Factual Information 2015:1.9 Communications/1.9.5 Satcom/1.9.5.3
This page contains an extract from MH370/01/15 Factual Information which accompanied the (first) Interim Statement released by The Malaysian ICAO Annex 13 Safety Investigation Team for MH370 on 8th March 2015.
1.9.5.3 SATCOM 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 MTSAT7 GESs). The SATCOM provided 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)
- 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).
- 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 1.9.5.4, times are truncated to the nearest second (the format is Hours Minutes:Seconds).
1. Prior to take-off, the SATCOM Logged On (normally) a number of times, the last time being at 16:00, 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 e-mail application sent a normal beginning-of-flight message at 16:42 (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 18:25 UTC, 07 March and 00:19 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 18:25 UTC and 00:19 UTC, the GES recorded abnormal frequency offsets for the burst transmissions 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 17:07 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 re-established the link at 18:25 UTC, 07 March 2014 (normal), but not after the SATCOM re-established the link at 00:19 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 Telephony Calls were placed to the cockpit from the MAS Operations Centre at Airline Operational Communications (AOC) Q10 priority level at 18:39 UTC and at 23:13 UTC, 07 March. 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 00:10 UTC, 08 March 2014. The two unanswered ground to air calls at 18:39 UTC and 23:13 UTC reset the Perth GES inactivity timer and hence the Log-On Interrogations were not always hourly.
11. The last transmission received from the SATCOM occurred at 00:19 UTC, 08 March 2014 and the SATCOM failed to respond to a series of three Log-On interrogations starting at 01:15 UTC, 08 March.
7 MTSAT – A series of Japanese weather and aviation satellites and GESs. MTSAT-1R and MTSAT-2 satellites are interoperable with Inmarsat satellites.
Source: Malaysian ICAO Annex 13 Safety Investigation Team for MH370, 8 March 2015, Factual Information MH370/01/15
The Factual Information was updated in 2018 by the Safety Investigation Report MH370/01/2018 which added new content but did not include all of the previous data.