N92MJRoberts John G SUPER BEAR · 1993

On June 20, 2015, about 0755 Pacific daylight time, a Roberts Super Bear, N92MJ, experienced a loss of engine power during the approach to land at La Grande/Union county Airport (LGD), La Grande, Oregon. The student pilot sustained minor injuries, and the flight instructor was not injured. The airplane sustained substantial damage to the firewall and fuselage structure. The airplane was registered to and operated by the student pilot under the provisions of 14 code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight originated from LGD at about 0715.

The student pilot reported that the purpose of the flight was to practice touch and go landings. After the third landing, the airplane lifted off the ground; shortly thereafter the engine surged and lost power followed by a second surge and loss of power. The flight instructor took control of the airplane and they impacted the ground at the end of the runway.

During a postaccident examination of the engine, overseen by a Federal Aviation Administration inspector, the spark plugs were removed and exhibited no abnormal oil residue or evidence of fouling. The cylinders were boroscoped and no unusual wear was observed on the cylinder walls, pistons, and piston rings. The propeller was rotated by hand and all four cylinders exhibited thumb compression. While the engine was being rotated, the magneto with the impulse coupling produced spark at the ignition leads. The other magneto did not have an impulse coupling and could not be tested.

The fuel tanks were boroscoped and no contaminants were observed. The main fuel screen was removed and found clean. The air filter to the carburetor was examined and it was not blocked. The carburetor was removed and further examined. The finger screen was removed and contained no contaminants. The venturi was tight and was clear of debris. The drain plug from the carburetor was removed and no fuel was observed within the bowl. The throttle and mixture linkages moved freely from stop to stop. The drain plug and fuel supply line were reconnected to the carburetor. Fuel was added to the left and right fuel tanks individually; the fuel flowed freely from each tank, through the fuel selector and into the carburetor.