SEA99GA085 · Cessna 182R

The flight was part of a U.S. Air Force-sponsored mountain flying training clinic. The planned flight route included a contour search pattern into a series of drainages along the Minam River valley, including the canyon in which the accident occurred. A trainee at the clinic who flew the accident flight route with the accident flight 'mentor' on the accident aircraft's previous flight reported that he had refused to fly into most of the drainages on the route, believing that the aircraft did not have sufficient climb capability or space to turn around in the drainages. This trainee reported that the route segment where the accident occurred was flown at 90 knots with 10 degrees of flaps. When the accident flight failed to return to base at the scheduled time and contact could not be established with the aircraft, a search was begun. The aircraft wreckage was located approximately two days later, with both occupants found fatally injured at the accident site. A chart of the planned flight route showed that at the approximate location of the crash site, a 135-degree turn was to be made to climb out, exit the training route and return to base. The accident site, located at the 5,400-foot level on sloping terrain, was approximately 1/2 mile beyond the depicted turn point (i.e., further into the canyon than planned.) Investigators found damage and impact signatures at the accident site consistent with an uncontrolled, relatively low-speed impact with the terrain, and the aircraft's flaps at 10 to 15 degrees, but no evidence of pre-impact mechanical problems with the aircraft. Based on a METAR observation taken about the estimated time the crash occurred, density altitude at La Grande, Oregon (approximately 19 nautical miles from, and 2,700 feet below the accident site) was computed to be approximately 5,000 feet.

Verbatim NTSB analysis and probable cause from the NTSB dataset