Incident Overview
A DC-9 aircraft, after departing and climbing to flight level 290, received an air traffic control clearance to descend to 17,000 feet mean sea level approximately 1 hour and 35 minutes into the flight. The captain initiated a descent at a rate of about 3,500 feet per minute and reduced speed to 280 knots.
Wake Turbulence Encounter
While passing through flight level 235 during the descent, the DC-9 encountered wake turbulence generated by a cargo Boeing 747 that was 12 nautical miles ahead and also descending to 17,000 feet. The captain responded by pitching the aircraft's nose up to exit the turbulent wake and requested increased separation from the preceding aircraft from air traffic control.
Injury to Crew
During the wake turbulence encounter, a flight attendant who was in the galley slipped and sustained a serious injury to her right ankle. No other injuries were reported.
Response and Aftermath
The crew continued the descent and landing without further incident. The aircraft and other occupants were not affected beyond the reported injury.