GE Aircraft Engines (GEAE) is urging several Bombardier CRJ operators to inspect CF34-3 engines and accelerate, if necessary, the replacement of the gearbox and stage-two high-pressure turbine blades.
The service bulletin was issued after earlier-than-expected wear in the gearbox and turbine blades were discovered in some four-year-old engines. Typically, these parts are replaced as part of the mid-life engine overhaul, but some operators are being forced to accelerate the replacements by several thousand hours.
Mesa Airlines, for example, says it was forced to remove prematurely six engines at 11,500h instead of the normal 15,000h interval. The operator says it incurred $3.1 million in one-time charges, but in an effort to avoid more unexpected removals, GE is installing new parts in other engines from the same "bad batch" at its own expense.
GE says 588 engines are included in its service bulletin, and the two affected parts are "long out of warranty", but GE is offering an "attractive commercial programme" with a different stage two high-pressure turbine blade and a gearbox with greater durability. New production CF34 engines already have these improved parts.
The service bulletin encourages operators of four-year-old CF34-3s to conduct a borescope to see if they need an earlier than scheduled upgrade. Operators can then decide, based on the wear of the questioned parts and their financials, about whether to proactively replace the parts before the mid-life upgrade.
Source: Flight International