Narrative:

After rotation runway xx I heard numerous clicking coming from the comms. I was conducting a discovery flight and expected the student had inadvertently activated the com. Neither my student nor I were engaging the transmit button but the [transmitter] was flashing quickly on the garmin 430 com (aircraft has a PS8000 audio panel and 1 com/nav G430). We were around 200 ft. AGL when I realized something had happened with the audio panel that gave me a stuck mic and also prevented me from hearing tower. I flipped to COM2 in the audio panel to stop blocking tower frequency; briefed the passengers on what was happening (stuck mic; will need to come around to land) and continued climbing out for a normal pattern. I flipped back to communication 1 to transmit into the blind my intentions (stuck mic; returning left traffic runway xx).at this point; the coms began behaving normally and I could hear tower again. Tower confirmed a stuck mic on ground and tower and gave me the option of continuing around runway xx or teardrop for runway xy (winds 260 at 8). I confirmed teardrop for runway xy and as I finished the transmission my mic became stuck again. I selected [transmission/receiver] on com 2 and [receiver] on com 1 to hear tower but no transmissions were able to be heard. I executed the teardrop and final for runway xy received the steady green light for landing. Once landed I asked tower for permission to roll to D for an exit to the south of the runway (permission request to be granted with a green light). I received no lights so I exited [taxiway] (north side of the runway) due to the B737 holding short of runway xx. On roll out onto [taxiway] I began to hear tower again and transmitted my intentions to hold short at [taxiway]. After this transmission I again got a hot mic and for the duration of the remainder of the flight/taxi was never able to hear over the coms again. Tower gave me a steady red light to remain where I was until the airport dispatched a vehicle to escort me back to the ramp. Once shut down I reported the failure to maintenance and reviewed the live ATC logs of ground and tower. On review; I found that I had experienced an intermittent hot mic on ground frequency prior to being cleared for taxi and takeoff but was not advised of the issue nor did I notice during taxi (taxi and takeoff clearance was received normally; hot mic was during taxi to runup and during runup). Maintenance reported that the audio panel had shorted out during the flight which caused the hot mic.

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Original NASA ASRS Text

Title: C172 instructor reported an audio panel failure on takeoff resulting in a return to the airport.

Narrative: After rotation Runway XX I heard numerous clicking coming from the comms. I was conducting a discovery flight and expected the student had inadvertently activated the com. Neither my student nor I were engaging the transmit button but the [transmitter] was flashing quickly on the Garmin 430 com (aircraft has a PS8000 audio panel and 1 Com/Nav G430). We were around 200 ft. AGL when I realized something had happened with the audio panel that gave me a stuck mic and also prevented me from hearing Tower. I flipped to COM2 in the audio panel to stop blocking Tower frequency; briefed the passengers on what was happening (stuck mic; will need to come around to land) and continued climbing out for a normal pattern. I flipped back to COM 1 to transmit into the blind my intentions (stuck mic; returning left traffic Runway XX).At this point; the coms began behaving normally and I could hear Tower again. Tower confirmed a stuck mic on Ground and Tower and gave me the option of continuing around Runway XX or teardrop for Runway XY (winds 260 at 8). I confirmed teardrop for Runway XY and as I finished the transmission my mic became stuck again. I selected [transmission/receiver] on Com 2 and [receiver] on Com 1 to hear Tower but no transmissions were able to be heard. I executed the teardrop and final for Runway XY received the steady green light for landing. Once landed I asked Tower for permission to roll to D for an exit to the south of the Runway (permission request to be granted with a green light). I received no lights so I exited [taxiway] (north side of the Runway) due to the B737 holding short of Runway XX. On roll out onto [taxiway] I began to hear Tower again and transmitted my intentions to hold short at [taxiway]. After this transmission I again got a hot mic and for the duration of the remainder of the flight/taxi was never able to hear over the coms again. Tower gave me a steady red light to remain where I was until the airport dispatched a vehicle to escort me back to the ramp. Once shut down I reported the failure to Maintenance and reviewed the LIVE ATC logs of Ground and Tower. On review; I found that I had experienced an intermittent hot mic on ground frequency prior to being cleared for taxi and takeoff but was not advised of the issue nor did I notice during taxi (Taxi and Takeoff clearance was received normally; hot mic was during taxi to runup and during runup). Maintenance reported that the audio panel had shorted out during the flight which caused the hot mic.

Data retrieved from NASA's ASRS site 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.