Accident Details
On September 18, 2016, at about 0950 Pacific daylight time, a Cessna 120 airplane, registration N76284, veered off the runway during the landing roll and nosed over at Yolo County Airport (DWA) in Davis, California. The empennage sustained substantial damage. The pilot sustained minor injuries and the sole passenger sustained serious injuries. The airplane was registered to a private individual and operated by the pilot as a visual flight rules (VFR) local personal flight under 14 CFR Part 91. Visual meteorological conditions prevailed; no flight plan was filed. The flight originated from DWA at about 0840 PDT.
Sequence of Events
The pilot reported that during the landing roll, the airplane "began suddenly swerving with increasingly tremendous centrifugal force to the left" and did not respond to opposite rudder inputs. The airplane veered off the runway to the left into a freshly plowed field. During the runway excursion, it crossed over a dirt trench and then nosed over.
Restraint System Failure
During the nose over, the center safety belt bracket, which secures the pilot and front seat passenger's seatbelts to the cabin floor, failed. The pilot was released from his seatbelt. Examination revealed that the aluminum center safety belt bracket, likely installed when the airplane was manufactured in 1946, had failed in shearing overstress. Shortly after manufacture, the manufacturer began installing a steel center safety belt bracket in new production airplanes.
Service Bulletin
Following a similar accident (ERA14FA327), the manufacturer issued a service bulletin on February 17, 2015, calling for inspection of the center safety belt bracket on all Cessna 120 and 140 airplanes to determine if the latest type (steel) bracket was installed, and replacement of any older aluminum brackets with the latest type.
Maintenance Awareness
During a telephone conversation, the mechanic who completed the airplane's annual inspection stated he was unaware of the service bulletin related to the center safety belt bracket.
Fleet Statistics
A review of the FAA aircraft registry database found approximately 2,145 airplanes manufactured with this center safety belt bracket currently registered in the United States. Of these, about 2,099 (98%) were manufactured before the effectivity of the material change.