N86H

On November 13, 2023, about 0800 Pacific standard time, a Cessna 310D, N86H, was substantially damaged when it was involved in an accident near Hayden, Idaho. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot, who did not possess an airplane class multi-engine rating, reported that he had departed Coeur d'Alene Airport - Pappy Boyington Field (COE), Hayden, Idaho, with an intended destination of Nampa, Idaho. As the airplane climbed through 4,500 ft, the pilot retarded both engine throttles and noticed the left engine manifold pressure would not decrease below 21 inches. Despite his efforts to troubleshoot the difference in manifold pressure between the two engines, he was unsuccessful and the left engine was unresponsive. The pilot decided to return to COE for a precautionary landing.

While on final approach, as the airplane neared the approach end of runway 2, the airspeed decayed to 80 mph, and the pilot “pushed props to full instantly.” Subsequently, the airplane began to roll left and the stall horn sounded. The pilot reported that he applied rudder and aileron inputs before he lowered the nose until the airplane impacted terrain.

A security camera video at a nearby business captured the airplane on approach. As the airplane overflew a road located about 1,000 ft from the approach end of runway 2, the airplane pitched up and began to bank left and right. The airplane subsequently rolled to the left and pitched downward as it descended from view behind a building.

Several witnesses stated the airplane appeared slow during the approach before it pitched up, rolled left, and impacted terrain. According to a first responder who treated the pilot at the accident site, the pilot told him that “the throttle stuck.”

Postaccident examination of the wreckage revealed the fuselage and wings sustained impact damage, the empennage had partially separated from the fuselage, and the engines had separated from the engine nacelles. The engine throttle, propeller, and right mixture levers were found positioned fully forward, and the left mixture lever was found in the idle-cutoff position.

Examination the engines did not reveal any evidence of a preexisting mechanical malfunction that would have precluded normal operation.

During examination of the left engine, the installation of the left throttle control cable end had a piece of sectioned aluminum tubing wrapped around and affixed to the outside of the throttle control cable conduit and throttle cable with 2 metal worm-drive hose clamps. The entire throttle cable assembly was attached to a bracket with a rubber-cushioned support clamp, as seen in figure 1. When the throttle cable was moved by hand, the throttle cable, aluminum piece, and throttle conduit slid through the support clamp.

The maintenance manual and parts catalog showed that the throttle cable is normally housed within a conduit and attached to the bracket with a support clamp.

Figure 1: Left engine throttle cable installation (Photo courtesy of Textron Aviation, with NTSB annotations)

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.