Narrative:

Climbing to 2500 ft MSL and heading northwest; I was bound for the far north end of the lake to practice maneuvers in preparation for my private pilot check ride. As I began to set up in preparation for the practice; my aircraft suddenly entered a 20-30 degree right bank; without my input. I overcame the controls and returned the wings to level; at which time the aircraft again began to bank right. I overcame the input again and immediately began looking for an emergency landing spot as I felt the aircraft could become uncontrollable at any moment. The controls continued to attempt turn the aircraft to the right; however; I called mayday; mayday on ZZZ unicom; stated that I was over the north end of the lake and was going down. I saw 2 possible landing sites; one of which was a road surrounded by trees; and the other a short street that appeared to have few if any homes or obstructions. I made the decision to land on the street; began a descent while controling the aircraft; and landed without incident. I taxied the aircraft into a grassy area off the road; shut down according to the checklist; and exited the aircraft. All utilities in the area were underground and there was only 1 home on the street. I used the 1 homeowner's phone to call the FBO; as I had no cell phone service in this remote location. I notified them I had landed with no damage to the aircraft and they began notifying everyone necessary. After the operations manager arrived he stated he felt that I had inadvertently engaged the autoplt. I checked the autoplt switches and both were in the 'off' position. An instructor pilot arrived; after clearance from the FAA representative; disabled the autoplt by pulling the circuit breaker out and flew the aircraft back to ZZZ. In retrospect; I wish I had been familiar with the autoplt operation and what might happen if it were inadvertently engaged. I have never flown the aircraft with the autoplt engaged and was only minimally aware the aircraft even had one. I am certainly aware of what can happen now and I know where the circuit breaker is located if needed. The WX at this time was clear; visibility was excellent and no damage occurred to the aircraft or property; and no injury to any person. Supplemental information from acn 770804: since the occurrence; I have personally changed my training procedures to include; early on in training; the use and disabling of autoplts installed in any aircraft I conduct training in.

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Original NASA ASRS Text

Title: INEXPERIENCED STUDENT PLT; UNFAMILIAR WITH THE AUTOPLT IN THE C172; MAKES OFF FIELD LANDING WHEN IT ENGAGES; LEADING HIM TO CONCLUDE HE WAS EXPERIENCING A MALFUNCTION OF THE FLT CONTROLS.

Narrative: CLBING TO 2500 FT MSL AND HDG NW; I WAS BOUND FOR THE FAR N END OF THE LAKE TO PRACTICE MANEUVERS IN PREPARATION FOR MY PVT PLT CHK RIDE. AS I BEGAN TO SET UP IN PREPARATION FOR THE PRACTICE; MY ACFT SUDDENLY ENTERED A 20-30 DEG R BANK; WITHOUT MY INPUT. I OVERCAME THE CTLS AND RETURNED THE WINGS TO LEVEL; AT WHICH TIME THE ACFT AGAIN BEGAN TO BANK R. I OVERCAME THE INPUT AGAIN AND IMMEDIATELY BEGAN LOOKING FOR AN EMER LNDG SPOT AS I FELT THE ACFT COULD BECOME UNCTLABLE AT ANY MOMENT. THE CTLS CONTINUED TO ATTEMPT TURN THE ACFT TO THE R; HOWEVER; I CALLED MAYDAY; MAYDAY ON ZZZ UNICOM; STATED THAT I WAS OVER THE N END OF THE LAKE AND WAS GOING DOWN. I SAW 2 POSSIBLE LNDG SITES; ONE OF WHICH WAS A ROAD SURROUNDED BY TREES; AND THE OTHER A SHORT STREET THAT APPEARED TO HAVE FEW IF ANY HOMES OR OBSTRUCTIONS. I MADE THE DECISION TO LAND ON THE STREET; BEGAN A DSCNT WHILE CTLING THE ACFT; AND LANDED WITHOUT INCIDENT. I TAXIED THE ACFT INTO A GRASSY AREA OFF THE ROAD; SHUT DOWN ACCORDING TO THE CHKLIST; AND EXITED THE ACFT. ALL UTILITIES IN THE AREA WERE UNDERGROUND AND THERE WAS ONLY 1 HOME ON THE STREET. I USED THE 1 HOMEOWNER'S PHONE TO CALL THE FBO; AS I HAD NO CELL PHONE SVC IN THIS REMOTE LOCATION. I NOTIFIED THEM I HAD LANDED WITH NO DAMAGE TO THE ACFT AND THEY BEGAN NOTIFYING EVERYONE NECESSARY. AFTER THE OPS MGR ARRIVED HE STATED HE FELT THAT I HAD INADVERTENTLY ENGAGED THE AUTOPLT. I CHKED THE AUTOPLT SWITCHES AND BOTH WERE IN THE 'OFF' POS. AN INSTRUCTOR PLT ARRIVED; AFTER CLRNC FROM THE FAA REPRESENTATIVE; DISABLED THE AUTOPLT BY PULLING THE CIRCUIT BREAKER OUT AND FLEW THE ACFT BACK TO ZZZ. IN RETROSPECT; I WISH I HAD BEEN FAMILIAR WITH THE AUTOPLT OP AND WHAT MIGHT HAPPEN IF IT WERE INADVERTENTLY ENGAGED. I HAVE NEVER FLOWN THE ACFT WITH THE AUTOPLT ENGAGED AND WAS ONLY MINIMALLY AWARE THE ACFT EVEN HAD ONE. I AM CERTAINLY AWARE OF WHAT CAN HAPPEN NOW AND I KNOW WHERE THE CIRCUIT BREAKER IS LOCATED IF NEEDED. THE WX AT THIS TIME WAS CLR; VISIBILITY WAS EXCELLENT AND NO DAMAGE OCCURRED TO THE ACFT OR PROPERTY; AND NO INJURY TO ANY PERSON. SUPPLEMENTAL INFO FROM ACN 770804: SINCE THE OCCURRENCE; I HAVE PERSONALLY CHANGED MY TRAINING PROCS TO INCLUDE; EARLY ON IN TRAINING; THE USE AND DISABLING OF AUTOPLTS INSTALLED IN ANY ACFT I CONDUCT TRAINING IN.

Data retrieved from NASA's ASRS site as of May 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.