Narrative:

Was conducting a flight review for a private pilot with approximately 400 hours total time. The student was given a simulated emergency; which called for resetting the charging system by cycling the alternator off; then back on. Upon returning the alternator switch to the on position; we noticed an extremely large rate of charge indicated (60 amps) followed several seconds later by a complete electrical failure. After a few mins of troubleshooting; we determined that we were unable to restore power. We decided that due to the suddenness of the failure there was a chance that there was a short in the system that may pose a fire hazard; so it would be wise to divert to the nearest airport. We elected to land at ZZZ1 as it was the nearest airport. ZZZ2 was also nearby; but its runway had been closed for repaving. The next nearest non-twred airport was roughly 20 mi away. We entered the area; and circled the tower at 2500 ft MSL or 600 ft above the pattern. After several orbits around the tower we hadn't yet received a light signal; we determined that it would be best to survey the traffic flow; enter the pattern and land. We decided that if we didn't see a signal on final; we would make it a low approach to avoid a possible conflict with potential traffic on the crossing runway. As we had no visible signal; we made a low approach hoping to revive a signal at which point; we could cut the power and land on the remaining runway. We didn't get a signal; so we went around and decided that we would make the next landing whether we received a signal or not. We knew that after the low approach the tower was obviously aware of our presence whether or not we got a signal. We made our landing without incident. After debriefing with the controller; I asked if there was anything I could have done differently. He stated that he would have made the landing on the first approach as he had given us a signal; but I was unable to see it; as was my student who I had instructed to watch for a signal while I flew the aircraft. We determined that the bright lighting conditions had made the light difficult to see. If I had to do it again; I probably would have made the first landing attempt as I could have stopped short of the crossing runway negating the risk of a collision at the intersection.

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Original NASA ASRS Text

Title: FOLLOWING A COMPLETE ELECTRICAL FAILURE; PRIVATE PLT AND FLT INSTRUCTOR OF C172 MAKE A NORDO APCH AND GAR AWAITING LIGHT SIGNAL FROM TOWER. LAND SAFELY FOLLOWING SECOND TOUR OF THE TRAFFIC PATTERN.

Narrative: WAS CONDUCTING A FLT REVIEW FOR A PVT PLT WITH APPROX 400 HRS TOTAL TIME. THE STUDENT WAS GIVEN A SIMULATED EMER; WHICH CALLED FOR RESETTING THE CHARGING SYS BY CYCLING THE ALTERNATOR OFF; THEN BACK ON. UPON RETURNING THE ALTERNATOR SWITCH TO THE ON POS; WE NOTICED AN EXTREMELY LARGE RATE OF CHARGE INDICATED (60 AMPS) FOLLOWED SEVERAL SECONDS LATER BY A COMPLETE ELECTRICAL FAILURE. AFTER A FEW MINS OF TROUBLESHOOTING; WE DETERMINED THAT WE WERE UNABLE TO RESTORE PWR. WE DECIDED THAT DUE TO THE SUDDENNESS OF THE FAILURE THERE WAS A CHANCE THAT THERE WAS A SHORT IN THE SYS THAT MAY POSE A FIRE HAZARD; SO IT WOULD BE WISE TO DIVERT TO THE NEAREST ARPT. WE ELECTED TO LAND AT ZZZ1 AS IT WAS THE NEAREST ARPT. ZZZ2 WAS ALSO NEARBY; BUT ITS RWY HAD BEEN CLOSED FOR REPAVING. THE NEXT NEAREST NON-TWRED ARPT WAS ROUGHLY 20 MI AWAY. WE ENTERED THE AREA; AND CIRCLED THE TWR AT 2500 FT MSL OR 600 FT ABOVE THE PATTERN. AFTER SEVERAL ORBITS AROUND THE TWR WE HADN'T YET RECEIVED A LIGHT SIGNAL; WE DETERMINED THAT IT WOULD BE BEST TO SURVEY THE TFC FLOW; ENTER THE PATTERN AND LAND. WE DECIDED THAT IF WE DIDN'T SEE A SIGNAL ON FINAL; WE WOULD MAKE IT A LOW APCH TO AVOID A POSSIBLE CONFLICT WITH POTENTIAL TFC ON THE XING RWY. AS WE HAD NO VISIBLE SIGNAL; WE MADE A LOW APCH HOPING TO REVIVE A SIGNAL AT WHICH POINT; WE COULD CUT THE PWR AND LAND ON THE REMAINING RWY. WE DIDN'T GET A SIGNAL; SO WE WENT AROUND AND DECIDED THAT WE WOULD MAKE THE NEXT LNDG WHETHER WE RECEIVED A SIGNAL OR NOT. WE KNEW THAT AFTER THE LOW APCH THE TWR WAS OBVIOUSLY AWARE OF OUR PRESENCE WHETHER OR NOT WE GOT A SIGNAL. WE MADE OUR LNDG WITHOUT INCIDENT. AFTER DEBRIEFING WITH THE CTLR; I ASKED IF THERE WAS ANYTHING I COULD HAVE DONE DIFFERENTLY. HE STATED THAT HE WOULD HAVE MADE THE LNDG ON THE FIRST APCH AS HE HAD GIVEN US A SIGNAL; BUT I WAS UNABLE TO SEE IT; AS WAS MY STUDENT WHO I HAD INSTRUCTED TO WATCH FOR A SIGNAL WHILE I FLEW THE ACFT. WE DETERMINED THAT THE BRIGHT LIGHTING CONDITIONS HAD MADE THE LIGHT DIFFICULT TO SEE. IF I HAD TO DO IT AGAIN; I PROBABLY WOULD HAVE MADE THE FIRST LNDG ATTEMPT AS I COULD HAVE STOPPED SHORT OF THE XING RWY NEGATING THE RISK OF A COLLISION AT THE INTXN.

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.