VFR into IMC · NTSB WPR11FA156
DOUGLAS AD-4N — Twin Falls, ID
| Date | March 8, 2011 |
| Location | Twin Falls, ID |
| Aircraft | DOUGLAS AD-4N |
| Purpose of flight | Personal |
| Conditions | Day · Instrument Meteorological Cond |
| Phase / occurrence | Enroute VFR encounter with IMC |
| Pilot age | 55 |
| Pilot total time | 1,826 hrs · Experienced |
| Time in type | Unknown |
| Fatalities | 2 |
Probable cause
NTSB findings
- Personnel issues-Psychological-Perception/orientation/illusio-Spatial disorientation-Pilot - C
- Personnel issues-Task performance-Use of equip/info-Aircraft control-Pilot - C
- Environmental issues-Conditions/weather/phenomena-Ceiling/visibility/precip-Clouds-Not specified
- Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Pitch control-Not specified - C
What happened
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.