The US Federal Aviation Administration is requiring immediate inspection and replacement of high-pressure turbine disks used in Williams Rolls-Royce FJ44 turbofans which have twice failed on Cessna CitationJets.
The airworthiness directive (AD) affects the early-model FJ44-1A turbofan engines which power some CitationJets. The Directive orders immediate and recurring eddy current inspections for possible cracks in HPT disk blade -retention posts. It also requires eventual replacement with advanced design HPT disks.
The action has been prompted by two non-fatal incidents involving twin-engined CitationJets which suffered HPT disk blade retention post separations. Williams International says that damage was limited to the engine and, in one case, the nacelle.
The US engine maker had already implemented an FJ44 turbine upgrade programme designed to solve turbine-blade attachment problems in engines which incorporated the early disk design. The new design, which is now standard, reduces the level of stress by 45%, says the company.
Williams International initiated a no-cost replacement programme in early November, and the 43 highest time engines in the field have been upgraded. The work takes no more than two days.
The AD calls for all FJ44s incorporating the early design turbine to be upgraded by 1 July.
Source: Flight International
