Cessna 172G N3971L accident near Provo, Utah

Probable cause

The pilot's exceedance of the airplane's critical angle of attack during a chandelle maneuver, which resulted in an aerodynamic stall and descent into trees and terrain. Contributing to the accident was the pilot’s decision to maneuver into a canyon and rising terrain for unknown reasons and his inadequate performance planning.

NTSB analysis

The commercial pilot and two pilot-rated passengers were on a cross-country flight to build flight hours. According to the surviving passenger, he believed that the pilot’s intent was to maneuver to remain outside of the Provo Municipal Airport Class D airspace, as well as the Salt Lake City Class B airspace, directly to Driggs, Idaho. Shortly after departure, the pilot maneuvered the airplane to the north, just west of Buckley Mountain in Provo, Utah, and into a canyon with rising terrain leading to Corral Mountain, which peaked at 10,100 ft mean sea level (msl). The passenger also stated that he was unable to hear any conversation between the pilot and pilot-rated passenger in the front seat, nor did he hear why the pilot chose to fly into the canyon. He also reported windy conditions in the canyon, hearing the airplane's stall warning sound after the pilot attempted a tight, right 180° turn, and seeing the airplane in a nose-high attitude before hitting trees and terrain. The airplane’s wings and fuselage were substantially damaged.

Postaccident examination of the airplane and engine did not reveal any preimpact malfunction or anomalies that would have precluded normal operation. Mechanical continuity was established throughout the rotating group, valvetrain, and accessory section as the crankshaft was manually rotated at the propeller by hand. Fuel flow and flight control continuity were confirmed.

Performance calculations showed that the pilot’s inadequate performance planning contributed to the accident. According to the Pilot’s Operating Handbook (POH), at 5,000 msl and 41° F, the airplane’s maximum climb capability was 610 ft/min at 66 kts indicated airspeed (IAS), requiring 6.5 nm to clear the advancing mountain peak. At 10,000 ft msl and 23°F, the maximum climb rate was 380 ft/min at 64 kts IAS, requiring 10 nm to clear the peak. According to the airplane’s last track data point, it would have had to climb about 3,000 ft in 2 nm to clear the advancing peak. The track data suggests they were likely climbing at approximately 610 ft/min when the pilot decided to turn the airplane around.

The surviving passenger’s statement showed that the pilot likely determined they would not clear the 10,100 ft peak and then attempted a chandelle maneuver to turn the airplane around while attempting to climb. The passenger recalled hearing the stall warning horn while the airplane was in a nose high attitude before they impacted trees. This suggests the pilot likely failed to maintain airspeed during the maneuver, which resulted in an exceedance of the airplane’s critical angle of attack and an aerodynamic stall. The steep impact angle indicated by the debris field suggests the airplane then descended into trees and terrain.

Text from the NTSB. Open the NTSB docket for WPR24FA035 for the full record.