What happened
On 1HM September 2005, a F-Swearing SA227-AC passenger flight, registration PH-DYM, was preparing for a charter departure from Rotterdam Airport to Birmingham. As the crew transitioned the engine speed levers from taxi to flight position, a nose wheel steering fault indicator illuminated. While the crew initially believed the issue was simply a failure to engage the steering switch on the throttles, the aircraft began to deviate toward the left side of the runway during the takeoff roll.
As the aircraft reached speeds between 50 and 60 knots, the crew attempted to use the brakes and rudder to correct the path and subsequently aborted the takeoff. However, the aircraft could not be maintained on the runway. The plane exited the paved surface onto a soft grass area. The left landing gear sank into the soft ground, causing the gear to break off and the left wingtip to strike the earth. This triggered a ground loop that resulted in the failure of both the right and nose landing gear. Despite the severe damage to the airframe, the evacuation of the seventeen passengers and two crew members was completed without incident, though one passenger required medical evaluation for minor injuries.
The investigation
The investigation involved analyzing cockpit voice and flight data recorders, radio transmissions, and technical inspections by the National Aerospace Laboratory. Investigators examined tire tracks on the runway, which indicated the directional deviation began almost immediately at the start of the takeoff roll.
Technical analysis focused on the nose wheel steering system. While the crew initially suspected a manual error regarding the steering switch, the laboratory identified a hydraulic leak within the steering system. This leak caused the nose wheel to receive an uncommanded steering input to the left. The investigation also noted that the aircraft's manufacturer's successor had previously been aware of similar steering issues, which were addressed in maintenance instructions issued in 2009 regarding the replacement of the manifold and arming valve assembly.
Findings
- The primary cause of the excursion was a hydraulic leak in the nose wheel steering system.
- The leak caused the nose wheel to rotate uncommandedly to the left, making the aircraft difficult to control via rudder pedals.
- The aircraft's departure from the runway was exacerbated by the soft ground conditions outside the runway perimeter, which led to the structural failure of the landing gear.