Flight Design Gmbh CTLS N521CT accident near Racine, Wisconsin

Probable cause

The fatigue failure of the carburetor throttle control cable, which resulted in a partial loss of engine control.

NTSB analysis

During a solo cross-country flight, the student pilot returned to the departure airport after the engine began to vibrate when power was reduced. She attempted three landings that were aborted due to excessive airspeed. During the fourth landing attempt, the airplane touched down fast and bounced several times on the runway. The student pilot aborted the landing and added full engine power to climb, but the airspeed decreased. The airplane collided with a tree and a building and was destroyed by impact forces.

Postaccident examination of the airplane revealed that one of the two throttle control cables had separated from its carburetor at the control arm. The cable separation from the carburetor resulted in the carburetor’s spring-loaded throttle control moving to full throttle while the second carburetor would have been at a position selected by the cockpit throttle control. When the pilot reduced the cockpit throttle control for landing, the carburetor with the broken cable would have continued operating at maximum throttle regardless of the cockpit throttle control position, which likely resulted in the engine vibration and the excessive airspeed for landing.

Metallurgical examination of the separated control cable revealed that a tightly focused clamping force on the carburetor cable attachment bolt resulted in fatigue failure of the cable.

Text from the NTSB. Open the NTSB docket for CEN21LA222 for the full record.