What happened
On the morning of 1 March 2025, a pilot operating a KFAB Explorer with registration ZU-WAG was conducting a local flight near Howick Aerodrome in KwaZulu-Natal. The flight, performed under visual meteorological conditions, was intended to be a routine mission involving upper air work.
While flying on the right downwind leg for Runway 34 at approximately 4,10 and 500 feet above ground level, the pilot experienced a sudden and severe loss of control. The pilot reported that the aircraft began handling erratically, similar to a heavy crosswind, despite light and variable winds. Specifically, the pilot discovered that the ailerons and flaps had ceased to function. Attempting to steer using only the rudder caused the aircraft to yaw uncontrollably. To avoid a high-risk low-altitude stall or spin, the pilot executed a controlled forced landing into a nearby cultivated maize field. The aircraft sustained substantial damage, but the pilot escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's complex construction history. The KFAB Explorer had a long and fragmented assembly process, having changed owners and builders five times since its initial kit purchase in 2013.
Upon inspecting the flight control system, investigators located the dislodged bolt on the aircraft's belly fabric. The investigation revealed that the aileron/flap mixer assembly had been constructed using wooden bushes, a direct violation of the manufacturer's Fuselage Assembly Manual. Furthermore, the bolts used in this assembly were of an incorrect, shorter length than specified, and the required self-locking nuts were absent. Because the mixer assembly is located behind the seats and covered by fabric, the defect was not visible during standard preflight inspections.
Findings
- The primary cause of the loss of control was a mechanical failure involving a bolt that became dislodged from the aileron/flap mixer assembly.
- The assembly utilized wooden bushes instead of the required components, which caused the bolt to rotate within the bush rather than the bush rotating within a sleeve. This friction eventually wore down the assembly until the bolt could no longer be secured.
- The bolts used were of a substandard length and lacked the necessary self-locking nuts mandated by the assembly manual.
- The pilot's decision to perform a forced landing in a maize field prevented a more serious accident involving a stall or spin.
Safety action
While no immediate regulatory actions were taken following this specific incident, the investigation highlights the significant risks posed by unauthorized modifications in home-built aircraft. There is a noted need for strict adherence to manufacturer assembly manuals to ensure the airworthiness of kit-built aircraft.