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Why not to water wash engine of Aircraft flown through Volcanic Ash?

Why not water wash the engine of Aircraft flown through Volcanic Ash?

  •  The Volcanic ash particles in the atmosphere can abrade nose surfaces, including windshields, fuselage skin & compressor fan blades. Contamination also can lead to the failure of critical navigational & operational instruments.
  • Ash particles sucked into an engine can melt quickly & accumulate as re-solidified deposits in cooler parts, degrading engine performance even to the point of in-flight compressor stall and IFSD.
  • Out of 79 Known Incidents(1953-2011),26 involved insignificant to very severe aircraft damage, including 9 cases where engine failure occurred during the flight.

Why 'NO' water-wash of engines?

  • On water wash of an engine, that has been exposed to volcanic ash, Particles may accumulate in the HPT nozzle vanes & HPT blade cooling paths. Material may accumulate in the HPC rotor spools and causes rotor imbalance.
What is recommended?
  • Follow AMM.
  • Visually check the engine for evidence of damage or excessive erosion.
  • Borescope inspect the High-Pressure Compressor(HPC) & the High-Pressure Turbine(HPT) for evidence.
  • Replace scavenge oil filter, Drain & replace oil.
  • Contact OEM on limit exceed.

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