WPR14FA132 · Cessna 120

The owner/pilot regularly made roundtrip flights between his home airport and another airport located about 25 miles to the northwest. A north-south mountain range, with peaks ranging between 8,300 and 9,400 ft above mean sea level (msl), separated the two airports. Due to the limited climb capability of the airplane, on each leg, the pilot would climb parallel to the mountain range until he gained sufficient altitude and then turn to cross the range. Thus, the pilot's normal westbound (outbound) crossing segment was situated well north of his eastbound (return) crossing segment. The pilot typically crossed the mountain range at an altitude of 8,500 to 9,000 ft msl, which provided limited terrain clearance.

After successfully completing the outbound trip in the morning, the pilot departed on the 30-minute return trip in the late afternoon likely about 1 hour before sunset. The pilot did not return home, and the airplane was reported missing on the following day about the same time that another pilot who was overflying the mountain range spotted the wreckage. The accident site was located at an elevation of about 6,200 ft msl about 7 miles north of the pilot's normal return trip crossing location, likely indicating that the pilot had turned early to cross the mountain range. Examination of the accident site indicated that the airplane impacted a hillside in a steep descent with a nose-down attitude. The airplane heading at the time of impact was about opposite of that required for the intended flight.

The impact trajectory and attitude, airplane heading, and accident location are consistent with the airplane exceeding the critical angle of attack and entering an aerodynamic stall during the pilot's execution of a course reversal turn. It is unknown why the pilot attempted to cross the mountain range at a different location than the one he normally used. It is possible that he turned early in order to cross before nightfall. Because he made the attempt to cross significantly closer to the departure airport than normal, there was a reduced amount of time and distance for the airplane to climb to an altitude sufficient to clear the mountain range.

Propeller damage signatures indicated that the engine was developing power at the time of impact. Except for the engine primer handle, which was found in the unlocked and partially extended position, no pre-impact mechanical anomalies or deficiencies were noted with the engine or airframe. If the engine primer was unlocked during the flight, the engine would likely have been running rich, possibly resulting in reduced power and climb capability. However, the investigation was unable to determine whether the engine primer was unlocked during the flight or became unlocked during the accident sequence. A pilot report from earlier in the day indicated turbulence and downdrafts in the vicinity, which, if present during the accident flight, could have reduced the airplane's ability to clear rising terrain.

The premature eastbound turn, possibly in combination with reduced climb capability due to reduced engine power, downdrafts, or both, placed the airplane in a situation that prevented a successful crossing and that the pilot failed to respond to until it was too late to escape. The pilot's decision to reverse course may have been delayed because he had made many previous successful crossings and had a habit of crossing the range with limited terrain clearance. The delayed decision resulted in the pilot attempting the course-reversal turn without sufficient airplane performance capability to successfully complete it.

Verbatim NTSB analysis and probable cause from the NTSB dataset