We are seeing an increase in the number of questions from operators about engines that have not been preserved. Some are experiencing the unfortunate effects of long-term storage of their TFE731 engines when proper procedures have not been followed. That is the engines end up on the DERB (damaged engine review board) list.
A typical work scope for an unpreserved engine is a complete teardown to inspect all mainline bearings and the exchange of the fuel pump, fuel control, fuel manifolds, oil pump, among other items and the replacement of all accessory/transfer gearbox bearings. There are additional costs associated with this type of work scope, including other squawks found at disassembly, engine changes and shipping.
These are very costly repairs that engine programs, such as MSP or JSSI, will not pay for. The time and money it takes to follow the proper preventative procedures is well worth the effort.
The TFE731 manual states that an engine installed on the aircraft must be spooled every four weeks with N1 rotation. Additionally, if the engines are non-operation beyond six months, the fuel system must be preserved. These actions need to be documented. The details of proper preservation are in the light maintenance manual, Ch 72-00-00/Servicing/Preservation.
The most popular and probably the easiest way to avoid presentation issues is to run the engines once a month and document it in the logbooks.
Engine preservation is just as important as other maintenance items and proper records must be kept just like any other normal maintenance items.
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