Timeline/Pre-Flight/1554:31 UTC

MH370 DECODED
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Event Summary

23:54:31 MYT Friday, 7 March 2014

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Malaysia Airlines Operations Centre contacted MH370 by sending an ACARS message (over VHF) suggesting that VHF3 be switched (from data) to voice if the SATCOM system was operational (serviceable). Future communications to and from the aircraft by ACARS would then be (automatically) sent via the SATCOM system.


Event Details

  1. Safety Investigation Report MH370/01/2018 Appendix 1.9A


    Time
    15:54:31
    Trans
    46817955
    Direction
    Outgoing Uplink
    AN
    9M-MRO
    FI
    MH0370
    Medium
    KUL
    Machine
    MHKULKJACM001
    Raw DTG
    071554
    SMI
    CMD
    Application
    RELAY
    Status
    Uplink Sent
    Message Type
    Frequency Auto-tune -- Frequency Auto-tune B777
    Source/Destination
    BKKXCXA

    QU BKKXCXA
    .DPCCAMH 071554
    CMD
    AN 9M-MRO/FI MH0370/GL KUL/MA 988I
    - QUDPCCAMH~1RA101071554
    Message:
    SWITCH VHF3 TO VOICE
    (131.550)
    IF SATCOM SERVICABLE
    FROM MH OPS



    Time
    15:54:31
    Trans
    46817955
    Direction
    Outgoing Ground
    AN
    9M-MRO
    FI
    MH0370
    Medium
    KUL
    Machine
    MHKULKJACM001
    Raw DTG
    071554
    SMI
    CMD
    Application
    BATAPCNX
    Status
    Routed
    Message Type
    Source/Destination
    BATAP_TO_MSW

    QU BKKXCXA
    .DPCCAMH 071554
    CMD
    AN 9M-MRO/FI MH0370/GL KUL/MA 988I
    - QUDPCCAMH~1RA101071554
    Message:
    SWITCH VHF3 TO VOICE
    (131.550)
    IF SATCOM SERVICABLE
    FROM MH OPS



    Time
    15:54:36
    Trans
    46817955
    Direction
    Incoming Downlink
    AN
    9M-MRO
    FI
    MH0370
    Medium
    KUL
    Machine
    MHKULKJACM001
    Raw DTG
    071554
    SMI
    MAS
    Application
    RELAY
    Status
    Normal
    Message Type
    MAS-S (successful)
    Source/Destination
    BKKXCXA

    QU DPCCAMH
    .BKKXCXA 071554
    MAS
    AN 9M-MRO/FI MH0/MA 988S
    DT BKK KUL 071554 S05A




Notes

  1. ACARS can send data via the satellite communications system (SATCOM) or over a VHF data-link. The VHF radio must be switched from voice to data for this to occur.
  2. VHF radio is commonly used for data at or near an airport, where the service provider has a transceiver to provide the ACARS service.
  3. It seems that for flight MH370, ACARS was initially communicating via VHF.
  4. This message from Malaysia Airlines Operations Centre suggests that the VHF radio be switched to voice-only, using channel 131.550 MHz - if the SATCOM is serviceable, meaning that the SATCOM could transmit and receive future ACARS messages.
  5. This ACARS message was included in the Safety Investigation Report MH370/01/2018 Appendix 1.9A but not in the previous version Factual Information MH370/01/15 Appendix 1.9A.