Narrative:

I planned a flight to destination via hudson corridor. Flight plan was approximately 360 miles using approximately 31 gallons and 2.75 hours. I plan for 5 hours of fuel on board with 49 gal usable. Upon leveling at 1100 feet over the hudson river; I encountered severe turbulence. The turbulence slammed my passenger and myself into the roof of the cockpit hard enough to knock headsets off our head and onto the floor. I assessed the situation and the plane was flying with no control issues and we continued an uneventful flight down the hudson river past nyc. I activated all lighting for VFR flight down hudson as advised. We departed west with VFR flight following. Approximately 20 minutes later I saw the alternator gauge reading discharge. I turned off the strobes and navigation lighting; thinking that having all lighting on had caused a drain in the battery. I also noticed my right tank fuel gauge was showing low. I switched tanks with the left fuel tank showing 3/4 tank. I continued assessing the discharge. Approximately 20 minutes from destination both fuel tanks were showing close to empty. I contacted a nearby airport approach and notified them of my intent to land at an alternate. They acknowledged and my radios and all electrical went dead at that time. My fuel gauges also showed empty. I elected to make a emergency landing not knowing if I was actually out of fuel or the fuel system had been damaged in the turbulence and I assumed I had a fuel emergency and a complete electrical system failure. I carry a hand held radio in my flight bag for communications emergencies. I had my passenger get it but she was not familiar with it and did not get it turned on. As I approached the airport I did not see any aircraft in the pattern or any light signals from the tower. I don't think they knew I was coming or were ever advised. I was high and the windsocks were showing a strong cross wind so I elected to land on or close to another runway which was longer and had favorable winds. I saw the X on the end of the runway; as I got lower I saw the barriers across the runway. I opted to land to the side of the runway in the grass to avoid the barriers. As I got lower I noticed there was room on the side of the runway to land without striking the barriers. I elected that option and made a landing without incident. I was met by the airport manager as I pulled off the runway. I had the electrical system checked by the FBO and it was determined the turbulence had caused the alternator breaker to pop. They could not identify as to why turbulence would cause the breaker to pop. The turbulence had caused the alternator circuit breaker to pop which I did not see and did not diagnosis. Before departing; I took on approximately 35 gallons which gave me approximately 14 gallons left in both tanks. I am scheduling a review of emergency procedures and electrical systems with our club CFI and maintenance officer.

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Original NASA ASRS Text

Title: A C177B diverted to a nearby airport when he suffered an electrical failure perhaps the result of a brief encounter with severe turbulence earlier in the flight.

Narrative: I planned a flight to destination via Hudson Corridor. Flight plan was approximately 360 miles using approximately 31 gallons and 2.75 hours. I plan for 5 hours of fuel on board with 49 gal usable. Upon leveling at 1100 feet over the Hudson River; I encountered severe turbulence. The turbulence slammed my passenger and myself into the roof of the cockpit hard enough to knock headsets off our head and onto the floor. I assessed the situation and the plane was flying with no control issues and we continued an uneventful flight down the Hudson River past NYC. I activated all lighting for VFR flight down Hudson as advised. We departed west with VFR flight following. Approximately 20 minutes later I saw the alternator gauge reading discharge. I turned off the strobes and navigation lighting; thinking that having all lighting on had caused a drain in the battery. I also noticed my right tank fuel gauge was showing low. I switched tanks with the left fuel tank showing 3/4 tank. I continued assessing the discharge. Approximately 20 minutes from destination both fuel tanks were showing close to empty. I contacted a nearby airport approach and notified them of my intent to land at an alternate. They acknowledged and my radios and all electrical went dead at that time. My fuel gauges also showed empty. I elected to make a emergency landing not knowing if I was actually out of fuel or the fuel system had been damaged in the turbulence and I assumed I had a fuel emergency and a complete electrical system failure. I carry a hand held radio in my flight bag for communications emergencies. I had my passenger get it but she was not familiar with it and did not get it turned on. As I approached the airport I did not see any aircraft in the pattern or any light signals from the tower. I don't think they knew I was coming or were ever advised. I was high and the windsocks were showing a strong cross wind so I elected to land on or close to another runway which was longer and had favorable winds. I saw the X on the end of the runway; as I got lower I saw the barriers across the runway. I opted to land to the side of the runway in the grass to avoid the barriers. As I got lower I noticed there was room on the side of the runway to land without striking the barriers. I elected that option and made a landing without incident. I was met by the airport manager as I pulled off the runway. I had the electrical system checked by the FBO and it was determined the turbulence had caused the alternator breaker to pop. They could not identify as to why turbulence would cause the breaker to pop. The turbulence had caused the alternator circuit breaker to pop which I did not see and did not diagnosis. Before departing; I took on approximately 35 gallons which gave me approximately 14 gallons left in both tanks. I am scheduling a review of emergency procedures and electrical systems with our club CFI and maintenance officer.

Data retrieved from NASA's ASRS site as of April 2012 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.