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Details of the final turn South made by MH370 are not known. This Section provides an overview of what is known, or inferred by other data.

Andaman Sea to North Indian Ocean

From 2:22 MYT to 2:39:52 MYT Saturday, 8 March 2014
(18:22 UTC to 18:39:52 UTC Friday, 7 March 2014)


At the time of the last primary radar observation of MH370 at 0222:12 MYT the aircraft was located north-east of the northern tip of Sumatra and was heading north-west towards the Andaman Sea.

At 0341:00 MYT the Inmarsat ground station initiated a Log-On Interrogation, with a response from the SATCOM on MH370. Analysis of the metadata associated with this transmission indicated that the aircraft was, at that time, travelling south.

So, at some time between 0222:12 MYT and 0341:00 MYT, MH370 changed direction and turned south.

The sections below provide more detail in support of this statement, and also some refinements which narrow the time range during which the turn was made.

6. Summary: The Turn South

The satellite communications company Inmarsat developed an innovative method to use the metadata from satellite communications with MH370 to determine its' approximate distance from the satellite during events called 'handshakes' which were two-way communications between MH370 and a ground station in Perth, Western Australia. The metadata involved two measurements - the Burst Timing Offset and the Burst Frequency Offset. The calculations performed by Inmarsat were peer reviewed and subsequently refined by many experts, including mathematicians at the Defence Science and Technology Group in Australia. Transmissions prior to a turn when MH370 was still heading north west along the Malacca Strait, and transmissions after a turn when MH370 was heading south, have narrowed the time that a turn was made to between 1828:05 UTC (0228:05 MYT) and 1839:52 UTC (0239:52 MYT).

Focussing on only one type of metadata - the Burst Timing Offset - yields two valid directions for MH370 to travel. These were called the 'Northern Corridor' and the 'Southern Corridor' and are defined by seven arcs representing the distance between MH370 and the satellite at the time of each of seven 'handshakes'. None of the countries on the Northern Corridor had any radar record of MH370 flying through their airspace, and no wreckage has been found in those areas.

The second type of metadata - the Burst Frequency Offset - provided investigators with evidence that MH370 travelled south. The measurements were compared with and validated by data from other flights; and the conclusion that MH370 not only turned south but also ended the flight in the south Indian Ocean is consistent with all other evidence available to date, for example debris recovered which would have drifted from the crash site.

The unsuccessful attempts to locate the aircraft does not invalidate the above statements and conclusion. It is merely a confirmation of how large the Indian Ocean is, and the complexity of the task. That we know anything at all about the flight after MH370 left Malaysian airspace and flew beyond Malaysia's military radar capability is a tribute to all those scientists, engineers and mathematicians who have devoted so much energy to solving such a complex enigma.

02:22:12 MYT
Heading: observed to be heading towards waypoint MEKAR on Airway N571 when it finally disappeared at 0222:12 MYT, 10 nm after waypoint MEKAR.

02:25:27 MYT

SATCOM Log-On, initiated from the aircraft terminal.

  1. This is the first ‘handshake’.
  2. This marks the end of the link lost period that began at sometime between 1707:48 and 1803:41.
  3. This log-on request suggests that whatever caused the SATCOM link loss to occur between 1707:48 and 1803:41 had been reversed.

02:25:34 MYT

The SATCOM link becomes available (for both voice and data - Class 3) once more and normal SATCOM operation resumes (except that there is no Data-2 ACARS traffic).

No Flight ID was sent to the GES during the Log-On. This implies that the SDU stopped receiving a valid Flight ID from the AIMS at sometime between 1642:04 and 1825:00.

The possible reasons for the link loss and the subsequent Log-On that took place at 1825:00 have been investigated and are detailed in Table 2.5A. There are many quite complicated scenarios that could have caused the 1825:00 Log-On. However, the most likely reason is a power interrupt to the SATCOM avionics, of a duration greater than 22 minutes (the time between events 7 and 9) and less than 78 minutes (the time between events 6 and 9).

02:27:03 MYT

The IFE sets up a Data-3 ground connection (X.25 circuit) over SATCOM for an SMS/e-mail application after the SATCOM link is re-established.

02:28:05 MYT

The IFE sets up a Data-3 ground connection (X.25 circuit) over SATCOM for a BITE application after the SATCOM link is re established.

02:38:51 MYT

Malaysia Airlines ODC sent a test message to MH370, requesting an acknowledgement. The message was also re-transmitted at 0239:52 MYT, 0240:42 MYT and 0241:52 MYT. The automated response was 'failed'.

02:39:52 MYT

Ground-to-air telephony call placed from a number with country code 60 (Malaysia)

4. Telephone Call at 1839:52 MYT

Malaysia Airlines made two attempts to contact MH370 by telephone over the satellite communications system. The first was at 1839:52 UTC (0239:52 MYT). Analysis of the metadata related to this transmission - the Burst Frequency Offset (BFO) indicates that MH370 was heading south at that time. For interest, here is an extract from the paper Bayesian Methods in the Search for MH370[1] which 'explains' the analysis:-

The first call occurred from 18:39:53 to 18:40:56 and is important because the measured BFO is significantly different from the BFO on the R1200 measurement preceding it at 18:28:15. The R1200 BFO value is consistent with the speed and direction of the aircraft while under radar coverage whereas the later C-channel BFO value is not. Assuming that the change in BFO implies a turn, the difference between the BFO predicted by using a MATLAB model of the SDU software1 and the measured BFO on the C-channel was analysed as a function of post-turn direction and for a range of aircraft speeds and turn times between 18:28:15 and 18:39:53. Figure 5.6 shows the residual error and it clearly demonstrates that only Southerly track angles are consistent with the C-channel measurements. The model predicted BFO values of Northerly paths are more than 10 standard deviations away from the measured BFO.

After the successful log-on by the satellite data unit of MH370, the In-Flight Entertainment System set up a connection over the satellite link (for built-in test equipment) at 1828:05 UTC. At that time, MH370 was still north of Sumatra and on much the same heading as the last primary radar observation. When this metadata (the Burst Frequency Offset measurement) was compared with the BFO values for the phone call at 1839:53 UTC they were not the same. So the aircraft must have changed direction. By considering both a northerly change and a southerly change the mathematicians found that the direction with the highest probability, was to the south.

So, it is reasonable to say that the turn to the south began at some time between 1828:05 UTC (0228:05 MYT) and 1839:52 UTC (0239:52 MYT).

Notes and References
  1. Bayesian Methods in the Search for MH370, Samuel Davey, Neil Gordon, Ian Holland, Mark Rutten and Jason Williams, © Commonwealth of Australia 2016. ISBN 978-981-10-0379-0 (eBook)
    The authors collaborated on this project for the Defence Science and Technology (DST) Group (Australia) to support the Australian Transport Safety Bureau underwater search for MH370.

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