In-flight upset - 154 km west of Learmonth, WA, 7 October 2008,

4.3.2 Seat belt examinationsSix passengers reported that they were seated with their seat belt fastened at thetime of the first in-flight upset, but that the belt became unfastened and did notrestrain them in their seats. None of the six passengers could provide details of howtheir belts released, and no other passengers reported any problems with theoperation of their seat belts.The seat belts on the aircraft were a very common type of lap belt with a lift-leverbuckle. The investigation examined a sample of 51 belts on the occurrence aircraft.The sample included the belts of four of the passengers who had reported seat beltproblems before the examination was conducted (November 2008). 184 It alsoincluded the belts of passengers that the investigation knew had received hospitaltreatment but did not know if they were wearing a seat belt. No problems wereidentified with the condition of the webbing, buckle or connector of any of the 51belts examined.During the seat belt examinations, investigators identified a scenario that couldresult in a seat belt being inadvertently unfastened. The scenario involved thebuckle of a very loosely-fastened belt catching on the underside of the seat’s rightarmrest. The examinations also noted that belts that were fastened this looselyposed a significant injury risk, even if they remained fastened. Only three of the sixpassengers who reported a problem advised that they had their belts looselyfastened.The inadvertent release scenario had not been identified in previous investigationsinvolving in-flight upsets. It was not possible to determine whether the scenarioactually occurred to the three passengers who reported having loosely-fastened seatbelts on the occurrence flight.Further information on the seat belt design and the examination of the inadvertentrelease scenario are provided in Appendix J.4.4 Seat belt requirements4.4.1 Regulatory requirements and guidanceUse of seat beltsAustralian Civil Aviation Regulation (CAR) 251(1) stated:...seat belts shall be worn by all crew members and passengers:(a) during take-off and landing;(b) during an instrument approach;(c) when the aircraft is flying at a height of less than 1,000 feet above theterrain; and(d) at all times in turbulent conditions.184Two of the six passengers who reported that they were wearing their seat belts but that their beltsdid not restrain them provided their reports after November 2008.- 171 -