Amateur-built Glasair II SFT N952W accident near Forest, Virginia

Probable cause

The installation of a non-failsafe coupler that resulted in the separation of the throttle cable from the throttle arm and a subsequent partial loss of engine power.

NTSB analysis

During initial climb on a crosswind leg of the airport traffic pattern, the experimental amateur-built airplane exhibited a partial loss of engine power. The pilot attempted to glide the airplane to an upwind landing, but overshot the runway and landed in a field, resulting in substantial damage.

Postaccident examination of the wreckage revealed that a threaded coupler between the throttle rod end and throttle cable had loosened and disconnected the cable from the throttle arm. This allowed the arm to move toward idle position. Use of a throttle cable coupler was likely a custom installation, and was not provided by the kit manufacturer. The installation provided a means to adjust the throttle cable; however, it also proved to be a single point of failure as there was no means to secure the coupler, such as a cotter pin or safety wire.

Text from the NTSB. Open the NTSB docket for ERA25LA011 for the full record.