Timeline/ANDS-NIO/0225:27 MYT

MH370 DECODED
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Event Summary

02:25:27 MYT Saturday, 8 March 2014

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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.


Event Details

  1. Safety Investigation Report MH370/01/2018 Satellite Ground Station Logs - Key Observations

    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.




Notes

Source: Safety Investigation Report MH370/01/2018 2.5.1 Summary of Key Observations of the SATCOM Ground Station Logs

3) The SATCOM link was available for most of the flight, excluding periods leading up to 1825 on 07 March 2014 and 0019 on 08 March 2014.

4) When the SATCOM link was re-established at the above times, no Flight ID was present. This implies that a valid Flight ID probably stopped being sent to SATCOM at some time between 1642 (when the IFE reported the correct Flight ID) and 1825 (when the SATCOM Logged On with no Flight ID) on 07 March 2014. The possible reasons for the link losses and the subsequent Log-Ons that took place at 1825 and 0019 have been investigated and are detailed in tables in Section 2.5.2. There are many quite complicated scenarios that could have caused the 1825 Log-On. However, the most likely reason is a lengthy power interrupt to the SATCOM. The most likely reason for the 0019 Log-On was also a power interrupt to the SATCOM.

5) During the two in-flight Log-Ons at 1825 and 0019, the GES recorded abnormal frequency offsets for four burst transmissions from the SATCOM. After extensive analysis, the following explanations have emerged. The 1825 Log-On Request had a non-zero BER and could therefore have been logged at the Ground station with a BFO measurement error suggesting that the BFO figure may not be reliable.

a) 1825 Log-On Acknowledge - Most likely due to the power-on drift of the SDU Oven Controlled Crystal Oscillator (OCXO), thus endorsing the belief that the 1825 Log-On was preceded by a lengthy power interrupt.

b) 0019 Log-On Request - Could have been due to uncompensated vertical velocity, indicating that the aircraft was likely to be descending at this time. Alternatively, it could have been due to the OCXO warm up drift, or it could have been due to a combination of uncompensated vertical velocity and OCXO warm up drift.

c) 0019 Log-On Acknowledge - Could have been due to uncompensated vertical velocity, indicating that the aircraft was likely to be descending at this time. Alternatively, it could have been due to the OCXO warm up drift, or it could have been due to a combination of uncompensated vertical velocity and OCXO warm up drift.

d) It has not been possible to attribute specific correction values to the 1825 Log-On Acknowledge and 0019 Log-on Request and Log-On Acknowledge BFOs, so it was excluded from the Doppler calculations undertaken by the Aircraft Flight Path/Performance Subgroup. In the case of the 1825 Log-On Acknowledge, the following subsequent bursts were used instead, as the frequency is more stable at these times:

i) 1828:05.904 Data-3 R-Channel burst.

ii) 1828:14.905 Data-3 R-Channel burst.

6) There is no indication of the SATCOM link being manually Logged Off from the cockpit (via a Multi-function Control Display Unit [MCDU]). Such activity would have been captured in the GES logs, but it was not.


Source: Safety Investigation Report MH370/01/2018 2.5.1 Summary of Key Observations of the SATCOM Ground Station Logs

8) The IFE equipment set up two ground connections over SATCOM (for the SMS e-mail application and Built-In Test Equipment (BITE) application) after the SATCOM re-established the link at 1825 on 07 March 2014 (normal), but not after the SATCOM re-established the link at 0019 on 08 March 2014 (abnormal). In the 0019 case, it is possible that the IFE was no longer powered, or failed, or that the IFE and/or the SATCOM became inoperative before the connections could be set up. At no time during the flight was any user data sent over the link by means of the SMS/e-mail application.