Safety Investigation Report 2018:1 Factual Information/1.9/1.9.5 Satcom/3
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
1.9.5 Satellite Communications
3) Satellite Communications Ground Station Logs of the Event - Summary
The SATCOM utilised the Inmarsat Indian Ocean Region (IOR) I-3 satellite and the associated Perth Ground Earth Station (GES) throughout the flight. Inmarsat has confirmed that during the flight, no SATCOM signalling or traffic was routed via any other satellites (including MTSAT) to any other GESs (including MTSAT11 GESs).
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11 MTSAT - A series of Japanese weather and aviation satellites and GESs. MTSAT-1R and MTSAT-2 satellites are interoperable with Inmarsat satellites.
The SATCOM provides the Satellite link for the following functions:
- Cockpit Voice - Call control via the Multi-function Control and Display Units (MCDUs) and audio via the cockpit Audio Management Unit (AMU) and associated headsets;
- Cockpit Packet Data (Data-2) - Interface via the ACARS Management Unit (MU); and
- Cabin Packet Data (Data-3) - Interface via the Panasonic System 3000i IFE equipment:
The GES logs contain the following key information for each transmission to and from the aircraft:
- Time tag, Satellite and GES (Note: the timestamp accuracy does vary between the different logs, but should always be <1 second, and usually to a few milliseconds);
- Channel Type, Channel Number (frequency), Received Carrier/Noise Density Ratio (C/No), channel Bit-Error-Rate (BER), Burst Frequency Offset (BFO) and Burst Timing Offset (BTO, or round trip delay); and
- All payload data (excluding voice frames) contained within the transmission - these are known as the Signal Unit contents.
The events are summarised below. All times are in UTC. In the summary below, times are truncated to the nearest minute (the format is Hours Minutes) and in Section 1.9.5 para. 4), times are truncated to the nearest second (the format is Hours Minutes:Seconds).
| No. | Summary of SATCOM Ground Station Logs |
|---|---|
| 1. | Prior to take-off, the SATCOM Logged On (normally) a number of times, the last time being at 1600, when it sent a valid Flight ID to the GES. The SATCOM link was available for both voice and data (known as Log-On Class 3). |
| 2. | After take-off, the IFE SMS email application sent a normal beginning-of-flight message at 1642 (containing the correct Airborne Earth Station [AES ID], Flight ID "MAS370", origin airport "WMKK", and destination airport "ZBAA"), indicating that the IFE was receiving the valid Flight ID, origin airport and destination airport from AIMS and the ICAO (AES) ID from the Satellite Data Unit (SDU) at this time. |
| 3. | The SATCOM link was available for most of the flight, excluding periods leading up to 1825 UTC, 07 March and 0019 UTC, 08 March 2014. |
| 4. | When the SATCOM link was re-established at the above times, no Flight ID was present |
| 5. | During each of the two in-flight Log Ons at 1825 UTC and 0019 UTC, the GES recorded abnormal frequency offsets for the burst transmission from the SATCOM. |
| 6. | There is no indication of the SATCOM link being manually Logged Off from the cockpit (via an MCDU). Such activity would have been captured in the GES logs, but it was not. |
| 7. | No Data - 2 ACARS traffic was observed after 1707 UTC 07 March 2014. |
| 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 reestablished the link at 1825 UTC, 07 March 2014 (normal), but not after the SATCOM re-established the link at 0019 UTC, 08 March (abnormal). At no time during the flight was any user data sent over the link by means of the SMS/e-Mail application. |
| 9. | Two Ground-to-Air Telephone Calls were placed to the cockpit from MAS Operations Centre (MOC) at Airline Operational Communications (AOC) Q10 priority level at 1839 UTC and at 2313 UTC, 07 March 2014. Neither of the calls was answered. |
| 10. | The SATCOM responded normally to a series of roughly hourly Log-On Interrogations from the Perth GES, up to and including a Log-On Interrogation at 0011 UTC, 08 March 2014. The two unanswered ground to air calls at 1839 UTC and 2313 UTC reset the Perth GES inactivity timer and hence the LogOn Interrogations were not always hourly. |
| 11. | The last transmission received from the SATCOM occurred at 0019 UTC, 08 March 2014 and the SATCOM failed to respond to a series of three Log-On interrogations starting at 0115 UTC, 08 March 2014. |