Accident Overview
On November 13, 2023, at about 0800 Pacific standard time, a Cessna 310D (registration N86H) was substantially damaged in an accident near Hayden, Idaho. The pilot sustained minor injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight Sequence
The pilot, who did not possess an airplane class multi-engine rating, departed from Coeur d'Alene Airport - Pappy Boyington Field (COE) in Hayden, Idaho, with the intended destination of Nampa, Idaho. While climbing through 4,500 feet, the pilot retarded both engine throttles and observed that the left engine manifold pressure would not decrease below 21 inches of mercury. Despite troubleshooting efforts, the left engine remained unresponsive. The pilot decided to return to COE for a precautionary landing.
During the final approach to runway 2, as the airplane neared the approach end, the airspeed decayed to 80 mph. The pilot reported pushing the propeller controls to full instantly. Subsequently, the airplane began to roll to the left and the stall horn activated. The pilot applied rudder and aileron inputs and lowered the nose before the airplane impacted terrain.
Witness and Video Evidence
A security camera video from a nearby business captured the airplane on approach. As it overflew a road about 1,000 feet from the approach end of runway 2, the airplane pitched up and began to bank left and right. It then rolled left and pitched downward as it descended from view behind a building. Several witnesses reported that the airplane appeared slow during the approach before pitching up, rolling left, and impacting terrain. A first responder who treated the pilot at the accident site stated that the pilot told him “the throttle stuck.”
Wreckage Examination
Postaccident examination revealed that the fuselage and wings sustained impact damage, the empennage had partially separated from the fuselage, and both engines had separated from their nacelles. The engine throttle, propeller, and right mixture levers were found fully forward, while the left mixture lever was in the idle-cutoff position. Examination of both engines found no evidence of a preexisting mechanical malfunction that would have precluded normal operation.
During inspection of the left engine, the throttle control cable end had a piece of sectioned aluminum tubing wrapped around and affixed to the outside of the cable conduit and cable with two metal worm-drive hose clamps. The entire throttle cable assembly was attached to a bracket with a rubber-cushioned support clamp. When moved by hand, the throttle cable, aluminum piece, and conduit slid through the support clamp. The maintenance manual and parts catalog indicate that the throttle cable is normally housed within a conduit and attached to the bracket with a support clamp. The airplane’s maintenance records were not made available for review, and it was not determined when the repair on the throttle cable had been performed.