Summary
The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD), applicable to Turbomeca Arriel 1 A, 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 proposal would add additional engine models to the applicability section, would eliminate the installation of modification TU 197 as a terminating action to the repetitive checks, would require additional inspections for engines that have modification TU 197 installed, and would require the replacement of modifications TU 76 and TU 197 with modification TU 202, as a terminating action to the repetitivechecks and inspections. This proposal 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. The actions specified by the proposed AD are intended 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.