There have been two new developments in the search for Malaysia Airlines flight MH370, but neither gives cause for optimism to relatives of those lost with the aircraft.

In the interests of information transparency, raw communications data relating to the satellite communication exchanges with the aircraft that enabled the search to be directed to the Indian Ocean west of Australia have now been released. Also, a day after that development, Australian authorities announced that they have stopped searching for crash debris in the area where the vessel ADV Ocean Shield detected underwater acoustic signals in early April.

The Australia-based Joint Agency Coordination Centre (JACC) says the Bluefin-21 autonomous underwater vehicle was pulled up on 28 May after searching over 850km2 of the ocean floor. Analysis of data the device gathered shows no signs of wreckage from the Boeing 777-200ER that disappeared on 8 March with 227 passengers and 12 crew on board. The JACC says: “The Australian Transport Safety Bureau [ATSB] has advised that the search in the vicinity of the acoustic detections can now be considered complete and, in its professional judgement, the area can now be discounted as the final resting place of MH370.”

The announcement followed media confusion stemming from unofficial comments by a US Navy official. During a CNN interview, the navy’s deputy director of ocean engineering, Michael Dean, said that acoustic signals detected in early April – on the basis of which the location of the Bluefin-21’s search was determined – have subsequently been deemed by the USA and other nations to have been produced by a source other than MH370’s flight data or cockpit voice recorder. The USN was quick to issue a statement saying the official’s comments were “premature”.

On 11 April, Australian prime minister Tony Abbot had expressed confidence that the acoustic signals detected indicated the search was close to locating the missing aircraft, but he backed down significantly the following day, indicating a much lower level of confidence.

Malaysia’s release of the raw satellite data detailing MH370’s electronic “handshakes” with an Inmarsat satellite on 8 March during its ill-fated flight is part of an effort to bring greater transparency to information about the subsequent search. The disclosure of the Inmarsat data will also give external consultants and experts an opportunity to examine what has so far provided the only clue to the possible final position of the lost aircraft. A few days after this release, however, no independent agency had come up with an interpretation that challenges the conclusions about the oceanic area in which the aircraft is believed to have come down.

The information is contained in a 47-page transcript of numbers that quantify satellite transmissions and handshake responses recorded by Inmarsat. Produced by the UK-based satellite communications company, it contains brief explanatory notes at salient moments during the flight, such as the aircraft’s last Aircraft Communications and Reporting Addressing System (ACARS) transmission.

Signals commenced at 16:00:13 GMT on 7 March with a “Log-on/Log-off Acknowledge” event. This would have been just after midnight local time over the Gulf of Thailand on 8 March. After some 30 pages of routine transmissions, the “last acknowledged ground-to-air DATA-2 ACARS” message came at 17:07 GMT (01:07 local time), the report notes. Eventually, the final transmission was recorded at about 08:18 local time, when, it is believed, the aircraft would have been running out of fuel.

Meanwhile, the ATSB is preparing for a larger underwater search for MH370. To begin in August and take 12 months to complete, this will cover an area of up to 60,000km2.

“The ATSB will use data obtained from a comprehensive bathymetric survey of the search area to identify and prioritise areas of the search zone,” it explains. Currently under way, this “will essentially provide a map of the search zone, charting the contours, depths and hardness of the ocean floor”.

The extended search for the lost aircraft, which will be conducted by private contractors, will use specialist equipment capable of operating at depths of “at least 6,000m”. It will include a towed sonar, autonomous underwater vehicle and advanced optical imaging equipment.

Keeping up the pressure on behalf of relatives of the many Chinese passengers on MH370, Chinese premier Li Keqiang has urged the Malaysian authorities to develop a new search plan. Li’s statement followed a meeting with Malaysian prime minister Najib Razak on 29 May.

Additional reporting by David Kaminski-Morrow and David Learmount

Source: Flight International