Finally, some progress on identifying the location of missing Malaysia Airlines flight MH370, with signals detected that might have come from the plane. Crikey aviation expert Ben Sandilands explains what’s been found so far, what it might mean, and where the search will go from here …

We might have heard a ping from the black box. What’s the next step?

The next physical development in the search for missing flight MH370 is likely to be the positive identification of its wreckage on the floor of the Indian Ocean around 1000 kilometres from Learmonth, Western Australia.

That proof positive is expected to be made by a side-scan sonar-equipped untethered submersible called Bluefin-21 deployed from the Australian Defence vessel Ocean Shield over the site of signals that match the frequency of pingers attached to the missing plane’s two flight recorders.

However, that matching process could also be achieved by the continuing ocean surface search for floating objects that are unmistakably from the Malaysia Airlines 777-200ER that disappeared from air traffic control radar screens early in its flight from Kuala Lumpur to Beijing on March 8 with 239 people on board.

And if we learn for sure we’re looking in the right place?

If Bluefin-21 finds something that scans like metal wreckage some 4500 metres below Ocean Shield’s location, it will then be sent down a second time with cameras instead of sonar in its equipment bay. If the photos confirmed the location of the heavier parts of the Malaysia Airlines jet, a recovery operation would begin in earnest.

Do we have the technology to get at the black box and voice recorder, if they’re down there?

The head of Australia’s special Joint Agency Co-ordination Centre, former Air Chief Marshal Angus Houston (pictured, his finger pointing to the map), has already cautioned that while Bluefin-21 is technically capable of recovering the cockpit voice and flight data recorders, any wreckage might be deeper than its 4500-metre operational limit. This would result in a delay while larger, more capable recovery equipment was brought to the scene, and that could take weeks.

Ocean Shield made its breakthrough detections of signals at the black box beacon frequency using a US Navy-provided towed hydrophone at depths of up to 3000 metres. That device involves lowering around 6000 metres of cables, and procedures for managing this heavy and extensive assemblage are exacting and very time-consuming.

What makes us think we might have found the plane this time?

Behind the scenes over the weekend a multi-national team of experts assisting the Malaysian inquiry into MH370’s disappearance made some crucial refinements to modelling trying to predict the most likely impact points for the jet in the Indian Ocean after it ran out of fuel.

The key to its considerations was a set of electronic traces the jet had made in a regular “standby” or “handshake” mode between its automated flight performance messaging system and an Inmarsat satellite.

After the flight left KL there were six such transmissions, the last being seven hours and 31 minutes after wheels up. But eight minutes after the sixth completed handshake signal there was an unexpected and incomplete signal from the jet, which is now believed to have ended when it hit the water.

The KL investigation team was able to reduce the arc of possible locations at which that final transmission ended to a 550 kilometres long stretch of the Indian Ocean off the WA coast, where the Australia’s Ocean Shield happened to be listening for pinger signals at the northern extent, while China’s Haixun 01 carrying out similar work, with less sophisticated equipment but no doubt similarly expert intelligence, at its southern end.

Are bodies likely to be recovered?

As proved to be the case with the deep ocean retrieval of flight recorders and other items from the mid-Atlantic crash site of Air France flight AF447 in 2009, biological activity at great depths may be sufficiently slow to allow the recovery of some of the victims of the MH370 crash.

More than 100 of the 228 people who died in the Air France disaster were recovered from the sea floor in 2011, while a smaller number were found on the surface in the weeks after the crash.

What on earth happened to that plane to cause it to crash so far off course?

Parallel with the physical identification and retrieval of wreckage from MH370 is the criminal investigation, which is trying to find out who is behind the loss of the aircraft, and for what motives.

Malaysian authorities have already said they believe MH370 was deliberately diverted from its intended course when it was over the Gulf of Thailand on its way to Beijing. The possibility that the aircraft’s control systems were hacked or sabotaged has circulated in established IT forums, although experts have been unable to propose how external connections or even passenger interference with those systems could have occurred, since there are no wireless or wired points of access to that particular type of airliner’s flight control computers from unauthorised locations.

Will the data recorders and voice recorder tell us anything?

Assuming the flight data and cockpit voice recorders are retrieved and read, many crucial insights into what happened to MH370 will be revealed.

Even if the cockpit voice recorder has been overwritten, the last two hours or so of noises or words picked up around the pilot and observer seats will reveal important clues as to what was going on before the crash.

The flight data recorders will cover a much longer period and include cabin pressure changes, the opening and closing of the cockpit door, the exact inputs to controls made from each pilot seat as well as the shared console of instruments, and the activation of pre-recorded cabin announcements.

The truth as to what happened to MH370 lies silent on the floor of the Indian Ocean. Its time to be heard draws nearer.