AD NUMBER: 2008-13-01
MANUFACTURER: Fokker
SUBJECT: Airworthiness Directive 2008-13-01
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: During scheduled X-ray inspections of Fokker 50 (F27 Mark 050) engine mounting frames, welding defects were discovered. In two forward frames and one aft frame, defects were found in a total of 4 weld locations. Investigation showed that during manufacture of the frames, when the tubes were welded to the end fittings, unintentional sideways movement of the electric arc resulted in some welds running beside the borderline for apart of the tube circumference. Where a weld runs beside the borderline, there is no connection between tube and end fitting for that part of the circumference, directly affecting the structural integrity of the engine mounting frame connections. The defective welding process appears to have happened at some of the welds in an unknown number of engine mounting frames. This condition, if not corrected, could lead to failure of the engine mounting frame in cases where multiple welds are severely affected, potentially resulting in in-flight loss of an engine. * * * This AD requires actions that are intended to address the unsafe condition described in the MCAI.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/