• Thu
  • Dec 18, 2014
  • Updated: 9:38am
Malaysia Airlines flight 370

How satellite ‘pings’ revealed missing Malaysia flight MH370’s final path

First time technique has been used by Inmarsat to locate plane

PUBLISHED : Tuesday, 25 March, 2014, 10:40am
UPDATED : Wednesday, 26 March, 2014, 7:54am

The satellite operator Inmarsat revealed how it managed to work out which direction the missing Malaysia Airlines plane flew in by measuring the Doppler effect of hourly ‘pings’ from the aircraft.

Malaysia’s prime minister announced earlier that the Inmarsat analysis of flight MH370’s path placed its last position in remote waters off Australia’s west coast, meaning it can only have run out of fuel above the southern Indian Ocean.

Inmarsat explained how they plotted models of the flight’s route by measuring the Doppler effect of satellite pings, giving corridors arcing north and south along which the plane could have flown for at least five hours.

Despite the plane’s communication systems being switched off, satellite pings were still bouncing back from the aircraft, which vanished on March 8 with 239 people on board while flying from Kuala Lumpur to Beijing.

The pings are sent from a ground station to a satellite, then onto the plane, which automatically sends a ping back to the satellite and down to the ground station.

They do not include global positioning system (GPS) data, time or distance information.

So the British satellite operator measured the amount of time it took for the pings to be returned.

“We looked at the Doppler effect, which is the change in frequency due to the movement of a satellite in its orbit,” Chris McLaughlin, Inmarsat’s senior vice president of external affairs, told Britain’s Sky News television.

“What that then gave us was a predicted path for the northerly route and a predicted path the southerly route.”

“We don’t know whether the plane stayed at a constant speed; we don’t know whether its headings changed subsequently,” he explained.

Therefore, “we applied the autopilot speeds - about 350 knots. We applied what we knew about the fuel and range of the aircraft to hit the series of ping information we had.

“Normally you’d want to triangulate, often you’d have GPS. But because aircraft in that region are not mandated to send out signals of their location we were working from blind, so this is very much a unique approach - the first time it’s been done.”

They then compared those figures to data from other Malaysia Airlines planes and similar flight routes, which definitively showed the plane could only have been going down the southern corridor, and would eventually have run out of fuel.

They established an “extraordinary matching” between Inmarsat’s predicted southern path and readings from other planes on such routes.

The BBC reported that as far as could be worked out, the plane was flying at a cruising height, above 30,000 feet (9,100 metres). They found no evidence of fluctuating heights.

Inmarsat handed over new information to Britain’s Air Accidents Investigation Branch on Sunday for checking.

“By yesterday they were able to definitively say that the plane had undoubtedly taken the southern route,” said McLaughlin.

He called for all commercial aircraft to be fitted with existing technology that would mean a plane cannot go missing.

Videographic: The flight path Malaysia Airlines flight MH370 is believed to have taken



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This article is now closed to comments

you know what's crazy ? people like xyz who are arm chair pilots talking about stuff they know nothing about.
so tell me this xyz -- if you are flying along and suddenly have a smouldering electrical fire and it's coming from the transponder would you turn it off ? or hey -- lets' just leave it on and throw a bucket of water on it -
I have concerns that the satellite data is actually sealed and not being made available until the search is completed. I question why? I have followed the analysis as provided by the British Air Accidents Team and Inmarsat and have a suspicion that the path taken to the final supposed search location is incorrect. A more direct mathematical analysis of intersection points of the 6 ping range lines with cruising speed ( of 350 knots) loci would provide a more accurate flight path and destination location of the plane. There can only be a maximum of 32 possible locations in the north and 32 possible locations in the south for a total of 64 ( 2 to the power of 6). We are only provided the last range of the plane from the satellite at 8:11 am. What about the range at 3:11, 4:11, 5:11, 6:11 and 7:11 am?


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