Factual Information 2015:1.9 Communications
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.
SECTION 1.9 COMMUNICATIONS
1.9.1 High Frequency (HF) System
This aircraft was installed with Collins HFS-900 HF System. The HF communication system on this aircraft uses two HF systems with a common HF antenna to transmit and receive radio frequency (RF) signals in the HF range.
The HF transceiver operates within the frequency range of 2,000 MHz to 29,999 MHz and one KHz channel spacing.
The Left Transfer bus sends 115V AC three-phase power to the Left HF communication. The Left HF communication transceiver supplies 115V AC single phase to the Left HF antenna coupler for operational power. It also supplies 28V DC for the key interlock function. The Right HF communication system is the same as the Left, except that it uses power from the Right AC Sec 2 bus.
1.9.2 Very High Frequency (VHF) System
This aircraft was installed with Collins VHF-900B VHF System. The VHF communication system permits voice and data communication over line-of-sight distances. It permits communication between aircraft or between ground stations and aircraft. The VHF system operates in the VHF aeronautical frequency range of 118.000 MHz to 136.992 MHz.
The VHF communication system on this aircraft uses three VHF systems. Each VHF system has a VHF antenna and a VHF communication transceiver.
The VHF communication system connects with Selective Calling Equipment (SELCAL) decoder that starts an alert when a call comes in for that aircraft.
The captain’s flight instrument bus sends 28V DC to the Left VHF communication transceiver and the Left Radio Tuning Panel (RTP). The Left Main DC bus sends 28V DC to the centre VHF communication transceiver and the centre RTP.
The Right Main DC bus sends 28V DC to the right VHF communication transceiver and the right RTP.
1.9.3 Air Traffic Control (ATC)/Mode S Transponder System
This aircraft was installed with Bendix/King TRA-67A Mode S transponder. The ATC ground stations interrogate the airborne ATC/Mode S transponder system as shown in Figure 1.9A below.
The ATC/Mode S transponder replies to the interrogations in the form of coded information that the ground station uses. The ground station uses a Primary Surveillance Radar (PSR) to get radar returns from aircraft within the radar range. To make a communication link with the aircraft in the radar range, the ground station uses a Secondary Surveillance Radar (SSR) to interrogate the ATC/Mode S transponder. The ground station transmits a side lobe suppression signal to inhibit close ATC replies that come from a SSR side lobe transmission. On the ground radar display, the ATC operator sees the radar returns, altitude, and a four digit aircraft identifier. The ATC operator also sees aircraft derived Enhanced Surveillance downlink data on the ground station radar display, such as Magnetic Heading, Air Speed (Indicated Air Speed and Mach number), Ground Speed, Roll Angle, Selected Altitude, True Track Angle, and Vertical Rate. The ATC/Mode S transponder also replies to mode S interrogations from the Traffic Alert and Collision Avoidance Systems (TCAS) of other aircraft. ATC/Mode S transponders with Extended Squitter function provide broadcast of Global Position System (GPS) position and velocity data.
The Left ATC/Mode S transponder gets 115V AC power from the AC Standby bus. The Right ATC/Mode S transponder gets 115V AC power from the Right AC Transfer bus. The dual transponder panel gets 115V AC power from the AC Standby bus. ATC/Mode S transponder power system is shown in Figure 1.9B below.
This system can be deactivated (turned OFF) by pulling the circuit breakers located at the P11 overhead circuit breaker panel or by selecting Transponder Mode Selector (Transponder Panel) to “STBY” position.
The transponder on the occurrence flight was operating satisfactorily up to the time it was lost on the ATC radar screen at 1721.13 UTC, 07 March 2014 (0121:13 MYT, 08 March 2014). There was no message received from the aircraft to report a system failure.
