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WPR13CA018

2012-10-18 · Twin Bridges, Montana, United States · None · 1 aircraft · Status: Completed

Airport K7S1

Aircraft involved

Probable cause & findings

The airplane builder’s failure to rig the flight controls correctly, which resulted in a loss of control after takeoff.

Factual narrative

The pilot attempted to perform a full-flap soft-field takeoff in the experimental light sport airplane. The pilot had flown about 16 hours in the accident airplane in the 4 months since he purchased it from the airplane builder; however, this was his first attempted full-flap soft-field takeoff in this airplane. As the airplane left the ground, it rolled abruptly to the right. The right wing tip struck the ground, and the airplane cartwheeled, coming to rest pointing in the opposite direction of intended travel. The right wing and fuselage were substantially damaged. Postaccident examination revealed that the airplane's flaperons were misrigged and that the resultant difference in flaperon deflection was more extreme in the full flap position. In the full flap position with a full left control deflection input, the right flaperon moved 3 degrees more and the left flaperon 3 degrees less than they would have if properly rigged. The asymmetric nature of the flaperon deflections induced an adverse yaw to the right despite the pilot's corrective control inputs. Examination of the airplane maintenance logbook revealed that the airplane builder performed the most recent annual airworthiness inspection 4 1/2 months before the accident. The pilot attempted to perform a full-flap soft-field takeoff in the experimental light sport airplane. The pilot had flown about 16 hours in the accident airplane in the 4 months since he purchased it from the airplane builder; however, this was his first attempt at full-flap soft-field takeoff in this airplane. As the airplane left the ground, it rolled abruptly to the right. The right wing tip struck the ground, and the airplane cartwheeled, coming to rest pointing in the opposite direction of intended travel. The right wing and fuselage were substantially damaged. Postaccident examination revealed that the airplane's flaperons were misrigged and that the resultant difference in flaperon deflection was more extreme in the full flap position. In the full flap position with a full left control deflection input, the right flaperon moved 3 degrees more and the left flaperon 3 degrees less than they would have if properly rigged. The asymmetric nature of the flaperon deflections induced an adverse yaw to the right despite the pilot's corrective control inputs. Examination of the airplane maintenance logbook revealed that the airplane builder performed the most recent annual airworthiness inspection 4 1/2 months before the accident. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12

NTSB Findings

FAA avdata. C = Cause, F = Factor.

  • C Aircraft-Aircraft systems-Flight control system-Aileron control system-Incorrect service/maintenance - C
  • C Aircraft-Aircraft systems-Flight control system-TE flap actuator-Incorrect service/maintenance - C
  • C Personnel issues-Task performance-Maintenance-Scheduled/routine maintenance-Owner/builder - C

Verbatim from NTSB's published report. Source file NTSB_2012_WPR13CA018.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

Related research

Matched on aircraft type or causal vocabulary (loss of control, maintenance). All research papers