Airworthiness Directives; General Electric Aircraft Engines CF34 Series Turbofan Engines

This amendment supersedes an existing airworthiness directive (AD), applicable to General Electric Aircraft Engines (GE) CF34 series turbofan engines, that currently requires installation of a main fuel control (MFC) that incorporates a flange vent groove and installation of an MFC with improved overspeed protection. This amendment requires replacement of Buna-N O-rings with Viton O-rings or a new location of the vent groove on the MFC mounting flange, or installation of an MFC with improved overspeed protection. This amendment is prompted by the determination that the location of the reworked vent groove was ineffective, and that replacement of Buna-N preformed packings with Viton preformed packings will alleviate the unsafe condition. The actions specified by this AD are intended to prevent uncommanded engine accelerations, which could result in an engine overspeed, uncontained engine failure, and damage to the airplane.