What happened
On October 27, 2010, an Ilyushin 76 TD, registration EK76442, operated by Phoenix Avia, experienced an engine failure while taxiing at Dubai International Airport. During the routine line-up checks, the crew advanced the four engines to 80% power to monitor vital parameters such as oil pressure, temperature, and vibration. Approximately 20 seconds into this procedure, the pilot noticed low oil pressure and a red vibration alert on engine number 2.
In response, the crew immediately reduced power on all engines and shut down engine number 2. The aircraft returned to the cargo stand at E23, where the crew disembarked without further incident. No injuries were reported among the 7 crew members on board.
The investigation
Investigators from the GCAA AAIS examined the engine and the fuel supply to determine the cause of the malfunction. While the aircraft's compressor remained undamaged, a detailed teardown of the engine revealed significant destruction within the turbine section. Specifically, several turbine blades and nozzle guide vanes had disintegrated or been ripped from their mounts.
Analysis of the fuel drained from the constant-speed drive governor revealed that the gum content significantly exceeded permissible safety standards. Furthermore, investigators found that the fuel nozzles were partially obstructed by foreign deposits, which had altered the fuel spray pattern. This obstruction created a "torch effect," where the flame became concentrated in specific areas rather than being distributed evenly.
Findings
- The primary cause of the engine failure was internal damage caused by heat stress resulting from the use of highly contaminated fuel.
- Excessive gum levels in the fuel led to deposits that clogged the fuel nozzle orifices.
- The resulting uneven fuel atomization created localized high-temperature zones, causing the stage 2 nozzle guide vane to fail and fragment.
- The engine's existing inspection program and the operator's quality assurance system were insufficient to detect the accumulation of these deposits or to audit the quality of fuel at outstations.
- Standard fuel contamination detectors used during refueling were unable to identify the high concentration of gum in the fuel.
Safety action
Following the investigation, several safety recommendations were issued:
- The operator was advised to perform hot section inspections on all similar engines within its Ilyushin 76 TD fleet and to enhance inspection techniques for fuel nozzles.
- The operator was directed to strengthen its quality system to include audits of fuel stations and contamination control during refueling.
- The Armenian civil aviation authority was recommended to increase oversight of the operator's maintenance and quality systems.
- The GCAA recommended establishing a random fuel sampling system in cooperation with specialized laboratories.