Incident Description
After being cleared to climb from 6,000 feet, the pilot began advancing the throttles to set climb power when a loud bang was heard. Indications of a No. 2 engine failure were noted. The pilot secured the affected engine and performed an uneventful landing.
Engine Examination
Inspection of the failed Williams-Rolls FJ44-1A engine showed an uncontained high pressure turbine (HPT) disk blade retention post failure. The HPT disk (part number 48629) had a blade retention post fractured adjacent to the bottom of the blade slots, causing three adjacent HPT blades to break loose. Subsequently, the upper portion of the fuel-oil heat exchanger mount pad was fractured, resulting in an oil leak.
Metallurgical Findings
Metallurgical examination determined that the primary failure was the release of a blade retaining lobe just below a fret zone. Creep fatigue was found at the failed blade retaining holes. No evidence of gross overheating was noted. The failed disk was of an older design.
Corrective Actions
As a result of the incident, Williams-Rolls issued Alert Service Bulletins No. FJ44-A72-30 and -31, which describe procedures for eddy current inspection (ECI) of HPT disk blade retention posts to locate possible cracks and for replacing existing HPT disks with an advanced-design disk. Additionally, Airworthiness Directive (AD) 97-01-05 was issued mandating initial and recurring ECIs of the HPT disks and replacement with improved disks. A more durable fuel-oil mounting pad was under development for the FJ44-2 engine.