What happened
On April 30, 2011, an Aero Vodochody L-39/139 Albatros, registered RA-3514K, departed from Bordeaux-Mérignac for a discovery flight. After approximately ten minutes of flight near Cap Ferret, the aircraft began its return toward Bordeaux. Shortly before entering the Bordeaux CTR at 1,500 ft, the turboreactor experienced a significant loss of power.
The pilot observed the low oil pressure warning light flashing several minutes before the engine eventually stopped. Following the engine failure, the aircraft entered a glide for approximately one minute before crashing into a forest in Sainte-Hélène. The impact caused the aircraft to be destroyed and ignited a fire that spread through several hectares of woodland. The pilot and one passenger sustained injuries, but both were able to exit the cockpit following the crash.
The investigation
Investigators examined the wreckage and found the aircraft resting on the ground with its landing gear retracted. The engine, an Ivchenko AI 25TL, showed extensive internal damage. Metallurgical analysis revealed that the low-pressure turbine blades were broken and there was evidence of melting in the high-pressure turbine components, indicating abnormal temperature elevations.
Video analysis from cockpit and external cameras confirmed that the oil pressure gauge dropped to zero roughly six minutes and 50 seconds before the accident, with the low oil pressure warning light appearing intermittently for about 49 seconds. The investigation also noted that the Exhaust Gas Temperature (EGT) instrument's redline was set at 715 °C, exceeding the flight manual's limit of 670 °C. Furthermore, spectral analysis of the lubricating oil revealed it was thicker than the manufacturer's specifications.
Findings
- The engine failure was caused by the destruction of the rear section of the turboreactor, which resulted in a total loss of thrust.
- This destruction may have been caused by creep deformation of turbine blades due to operating temperatures exceeding specified limits over a significant period.
- The degradation of the high-pressure compressor bearing may have been exacerbated by intermittent or ineffective lubrication, as evidenced by the observed low oil pressure.
- The pilot elected to perform a forced landing rather than use the emergency ejection system because he feared the physical risks the ejection process posed to the inexperienced passenger.