1.9.4 Aircraft Communications Addressing and Reporting System (ACARS)
ACARS is a digital data-link system that manages flight plan and maintenance data between the aircraft and the Ground Service Provider (GSP) by using radio i.e. VHF or satellite communications (SATCOM) as shown in Figure 1.9C below. ACARS provides message communication between aircraft and its base (ground). The following messages are transmitted:
a) Out of the gate, Off the ground, On the ground, and Into the gate (OOOI) events
i. Out of the gate event: Departure from the gate with all doors closed and parking brake released
ii. Off the ground event: Take-off with the nose gear squat switch extended.
iii. On the ground event: Touch down with the nose gear squat switch compressed.
iv. Into the gate event: Parked at the gate with the parking brake set and the door open.
b) Flight plans: ACARS interfaces with Flight Management Systems (FMS) acting as the communication system for flight plans to be sent from the ground to the FMS. This enables the aircraft to update the FMS while in flight, and allows the flight crew to evaluate the alternative flight plans including the status of connecting flights.
c) Weather information: ACARS interfaces with FMS, acting as the communication system for weather information to be sent from the ground to the FMS. This enables the aircraft to update the FMS while in flight, and allows the flight crew to evaluate new weather conditions.
d) Equipment health: ACARS is used to send information from the aircraft to ground stations about the conditions of various aircraft systems and sensors in real-time. Maintenance faults and abnormal events are also transmitted to ground stations along with detailed messages, which are used by MAS for monitoring equipment health, and to better plan the repair and maintenance activities.
e) Aircraft positions which provide latitude and longitude, altitude, speed, total air temperature total remaining fuel, wind direction and speed and heading.
f) Engine performance data which provide engine data during take-off, climb, cruise and approach.
ACARS interfaces with interactive display units in the cockpit, which flight crews can use to send and receive technical messages and reports to or from ground stations, such as a request for weather information or clearances or the status of connecting flights. The response from the ground station is received on the aircraft via ACARS as well.
The ACARS communicates through either SATCOM or VHF. The VHF transceiver can also be used for voice transmission when ACARS is switched from the data mode to the voice mode.
In the event that the aircraft ACARS unit has been silent for longer than a pre-set time interval, the ground station can ping the aircraft (directly or via satellite). A ping response indicates a healthy ACARS communication.
Pre-set time interval for MAS B777 is 30 minutes. When the aircraft ACARS is silent for more than 30 minutes, MAS Operation Control Centre (OCC) will send a text message via ACARS to the cockpit or will call the cockpit via SATCOM.
1.9.4.1 ACARS Traffic Log
ACARS traffic log messages sent/received to/from 9M-MRO between 1554:41 UTC, 07 March 2014 (2354:41 MYT, 08 March 2014) until 1815:25 UTC, 07 March 2014 (0215:25 MYT, 08 March 2014) is shown in Appendix 1.9A. Some key events are extracted and explained below.
At 1554:41 UTC, 07 March 2014, ACARS data link was fully established on SATCOM transmission and at 1556:08 UTC the flight information (FI) MH0370 and Aircraft Number (AN) 9M-MRO were keyed in by the crew as per Figure 1.9D below.
Notice to Crew (NOTOC) was sent at 1606:15 UTC on 07 March 2014 (0006:15 MYT, 08 March 2014) direct to the aircraft printer and to be printed out by the crew.
NOTOC from the ground station to the cockpit stated the special loads of total 4,566 kg of mangosteen fruit were carried on board. Details of the mangosteens were: 1,128 kg at station 41L, 1,152 kg at station 41R, 1,148 kg at station 43L and 1,138 kg at 44L respectively (Refer to Section 1.18.2 for details of cargo carried).
Declaration of “there is no evidence that any damaged or leaking packages containing dangerous goods have been loaded on the aircraft at this station” was also written in the NOTOC message.
(Figure 1.9E above shows the snapshot of the ACARS NOTOC message).
Aircraft final loadsheet was sent via ACARS at 1606:32 UTC, 07 March 2014 (0006:32 MYT, 08 March 2014) direct to the aircraft printer and to be printed out by the crew. Details of aircraft weight as stated in the final loadsheet are discussed in Section 1.6.4. Figure 1.9F below shows the snapshot of the final loadsheet of this aircraft.
Pilot acknowledgement and confirmation of the final loadsheet is shown in the ACARS snapshot in Figure 1.9G below.
Data on aircraft APU is shown in Figure 1.9H below. APU report generated by ACMS sent via ACARS at 1629:33 UTC stated the total APU cycles and hours were 15,699 cycles and 22,093 hours. APU hours for the previous flight was 4 hours.
