The TRUEngine designation also facilitates CFM’s ability to provide technical support. Jet engines contain multiple, complex systems whose interactions must be carefully controlled. CFM’s engine support is built upon technical expertise for genuine CFM56 parts and configurations, as well as data gained from the vast operational history of the global CFM56 engine population. A modern high-by-pass ratio turbofan engine is an extremely complex and sophisticated piece of equipment that is designed by each manufacturer to function effectively, efficiently and economically (and in an environmentally-friendly manner) with all its thousands of parts operating within pre-determined parameters and with each individual part mutually dependent upon every other component. The original manufacturers argue that by changing one or more parts in the engine for ones that may be cheaper — parts manufacturer approval (PMA) parts — at least when initially purchased, may result in reliability issues, not to mention the possibility that the asset may realise considerably less financial return when it is eventually sold.
They are also concerned that the modification of engines they design and build, beyond the type-certified configuration, reduces their ability to provide technical support. These concerns resulted in the FAA’s Aircraft Certification Service issuing a ‘special airworthiness information bulletin’ (SAIB) in August 2008 alerting owners, operators and certificated repair and maintenance providers of the ‘responsibilities of type and production certificate (TC/PC) holders, supplemental type certificate (STC) holders and the PMA holders to support the continued operational safety (COS) of their product or part design.
Advanced design tools help keep CFM56 engines on-wing longer When CFM was designing the -7B engine, now used exclusively on 737NGs , future maintenance was one of the major contributing factors considered by the engineers. Use of the latest digital product definition tools at all stages of the engine’s design helped to reduce definition cycle time and the first -7B engines came to production faster than had ever been done in the industry before. With full implementation of the advanced CATIA numerical sys-
The CFM56-7 rotor.
The Engine Yearbook 2011
51