Tucumseh's posting 5521 stirred my memory of accidents to three of British Airways Helicopters Ltd six BV 234 (civilianised Chinooks) 1983 - 1986. One was an engine fire, one was a control problem which caused the pilot to ditch and one was a catastophic desynchronisation of the twin rotors. Only the last one caused any fatalities (45 of the 47 pob). If anyone is interested, the AAIB Formal Reports are 7/84, 5/87 and 2/88.