Narrative:

On left downwind for runway 17R after multiple night landings; I heard an unusual sound from COM1 radio; and then experienced dimmed and erratic cockpit lighting. I suspected potential electrical failure was imminent and tried to contact the tower but was unsuccessful. COM1 failed completely at this point. I attempted to contact tower on COM2 radio but was unsuccessful.I observed traffic on final; waited for it to pass off my left and then turned base and final. COM2 led's were flashing erratically; and cockpit panel lighting was dim to non-existent. I made additional attempts to contact the tower; but heard no response. On final; I observed no ATC light signals clearing me to land; so I maintained approximate pattern altitude and flew over the runway to remain in the pattern. I also noted departing traffic on the runway and side-stepped to the right to maintain visual separation from this traffic. I followed this traffic ahead as it turned crosswind and downwind. I cycled the master switch in an attempt to solve the electrical problem; as per poh guidance; but this did not help. I squawked 7600 in case ATC was still getting transponder returns. I made additional attempts to contact ATC without success and noted I could not hear any radio transmissions even with the COM2 squelch button held in. I used my flashlight (on a string around my neck) to view flight instruments. After turning base and final; I observed a steady green ATC 'cleared to land' light signal and landed on runway 17R without flaps. My landing and taxi lights were inoperative at this point. After touchdown; I rolled out longer than usual; probably due to lack of flaps and perhaps higher than usual airspeed on final. I noted the right toe brake was somewhat 'mushy' during the rollout; and decided to let the aircraft slow without using brakes to maintain directional control. I eventually turned off onto the taxiway close to the south end of runway 17R; using my handheld flashlight to help see taxiway markings.after clearing the runway; I faced the tower waiting for additional light signals but observed none. I had very dim cockpit lighting. I could not determine if my navigation lights or flashing red anti collision lights were lighted at all. I decided it safest to taxi very slowly holding my flashlight out the open left window to observe taxiway markings and warn any potential approaching traffic. I taxied very slowly. Upon approaching the intersection of taxiways foxtrot and echo; I stopped and waved my flashlight in the direction of the tower. I observed a flashing green ATC 'cleared to taxi' light signal and proceeded to taxi slowly towards parking. I shutdown the aircraft prior to reaching the hangar; and pulled it the remaining distance to the hangar with a tow bar. After refueling and record keeping; I telephoned the flying club's maintenance officer and reported the problem. I also noted details in the club logbook. I later telephoned the club president to make sure he was aware of the situation and was advised the aircraft is now in maintenance; and the root cause of the problem is not yet known.

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Original NASA ASRS Text

Title: While practicing night landings at a Towered airport the pilot of a C-172 suffered an electrical failure and the associated loss of comm capability. He remained in the pattern and made a pass above the runway alerting the Tower as to his problem and on the subsequent pass was given light signal clearances to land and to taxi in.

Narrative: On left downwind for Runway 17R after multiple night landings; I heard an unusual sound from COM1 radio; and then experienced dimmed and erratic cockpit lighting. I suspected potential electrical failure was imminent and tried to contact the Tower but was unsuccessful. COM1 failed completely at this point. I attempted to contact Tower on COM2 radio but was unsuccessful.I observed traffic on final; waited for it to pass off my left and then turned base and final. COM2 LED's were flashing erratically; and cockpit panel lighting was dim to non-existent. I made additional attempts to contact the Tower; but heard no response. On final; I observed no ATC light signals clearing me to land; so I maintained approximate pattern altitude and flew over the runway to remain in the pattern. I also noted departing traffic on the runway and side-stepped to the right to maintain visual separation from this traffic. I followed this traffic ahead as it turned crosswind and downwind. I cycled the Master switch in an attempt to solve the electrical problem; as per POH guidance; but this did not help. I squawked 7600 in case ATC was still getting transponder returns. I made additional attempts to contact ATC without success and noted I could not hear any radio transmissions even with the COM2 squelch button held in. I used my flashlight (on a string around my neck) to view flight instruments. After turning base and final; I observed a steady green ATC 'cleared to land' light signal and landed on Runway 17R without flaps. My landing and taxi lights were inoperative at this point. After touchdown; I rolled out longer than usual; probably due to lack of flaps and perhaps higher than usual airspeed on final. I noted the right toe brake was somewhat 'mushy' during the rollout; and decided to let the aircraft slow without using brakes to maintain directional control. I eventually turned off onto the taxiway close to the south end of Runway 17R; using my handheld flashlight to help see taxiway markings.After clearing the runway; I faced the Tower waiting for additional light signals but observed none. I had very dim cockpit lighting. I could not determine if my navigation lights or flashing red anti collision lights were lighted at all. I decided it safest to taxi very slowly holding my flashlight out the open left window to observe taxiway markings and warn any potential approaching traffic. I taxied very slowly. Upon approaching the intersection of taxiways Foxtrot and Echo; I stopped and waved my flashlight in the direction of the Tower. I observed a flashing green ATC 'cleared to taxi' light signal and proceeded to taxi slowly towards parking. I shutdown the aircraft prior to reaching the hangar; and pulled it the remaining distance to the hangar with a tow bar. After refueling and record keeping; I telephoned the Flying Club's Maintenance Officer and reported the problem. I also noted details in the club logbook. I later telephoned the club president to make sure he was aware of the situation and was advised the aircraft is now in maintenance; and the root cause of the problem is not yet known.

Data retrieved from NASA's ASRS site as of July 2013 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.