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

systems), radio transmitters, and in-flight entertainment system. In addition, therewere also no faults reported with these systems during the occurrence flights, ornotable problems reported in the occurrence aircraft’s recent maintenance records.Other potential onboard sources of EMIThe cargo manifests for the three occurrence flights were examined for items thatmight have been possible sources of electromagnetic interference and none wereidentified. Following the 7 October 2008 occurrence, all of the cargo was removedfrom the aircraft and inspected for items that might have been possible sources ofelectromagnetic interference. None were identified. The investigation did notdetermine whether any of the passengers’ luggage could have included poweredelectronic devices, although it was considered unlikely that such devices could haveprovided a significant level of emissions.The investigation surveyed passengers and flight crew from the 7 October 2008flight about whether any PEDs were in use during the flight, with a particular focuson devices such as mobile phones and laptops that were capable of transmittingsignals. 145 Although any electronic device can cause interference, those whichtransmit via radio waves create the highest risk. Overall, only a small number 146 ofPEDs were reported to be on at the time of the occurrence. All were reported to bein the appropriate flight mode, and no problems were reported with the performanceof the devices.Expert advice was obtained from a major telecommunications company regardingthe aircraft locations at the time of the three events, the ranges from the mobilephone base stations 147 , the performance characteristics of mobile phones when inandout-of-range of a base station, and the network transmission technology in useat the time (that is, CDMA and GSM 148 ). The company advised that the location ofthe 12 September 2006 occurrence was too far from the nearest base station for amobile phone to have been useable on board the aircraft, and the 7 October 2008occurrence was possibly but unlikely to have been within range. Mobile phoneactivity through base stations closest to the location of the 7 October 2008occurrence were reviewed to identify any evidence that a mobile phone on theaircraft may have been making or receiving transmissions, and no such evidencewas identified. 149145146147148149All the crew were interviewed about a range of topics, including PEDs. The passengerquestionnaire asked passengers about any PEDs they were using, or that were in use by otherpassengers nearby. Further details on the questionnaire are provided in Appendix I.Based on passenger questionnaires and interviews, there were at least seven laptops in use duringthe flight, three mobile phones (in the appropriate flight mode), and at least two other electronicdevices. Almost all of these devices were being used in the centre or rear sections of the cabin.Mobile telephones generally do not transmit unless they are within range of a base station, or ifthey are connecting to a nearby device via a short-range wireless technology such as Bluetooth.Other PEDs, including laptop computers and hand-held games, can also produce significantemissions through similar technologies.CDMA: Code division multiple access. GSM: Global System for Mobile Communications.This search would not have identified mobile phones that were turned on and not in flight mode,and which did not or receive a call or message during the period of interest.- 140 -