Airworthiness Directives; AlliedSignal, Inc. TFE731-3 Series Turbofan Engines

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This amendment supersedes an existing priority letter airworthiness directive (AD), applicable to certain AlliedSignal, Inc. TFE731-3 series turbofan engines, that currently requires a revision to the Limitations Section of the Airplane Flight Manual (AFM) to provide procedures for monitoring engine performance in order to detect A5 seal cracking and opening before first stage low pressure (LP) turbine disk failure. Additionally, the revision to the AFM requires a procedure for verification of LP rotor (N1) rotation during engine start to detect rotor lockup due to first stage LP turbine rotor creep. This amendment maintains those requirements for engine and flight data monitoring, adds a more stringent procedure for verifying rotor lockup during engine start and for detection of rubbing noises, and requires replacement of A5 seals with a redesigned seal. Replacement of A5 seals with a redesigned seal constitutes terminating action to the monitoring requirements. This amendment is prompted by reports of an additional first stage LP turbine disk failure due to A5 seal cracking. The actions specified by this AD are intended to prevent uncontained failure of the first stage LP turbine