Investigation of In-Flight Shutdown of Turboprop Engine Due to Electrical Discharge Damage
A turboprop training aircraft experienced an in-flight shutdown failure with complete seizure of its propeller. Disassembly of the mishap engine revealed that many of the engine components were severely damaged. The laboratory investigation of the failed engine components determined that mechanical failure of the driveshaft bearing in the gearbox was the principal contributing factor that led to in-flight complete seizure of the propeller shaft. Microscopic examination of the failed bearing remnants found electrical arc-induced pittings which played a role as crack initiation sites resulting in premature rolling contact fatigue cracking during continued engine operation. The investigation established clear evidence of electrical discharge damage (EDD) on engine components connecting from the starter-generator to the failed input driveshaft bearing. The evidence of EDD observed in multiple elements located along the electrical current path and the residual magnetism measurement suggested that the starter-generator is highly associated with the source of the EDD.
KeywordsElectrical discharge damage Turboprop engine Bearing Starter-generator Electrical arc
The author would like to acknowledge the assistance of all the staff members of the failure analysis lab in ATRI at various stages in this investigation. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
- 1.ATSB Transport safety investigation report, Engine failure lake burbury, Feb 2006Google Scholar
- 2.ATSB Transport safety investigation report, Total power loss, VH-UMV near Cairns Airport, Queensland, Dec 2009Google Scholar
- 3.A. Becker, S. Abanteriba, Electric discharge damage in aircraft propulsion bearings. J. Eng. Tribol. 228, 104–113 (2014)Google Scholar
- 5.J. Jumonville, E. Rasmussen, Two unusual and catastrophic bearing failures caused by electrical arcing in the oil film, their causes, and the surprisingly simple solutions that cured them. In Proceedings of the 30th Turbomachinery Symposium, Turbomachinery Laboratory, Texas A&M University (2001), pp. 1–8Google Scholar
- 6.K. Chmelik, V. Cech, J. Foldyna, Influence of electric discharges on bearings of electric machines. Adv. Electr. Electron. Eng. 5, 258–262 (2006)Google Scholar
- 7.D. Jiles, Introduction to Magnetism and Magnetic Materials, 3rd edn. (CRC Press, Boca Raton, 2016)Google Scholar