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

equiring cabin crew to enforce the use of seat belts when the sign is not illuminatedwould create difficulties in the relationship between the crew and passengers.Engineering solutions, such as automated reminders built into the seats, would bedifficult to implement and justify, particularly for existing seats.The aviation industry needs to conduct further research into the reasons why somepassengers do not wear seat belts, and the effectiveness of different communicationtechniques for increasing seat belt use. Limited research has been done in theseareas to date. More frequent reminders during a flight, more variety in thecommunications, or messages targeted for specific demographic groups all have thepotential to increase compliance. Using examples such as the present accident mayalso be useful in some types of communications.5.4.2 How seat belts are wornTo be effective, seat belts need to be worn low and tight across the hips. Keeping aseat belt tight is most important during takeoff and landing, and it does notnecessarily need to be as tight during cruise except during turbulent conditions.However, a seat belt should still be relatively firmly fastened during cruise, as asignificant degree of slack will increase the risk of injury in the event of anunexpected upset.A significant proportion (48%) of the 98 passengers who completed the ATSBquestionnaire indicated that they wore their seat belt ‘loosely’ during cruiseactivities, and 16 of the 81 passengers that were known to be wearing seat belts atthe time of the first upset reported that their belts were loosely fastened. However,there was little evidence that incorrect seat belt wearing contributed to injuries. Theinjury rate for passengers who said their seat belts were loosely fastened was nodifferent to the rate for those who said their belts were tightly fastened, althoughonly a small sample size was involved. It is possible that many passengers’understanding of the term ‘loosely’ simply meant that their seat belt was looser thanduring takeoff, even though it was still relatively firm.Overall, the issue of how seat belts are worn during the cruise phase of flightappears to be a less important issue than whether the seat belts are actually worn inthe first place. It is worth noting that operators typically instruct passengers to weartheir seat belts ‘low and tight’ for the takeoff, but generally provide no reminders ofhow they should be worn after the takeoff. In some cases the advice to passengersindicates that the seat belts can be loosened after takeoff, but does not reinforce theneed for the belts to still be relatively firm and worn across the hips. More detailedguidance for passengers on this topic would be useful.5.5 Other aspects5.5.1 Response to the 12 September 2006 eventIn theory, the 12 September 2006 occurrence provided an opportunity for theADIRU data-spike failure mode and the design limitation of the A330/A340 flightcontrol system to be identified before the 7 October 2008 occurrence. In reality,based on the available information, there were good reasons for not conducting anyfurther investigation at the time.- 206 -