Event CEN17LA224

Factual narrative

On June 7, 2017, about 0930 central daylight time, an experimental amateur-built SD-1A airplane, N31313, was substantially damaged during a precautionary landing at Dodge County Airport (KUNU), Juneau, Wisconsin. The private-rated pilot was not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no Federal Aviation Administration (FAA) flight plan had been filed for the flight. The local flight had departed about 0900. According to the pilot, immediately after takeoff the left wing felt "extremely heavy" and required an "exceptional amount of right aileron" to maintain level flight. The pilot was able to fly the airplane around the traffic pattern and perform a precautionary landing on runway 20. During the landing, the airplane bounced, and turned to the right. The left main landing gear collapsed, and the engine mount was substantially damaged. According to the FAA inspector who responded to the accident, the wings had been taken off the airplane prior to its purchase. The pilot purchased the airplane in April of 2016. During the reinstallation of the wings, in April of 2017, the pilot installed the wing bolts where he thought they should go. He did not perform any measurements during this reinstallation. The Airframe and Powerplant Mechanic who signed off on the condition inspection did not confirm the position of the wings and more specifically, the angle of incidence. The accident flight was the first flight after the reinstallation of the wings. Postaccident examination of the airplane revealed that the flight controls were continuous and correct; however, the angle of incidence, on the wings, was incorrect. No other anomalies were noted that would have precluded normal operation. The private pilot stated that, immediately after takeoff, the left wing felt "extremely heavy" and required "an exceptional amount of right aileron" to maintain level flight. During the precautionary landing, the airplane bounced, turned left, and the left main landing gear collapsed. The pilot had recently reinstalled the wings; however, he made no measurements during the reinstallation, and the mechanic who signed off on the condition inspection did not confirm the wings' angle of incidence. Postaccident examination of the airplane revealed that the angle of incidence was incorrect. Given this was the first flight since the reinstallation of the wings, it is likely the incorrect angle of incidence led to the pilot's difficulty controlling the airplane. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12

NTSB Findings

Hierarchical cause / factor breakdown from the FAA bulk avdata database. Each finding tagged C (Cause) or F (Factor).

• C Aircraft-Aircraft structures-Wing structure-Flight surfaces (wing)-Incorrect service/maintenance - C
• C Personnel issues-Task performance-Maintenance-Installation-Pilot - C
• C Aircraft-Aircraft handling/service-Maintenance/inspections-(general)-Incorrect service/maintenance - C
• F Personnel issues-Task performance-Inspection-Post maintenance inspection-Pilot - F
• F Personnel issues-Task performance-Inspection-Post maintenance inspection-Maintenance personnel - F