NTSB Identification: WPR11FA156
14 CFR Part 91: General Aviation
Accident occurred Tuesday, March 08, 2011 in Twin Falls, ID
Probable Cause Approval Date: 05/30/2013
Aircraft: DOUGLAS AD-4N, registration: N2088G
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The non-instrument-rated pilot was on a cross-country flight when the airplane impacted terrain. According to limited radar data, after departure the flight proceeded northwest and climbed to 6,500 feet mean sea level (msl). Only segments of the flight were visible due to the low altitude range of the radar. The flight track continued northeast to its last target at an altitude of 7,900 feet msl and about 0.25 mile from the accident site. Terrain elevation at the accident site was about 6,600 feet msl.

A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Ground scar analysis, impact signatures, and wreckage fragmentation patterns indicated that the airplane impacted terrain in a steep, nose-down attitude with high forward velocity.

Analysis of available weather information indicated that conditions likely produced restricted visibility in the area at the time of the accident. The restricted visibility conditions would have been conducive to the development of spatial disorientation.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The non-instrument-rated pilot’s encounter with localized instrument meteorological conditions, which resulted in spatial disorientation and a loss of airplane control.

Full narrative available

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