CESSNA 170 near Moab, UT — 2017-08-04

Probable cause

The pilot’s improper decision to depart in unfavorable weather conditions, which resulted in a hard, forced landing.

NTSB narrative

According to the pilot, he and his passenger were waiting in the fixed-base operator building for the storm system to pass. When the storm system appeared to have passed and the wind had calmed significantly, the pilot checked the Automated Surface Observing System and took off from runway 21. During the initial climb, the pilot observed "just beyond the end of the pavement was the obvious sign of a small microburst developing with blowing dust curling up in several different directions centered just to the right of the centerline, and it was growing spreading out quickly." The pilot was able to climb the airplane to about 400 ft before encountering wind at the departure end of the runway. He made a slight left turn to avoid power lines and performed a forced landing. The airplane landed hard and sustained substantial damage to both wings, the fuselage, and empennage. The Special METAR reported that, about the time of the accident, the wind was from 280° at 23 knots, gusting to 34 knots. The visibility was 10 statute miles with light rain. There were few clouds at 3,500 ft, and the ceiling was broken at 9,000 ft and 11,000 ft. The temperature was 84°F, and the dew point was 45°F. The altimeter setting was 30.06 inches of mercury. The peak wind was from 10° at 40 knots at 1903, and the wind shifted direction at 1910. The rain began at 1958 with trace precipitation. The density altitude was 7,164 ft. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.

Analysis

Primary failure mode

Controlled flight into terrain

First missed decision gate

Pilot could have delayed takeoff until conditions were more stable.

NTSB coding

• Windshear or thunderstorm · Enroute-climb to cruise
• Decision Making / Judgment

Evidence available

• Photos
• 4 docket documents

Docket documents4

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Pilot's Statement and Recommendationsinterview
• Density Altitudeother
• Photos (Courtesy of Pilot)photos

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