Cessna T337G N337KN accident near Gold Hill, Colorado

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack while maneuvering with one engine inoperative, which resulted in an aerodynamic stall/spin and impact with terrain.

NTSB analysis

The pilot and passengers departed on a local sightseeing flight in the twin-engine, centerline-thrust airplane. ADS-B data showed the airplane depart toward mountainous terrain in the general direction of the planned tour route. The airplane’s climb rate appeared appropriate and consistent with normal operation until the airplane leveled off about 11 minutes later, at an altitude about 9,500 ft mean sea level (msl) about 3,000 ft below a typical cruise altitude for that flight. A short time later, the airplane slowed and entered a left descending turn, reaching a descent rate of almost 6,000 ft per minute (fpm).

Witnesses near the accident site reported observing the airplane flying low overhead. The right wing rose abruptly, dropped, and the left wing rose as the airplane entered a nose-down attitude and began to “corkscrew.” One witness stated that the engine noise stopped as the airplane entered the descent. The witness also stated that, up until that point, the engine(s) sounded like they were “struggling.”

The airplane impacted wooded terrain about 7,800 ft msl and came to rest upright. The ground scars, impact signatures observed on the trees, and wreckage signatures indicated that the airplane impacted terrain in a nose-low attitude, consistent with a spin. A post-impact fire consumed most of the airframe. Both the front and rear engines sustained extensive thermal and impact damage, and the propeller for the rear engine was found in the feathered position.

A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation; however, the scope of the examination was limited due to the extensive thermal and impact damage, and a mechanical issue could not be ruled out. The feathered position of the rear engine’s propeller suggests that it is likely that the engine had lost power or been shut down; however, the reason could not be determined based on the available information.

It is possible that the pilot was attempting to return to the airport when the accident occurred. Given the high density altitude conditions present at the time of the accident, the airplane’s single-engine climb performance would have been marginal. Additionally, although the pilot’s logbook was not available for review, he was recently hired by the accident operator and had accumulated about 3.5 total hours in the accident airplane since he was hired. According to the operator, the pilot’s training in the accident airplane did not include an engine shutdown; instead, a loss of engine power was simulated by reducing the throttle.

The circumstances of the accident are consistent with the pilot’s exceedance of the airplane’s critical angle of attack while maneuvering with one engine inoperative, which resulted in an aerodynamic stall/spin and loss of control. Due to the extensive thermal and impact damage, the investigation was not able to determine why the rear engine was not operating.

Text from the NTSB. Open the NTSB docket for WPR22FA256 for the full record.