Airworthiness Directives; Robinson Helicopter Company (RHC) Model R44 Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 98-12-19 which was sent previously to all known U.S. owners and operators of RHC Model R44 helicopters by individual letters. This AD requires, within 5 hours TIS, a dye penetrant inspection of each main rotor blade skin (blade skin) around both inboard trim tab alignment rivet holes. Thereafter, a repetitive visual inspection of the blade skin around both inboard trim tab alignment rivet holes is required prior to the first flight of each day or at intervals not to exceed 5 hours TIS, whichever occurs first. This amendment is prompted by an incident in which a crack in the main rotor blade resulted in a forced landing. Subsequent investigations revealed that the manufacturing process utilized to drill the trim tab alignment rivet holes in the blade skin can allow a fatigue crack to originate at these holes and propagate in the skin. This condition, if not corrected, could result in failure of the main rotor blade and subsequent loss of control of the helicopter.