Narrative:

After an uneventful training flight from vny to st paula with multiple touch-and-go lndgs, we climbed up to 3500 ft MSL and started back. Just as we were recovering from a practice approach to landing stall (power off stall), at the point of power application, the engine made a loud sound and began vibrating. As we had previously practiced simulated engine failures, I had my student check: seat belts tight, fuel on both, mixture rich, carburetor heat on, magnetos left/right/both (normal drop), primer locked, and I called vny tower, informing them I had a partial power failure, was declaring an emergency and heading direct for the airport. We were about 15 NM wnw and the tower gave us a squawk code and asked if I thought I could make it to the airport. I said I would decide at the east side of the last suitable off airport landing site (chatsworth reservoir -- a dry wash which I knew had 2 dirt roads). Having lost 1000 ft in about 5 mi, I told tower I was landing in the reservoir and requested assistance in case things didn't work out. By the time I turned base for a dirt road I could barely make out, a police helicopter arrived and lit up a landing area and tree I was able to avoid before touchdown. There were a few scratches from bushes I scraped, but otherwise no injury or damage. One spark plug was found missing, replaced and the aircraft run up and inspected. After measuring available space and determining it safe to take off, I flew the plane back to vny. I may have been able to make it to vny on the night of the occurrence, but elected to land off airport.

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Original NASA ASRS Text

Title: CFI AND SPI IN AN EMER OFF ARPT LNDG DURING A NIGHT OP IN A C172. FLT ASSIST FROM POLICE ROTARY WINGED TFC TO LIGHT UP LNDG AREA.

Narrative: AFTER AN UNEVENTFUL TRAINING FLT FROM VNY TO ST PAULA WITH MULTIPLE TOUCH-AND-GO LNDGS, WE CLBED UP TO 3500 FT MSL AND STARTED BACK. JUST AS WE WERE RECOVERING FROM A PRACTICE APCH TO LNDG STALL (PWR OFF STALL), AT THE POINT OF PWR APPLICATION, THE ENG MADE A LOUD SOUND AND BEGAN VIBRATING. AS WE HAD PREVIOUSLY PRACTICED SIMULATED ENG FAILURES, I HAD MY STUDENT CHK: SEAT BELTS TIGHT, FUEL ON BOTH, MIXTURE RICH, CARB HEAT ON, MAGNETOS L/R/BOTH (NORMAL DROP), PRIMER LOCKED, AND I CALLED VNY TWR, INFORMING THEM I HAD A PARTIAL PWR FAILURE, WAS DECLARING AN EMER AND HDG DIRECT FOR THE ARPT. WE WERE ABOUT 15 NM WNW AND THE TWR GAVE US A SQUAWK CODE AND ASKED IF I THOUGHT I COULD MAKE IT TO THE ARPT. I SAID I WOULD DECIDE AT THE E SIDE OF THE LAST SUITABLE OFF ARPT LNDG SITE (CHATSWORTH RESERVOIR -- A DRY WASH WHICH I KNEW HAD 2 DIRT ROADS). HAVING LOST 1000 FT IN ABOUT 5 MI, I TOLD TWR I WAS LNDG IN THE RESERVOIR AND REQUESTED ASSISTANCE IN CASE THINGS DIDN'T WORK OUT. BY THE TIME I TURNED BASE FOR A DIRT ROAD I COULD BARELY MAKE OUT, A POLICE HELI ARRIVED AND LIT UP A LNDG AREA AND TREE I WAS ABLE TO AVOID BEFORE TOUCHDOWN. THERE WERE A FEW SCRATCHES FROM BUSHES I SCRAPED, BUT OTHERWISE NO INJURY OR DAMAGE. ONE SPARK PLUG WAS FOUND MISSING, REPLACED AND THE ACFT RUN UP AND INSPECTED. AFTER MEASURING AVAILABLE SPACE AND DETERMINING IT SAFE TO TAKE OFF, I FLEW THE PLANE BACK TO VNY. I MAY HAVE BEEN ABLE TO MAKE IT TO VNY ON THE NIGHT OF THE OCCURRENCE, BUT ELECTED TO LAND OFF ARPT.

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.