Sydney: Air crash investigators probing the disappearance of MalaysiaAirlines MH-370 have discovered possible new evidence of tampering with the plane's cockpit equipment.



A report released by Australian air crash investigators has revealed that the missing Boeing 777 suffered a mysterious power outage during the early stages of its flight, which experts believe could be part of an attempt to avoid radar detection.



According to the report, the plane's satellite data unit made an unexpected "log-on" request to a satellite less than 90 minutes into its flight from the Malaysian capital, Kuala Lumpur, to the Chinese city of Beijing.

The reports says the log-on request - known as a "handshake" - appears likely to have been caused by an interruptionof electrical power on board the plane.



"A log-on request in the middle of a flight is not common," said the report, by the Australian Transport Safety Bureau. "An analysis was performed which determined that the characteristics and timing of the logon requests were best matched as resulting from power interruption."

David Gleave, an aviation safety expert from Loughborough University, said the interruption to the power supply appeared to be the result of someone in the cockpit attempting to minimise the use of the aircraft's systems.

The action, he said, was consistent with an attempt to turn the plane's communications and other systems off in an attempt to avoid radar detection.



"A person could be messing around in the cockpit which would lead to a power interruption," he said. "It could be a deliberate act to switch off both engines for some time. By messing about within the cockpit you could switch off the power temporarily and switch it on again when you need the other systems to fly the aeroplane."



Power failure

Inmarsat, the company that officially analysed flight data from MH370, has confirmed the assessment but says it does not know why the aircraft experienced a power failure.



"It does appear there was a power failure on those two occasions," Chris McLaughlin, from Inmarsat, told The Telegraph. "It is another little mystery. We cannot explain it. We don't know why. We just know it did it."



The Australian report released by Australian authorities has revealed that the Boeing 777 attempted to log on to Inmarsat satellites at 2.25am, three minutes after it was detected by Malaysian military radar.



This was as the plane was flying north of the Indonesian island of Sumatra. The aircraft had already veered away from the course that would have taken it to its destination of Beijing, but had not yet made its turn south towards the Indian Ocean.



The aircraft experienced another such log-on request almost six hours later, though this was its seventh and final satellite handshake and is believed to have been caused by the plane running out of fuel and electrical power before apparently crashing, somewhere in the southern Indian Ocean.

The other five handshakes were initiated by the satellite ground station and were not considered unusual.

Asked whether the power interruption could have been caused by a mechanical fault, Mr Gleave said: "There are credible mechanical failures that could cause it. But you would not then fly along for hundreds of miles and disappear in the Indian Ocean."



Another aviation expert, Peter Marosszeky, from the University of New South Wales, agreed, saying the power interruption must have been intended by someone on board. He said the interruption would not have caused an entire power failure but would have involved a "conscious" attempt to remove power from selected systems on the plane.



"It would have to be a deliberate act of turning power off on certain systems on the aeroplane," he said. "The aircraft has so many backup systems. Any form of power interruption is always backed up by another system.



"The person doing it would have to know what they are doing. It would have to be a deliberate act to hijack or sabotage the aircraft."



An international team in Malaysia investigating the cause of the crash has not yet released its findings formally, but has indicated it believes the plane was deliberately flown off course.

The plane disappeared on March 8 with 239 passengers aboard but an international air, sea and underwater search has failed to find any wreckage.



The Australian report added that the plane appeared to have flown on autopilot across the Indian Ocean and that the crew and passengers were likely to have been unresponsive due to lack of oxygen during the southward flight.



It has recommended an underwater search in an area about 1,100 miles west of Australia, around the location where the plane's seventh "handshake" is believed to have occurred.



The report also notes that the plane's in-flight entertainment system delivered a satellite message 90 seconds after the first power failure -- but not after the second failure hours later. This, it says, "could indicate a complete loss of generated electrical power shortly after the seventh handshake".



The new underwater search will begin in August and cover about 23,000 square miles. It is expected to take up to a year.