NTSB Identification: ATL89FA161.
The docket is stored on NTSB microfiche number 41203.
Scheduled 14 CFR DELTA AIRLINES, INC.
Accident occurred Friday, June 16, 1989 in JACKS CREEK, TN
Probable Cause Approval Date: 06/26/1992
Aircraft: LOCKHEED L1011-385-1, registration: N721DA
Injuries: 7 Serious,23 Minor,259 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE FLIGHT WAS DESCENDING TO FL230 WHEN IT ENCOUNTERED SEVERE CLEAR AIR TURBULENCE. SEVEN PASSENGERS RECEIVED SERIOUS INJURIES; 11 OVERHEAD PAX SERVICE PANELS BROKEN. THE PILOT HAD EARLIER REPORTED TO ATC ENCOUNTERING LIGHT-TO-MODERATE TURBULENCE THROUGHOUT THE DESCENT, HAD INFORMED THE CABIN CREW OF THE TURBULENCE, AND HAD TURNED THE SEAT BELT SIGN ON. THE PASSENGERS WERE INFORMED OF THE SEAT BELT SIGN AND WERE INSTRUCTED TO SECURE THEIR SEAT BELTS. THOSE PASSENGERS SUSTAINING SERIOUS INJURIES CONFIRMED DURING INTERVIEWS THAT THEIR SEAT BELTS WERE NOT FASTENED. AREA FORECAST ISSUED AT 0545 AND VALID AT TIME OF OCCURRENCE CONTAINED NO FORECAST FOR TURBULENCE EXCEPT IN THE VICINITY OF CONVECTIVE ACTIVITY. AREA FORECAST ISSUED AT 1445 AND VALID AT TIME OF THE OCCURRENCE FORECAST MODERATE TURBULENCE BETWEEN 18,000 AND 42,000 FEET. SIGMET ISSUED AT 1350 FORECAST MODERATE OCCASIONAL SEVERE TURBULENCE ABOVE 27,000 FEET.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

FAILURE OF THE PASSENGERS TO REMAIN SEATED WITH THEIR SEAT BELTS FASTENED AS THE AIRPLANE ENCOUNTERED UNFORECAST SEVERE CLEAR AIR TURBULENCE.

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