Date: 201504
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction; Troubleshooting; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted
Contributing factors: Equipment / Tooling
Primary problem: Equipment / Tooling

Narrative: While on climb out from EWR the First Officer (FO) and I noticed a red STKMIC indication on Comm 2. We figured out that Comm 2 was continuously transmitting on its own without any sound being picked up by any of the microphones (O2 masks; headsets; hand mic; etc.). About an hour and a half into the flight the flight attendants called via the EMER call and asked if we had been calling the cabin because there had been numerous hi-lo chimes but when they picked up the interphone there was no one on the line. As they were describing the problem the connection between the flight attendants and the fight deck cut out. We tried to contact the flight attendants back by pressing CABIN on the audio panel but there was no chime that sounded in the cabin and it did not connect. We pressed the EMER button and it connected but did not chime the flight attendants; it just happened to be that the flight attendants were still talking and did not knew we had been cut off. We established that we would use 3 knocks on the door and a note slipped through the top if they needed to get a hold of us and 5 knocks on the door if it was an emergency. As the FO and I started trouble shooting; we looked into the MEL book for what the operating procedure would be with an inoperative Comm 2. It advised to put Comm 3 into VOICE mode and use that as a second radio. When we did that we discovered that it also continuously transmitted just like what was happening to Comm 2 and it was unable to be used for voice communication. We sent several messages to dispatch and it worked normally for all ACARS functions. Then the FO and I looked into the MEL book to find what the operating procedure was for a failed intercom. It advised that at least one flight attendant station needed to be fully operative. Both flight attendant stations were affected and the cabin was unable to get a hold of us by normal means. We tried to contact the cabin via interphone again and none of the buttons on the audio panel worked by sending a chime; so we made a PA for the FA's to call the flight deck and we just happened to press the EMER button as they were talking into the interphone again. It only worked for a few seconds before cutting out again. At that time we discussed with between ourselves dispatch about diverting to MEM because it was just under 100 miles ahead. We were also unsure if there would be further communications failures; we were already down to Comm 1 for the only radio that could be used for voice communications; and we were unable to communication with the cabin by a normal means. We diverted to MEM to avoid any further failures. While on descent into MEM; the cabin interphone system started to continuously chime the flight attendants without any action from us. It only stopped if the flight attendants took the phone off the hook. We deplaned the passengers once getting to the gate and eventually the flight was cancelled.A decision was made to divert to MEM after experiencing a failure of Comm 2; Comm 3 for voice communications; and an abnormally functioning interphone system. We were unsure if there would be further problems and a possibility of losing all communications and felt that diverting would be the most prudent course of action.


Second narrative: During climb out we noticed a red 'micstk' message located on com2. We proceeded to trouble shoot and determined that it wasn't either of our mics or the jumps seat mic transmitting; however com 2 was inoperative. We also looked in the AOM for this message but we unsuccessful. Then we noticed the Flight Attendants (FA) were calling us with the emergency channel on the interphone. It was difficult to hear what they were saying but we determined they thought we had called them (which we did not) but they would call us back. The Captain then looked in the Mel book and read that if COM2 was into we are to use com3 in voice mode. We attempted to do so but ran into the same problem as incurred with com2. Then FA's tried calling again however no chimes or lights occurred when we called them or they called us. Communication was only possible over emergency channel but for only a few seconds. We were constantly pushing the emergency button in order to hopefully maintain a conversation because it would inadvertently cut off. So now down to 1 com (com1); unable to communicate with the cabin and having no clue why all of these electrical/communication problems were occurring. We decided it was necessary to divert to MEM.


Synopsis: Pilots report of an equipment stuck microphone that was used between the cockpit and the cabin. The problem could not be rectified so they had to divert and landed in an emergency condition.