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B-27 Page 2 of 4 D6-27370-866-EGP
Flight Crew Operations Manual Bulletin No. EGP-27 R1, Dated June 5, 2013 (continued)
The airplane is equipped with an FMC that has ATS data link functionality
enabled in its OPC (Operational Program Configuration) software. If the
airplane has logged onto an Air Traffic Services (ATS) connection, the FMC
attempts to send an ADS downlink via HF or SATCOM. If the data link
transmission medium (either HF or SATCOM) is interrupted and the FMC
message is not cleared by the FMC (due to transmission interruption or data
conflict between the airplane and ground station) it can remain in the FMC
message queue. This can result in very sluggish FMC operation and can possibly
result in the FMC performing a software restart.
AOC Datalink issue:
On airplanes with ACARS Management Unit (MU) or Communications
Management Unit (CMU), if the VHF radio is used in DATA mode when the
airplane is not within the range of the service provider, the automatic ACARS
service provider sign-in message will not be acknowledged. The sign-in message
will also not be acknowledged when the operator does not have a subscription to
an ACARS service provider.
The lack of acknowledgement causes the message to be retained in the FMC
queue which may result in flashing of the FMC prompt on the MCDU Menu
page or slowdown of FMC operation.
A correction to the software to provide a fix for both conditions is planned for
FMC Update U11.
Operating Instructions
To avoid the ATS Datalink condition, do not log onto ATS.
To avoid the AOC Datalink condition, do not use the VHF radio in DATA mode
when outside the service range of the ACARS service provider, or if the airline
does not have a subscription to an ACARS service provider.
On the ground:
After power up, switch the VHF radio to VOICE mode from DATA mode.
If either problem occurs in flight:
1. Select the VHF radio to VOICE mode from DATA mode
2. Set the FMC Source Select switch to BOTH ON R (if dual FMC installed).
This facilitates logging off SATCOM (if installed). The switch can be set
back to NORMAL after logging off
3. Logoff the SATCOM system (if installed)
4. If HF datalink is present, select the HF radio to VOICE mode from DATA
mode
5. Do not use ATS or AOC Datalink for the rest of the flight
September 24, 2015
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