What happened
On 17 December 1998, a Fokker F27 Mark 500, registration G-JEAE, was performing a scheduled public transport flight from Ronaldsway Airport on the Isle of Man to Bristol Airport. The flight, which was part of the first officer's initial line training, proceeded normally through the ILS approach to Runway 27. The weather featured a 14-knot crosswind from the left and visibility of 6,000 metres.
Upon touchdown at approximately 95 knots, the crew maintained the aircraft on the centerline. As the aircraft decelerated, the commander noted that the first officer's aileron input had returned toward neutral and prompted him to reapply into-wind aileron. While the aircraft was traveling at roughly 60 knots, it experienced a sudden and violent swing to the left. Despite the commander's attempts to use both the rudder and the nosewheel steering to correct the path, the aircraft left the paved surface. The aircraft eventually came to a halt with its left main landing gear on the grass, while the nose and right main gear remained on the runway. There were no fatalities, though one passenger sustained a minor injury.
The investigation
The AAIB examined the aircraft's flight data recorder and cockpit voice recorder. The FDR data confirmed that the approach and landing were normal, but recorded heading oscillations that began to diverge at 60 knots, showing a significant heading change over a four-second period.
Investigators also performed a detailed examination of the runway and tyre marks. The tracks showed the aircraft traveled straight for 150 metres before the abrupt leftward swing. Marks from the right main gear tyres indicated they were more heavily loaded during the swerve, while the left main gear tyre showed evidence of anti-skid system activation.
Technical inspections of the Fokker F27 Mark 500 landing gear, brakes, and steering systems revealed no mechanical malfunctions. A subsequent high-speed taxi test under similar weather conditions demonstrated normal handling characteristics.