WPR19LA141 · Flight Design CTLS Undesignat

The pilot departed on a local flight with a passenger to a nearby lake. As the airplane reached the lake, the pilot perceived a sudden increase in his indicated airspeed. He responded by retarding the throttle to the idle position then advancing the throttle back to full power, at which point he observed a warning light for an engine control unit “Lane B” failure and a message on the primary flight display (PFD), “Rotax: Land Aircraft.” The pilot immediately returned to the airport and performed a rapid descent when he realized that he was high for the approach. He was unsuccessful in reducing his airspeed while over the first half of the runway and decided to execute a go-around maneuver as the airplane passed midfield. An eyewitness reported that when he observed the airplane attempt the go-around at the end of the runway, the engine did not “initially” sound like it reached full power. The airplane subsequently stalled and impacted terrain. According to the engine manufacturer, the “Lane B” failure would not have affected engine performance, and recorded engine and aircraft parameters indicated the engine continued to run and respond to throttle position changes normally throughout the flight. The data showed the unexplained increase in airspeed occurred following a change in the throttle position and the resultant increase in engine rpm. The recorded data are consistent with the pilot’s account of events leading up to the point the go-around was initiated. The data indicated that the throttle was moved to 95% about 20 seconds before the airplane stalled. The engine rpm increased, but the airspeed decreased from 52 knots to 35 knots and the angle of attack increased to 99% during that time. A postaccident examination of the airplane revealed no preimpact mechanical failures or anomalies that could have precluded normal flight. The accident is consistent with the pilot failing to monitor the airplane’s performance during the return to the airport, which resulted in the need to go around due to being too fast to land on the remaining runway. During the go-around maneuver, the pilot did not advance the throttle to 100%, which resulted in the airspeed decreasing and angle of attack increasing until the airplane stalled.

Verbatim NTSB analysis and probable cause from the NTSB dataset