The Boeing 747 aircraft with 340 passengers and 22 crew aboard had to return to Heathrow airport after significant vibration was noted on one of the engines, shortly after departure for Kuala Lumpur on August 17, 2012, the report by the Air Accidents Investigation Branch (AAIB) said.
During the approach to land back at Heathrow, all three autopilots disengaged, the cockpit displays and lights flickered and a series of fault messages were displayed. There was a subsequent loss of power to some systems, but the captain managed to make a safe landing, the report said.
The jumbo jet had a cockpit voice recorder (CVR) - a device which can record the last two hours of cockpit conversations. The AAIB, which classed the incident as "serious" in its report, said the CVR continued to run for some time after the aircraft landed "and as a result all relevant CVR recordings were lost".
The AAIB said: "The investigation determined that the operator's procedures for the preservation of flight recording was not sufficiently robust to ensure that recordings would be preserved in a timely manner, following an incident or accident."
The report said that Malaysia Airlines had "expressed willingness to address this issue" and updated its procedures.
"The revised procedures require the commander to secure the recordings as soon as possible after a flight involving a serious incident by pulling and tagging or collaring the appropriate circuit breakers and, if the means for achieving this is not on the flight deck, the commander is required to ensure that the appropriate maintenance personnel take that action," the AAIB report said.
The AAIB said there had been a series of failures within the aircraft's electrical system. The report also listed action taken by Boeing after the incident, daily 'Mirror' reported.
Finding the black box is crucial to know why the Beijing- bound Flight MH370 with 239 people, including five Indians, veered off from its route after taking off from Kuala Lumpur on March 8. Malaysia has come under criticism for its handling of the search, with families of the passengers on the Boeing 777-200 plane accusing the authorities of a lack of transparency.
Investigators still do not know why MH370 strayed so far off course, after disappearing over the South China Sea between Malaysia and Vietnam.