What happened
On June 21, 2014, a Zlín Z 43, registration OK-FOK, was conducting a recreational flight near Liberec Airport (LKLB). Shortly after departing from runway 34, at an altitude of approximately 150 meters, the aircraft experienced a sudden engine failure. While the propeller continued to rotate, the engine lost all power.
The pilot identified a suitable landing area to the left of the flight path and executed a 12/0-degree turn to reach a meadow characterized by tall grass, approximately 0.9 meters high. During the landing roll, the aircraft's left wing struck a metal stake that was hidden within the tall vegetation. The impact caused damage to the leading edge of the center section and the lower wing skin, though the pilot and passenger escaped without injury.
The investigation
The ÚZPLN investigation focused on the cause of the engine failure and the subsequent damage during the landing. Technical examination of the M 337AK engine revealed that the mechanical drive of the LUN 5150.01 fuel injection pump had failed. Specifically, a component known as a drive arm (part no. Yc-119) had broken at the connection between the pump shaft and the camshaft.
An analysis performed by the engine manufacturer, LOM Praha, determined that the failure was due to a fatigue crack. This crack originated from non-metallic inclusions located near the surface of the component's raw material.
Findings
- The engine failure was caused by the interruption of the fuel pump drive due to the failure of the drive arm.
- The failure of the drive arm was the result of a material defect in the semi-finished product used to manufacture the component.
- The damage to the aircraft's wing during the landing roll was caused by a collision with a hidden metal stake in the tall grass.
- The pilot responded correctly to the emergency by selecting a suitable landing site and following established procedures.