Diamond Aircraft Ind Inc DA 40 N840DS accident near Lake Park, Georgia

Probable cause

The noninstrument-rated pilot’s improper decision to depart in dark, night marginal visual flight rules conditions, which resulted in his spatial disorientation and subsequent loss of airplane control.

NTSB analysis

Before departing at night for his destination airport, the noninstrument-rated pilot received a weather briefing, which advised of marginal visual flight rules (MVFR) conditions. The briefing also included an airmen's meteorological information advisory for developing instrument flight rules conditions due to low ceilings and mist. Shortly after takeoff, the pilot contacted a radar approach controller for visual flight rules flight-following services, and he was advised to squawk a beacon code, but, before the approach controller was able to identify the airplane on the radar, the pilot radioed, "I'm in trouble." Shortly after, both radar and radio contact were lost. Review of radar data indicated that the airplane's climb rate was steady until the airplane reached an altitude of about 2,100 ft msl. The airplane then began descending rapidly while turning right until it impacted terrain.

Examination of the wreckage did not reveal any evidence of preimpact failures or malfunctions of the engine or primary flight controls. However, examination of the elevator trim system revealed that the elevator trim cable was disconnected from the trim control wheel in the cockpit and that it had pulled out of a swaged rod end (bolt), which displayed a longitudinal crack on the outer surface of the swage.

Examination of the fracture surface revealed that the fracture occurred due to overstress. The examinations were not able to determine if the cable pulled out of the fitting during the accident sequence or if it was a pre-existing condition. Regardless, review of the elevator pitch control system revealed that, even if the elevator trim cable had disconnected in flight, it should not have led to an uncontrollable situation due to its redundant design.

At the time of the accident, both the sun and the moon were more than 15 degrees below the horizon. Further, warm, moist southerly wind ahead of an approaching cold front was producing variable clouds, and a band of low stratiform clouds with their tops near 4,000 ft existed over the area. Operating in MVFR conditions increases a pilot's workload and stress level because navigation becomes more difficult and reduces the margin of safety. As a result of the increased workload and stress level and the pilot's minimal simulated instrument time (about 7 hours); his minimal night experience (about 3 hours); the dark, night MVFR conditions; restricted visibility, including a lack of ambient light; and the sustained right turn and descent, it is likely the pilot experienced spatial disorientation and subsequently lost control of the airplane.

Text from the NTSB. Open the NTSB docket for ERA13FA083 for the full record.