A C150 ON A TRAINING FLT AT 3000 FT DIVERTED AND MADE AN OFF ARPT LNDG DUE TO COMPLETE LOSS OF ELECTRICAL PWR CAUSED BY A DEFECTIVE STARTER RELAY AND VOLTAGE REGULATOR.

Narrative

AS I WAS FLYING WITH MY STUDENT ON A LCL FLT TO PRACTICE MANEUVER; WE EXPERIENCED A COMPLETE ELECTRICAL FAILURE. I THEREFORE DECIDED TO HEAD BACK TO THE ARPT AND TERMINATE THE FLT; BUT ON OUR WAY BACK; I HEARD A NOISE THAT SOUNDED LIKE SOME ELECTRICAL WIRES WERE ARCING OR SHORTING. 15 MI AWAY FROM THE ARPT; I DECIDED TO LAND IN A GRASS FIELD TO PREVENT A POSSIBLE ELECTRICAL CABIN FIRE FROM STARTING. THIS LNDG WAS THEREFORE A PRECAUTIONARY LNDG IN THE INTEREST OF OUR SAFETY AND THAT OF THE AIRPLANE. I DIDN'T WANT TO CONTINUE THE FLT AND DEAL WITH A POSSIBLE EMER. AFTER TURNING OFF ALL ELECTRICAL SWITCHES; I MADE 3 LOW PASSES OVER THE FIELD TO MAKE SURE THE AREA WAS SUITABLE FOR LNDG. I THEN MADE A NO FLAP SOFT FIELD LNDG AFTER REVIEWING ALL CHKLIST ITEMS WITH MY STUDENT. THE FAA AND SHERIFF DEPT WERE NOTIFIED; ALONG WITH THE PROPERTY OWNER. I BELIEVE MY DECISION TO MAKE A PRECAUTIONARY LNDG WAS THE CORRECT ONE; NOT KNOWING WHAT THAT NOISE WAS. THERE WAS NO DAMAGE TO THE AIRPLANE NOR TO PROPERTY. NOBODY WAS INJURED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A C150 AND THE MAINT ACTION TAKEN WAS TO REPLACE THE STARTER RELAY AND THE VOLTAGE REGULATOR. THE RPTR ADVISED THE STARTER RELAY WAS STUCK CLOSED ENERGIZING THE STARTER CONTINUOUSLY AND THE VOLTAGE REGULATOR HAD FAILED ELECTRICALLY.