Engine take-off and climb reports transmitted via ACARS are explained in Section 1.6.3.8.
Engine parameter reports were transmitted to MAS and then to Rolls Royce for Engine Health Monitoring (EHM). Appendix 1.9A shows these data in coded form. The decoded data are shown in Appendix 1.6B.
The first (which was also the last) position report was transmitted via ACARS at [[Timeline/KLIA-SCS/0107:29 MYT|1707:29 UTC, 07 March 2014 (0107:29 MYT, 08 March 2014). This was a collation of 6 reports generated at 5-minute intervals by the system at Timeline/KLIA-SCS/0041:43 MYT|1641:43 UTC, 1646:43 UTC, 1651:43 UTC, 1656:43 UTC, 1701:43 UTC and 1706:43 UTC, 07 March 2014. Parameters transmitted are as per Table 1.9A below. The actual traffic log on the position report is reproduced in Figure 1.9I. Position reports were programmed to be transmitted every 30 minutes.
<section begin=Table 1.9A />
| Greenwich Mean Time (GMT) – UTC | 1641:43 | 1646:43 | 1651:43 | 1656:43 | 1701:43 | 1706:43 |
|---|---|---|---|---|---|---|
| Altitude (ALT) – Feet | 103 |
10,582 | 21,193 | 28,938 | 34,998 | 35004 |
| Calibrated Airspeed (CAS) – Knots. | 168.4 | 261.8 | 301.1 | 303.1 | 278.0 | 278.4 |
| MACH | 0.255 | 0.478 | 0.669 | 0.783 | 0.819 | 0.821 |
| Total Air Temperature (TAT) | 31.1 | 23.4 | 11.6 | 2.6 | -13.4 | -13.1° C |
| Static Air Temperature (SAT) | 27.3 | 10.4 | -11.8 | -27.4 | -43.9 | -43.8° C |
| Latitude (LAT) | 2.767 | 3.074 | 3.553 | 4.109 | 4.708 | 5.299 |
| Longitude (LONG) | 101.715 | 101.760 | 101.988 | 102.251 | 102.534 | 102.813 |
| Gross Weight (GWT) – Kg | 492,520 | 489,200 | 486,240 | 483,840 | 481,880 | 480,600 |
| Total Remaining Fuel Weight (TOTFW) – kg | 49,200 | 47,800 | 46,500 | 45,400 | 44,500 | 43,800 |
| Wind Direction (WINDIR) | 140.3 | 107.6 | 91.8 | 58.4 | 69.6 | 70.0 |
| Wind Speed (WINDSP) | 1.25 | 9.38 | 19.50 | 10.63 | 17.38 | 17.13 |
| True Heading (THDG) | -33.5 | 27.7 | 27.8 | 26.0 | 26.8 | 26.7 |
Note: The data in the ACARS message records an altitude of 103 ft at the (departure) time of 16:41 GMT (00:41 MYT).
Table 1.9A ACARS Position Report
<section end=Table 1.9A />
The first message sent to the aircraft cockpit printer from the MAS ODC was at 1803:23 UTC. The ACARS message requested the crew to contact the HCM ATCC immediately. The incoming downlink message at 1803:24 UTC showed the message failed to reach the aircraft. Messages are auto transmitted every 2 minutes and the message was retransmitted until 1843:33 UTC but all messages failed to get a response. Automated downlink message by ACARS showed ‘failed’. Message sent to the aircraft cockpit printer and the Automated Downlink messages are shown in Figures 1.9J and 1.9K, respectively.
1.9.5 Satellite Communications (SATCOM)
1.9.5.1 SATCOM System Description
SATCOM is an acronym of, and generic term for, satellite communications. SATCOM operates by using satellites to relay radio signals between the sender and receiver. It can cover far more distance and wider areas than other radios. SATCOM can be used to transmit words, pictures and other forms of information.
