National Parks Service Cessna 185E accident

The pilot departed on a U.S. Government flight for the Department of Interior, National Parks Service, with three park rangers, in a wheel/ski equipped airplane. The airplane was operated as a VFR, on-demand air taxi flight to the Denali National Park base camp, located at 7,200 feet msl on the Kahiltna glacier. The base camp is where the three rangers were to begin mountain patrol operations on Mt. McKinley, Alaska. Variable weather conditions with low ceilings near the base camp made landing at the base camp problematic throughout the day. When the pilot departed for the base camp, he opened a VFR flight plan, and was advised that an AIRMET for mountain obscuration and turbulence were current for the area. About 45 minutes after departure, the pilot talked via radio to another airplane pilot at the Kahiltna base camp, who advised the upper portion of the glacier was closed due to low clouds. The accident pilot commented that the weather had closed the lower portion of the glacier, and he was diverting toward the west, toward another glacier drainage. A ranger on-board the accident airplane contacted his ranger station by a hand-held radio and stated the flight was returning. The accident airplane did not return to its base, and was reported overdue. The wreckage was located the following day, scattered over about 1/2 mile. Evidence indicated the airplane broke apart in-flight. The left wing, left wing lift strut, the left landing gear strut, the left door and windshield, were located on the upper portion of a steep hillside. The engine struck the ground below the left wing, separating the propeller, and then tumbled downhill. The fuselage came to rest about 1/4 mile below the left wing, and was consumed by a postcrash fire. The airplane's wing spars, and each horizontal stabilizer had all negative bending signatures. The flap handle was found extended to 20 degrees. The airplane manufacturer does not publish any negative structural load factors for a flaps down configuration. A review of meteorological data revealed an occluded front with convective activity that progressed northward toward the accident area, accompanied by heavy rain and hail. The front was positioned near the accident area when the airplane was diverting away from the mountain. The pilot was the chief pilot for the operator. The director of operations for the company has the responsibility of operational control for the operator.

Verbatim NTSB analysis and probable cause from the NTSB dataset