Accident Overview
On July 19, 2016, at approximately 1030 Alaska daylight time, a tailwheel-equipped Cessna 185 (registration N85CF) experienced a separation of its left main wheel and axle from the landing gear leg during the landing rollout at an unimproved landing strip located about 20 miles northwest of Illiamna, Alaska. The airplane, operated by the commercial pilot under 14 Code of Federal Regulations Part 91 as a visual flight rules business flight, sustained substantial damage. The pilot and three passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed.
Pilot and Passenger Statements
In an interview with the National Transportation Safety Board investigator-in-charge on July 20, 2016, the pilot reported that after a normal landing on a flat, level ridgeline, the left wheel and axle separated during the rollout. The gear leg then dug into the gravel surface, causing a sudden left turn and subsequent ground loop. The left wing, left aileron, and elevator struck the ground, resulting in substantial damage. The left wheel assembly came to rest about 25 feet from the airplane.
A passenger stated during an interview that she did not perceive the landing as hard and did not feel the airplane hit anything during the rollout. The pilot noted on the NTSB Form 6120.1 that the landing was normal and he did not feel any impact. However, he mentioned that earlier in the week, while operating on large tundra tires, he inadvertently applied a side load to the landing gear during a landing on a hard-surfaced runway with a strong crosswind.
Metallurgical Examination
An NTSB metallurgist examined the left axle connecting bolts, which were identified as heavy duty and appropriate for installation per the Cessna 185 Illustrated Parts Catalog. Magnified examinations of the fracture surfaces revealed features and deformation patterns consistent with bending overstress separations. No indications of preexisting cracking or corrosion were observed.
Weather Conditions
The closest weather reporting facility, Illiamna Airport (about 20 miles southeast of the accident site), reported at 0953 the following conditions: wind from 320° at 10 knots gusting to 18 knots; clear sky; visibility 10 statute miles; temperature 63°F; dew point 48°F; barometric pressure 30.19 inHg.