What happened
On 19 December 2005, a charter flight operated by Silver Air s.r.o, flying from Prague Ruzyně (LKPR) to Amsterdam (EDDV), experienced a sudden failure of the right engine. The aircraft, an L 410UVP-E 8D with registration OK-WDC, was in the climb phase at flight level 70 near Slaný when the right engine ceased operation. At the time of the failure, the engine was operating in climb mode with a propeller speed of 1900 RPM, turbine gas temperature of 690°C, and 96% torque.
The crew responded by following established procedures to shut down the failed engine and performed a visual approach to runway 24 at Prague Ruzyně. The landing was completed safely, with no injuries to the crew or passengers and no damage to the airframe. However, the right engine sustained heavy damage to its primary components.
The investigation
The ÚZPLN investigation included a review of flight data recorder (FDR) parameters, which confirmed the sudden engine failure occurred without any prior exceedance of operating parameters. The investigation also involved a commissioned disassembly of the engine at the manufacturer's facility, attended by representatives from the manufacturer, the operator, and the Civil Aviation Authority.
As part of the technical analysis, specific turbine blade fragments were sent to the Department of Materials at CTU Prague for fractographic examination. The investigators also examined a separate event from three days prior, where a wind gust had overturned a parked aircraft, to determine if any damage to the left wing's auxiliary fuel tank could have contributed to the engine failure; no connection was found.
Findings
- The primary cause of the engine failure was the fatigue failure of the turbine blade necks on two specific generator turbine blades.
- The fracture of these two blades led to them breaking away from the turbine disc, which subsequently caused the failure of additional blades during operation.
- All crew members were properly qualified and met medical requirements.
- The aircraft was fully airworthy and maintained according to regulations.
- Meteorological conditions were CAVOK with light winds, and the airport infrastructure was fully operational.