Airworthiness Directives; Eurocopter Deutschland GmbH Model EC 135 Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 98-15-25, which was sent previously to all known U.S. owners and operators of Eurocopter Deutschland GmbH Model EC 135 helicopters by individual letters. This AD supersedes AD 98-09-11, applicable to Eurocopter Deutschland GmbH Model EC 135 helicopters, that required, before further flight, a tail rotor drive shaft vibration survey and installation of a Fenestron Shaft Retrofit Kit; inspecting the tail rotor drive shaft bearing (bearing) attaching lock plates for bent-open tabs, and broken or missing slippage marks; and visually inspecting each bearing support for cracks. This AD requires the same actions as the superseded AD, however it changes the required compliance time for the repetitive inspections. This amendment is prompted by reports of loose bearings and attachment bolts. This condition, if not corrected, could result in loose bearing attachment bolts, or cracked bearing supports, which could result in loss of drive to the tail rotor and subsequent loss of control of the helicopter.