Amid conflicting reports about whether the wreckage of the missing Malaysia Airlines Boeing 777-200 has been spotted, an expert in airborne search and rescue at sea highlights the challenging task facing the aerial armada searching for the aircraft.

“Search and rescue (SAR) is an incredibly hard mission, made more so when the datum (last location of the aircraft) is unclear,” says a source familiar with maritime patrol activities.

Initially, the airborne search would likely have used an expanding square or spiral search from the starting point, taking into account winds and currents that could "skew" the pattern of debris.

“The vague initial datum makes that area even larger, and time only expands it further,” he says.

The 777, registered 9M-MRO, lost contact with the Subang Air Traffic Control centre at around 01:30 local time on 8 March. Its last reported position was over an area of sea between Malaysia and Vietnam.

A perplexing element of the aircraft’s disappearance is the lack of a distress call or transponder signals. Flightglobal asked Malaysia Airlines about signals from the 777’s Aircraft Communications and Addressing and Reporting System (ACARS), but the carrier declined to comment citing “pending investigations” by Malaysia’s Department of Civil Aviation.

The search, which is entering its third day, involves over 30 aircraft and over 40 ships.

The expert says that the current SAR mission is similar to hunting for anti-shipping mines.

“Radar is a wide area search tool,” he says. “In this type of event, debris would typically be relatively small and floating low to the surface, making it very hard to "paint" with the radar. Additionally, floating debris has no Doppler speed relative to the surrounding ocean, so it would typically be filtered out by radar software intended to de-clutter the radar display. Turning off that feature would create a massive amount of clutter and sporadic returns, not adding much value.”

Electro-optical/infrared (EO/IR) sensors are also of dubious help. This long after the crash – if, indeed, MH370 went down in the sea – most of the debris would be the same temperature of the water, making it undetectable by IR.

And while the South China Sea and Gulf of Thailand are smaller bodies of water than the South Atlantic, where Air France flight AF447 crashed in 2009, it is still a vast area – and presents unique challenges.

A vast fleet of small fishing boats ply the South China Sea and Gulf of Thailand. Most of these do not carry an Automatic Identification System (AIS) transponder, which is common on larger vessels. These fishing boats make for small, slow moving contacts.

“Every one of these will appear as a target that the MPA crew would need to identify and rule out as potential large debris,” says the expert..

“The best sensor for SAR remains the human eye, which is why maritime patrol aircraft are all designed with the ability to fly low and slow to detect survivors or small debris.”

Source: Cirium Dashboard