how tech helped the hunt for flight MH370

When Malaysia Airlines Flight 370’s transponders were disabled on the flight deck and the plane failed to be positioned by either civilian or military radar there was still one piece of tech tracking the plane’s position: ACARS.

The Aircraft Comms Addressing and Reporting System, fitted in 90 per cent of commercial jets, is similar to SMS in that it’s used by pilots to send messages and receive weather reports. When a plane powers up, ACARS establishes a satellite link, but MH370’s was switched off. That’s not unusual for flights to China, as it is Malaysia Airlines procedure to power down the system because the service provider doesn’t cover China. However, pilots can’t disable their ACARS entirely.

Every aircraft has a unique code with the satellite and as long as the plane is powered up, that network connection remains. Any aircraft fitted with the system and still in powered flight will “ping” the satellite network of the operator every hour. It only stops this “electronic handshake” if the plane loses power completely.

Inmarsat recorded eight of these pings from Flight MH370 via its 3F1 satellite, which was in geostationary orbit over Asia. It then used these pings to plot the plane’s likely course after it had disappeared from everyone else’s grid.

After four days of data crunching Inmarsat established that the plane had travelled along one of two arcs, either heading north across southern and central Asia or south across the Indian Ocean, about 1,500 miles south west of Australia.

Further analysis of the Doppler effect of the pings, a phenomenon that alters the pitch according to whether the target is approaching or leaving an area, led Inmasat to deduce that the plane had taken the south-bound arc, reducing the search area by 97 per cent.