What happened
On July 12, 2018, at approximately 23:00 UTC, a Cessna C-501, registration LV-CGO, was cruising at flight level 340 when a passenger reported a burning odor. The crew initially attempted to mitigate the smell by turning off a coffee maker and lowering the cabin temperature. However, the odor returned and was accompanied by visible smoke. In response, the crew donned oxygen masks and performed an emergency landing at Rosario International Airport in Argentina. The aircraft landed safely on runway 20, and all occupants evacuated the aircraft without injury.
The investigation
Investigators examined the aircraft and found that the passenger cabin oxygen masks had deployed normally. While no immediate smell of burning was detected during the initial inspection, subsequent functional tests of the electrical and air conditioning systems revealed performance deficiencies and an abnormal high-frequency noise originating from the air cycle machine.
Further technical analysis of the air cycle machine, conducted in coordination with the manufacturer, revealed severe internal damage. The component, which had been installed in the aircraft for 28 years, showed a broken shaft, broken fan blades, and a destroyed compressor and turbine. The investigation ruled out external debris ingestion, as the air intake is protected by a grille.
Findings
- The smoke entered the cabin through the air conditioning system due to a structural failure within the air cycle machine.
- The failure was triggered by the breakage of a fan blade due to fatigue, which caused a significant imbalance in the rotating assembly.
- This imbalance led to the shearing of the machine's shaft and caused the compressor and turbine to rub against their housings, generating high temperatures and smoke.
Safety action
- The investigation highlights the necessity for operators to ensure all crew members are thoroughly trained to recognize the signs of smoke or fire and are proficient in the required emergency procedures.