Airworthiness Directives; Honeywell International Inc. Turboprop Engines

We propose to supersede Airworthiness Directive (AD) 88-12-10, which applies to certain Honeywell International Inc. (Honeywell) TPE331 turboprop engines. AD 88-12-10 requires reducing the life limit for certain second stage turbine rotors. Since we issued AD 88-12-10, we received a report that a TPE331-11U engine experienced an uncontained rotor separation. In addition, cracks were discovered through eddy current inspection (ECI) in the bore of the second stage turbine rotor assembly after publication of AD 88-12-10. This proposed AD would require removing certain second stage turbine rotors from service at a reduced life limit. We are proposing this AD to address the unsafe condition on these products.