The aircraft, 9M-MRO, was equipped with a SATCOM terminal that used the Inmarsat Classic Aero system. The Inmarsat system utilises a constellation of satellites to provide nearly global coverage, the exception being polar areas. The aircraft SATCOM system, also referred to as an Airborne Earth Station (AES) operates on L Band, transmits at 1.6 GHz and receives at 1.5 GHz. For this aircraft, the SATCOM system provided a total of five voice channels and one data channel. The satellite link provides the following functions:
The Earth or Ground Station uses C Band, transmits at 6 GHz and receives at 4GHz.
Inmarsat uses a network of Ground Earth Stations (GES) to communicate with the satellites and connect the SATCOM signal to other terrestrial data networks such a telephone systems, internet, etc.
When the SATCOM AES is first powered on, it sends a log-on request to the GES to initiate service. There are a number of channels available for messages to be sent between the Satellite and Earth Station. One of the channels is called the ‘common access channel’, which aircraft will constantly listen to when able to do so. If the GES has not heard from an aircraft for an hour after the last communication, it automatically transmits a ‘log on/log off’ (“ping”) message on the common access frequency using the aircraft’s unique identifier. If the aircraft receives its ‘unique identifier’, it returns a short message that it is still logged onto the network. Both the initial log-on request and the hourly ping have been termed as a ‘handshake'.
The SATCOM AES consists of the following equipment: Radio frequency unit (RFU), Radio frequency attenuator (RF ATTN), Radio frequency splitter (RFS), Class C high power amplifier (HPA), Class A high power amplifier (HPA), High power relay (HPR), three low noise amplifier/diplexers (LNA/DIPs), Low gain antenna (LGA), two beam steering units (BSUs), two high gain antennas (HGAs), Radio frequency combiner (RFC) and Satellite data unit (SDU).
The SATCOM avionics are located on the E11 rack, which is in the crown area aft of doors 3 left/right. The High Gain antennas are mounted above door 3 left and door 3 right. The Low Gain antenna is mounted on the fuselage centreline. The SATCOM Circuit Breakers (CB) are located in the Main Equipment Center (MEC).
The Satellite Data Unit (SDU) receives 115v ac from the Left Main bus.
The diagram in Figure 1.9L below shows the complete set of SATCOM units, including avionics, High Gain Antenna Subsystem and Low Gain Antenna Subsystem. It also shows interfaces to the aircraft cockpit and cabin systems and functions. The following notes are intended to be read in conjunction with Figure 1.9L:
- CDU (3) are the three Control Display Units, otherwise known as Multi-function Control Display Units (MCDUs).
- CPMU is Cabin Passenger Management Unit, which provides an interface between the Panasonic IFE and the SDU, for any Data-3 SMS/e-mail messages.
- AMU is the Audio Management Unit, which feeds cockpit audio to and from the SDU.
- CTU is the Cabin Telecommunications Unit, which provides an interface between the in-seat handsets and the SDU, for cabin telephony calls, were that functions available. In the case of 9M-MRO, the in-seat phones can only be used for seat-to-seat calling.
- AIMS Cabinet is one of two Airplane Information Management System cabinets, which route numerous information to and from the SDU, including ACARS data, Navigational data, AES ID and Flight ID.
- SATCOM Maintenance Switch is not relevant to this document, as no maintenance activity is possible in flight.
The photo in Figure 1.9M below shows the Honeywell/Racal (Honeywell/Thales) MCS-6000 SATCOM Units – RFU (left), SDU (centre) and HPA (right)
1.9.5.2 SATCOM Ground Station Logs of the Event – Introduction
Throughout the flight of MH370, the aircraft communicated through the Inmarsat Indian Ocean Region (IOR) I-3 Satellite and the GES in Perth, Australia.
Figure 1.9N shows the Inmarsat I-3 IOR Satellite Coverage Map. The blue lines represent the elevation angle to the IOR satellite for a SATCOM unit on the ground or in the air. Due to the satellite inclination, the elevation angles are approximate.
MH370 departed KLIA at 1642 UTC (0042 MYT, 8 March 2014). At 1707 UTC, the SATCOM system was used to send a standard ACARS report, normally sent every 30 minutes. This message indicated there was sufficient fuel for MH370 to remain airborne until approximately 0012 UTC [0812 MYT]. The ACARS reports expected at 1737 UTC and 1807 UTC were not received. The next SATCOM communication was a log-on request from the aircraft at 1825 UTC. From that point until 0010 UTC, SATCOM transmissions indicate that the link was available, although not used for any voice, ACARS or other data services. At 0019 UTC, the AES initiated another log-on request. This was the last SATCOM transmission received from the AES.
