What happened
On 27 October 2009, a Brussels Airlines Avro RJ100, registration OO-DWK, arrived at Brussels Airport from Berlin Tegel. While taxiing toward the gate, the flight crew identified a loss of pressure in the green hydraulic system, which subsequently resulted in the loss of nose wheel steering capabilities.
Simultaneously, cabin crew reported a high-pressure leak of hydraulic fluid into the passenger cabin. The leak originated near row 7, affecting the area between rows 3 and 9. The pressurized release of fluid caused significant contamination of the cabin interior and triggered panic among the 74 passengers on board. The aircraft was brought to a halt on the inner 9 taxiway, and an evacuation was conducted via the forward air stair.
While there were no fatalities, four passengers required medical attention at local hospitals due to skin irritation caused by contact with the fluid. The leak caused extensive damage to the aircraft's interior, contaminating electrical wiring, cabin lighting, floor structures, and various passenger service units.
The investigation
Investigators examined a stainless steel pipe from the green hydraulic system, which transports fluid from the hydraulic bay to the right-wing spoiler control valve and flap system. This specific component had been part of the aircraft since its original manufacture and had not been replaced during its operational life.
Metallurgical analysis conducted by BAE Systems revealed a linear defect on the inner surface of the pipe. This defect was located at the base of a weld and was linked to insufficient weld penetration. The investigation determined that the pipe failed at a bend where the weld defect and the structural weakness were positioned at a 90-degree angle to the top of the bend, making the area susceptible to high levels of fluctuating stresses.
Findings
- The primary cause of the hydraulic line rupture was metal fatigue originating from a defect at the weld joint.
- The failure was exacerbated by low levels of weld penetration during the pipe's manufacturing.
- The aircraft was otherwise in an airworthy condition at the time of the incident.