Jetstream 3202, G-BYRA
The incident occurred during a charter flight from Southampton Airport to Manchester Airport. The aircraft was passing FL120 in the climb when there was a loud bang from the area of the right engine. High levels of vibration did not permit reading of the engine instruments and control of the aircraft was difficult due to unexpectedly strong tendencies to yaw and roll. The right powerplant had suffered a major failure of the input stage to the reduction gearbox due to a fatigue fracture of the bull gear; this failure disconnected the propeller from the engine. The damaged bull gear was back-driven by the propeller resulting in high levels of vibration. The propeller’s variable pitch mechanism was unable to stabilise to the unloaded windmilling condition, resulting in oscillatory yaw and roll motions. The right engine was identified as not producing power and an abnormal checklist shutdown carried out. After the right propeller feathered a single-engine diversion to Farnborough was safely accomplished. Since this incident the engine manufacturer has introduced a completely redesigned bull gear assembly obviating the need for any safety recommendations.
G-BYRA-07-05.pdf (859.90 kb)