AD 98-04-12 63 FR 17677

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 98-04-12 which was sent previously to all known U.S. owners and operators of Robinson Helicopter Company (RHC) Model R44 helicopters by individual letters. This AD requires an initial and repetitive measurement of the lateral cyclic trim spring shaft (shaft) diameter and replacement of the shaft spring assembly (spring assembly) if the shaft diameter is excessively worn. Replacement of the spring assembly with a modified spring assembly is considered terminating action for this AD. This amendment is prompted by an incident in which a pilot felt binding in the cyclic control when attempting to move it to the left. A precautionary landing was made using only right-hand turns. Subsequent inspection revealed that a notch was worn in the shaft, which caused the shaft and spring to move from the lower mount and interfere with the lateral control. Inspection of a second RHC Model 44 helicopter revealed similar wear. Excessive wear can create a notch on the shaft, which can cause the spring assembly to move out of its lower mount. This condition, if not corrected, could lead to the shaft interfering with lateral cyclic control, which could result in loss of control of the helicopter.