A key question that has been on the lips of much of the public was how missing flight MH370 could still communicate with satellites, according to the latest Inmarsat information, when reports claim that the on-board ACARS system had been disabled?

The answer to this lies in the workings of the ACARS system itself. Aircraft Communications Addressing and Reporting System (ACARS) has been the industry standard data communications system since the 1970’s. Developed and introduced by ARINC Inc, ACARS gives a data link from air-to-ground, relaying critical information regarding the flight, aircraft systems and also gives the ground-based operators means to relay NOTAMs, weather data and in-flight messages to the flight deck.

If ACARS failed, or was manually disabled during the flight, how, then, did the satellite appear to receive information after this? ACARS carries satellite equipment outside the aircraft that cannot be tampered with while the plane is in flight. The internal workings of ACARS in the cockpit can be disabled with a simple manual action. This is possible because of the risk of electrical fire on the flight deck.
Although ACARS, once manually disconnected, will not relay information, the satellite equipment outside the aircraft will send and receive ‘pings’ or digital handshakes periodically to determine the status of the network.

It is these pings or handshakes that the satellite picked up. While the aircraft responded to these pings, it was clear that it had power, was likely intact and in flight, although this does not prove beyond doubt that it was not intact on the ground.

The search continues for flight MH370 and leaves many questions unanswered.