Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft Engines
This amendment supersedes an existing airworthiness directive (AD) that applies to Turbomeca Arriel 1A, 1 A1, 1 A2, 1 B, 1 C, 1 C1, 1 C2, 1 D, and 1 D1 turboshaft engines. That AD currently requires repetitive checks for engine rubbing noise during gas generator rundown following engine shutdown, and for free rotation of the gas generator by rotating the compressor manually after the last flight of the day. In addition, the AD 95-11-01 requires installation of modification TU 202 or TU 197 as terminating action to the repetitive checks. This amendment adds additional engine models to the applicability section, eliminates the installation of modification TU 197 as a terminating action to the repetitive checks, requires additional inspections for engines that have modification TU 197 installed, and requires the replacement of modifications TU 76 and TU 197 with modification TU 202, as a terminating action to the repetitive checks and inspections. This amendment is prompted by a report of an in-flight engine shutdown on an engine that had modification TU 197 installed, and the need to update the modification standard on certain engine models. We are issuing this AD to prevent engine failure due to rubbing of the 2nd stage turbine disk on the 2nd stage turbine nozzle guide vanes, which could result in complete engine failure and damage to the helicopter.