berlin airbus helicopters warn pilot tiger military helicopters careful rapid switch auto pilot manual mode turbulence initial indications switch may play role fatal crash mali unit european aerospace giant airbus say statement warn aim increase operators safety see indication possible root cause crash u.n. mission july kill crew members accord source see airbus helicopters bulletin carry warn bulletin say unexpected switch automatic manual flight mode may play role accident accord information currently available bulletin say whether unexpected switch happen automatically do manually german officials last week meet discuss accident mali desert decide maintain exist flight restrictions aircraft fail reach definite conclusion cause crash airbus say safety guidance send operators germany australia france spain mean standardise flight manuals remind operators crew must adjust attention environmental condition use auto pilot turbulence guidance reiterate passages already flight manuals instruct pilot intentionally enter areas moderate turbulence avoid fly areas severe turbulence german defence ministry report last month say tiger crash mali fly 250 kilometres 155 miles per hour height 550 metres 1,800 feet suddenly sink nose enter sharp dive helicopter crash 10 second late burst flame report however say early speculate cause crash german officials continue investigate cause crash officials say could take months complete probe time crash say sign helicopter down attack germany deployment four tiger helicopters mali early year controversial since aircraft require extra maintenance give strong heat environmental condition african country although officials say aircraft perform normally germany agree deploy tiger helicopters four nh-90 transport helicopters dutch military say could continue work mali germany increase support heavily debate parliament require waiver german military allow helicopters operate high temperatures germany currently 26 tiger helicopters airbus issue safety advice tiger helicopters fly turbulence