A sudden and complete loss of engine power that forced a Cessna 208 Caravan to make an off-airport emergency landing on Oct. 21, 2013, was caused by “improper maintenance that resulted in contamination of the engine’s compressor turbine disc and blade assembly by glass bead remnants, which resulted in a blade failure,” according to the NTSB’s final report issued last week. The turboprop single was on a Part 135 flight in Hawaii when the accident occurred. There were no injuries to the two pilots and eight passengers, although the aircraft was substantially damaged during the landing.
Post-accident examination of the engine revealed that all of the compressor turbine blades had separated. Glass beads and bead fragments were found embedded in areas consistent with the disc assembly having been cleaned by “aggressive glass media blasting in the assembled condition,” according to the Safety Board. The engine manufacturer specifies that glass media blast cleaning be performed with the disc and blades disassembled.
The disc assembly had been removed from the engine for repair by a powerplant maintenance facility in Eloy, Ariz., about two months before the accident, and this, the Safety Board said, “was likely when the glass bead cleaning occurred.”