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A CE152 on a training flight in bur airspace, has the alternator switch accidentally placed to the off position. When the electrical problem is diagnosed, the alternator switch is found off and returned to the on position. However, with the battery drained, the electrical charge is so great that the alternator begins to fail.
| Attributes | |
| ACN | 371928 |
| Time | |
| Date | 199706 |
| Day | Wed |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : bur |
| State Reference | CA |
| Altitude | msl bound lower : 4000 msl bound upper : 4000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : bur |
| Operator | general aviation : instructional |
| Make Model Name | Cessna 152 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise other descent other other |
| Flight Plan | None |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : single pilot instruction : instructor |
| Qualification | pilot : cfi |
| Experience | flight time last 90 days : 150 flight time total : 510 flight time type : 150 |
| ASRS Report | 371928 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : single pilot instruction : trainee |
| Qualification | pilot : student |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | none taken : unable none taken : insufficient time |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
My student and I were on a training flight. After about 45 mins of flying we noticed the low voltage light was on, and discovered that the alternator was turned off. My student must have knocked it off with his knee during the flight because if the alternator had been off since takeoff, we would have lost electrical power long before that. So we turned on the alternator and continued. On our descent to bur, our home port, we lost communications and electrical power. What happened was that as we reset the alternator it began to heavily charge the battery, which set off the circuit breaker. After the circuit breaker was tripped the alternator went off-line and we were just using the battery. The battery drained relatively quickly and we lost our electrical power. I made a precautionary landing at a nearby airport (class D) since I hadn't made contact with bur tower yet. After landing we discovered the popped-out circuit breaker and got back some electrical power. Apparently, as the mechanic told me later, something went wrong with the alternator because it wasn't charging properly. We had enough power to return to bur and grounded the airplane until the problem was fixed the next day.
Original NASA ASRS Text
Title: A CE152 ON A TRAINING FLT IN BUR AIRSPACE, HAS THE ALTERNATOR SWITCH ACCIDENTALLY PLACED TO THE OFF POS. WHEN THE ELECTRICAL PROB IS DIAGNOSED, THE ALTERNATOR SWITCH IS FOUND OFF AND RETURNED TO THE ON POS. HOWEVER, WITH THE BATTERY DRAINED, THE ELECTRICAL CHARGE IS SO GREAT THAT THE ALTERNATOR BEGINS TO FAIL.
Narrative: MY STUDENT AND I WERE ON A TRAINING FLT. AFTER ABOUT 45 MINS OF FLYING WE NOTICED THE LOW VOLTAGE LIGHT WAS ON, AND DISCOVERED THAT THE ALTERNATOR WAS TURNED OFF. MY STUDENT MUST HAVE KNOCKED IT OFF WITH HIS KNEE DURING THE FLT BECAUSE IF THE ALTERNATOR HAD BEEN OFF SINCE TKOF, WE WOULD HAVE LOST ELECTRICAL PWR LONG BEFORE THAT. SO WE TURNED ON THE ALTERNATOR AND CONTINUED. ON OUR DSCNT TO BUR, OUR HOME PORT, WE LOST COMS AND ELECTRICAL PWR. WHAT HAPPENED WAS THAT AS WE RESET THE ALTERNATOR IT BEGAN TO HEAVILY CHARGE THE BATTERY, WHICH SET OFF THE CIRCUIT BREAKER. AFTER THE CIRCUIT BREAKER WAS TRIPPED THE ALTERNATOR WENT OFF-LINE AND WE WERE JUST USING THE BATTERY. THE BATTERY DRAINED RELATIVELY QUICKLY AND WE LOST OUR ELECTRICAL PWR. I MADE A PRECAUTIONARY LNDG AT A NEARBY ARPT (CLASS D) SINCE I HADN'T MADE CONTACT WITH BUR TWR YET. AFTER LNDG WE DISCOVERED THE POPPED-OUT CIRCUIT BREAKER AND GOT BACK SOME ELECTRICAL PWR. APPARENTLY, AS THE MECH TOLD ME LATER, SOMETHING WENT WRONG WITH THE ALTERNATOR BECAUSE IT WASN'T CHARGING PROPERLY. WE HAD ENOUGH PWR TO RETURN TO BUR AND GNDED THE AIRPLANE UNTIL THE PROB WAS FIXED THE NEXT DAY.
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.