Narrative:

Established controller pilot datalink communications (cpdlc/ads) connection. Approaching fir received ATC message time-stamped xa:35Z instructing we contact ATC frequency 124.xx MHZ. Crew acknowledged ATC instructions via cpdlc at time xa:35Z; and attempted voice contact per ATC instructions. ATC message EICAS memo message and sending CDU prompt remained displayed for what would be a period of 6 minutes. After time-out period; CDU displayed ATC message not acknowledged. During this time interval crew unsuccessfully attempted contact ATC 124.xx MHZ. ATC sent a second datalink message after the auto-generated ATC message not acknowledged FMC alert message. This read: 'attempt voice contact ATC'. There was no print or send prompt to this second datalink communication; and this message was not recorded in the cpdlc log. However; either this second ATC datalink message; or-- more probably-- the timing out of the first message; allowed programming logic to re-enable CDU send prompt; which the PF immediately selected. This second response (to the first ATC message) is time-stamped xa:41Z. Meanwhile the pilot not flying was successful with voice relay through aircraft on frequency to ATC; and voice communications were soon established with ATC on an alternate frequency. The airplane ACARS system processes all company and ATC datalink messages to and from the airplane. At time xa:39Z we received; on ACARS; the first of three cabin write-up acknowledgments called in presumably by the chief purser. Crew's observation is this co-incidental occupation of FMC datalink processor/buffering delayed ATC datalink communication. As a crewmember on international flights; I have long been frustrated by some chief purser's habits of sending non-essential cabin items both without coordinating this activity with the flight crew on duty; and/or initiating sending no essential cabin items so early in the flight. Fom states 'purser will consult with captain prior to using ACARS'. Some do not. Some are briefed; as happened on this occasion; by a captain during preflight briefing; that using ACARS is appropriate and approved by the captain. This leaves timing of ACARS usage to the sole discretion of the chief purser; and its use may very well be at a time in flight that the captain never imagined. Additionally; pursers are not trained to envision how cabin write-ups affect the dispatch ability of an aircraft in event of diversion. I am not suggesting these write-ups not be recorded for the above reason; I am suggesting; however; that legality of dispatch makes it all the more important that the captain be advised immediately prior to using the cabin ACARS. At any rate; if indeed the use of the cabin ACARS interfered with ATC communications; as it appears it did; a wholly unacceptable-- an unnecessary-- communication interruption can occur. The use of the cabin ACARS must be limited to non-controller pilot datalink communications/ads operations. I believe this report is particularly important given a recent fleet communication regarding timeliness of aircrew responses to cpdlc instructions from ATC.

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Original NASA ASRS Text

Title: A pilot reported that the Flight Attendants use of the cabin ACARS during international operations interfered with CPDLC/ADS communications with ATC.

Narrative: Established controller pilot datalink communications (CPDLC/ADS) connection. Approaching FIR received ATC message time-stamped XA:35Z instructing we contact ATC frequency 124.XX MHZ. Crew acknowledged ATC instructions via CPDLC at time XA:35Z; and attempted voice contact per ATC instructions. ATC MESSAGE EICAS memo message and SENDING CDU prompt remained displayed for what would be a period of 6 minutes. After time-out period; CDU displayed ATC MESSAGE NOT ACKNOWLEDGED. During this time interval crew unsuccessfully attempted contact ATC 124.XX MHZ. ATC sent a second datalink message after the auto-generated ATC MESSAGE NOT ACKNOWLEDGED FMC alert message. This read: 'Attempt voice contact ATC'. There was no PRINT or SEND prompt to this second datalink communication; and this message was not recorded in the CPDLC log. However; either this second ATC datalink message; or-- more probably-- the timing out of the first message; allowed programming logic to re-enable CDU send prompt; which the PF immediately selected. This second response (to the first ATC message) is time-stamped XA:41Z. Meanwhile the pilot not flying was successful with voice relay through aircraft on frequency to ATC; and voice communications were soon established with ATC on an alternate frequency. The airplane ACARS system processes all Company and ATC datalink messages to and from the airplane. At time XA:39Z we received; on ACARS; the first of three cabin write-up acknowledgments called in presumably by the Chief Purser. Crew's observation is this co-incidental occupation of FMC datalink processor/buffering delayed ATC datalink communication. As a crewmember on international flights; I have long been frustrated by some Chief Purser's habits of sending non-essential cabin items both without coordinating this activity with the flight crew on duty; and/or initiating sending no essential cabin items so early in the flight. FOM states 'Purser will consult with Captain prior to using ACARS'. Some do not. Some are briefed; as happened on this occasion; by a Captain during preflight briefing; that using ACARS is appropriate and approved by the Captain. This leaves timing of ACARS usage to the sole discretion of the Chief purser; and its use may very well be at a time in flight that the Captain never imagined. Additionally; Pursers are not trained to envision how cabin write-ups affect the dispatch ability of an aircraft in event of diversion. I am not suggesting these write-ups not be recorded for the above reason; I am suggesting; however; that legality of dispatch makes it ALL THE MORE IMPORTANT that the Captain be advised IMMEDIATELY prior to using the cabin ACARS. At any rate; if indeed the use of the cabin ACARS interfered with ATC communications; as it appears it did; a wholly unacceptable-- an unnecessary-- communication interruption can occur. The use of the cabin ACARS must be limited to non-controller pilot datalink communications/ADS operations. I believe this report is particularly important given a recent fleet communication regarding timeliness of aircrew responses to CPDLC instructions from ATC.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.