Tuesday, March 25, 2014

MH370 signal loss consistent with fuel limit

MH370 Since Malaysia Airlines Flight MH370 vanished after mysteriously cutting communications with air traffic controllers, the aircraft's automated ping to Inmarsat's satellite has been the only clue to its final whereabouts.

Building on that data, authorities today revealed the aircraft finally "logged off" from the satellite network by 9.15am and the timing was consistent with the aircraft's fuel limit.
"No response was received from the aircraft at 0115 UTC (9.15am Malaysian time), when the ground earth station sent the next log on/log off message. This indicates that the aircraft was no longer logged on the network.
"Therefore, sometime between 0011 UTC (8.11am) and 0115 UTC (9.15am), the aircraft was no longer able to communicate with the ground station.
"This is consistent with the maximum endurance of the aircraft," acting Transport Minister Hishammuddin Hussein told a press briefing in Kuala Lumpur this evening.
To date, Malaysian authorities have not once uttered the word "crash" despite already indicating all passengers had likely perished after the plane went down in the Indian Ocean.
However, Hishammuddin's assertion that Inmarsat's satellite losing connection with MH370 by 9.15am gives an indication of the time frame the aircraft may have crashed.
It gives investigators an idea of MH370's final resting area as the aircraft could have still flown on between the last complete satellite handshake at 8.11am and 9.15am, when the connection was lost.
"I must emphasise that this is not the final position of the aircraft," he said in reference to the 8.11am handshake.
Partial ping discovered
The ping at 8.11am was first used by investigators to establish the northern and southern corridors search area. Since yesterday, the search area has been narrowed down to the south-most portion of the southern corridor.
Hishammuddin further revealed investigators have observed a seventh and partial handshake that was sent out at 8.19am from the aircraft.
"At this time this transmission is not understood and is subject to further ongoing work," he said.
This was on top of the previously reported six complete handshakes that were sent out with the last one being at 8.11am after the Aircraft Communications Addressing and Reporting System (Acars) was turned off.
These pings were also the basis of analysis that finally concluded that plane ended up in the southern Indian Ocean.
Responding to scepticism over investigators' confidence, Hishammuddin said Inmarsat and the Air Accidents Investigation Branch (AAIB) had measured the "Doppler effect" experienced by the pings which is also known as Burst Frequency Offset.
'Good correlation with southern corridor'
This measured Doppler effect was then plotted along side what the predicted Doppler effect would be if the plane had flown in the northern or southern corridor.
"The analysis showed poor correlation with the northern corridor, but good with the southern correlation corridor...
"In order to establish confidence in its theory, Inmarsat checked its predictions using information obtained from six other Boeing 777 aircraft flying on the same day in various directions. There was good agreement," he said.
The ping is sent out in a form of wave. The top point of every wave, like water ripples, spreads out uniformly.
However, when the wave is emitted from a moving object, then the speed of every wave points will vary, depending on a number of factors, including the object's own velocity relative to the receiver. 
The easiest way to observe the Doppler effect is in how the sound of the siren on board a moving police car appears to change as it passes an observer.
In this case, Hishammuddin said, the Burst Frequency offset changed depending on location of the aircraft on an arch of possible positions and the measured Doppler effect indicated in was in the southern Indian Ocean.

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