Cessna 177B N34903 accident near Elk River, Idaho

Probable cause

The pilot’s failure to maintain clearance from terrain while climbing in mountainous terrain during moderately high density altitude conditions, and conditions conducive to severe carburetor icing.

NTSB analysis

The pilot, one pilot-rated passenger, and a second passenger were conducting a cross-country flight to an airport located in a valley surrounded by mountainous terrain. The pilot had previously flown to the destination airport in a different make and model airplane. The pilot-rated passenger stated that he and the pilot discussed a plan to descend into the valley near the destination airport, overfly the runway to inspect it for hazards, continue north in the valley to climb, then return to land.

The pilot-rated passenger reported that, after conducting the runway overflight about 700 ft above the ground, all engine controls were confirmed full forward. The airplane continued flying north in the valley toward rising terrain, and the passenger identified a location on the chart that he felt would be best for the pilot to turn toward. The pilot turned the airplane earlier than the passenger had instructed him to, and the passenger alerted the pilot to the error; however, the pilot was focused on the instruments and did not respond. The pilot and the pilot-rated passenger recognized that the airplane was too low and checked to confirm that the airplane’s engine controls were full forward. The passenger encouraged the pilot to turn around and reported that the pilot slowed the airplane in an attempt to increase its rate of climb. He could not recall if the pilot attempted to turn the airplane. The airplane impacted trees and terrain about 5 nautical miles north of the airport, at an elevation of about 3,755 ft mean sea level (about 928 ft above airport elevation).

Examination of the wreckage revealed no evidence of preaccident mechanical malfunctions or failures that would have precluded normal operation; however, the extent of the engine exam was limited by postimpact fire damage. The wing flap jackscrew was found in a position consistent with the flaps being extended 30° at the time of the accident. If the flaps had been extended while the pilot attempted to climb the airplane out of the valley, the airplane’s climb performance would have been significantly reduced; however, it could not be determined when the flaps were extended relative to the impact with terrain.

The weather conditions at the time of the accident were conducive to serious carburetor icing at cruise and glide power settings at the altitudes the airplane was being operated. It is possible that carburetor icing had formed at some point during the flight, which would have degraded the airplane’s climb performance. The passenger did not report whether the pilot had applied carburetor heat, and the position of the carburetor heat control at the time of the accident could not be determined. Additionally, the calculated density altitude at the destination airport was about 3,300 ft and the density altitude at the accident site was about 4,400 ft; these conditions would also have had an adverse effect on the airplane’s climb performance.

The airplane was operated by a flying club whose policy required pilots to fly with an instructor if more than 120 days had passed since the pilot’s most recent flight. Club records indicated that the accident pilot’s most recent flight in a club airplane (the accident airplane) was 162 days before the accident. Other than the flights captured in flying club records, the pilot’s recency of experience, including his total experience in single-engine airplanes and his experience operating at mountain airports such as the accident airport, could not be determined, as his logbooks were not available for review.

Text from the NTSB. Open the NTSB docket for WPR24FA190 for the full record.