the warning horn and caution light at 94% to 96% revolutions- per-minute (RPM). This action would require installation of an improved throttle governor; an adjustment to the warning horn threshold to increase the RPM at which the warning horn and caution light activate; and, revisions to the R22 Rotorcraft Flight Manual that prohibit flight with the improved throttle governor inoperative, except in certain situations. This proposal is prompted by an FAA Technical Panel review of Model R22 accident history data which revealed that main rotor (M/R) blade stall at abnormally low M/R RPM resulted in accidents. The actions specified by the proposed AD are intended to minimize the possibility of pilot mismanagement of the M/R RPM, which could result in unrecoverable M/R blade stall and subsequent loss of control of the helicopter.