LAX08LA005

After descending to 750 feet above ground level (agl) while approaching an airport, the engine power output reduced to idle. The pilot followed unsuccessful emergency procedures to recover engine power. He then completed a forced landing in rough terrain, which resulted in substantial damage to the fuselage and wing. Investigators examined the engine but observed no preimpact malfunctions that would have precluded normal operation.

On October 6, 2007, at 1649 mountain standard time, a Cessna 150D, N4570U, collided with rough terrain during a forced landing near Strawberry, Arizona. The forced landing was precipitated by a loss of engine power during cruise. The airplane was operated by a private individual for a cross-country personal flight under the provisions of 14 CFR Part 91 of the Federal Aviation Regulations. The airplane sustained substantial damage. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at Payson, Arizona, at 1630, and was destined for Pine, Arizona.

In a written statement, the pilot reported that the takeoff was normal, and he conducted the climb at 72 miles per hour (mph). He leveled the airplane at 7,500 feet mean sea level (msl), and did not reduce power. Exhaust temperature was normal. Ten miles northwest of Payson, the pilot turned on carburetor heat, reduced power, and began a shallow left turn while descending to a private airstrip near Pine. After leveling at 750 feet above ground level (agl), he turned off the carburetor heat and began a shallow 360-degree right turn while maintaining 75 mph.

Upon resuming level flight, the engine unexpectedly reduced power to 1,150 revolutions per minute (rpm), but continued to run smoothly. The pilot increased both throttle and mixture with no results. He then verified that both magnetos were on, and cycled the fuel valve. Neither produced any results. He set the elevator trim for best glide and began evaluating headwind and landing options. Further emergency engine procedures failed to produce power gain.

At 100 feet agl, the pilot extended full flaps, opened the cabin door, flew the airplane just above stall speed, and prepared for a forced landing in rough terrain. At 3-5 feet agl, he fully leaned the mixture, closed the throttle, and flared until the airplane stalled at 3 feet agl. The wings were level at ground contact.

Post-flight examination revealed that both wing tips were crumpled upwards, and the landing gear was extensively damaged. The tail section and engine cowling were both heavily dented.

On December 12, 2007, an investigator from Teledyne Continental Motors (TCM) examined the engine under the supervision of a National Transportation Safety Board investigator. The investigator noted that a visual inspection revealed no preimpact mechanical damage to the engine case. All lines were connected. The propeller assembly remained connected to the engine via the crankshaft. Both propeller blade tips were twisted with chordwise scratching evident at the tips; from the tip to about 3 feet inboard. No other damage was evident on the propeller blades.

The TCM investigator removed the top spark plugs. The spark plugs were heavily sooted. Manual rotation of the propeller blades produced drive train mechanical continuity throughout the engine, and produced thumb compression in firing order.

The oil pump gear was intact, but separated from its housing. It rotated freely by hand with no binding evident. The carburetor separated from its attachment point, and could not be functionally tested. However, the throttle, mixture, and propeller cables remained attached. The throttle, mixture, and propeller levers were moved inside the cockpit, with no binding evident, and investigators observed corresponding movement of each lever at the carburetor attachment points. Investigators disassembled the carburetor; the bowl was dry, and they noted no discrepancies.

Investigators observed no preimpact malfunctions that would have precluded normal operation.