What happened
Following a landing at Melbourne Airport, an aircraft underwent a turn-around inspection where crews identified a low fluid level in the right hydraulic system. This loss of fluid was linked to a ruptured hydraulic hose located within the engine thrust reverser retraction circuit. Flight data analysis confirmed that the drop in hydraulic fluid levels occurred at the same time the thrust reverser was being retracted after the aircraft had landed.
During the event, Airport Rescue and Firefighting (ARFF) personnel conducted a visual inspection of the aircraft, noting what initially appeared to be smoke emanating from the engine area.
The investigation
The investigation focused on the source of the visible mist and the mechanical failure of the hydraulic component. Investigators examined the right hydraulic system and found that the hose in question is isolated during flight and only active during the thrust reverser retraction process.
Regarding the reported smoke, the investigation determined that the substance was likely mist rather than combustion-related smoke. The findings suggest the mist could have originated from hydraulic fluid leaking into the engine exhaust due to the hose rupture. Alternatively, the investigation considered that the mist might have been produced by the engine oil breather. This phenomenon, noted by Rolls Royce, involves a white-coloured mist resulting from incomplete air/oil separation within the breather system. It remains possible that both the hydraulic leak and the oil breather contributed to the visible mist.
Findings
- A hydraulic hose within the right engine thrust reverser retraction circuit failed during the retraction sequence on landing.
- The reduction in the right hydraulic system fluid level was consistent with a leak from this ruptured hose.
- The reported engine smoke was likely mist from hydraulic fluid entering the exhaust, mist from the engine oil breather, or a combination of both.