Cessna 172 N4108F accident near Mckenzie Bridge, Oregon

Probable cause

The pilot's delayed climb and misjudgment of the airplane’s performance and the runway distance needed to clear obstacles at the end of the runway, which resulted in a collision with trees and subsequent impact with terrain. Contributing to the accident was the pilot's insufficient experience landing and taking off at mountain airports.

NTSB analysis

After flying over mountainous terrain, the pilot attempted an approach into an airport with a 2,600-ft-long grass runway bordered by tall trees. Witnesses near the center of the runway described the airplane flying east over the runway about 5 ft above ground level when it came into their view. One witness stated that he could not hear any noise as the airplane came into view but that its wings rocked; he said he heard the engine power increasing and that the airplane may have started to climb when it reached his center of vision. A second witness stated that she heard the engine running and that the airplane began a slow climb and then disappeared from her view behind trees at a slightly higher altitude. About 15 minutes later, they saw smoke coming from the accident site. Impact signatures indicated that the airplane contacted treetops during the climbout; it then impacted the ground and came to rest inverted about 615 ft east of the departure end of the runway.

The witness statements support that the airplane was developing power when it began the climb. The propeller signatures were inconsistent with the engine producing power at the time of the impact; however, it is unknown if the pilot reduced power before impact. Rotational continuity of the engine and valve train could not be achieved because the engine crankcase and accessories were damaged by postcrash fire and the oil sump was destroyed. Although the crankshaft, camshaft, connecting rods, and piston were mostly damaged by postcrash fire, an examination of these components and the interior engine case revealed no indications of catastrophic engine failure.

Calculations based on takeoff and climb performance charts from the pilot's operating handbook showed that the airplane required a total takeoff distance of about 1,330 ft to clear a 50-ft obstacle at the end of the runway. However, the chart did not account for the 134 ft of rising terrain and 120-ft-tall trees at the end of the runway or the ambient temperature of about 98°F. The calculated density altitude on the day of the accident was 4,481 ft, which would have reduced the airplane's climb performance. Given these conditions, it is unlikely that the airplane was capable of clearing the rising terrain and tall trees at the end of the runway on the day of the accident.

Review of the pilot's logbook showed that he had not performed landings or takeoffs at mountain airports. Thus, he had insufficient experience to attempt a landing or takeoff at a short mountain airport runway bordered by trees on a day with a density altitude over 2,800 ft higher than the airport elevation. While it is unknown if the pilot had intended to perform a full-stop landing, a touch-and-go maneuver, or overfly the runway at a low altitude, he had selected a runway that was not recommended for takeoffs but was recommended for landing. The pilot likely misjudged the runway length needed and the airplane's performance when he chose to begin a climb about midfield in high density altitude conditions with rising terrain and 120-ft obstacles at the end of the runway.

Text from the NTSB. Open the NTSB docket for WPR19FA244 for the full record.