Narrative:

I departed gai at XA00 hours for a VFR flight to ytz. VFR conditions prevailed with winds from 260 degrees at 10 KTS and visibility 4-6 mi. At about XA30 hours, while flying near hagerstown, md, I began experiencing radio problems. At that time, I was in contact with, I believe, washington approach. Suddenly the communication and navigation lights on the panel began blinking and repeated 'bzzzz, bzzzz, bzzzz' sounds (like 2 hot wires touching each other) were coming from the panel. No smoke or smell was detected. At times the equipment would be dead silent, other times it would be buzzing and blinking, and occasionally it would be functioning normal. Review of panel instruments, electrical gauges, and breakers indicated no other visible problems. Since I was unable to identify any correctable problem, within mins I decided to declare an emergency and return to gai. I notified the ATC, with whom I had last contact, about my failing radio equipment, declared my emergency, and made a left u-turn for gai. I continued to transmit intermittently (variable interval of 2 mins) about my failing radios and navigation instruments, and occasionally would hear from washington approach but was unable to maintain any sustained dialogue. Initially I retained my assigned squawk from dulles approach, but later switched my transponder to 7700. Eventually I was handed off to baltimore approach who was able to give me a heading to gai. 45 mins later (from the time the problem was idented) I landed at gai without an incident. Callback conversation with reporter revealed the following information: reporter stated that it was found that the alternator belt was loose and not turning the alternator to produce electrical needs for the electrical equipment turned on. Thus, running down the battery until there was no electrical current left for the radio or panel lights.

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Original NASA ASRS Text

Title: CESSNA 172 PLT DECLARED AN EMER AND RETURNED TO LAND AFTER EXPERIENCING INTERMITTENT 2-WAY RADIO COMS AND INST PANEL LIGHTING.

Narrative: I DEPARTED GAI AT XA00 HRS FOR A VFR FLT TO YTZ. VFR CONDITIONS PREVAILED WITH WINDS FROM 260 DEGS AT 10 KTS AND VISIBILITY 4-6 MI. AT ABOUT XA30 HRS, WHILE FLYING NEAR HAGERSTOWN, MD, I BEGAN EXPERIENCING RADIO PROBS. AT THAT TIME, I WAS IN CONTACT WITH, I BELIEVE, WASHINGTON APCH. SUDDENLY THE COM AND NAV LIGHTS ON THE PANEL BEGAN BLINKING AND REPEATED 'BZZZZ, BZZZZ, BZZZZ' SOUNDS (LIKE 2 HOT WIRES TOUCHING EACH OTHER) WERE COMING FROM THE PANEL. NO SMOKE OR SMELL WAS DETECTED. AT TIMES THE EQUIP WOULD BE DEAD SILENT, OTHER TIMES IT WOULD BE BUZZING AND BLINKING, AND OCCASIONALLY IT WOULD BE FUNCTIONING NORMAL. REVIEW OF PANEL INSTS, ELECTRICAL GAUGES, AND BREAKERS INDICATED NO OTHER VISIBLE PROBS. SINCE I WAS UNABLE TO IDENT ANY CORRECTABLE PROB, WITHIN MINS I DECIDED TO DECLARE AN EMER AND RETURN TO GAI. I NOTIFIED THE ATC, WITH WHOM I HAD LAST CONTACT, ABOUT MY FAILING RADIO EQUIP, DECLARED MY EMER, AND MADE A L U-TURN FOR GAI. I CONTINUED TO XMIT INTERMITTENTLY (VARIABLE INTERVAL OF 2 MINS) ABOUT MY FAILING RADIOS AND NAV INSTS, AND OCCASIONALLY WOULD HEAR FROM WASHINGTON APCH BUT WAS UNABLE TO MAINTAIN ANY SUSTAINED DIALOGUE. INITIALLY I RETAINED MY ASSIGNED SQUAWK FROM DULLES APCH, BUT LATER SWITCHED MY XPONDER TO 7700. EVENTUALLY I WAS HANDED OFF TO BALTIMORE APCH WHO WAS ABLE TO GIVE ME A HEADING TO GAI. 45 MINS LATER (FROM THE TIME THE PROB WAS IDENTED) I LANDED AT GAI WITHOUT AN INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT IT WAS FOUND THAT THE ALTERNATOR BELT WAS LOOSE AND NOT TURNING THE ALTERNATOR TO PRODUCE ELECTRICAL NEEDS FOR THE ELECTRICAL EQUIP TURNED ON. THUS, RUNNING DOWN THE BATTERY UNTIL THERE WAS NO ELECTRICAL CURRENT LEFT FOR THE RADIO OR PANEL LIGHTS.

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.