Apart from a short period around 1825 UTC [0225 MYT, 8 March 2014], the SATCOM link was available for the major part of the flight. Data from the last seven ‘handshakes’ were used to help establish the most probable location of the aircraft. Initially only the first six of these ‘handshakes’ were considered to be complete. The seventh and last ‘handshake’ that was automatically initiated by the aircraft, was originally assessed as a partial ‘handshake’. Subsequent analysis confirmed the 7th handshake could be used to help determine the most probable flight path. Two unanswered ground-to-air telephone calls had the effect of resetting the activity log and hence increased the period between the ground initiated ‘handshakes’. The significant times used to identify the most probable final location of the aircraft are tabulated in Table 1.9B below. Details of the event’s SATCOM ground station logs are provided in paragraphs 1.9.5.3 and 1.9.5.4 below.
| SATCOM TRANSMISSIONS
|
TIME | ||
|---|---|---|---|
| UTC | MYT* | ||
| 1 | Aircraft departed KLIA | 1642 | 0042 |
| 2 | Last ACARS transmission | 1707 | 0107 |
| 3 | 1st handshake – log-on initiated by the aircraft | 1825 | 0225 |
| 4 | Unanswered ground-to-air telephone call | 1839 | 0239 |
| 5 | 2nd handshake initiated by ground station | 1941 | 0341 |
| 6 | 3rd handshake initiated by ground station | 2041 | 0441 |
| 7 | 4th handshake initiated by ground station | 2141 | 0541 |
| 8 | 5th handshake initiated by ground station | 2241 | 0641 |
| 9 | Unanswered ground-to-air telephone call | 2313 | 0713 |
| 10 | 6th handshake initiated by ground station | 0010* | 0810 |
| 11 | 7th handshake – log-on initiated by the aircraft | 0019* | 0819 |
| 12 | Aircraft did not respond to ‘handshake’ from Satellite Earth Ground Station | 0115* | 0915 |
| * 08 March 2014 | |||
Table 1.9B SATCOM ‘Handshakes’
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.
1.9.5.4 SATCOM Ground Station Logs - Key Observations in Chronological Order
1. 1250:19 - Prior to take-off, the SATCOM initiates a normal Log-On as Class 1 (data only capable) via the Pacific Ocean Region (POR) I-3 satellite, using the Low Gain Antenna (LGA) subsystem. No flight ID is sent to the GES at this time. This is the first SATCOM activity recorded at the GES since 0802:27.
2. 1555:57 - The SATCOM initiates a normal Log On Renewal as Class 1 (data only capable) via the POR I-3 satellite, using the LGA subsystem, this time with a valid Flight ID.
3. 1557:49 - The SATCOM initiates a normal Log-On as Class 3 (voice and data capable) via the POR I-3 satellite, using the High Gain Antenna (HGA) subsystem, with a valid Flight ID.
4. 1559:57 - The SATCOM initiates a Log-On handover as Class 3 (voice and data capable) to the IOR I-3 satellite, using the HGA subsystem, with a valid Flight ID.
5. 1642:04 - After take-off, the IFE SMS e-mail application sends a normal beginning-of-flight message.
a. The message contained the correct AES ID, Flight ID "MAS370", origin airport "WMKK", and destination airport "ZBAA".
b. This indicates that the IFE was receiving the Flight ID, origin airport and destination airport from AIMS and the ICAO (AES) ID from the SDU at this time.
6. 1707:48 - Last Acknowledged DATA-2 ACARS Message. No further SATCOM Data-2 ACARS messages or acknowledgements were received at the GES for the remainder of the flight.
7. 1803:41 - GES initiates a DATA-2 ACARS transmission (uplink), but receives no acknowledgement from the SATCOM.
a. Therefore, the SATCOM Link was lost at sometime between 1707:48 and 1803:41.
b. There is no evidence of a cockpit-initiated manual Log-Off of the SATCOM.
