Narrative:

During cruise at FL350 a bleed-through occurred on the #1 radio. We then realized we had no communication with ATC for an unknown period of time. Contact was established with center after numerous tries. We were queried as to cockpit security and flight security. A message was sent to dispatch via ACARS explaining the situation and a prompt response was received. The ACARS had not been receiving and we had a possible total communication failure with no cockpit indications. During the approach phase of the flight we experienced several problems communicating with norcal approach due to radio squelch bleed that sounded similar to an ACARS transmission. After a postflt discussion with maintenance, it was found that the communication system scan mask was set for the caribbean/mexico and not the continental united states, possibly explaining the lack of reception of numerous messages sent by dispatch to call attention to our NORDO status. During our no communication period, we received no radio, SELCAL or ACARS xmissions. Numerous people met the aircraft at the gate. We had 2 fam's on the flight and we were asked why the fam's were unable to be contacted airborne. Callback conversation with reporter revealed the following information: the reporter stated that the ACARS transmit and receive frequency options (scan mask) are normally automatically set by the ACARS software depending on the aircraft's geographical location. However, if the ACARS frequency selector is not in automatic the ACARS data frequencys are limited to the location manually set, ie, continental united states, europe, latin american and caribbean. Because the reporter's aircraft's frequency selection (scan mask) was set manually to latin america/mexico, the ACARS over the central united states could not receive messages from the company's dispatch who were attempting to give them a VHF frequency to talk to ZLC. The crew, however, knew nothing about the scan mask and, therefore, assumed an ACARS malfunction. There was also a concern among the ground tsa personnel about the security of the flight because of the NORDO status and the fact that the tsa fam agents who were also on the aircraft could not be contacted. Tsa briefed the crew about their status.

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Original NASA ASRS Text

Title: AN NORDO A320 EXPERIENCED A DISABLED ACARS BECAUSE THE SCAN MASK FREQ SELECTION WAS IMPROPERLY SET.

Narrative: DURING CRUISE AT FL350 A BLEED-THROUGH OCCURRED ON THE #1 RADIO. WE THEN REALIZED WE HAD NO COM WITH ATC FOR AN UNKNOWN PERIOD OF TIME. CONTACT WAS ESTABLISHED WITH CTR AFTER NUMEROUS TRIES. WE WERE QUERIED AS TO COCKPIT SECURITY AND FLT SECURITY. A MESSAGE WAS SENT TO DISPATCH VIA ACARS EXPLAINING THE SIT AND A PROMPT RESPONSE WAS RECEIVED. THE ACARS HAD NOT BEEN RECEIVING AND WE HAD A POSSIBLE TOTAL COM FAILURE WITH NO COCKPIT INDICATIONS. DURING THE APCH PHASE OF THE FLT WE EXPERIENCED SEVERAL PROBS COMMUNICATING WITH NORCAL APCH DUE TO RADIO SQUELCH BLEED THAT SOUNDED SIMILAR TO AN ACARS XMISSION. AFTER A POSTFLT DISCUSSION WITH MAINT, IT WAS FOUND THAT THE COM SYS SCAN MASK WAS SET FOR THE CARIBBEAN/MEXICO AND NOT THE CONTINENTAL UNITED STATES, POSSIBLY EXPLAINING THE LACK OF RECEPTION OF NUMEROUS MESSAGES SENT BY DISPATCH TO CALL ATTN TO OUR NORDO STATUS. DURING OUR NO COM PERIOD, WE RECEIVED NO RADIO, SELCAL OR ACARS XMISSIONS. NUMEROUS PEOPLE MET THE ACFT AT THE GATE. WE HAD 2 FAM'S ON THE FLT AND WE WERE ASKED WHY THE FAM'S WERE UNABLE TO BE CONTACTED AIRBORNE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT THE ACARS XMIT AND RECEIVE FREQ OPTIONS (SCAN MASK) ARE NORMALLY AUTOMATICALLY SET BY THE ACARS SOFTWARE DEPENDING ON THE ACFT'S GEOGRAPHICAL LOCATION. HOWEVER, IF THE ACARS FREQ SELECTOR IS NOT IN AUTOMATIC THE ACARS DATA FREQS ARE LIMITED TO THE LOCATION MANUALLY SET, IE, CONTINENTAL UNITED STATES, EUROPE, LATIN AMERICAN AND CARIBBEAN. BECAUSE THE RPTR'S ACFT'S FREQ SELECTION (SCAN MASK) WAS SET MANUALLY TO LATIN AMERICA/MEXICO, THE ACARS OVER THE CENTRAL UNITED STATES COULD NOT RECEIVE MESSAGES FROM THE COMPANY'S DISPATCH WHO WERE ATTEMPTING TO GIVE THEM A VHF FREQ TO TALK TO ZLC. THE CREW, HOWEVER, KNEW NOTHING ABOUT THE SCAN MASK AND, THEREFORE, ASSUMED AN ACARS MALFUNCTION. THERE WAS ALSO A CONCERN AMONG THE GND TSA PERSONNEL ABOUT THE SECURITY OF THE FLT BECAUSE OF THE NORDO STATUS AND THE FACT THAT THE TSA FAM AGENTS WHO WERE ALSO ON THE ACFT COULD NOT BE CONTACTED. TSA BRIEFED THE CREW ABOUT THEIR STATUS.

Data retrieved from NASA's ASRS site as of July 2007 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.