Malaysian officials non-committal on MH370 ACARS transmissions

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Officials investigating the disappearance of a Malaysia Airlines Boeing 777-200ER are tight-lipped about Aircraft Communications Addressing and Reporting System (ACARS) data reported by the aircraft.

Malaysia’s Department of Civil Aviation is examining ACARS data from the missing aircraft, but senior DCA officials declined to comment on their findings, if any. They also declined to say when ACARS data from flight MH370 will be released – or even if it will be.

In response to a question posed by Flightglobal about the aircraft’s ACARS data, one of the officials cited the “sensitivity of the investigations.”

The comments were made after a ministry of transport press conference scheduled for 1000 was cancelled, apparently indefinitely. According to the Twitter account of acting transport minister Hishamuddin Hussein, he instead embarked on one of the search and rescue flights looking for the aircraft in the Straits of Malacca on Malaysia’s west coast.

Media reports have said that no ACARS data was received from the aircraft when its transponder disappeared from radar at 0130 local time on Saturday 8 March. The aircraft mysteriously vanished halfway between the Malaysian town of Kota Bahru and the southern tip of Vietnam as it operated the Kuala Lumpur-Beijing route.

"All Malaysia Airlines aircraft are equipped with continuous data monitoring system called ACARS which transmits data automatically," says MAS. "Nevertheless, there were no distress calls and no information was relayed."

Presumably the aircraft would have transmitted ACARS data prior to its disappearance, but an industry source familiar with ACARS says this would be entirely dependent on the level of service enshrined in MAS’s ACARS contract with one of two ACARS service providers, ARINC or SITA.

Use of ACARS among carriers varies widely. Users of the service can have data transmitted at widely varying intervals, such as every minute to every thirty minutes.

When an aircraft is flying over land, ACARS data is transmitted via VHF to ground stations, but over water the data is transmitted to satellites.

Typically ACARS data has a narrow focus, with engine performance being the most widely monitored aspect of aircraft health. The flight crew can also deactivate ACARS transmissions if they elect to do so.

Nonetheless, ACARS data proved crucial for gaining an early understanding of Air France flight AF447, which crashed 1 June 2009. Within three days of this aircraft’s disappearance investigators released ACARS data, revealing that the aircraft had transmitted a number of failure reports for various aircraft systems.

It is far from clear, however, if ACARS data will be of similar use in the MH370 case.

The search for the missing aircraft, which carried 227 passengers and 12 crew, has entered its fourth day, with ships and aircraft scouring the Gulf of Thailand and the Straits of Malacca.