8. 1805:11 - GES initiates a DATA-2 ACARS transmission, but receives no acknowledgement from the SATCOM, indicating that there is still no SATCOM link at this time.
9. 1825:27 - SATCOM Log-On, initiated from the aircraft terminal.
a. This is the first ‘handshake’.
b. This marks the end of the link lost period that began at sometime between 1707:48 and 1803:41.
10. 1825:34 – SATCOM Log-On, successfully completed.
a. 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 which is normally transmitted at least once every 30 minutes).
b. No Flight ID was sent to the GES during the Log-On.
c. The GES recorded abnormal BFOs for the SATCOM Log-On Request and Log-On Acknowledge transmissions.
11. 1827:03 – 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.
12. 1828:05 – 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.
13. 1839:52 – Ground to Air Telephony Call Placed from a number with country code 60
a. Q10 Airline Operational Communications (AOC) Priority Level
b. This call would have been routed to the cockpit and should have resulted in a chime and an incoming visual annunciation on the Audio Control Panels (ACPs), and, if the appropriate SATCOM page was selected, then also on one or more MCDU.
c. The GES logs show zero duration, indicating that the call went unanswered. Note that there are two methods for the answering of an incoming call: Either by pressing the relevant Line Select Key on an MCDU, or by keying a microphone.
14. 1840:56 – The GES logs show that the unanswered Ground to Air telephony call was cleared by the calling party.
15. 1941:00 – Log-On Interrogation by the Perth GES, with a response from the SATCOM
a. This is the second ‘handshake’, whereby the GES inactivity timer has expired and the GES has sent a message to interrogate the status of the SATCOM.
b. The SATCOM responded normally and the SATCOM link was therefore available at this time.
16. 2041:02 – Log-On Interrogation by the Perth GES, with a response from the SATCOM
a. This is the third ‘handshake’.
b. The SATCOM responded normally and the SATCOM link was therefore available at this time.
17. 2141:24 – Log-On Interrogation by the Perth GES, with a response from the SATCOM
a. This is the fourth ‘handshake’.
b. The SATCOM responded normally and the SATCOM link was therefore available at this time.
18. 2241:19 – Log-On Interrogation by the Perth GES, with a response from the SATCOM
a. This is the fifth ‘handshake’.
b. The SATCOM responded normally and the SATCOM link was therefore available at this time.
19. 2313:58 - Ground to Air Telephony Call Placed from a number with country code 60
a. Q10 AOC Priority Level.
b. This call would have been routed to the cockpit and should have resulted in a chime and an incoming visual annunciation on the Audio Control Panels, and, if the appropriate SATCOM page was selected, then also on one or more MCDU.
c. The GES logs show zero duration, indicating that the call went unanswered. Note that there are two methods for the answering of an incoming call: Either by pressing the relevant Line Select Key on an MCDU, or by keying a microphone.
20. 2315:02 - The GES logs show that the unanswered Ground to Air telephony call was cleared by the calling party.
21. 0010:58 - Log-On Interrogation by the Perth GES, with a response from the SATCOM
a. This is the sixth ‘handshake’.
b. The SATCOM responded normally and the SATCOM link was therefore available at this time.
22. 0019:29 - SATCOM Log-On, initiated from the aircraft terminal. This is the seventh ‘handshake’.
23. 0019:37 - SATCOM Log-On, successfully completed
a. The SATCOM link becomes available (for voice and data – Class 3) once more and normal SATCOM operation resumes.
b. No Flight ID was sent to the GES during the Log-On.
c. The GES recorded an abnormal frequency offset for the SATCOM Log-On Request and Acknowledge transmissions.
d. The IFE did not subsequently establish the two Data-3 X.25 connections over the SATCOM.
e. Note that this is the last transmission received from the aircraft terminal.
24. 0115:56 - Log-On Interrogation by the Perth GES, with no response from the SATCOM
a. The SATCOM Link was lost at sometime between 0019:37 and 0115:56.
b. There is no evidence of a cockpit-initiated manual Log-Off of the SATCOM.
25. 01:16:06 – Log-On Interrogation by the Perth GES, with no response from the SATCOM
26. 01:16:15 – Log-On Interrogation by the Perth GES, with no response from the SATCOM
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.