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A C172 pilot reports a burning smell. After all equipment was turned off communication was reestablished. An emergency was declared. Master avionics switch very hot.
| Attributes | |
| ACN | 742531 |
| Time | |
| Date | 200706 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl single value : 3500 |
| Environment | |
| Flight Conditions | VMC VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : zzz.tower |
| Operator | general aviation : personal |
| Make Model Name | Skyhawk 172/Cutlass 172 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | None |
| Person 1 | |
| Affiliation | other |
| Function | flight crew : single pilot |
| Qualification | pilot : private |
| Experience | flight time last 90 days : 5 flight time total : 162 flight time type : 162 |
| ASRS Report | 742531 |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : landed in emergency condition flight crew : declared emergency |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Shortly after flying sbound over ZZZ1 while in the ZZZ sfr area; a burning smell appeared in the cockpit. I announced my position when I was leaving the sfr area. After this announcement; all the electrical equipment turned off. I switched the avionics master off and turned towards ZZZ2 airport. This switch; a metallic toggle switch; was burning hot. I turned off all components individually and then try to turn on some components individually. Communication #2 worked. I tuned in ZZZ2 control tower frequency and declared an emergency. After confirming my position; I was cleared to land and did. Callback conversation with reporter revealed the following information: reporter discovered after the flight that one of two wires on the master avionics switch was loose because the nut holding it on was not tight. As a result; current across the wire was increased; creating heat on the switch. That heat made the switch very hot and caused a burning smell from the wire's heated insulation.
Original NASA ASRS Text
Title: A C172 PILOT REPORTS A BURNING SMELL. AFTER ALL EQUIP WAS TURNED OFF COM WAS REESTABLISHED. AN EMER WAS DECLARED. MASTER AVIONICS SWITCH VERY HOT.
Narrative: SHORTLY AFTER FLYING SBOUND OVER ZZZ1 WHILE IN THE ZZZ SFR AREA; A BURNING SMELL APPEARED IN THE COCKPIT. I ANNOUNCED MY POS WHEN I WAS LEAVING THE SFR AREA. AFTER THIS ANNOUNCEMENT; ALL THE ELECTRICAL EQUIP TURNED OFF. I SWITCHED THE AVIONICS MASTER OFF AND TURNED TOWARDS ZZZ2 ARPT. THIS SWITCH; A METALLIC TOGGLE SWITCH; WAS BURNING HOT. I TURNED OFF ALL COMPONENTS INDIVIDUALLY AND THEN TRY TO TURN ON SOME COMPONENTS INDIVIDUALLY. COM #2 WORKED. I TUNED IN ZZZ2 CTL TWR FREQ AND DECLARED AN EMER. AFTER CONFIRMING MY POS; I WAS CLRED TO LAND AND DID. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER DISCOVERED AFTER THE FLT THAT ONE OF TWO WIRES ON THE MASTER AVIONICS SWITCH WAS LOOSE BECAUSE THE NUT HOLDING IT ON WAS NOT TIGHT. AS A RESULT; CURRENT ACROSS THE WIRE WAS INCREASED; CREATING HEAT ON THE SWITCH. THAT HEAT MADE THE SWITCH VERY HOT AND CAUSED A BURNING SMELL FROM THE WIRE'S HEATED INSULATION.
Data retrieved from NASA's ASRS site as of January 2009 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.