ATC Lasham Borescope Inspection
RVI Ltd was contracted by ATC Lasham Ltd to perform a routine “hot section” borescope inspection of both CFM56-3 engines on a Boeing B737-400 aircraft operated by Aero Contractors.
Engine Inspection
The “hot section” borescope inspections consisted of the inspection of the combustion chamber liners, the fuel burners and the nozzle guide vanes in one module then the borescope inspection of the high pressure turbine blades in another module.
We had been informed that there were no known issues with either engine with regards to vibration, EGT or fuel flow so expected to find only minimal wear and tear when we found the defect the engineering rep the preparation engineers and us were very surprised the engine was able to run with no adverse indications.
Engine Reporting
This engine could not remain in service as the damage is way beyond the allowable Aircraft Maintenance Manual limits. It was removed and sent away for repair which meant the operator had to lease an engine for several weeks while their engine was being repaired.
The other engine inspection went very well with only the usual minor defects being found and RVI Ltd was able to issue an EASA form 1 allowing this engine to continue in service.
Conclusion
This model of engine “The CFM56-3” has been in operation since 1984 and with findings like this being very rare and the fact that this engine had been operating normally prior to the inspection is a testament to the strength and durability of the CFM56 engines and in particular the -3 series of engines.