What happened
On July 30, 2022, a Skandinavisk Aero Industri KZ VII, registration OY-EPS, was performing local VFR maneuvers at Nordborg Airport (EKNB) when it entered an unrecoverable descent. The aircraft, which was undergoing a flight test program following a major restoration, was being operated by two pilots. During a series of touch-and-go landings, the aircraft experienced a high flare that resulted in the wheels briefly leaving the runway.
In an attempt to prevent the aircraft from settling into a high-nose, low-power state at low altitude, the pilot in the left seat increased engine power to full throttle. This sudden surge in power was perceived by the pilot in the right seat as a physical "tap" on the control stick. Drawing on a habit developed during previous flights in tandem-seat aircraft, the right-seat pilot interpreted this movement as a signal that control had been transferred to him. Consequently, he removed his hands from the controls without a verbal confirmation of the transfer.
As the aircraft began to bank sharply toward a nearby wooded area, the pilot in the left seat attempted to intervene. However, when the pilot in the right seat reached for the right-side joystick handle to correct the bank, the handle slipped out of its mounting on the Y-shaped control column. This mechanical failure left both pilots without effective means to steer the aircraft, leading to a collision with the top of an oak tree in a nearby hedgerow and a subsequent impact with the ground.
The investigation
The investigation by AIB Denmark focused on the sequence of events leading to the loss of control and the physical state of the aircraft's control column. Investigators examined the flight logs, the aircraft's maintenance history, and the cockpit ergonomics.
Technical examination of the wreckage revealed that the right-side joystick handle was not secured to the Y-junction of the control column with a bolt or similar fastening mechanism. While the aircraft's flight manual noted that the right-side controls could be removed, it contained no instructions regarding the securing of the handle to the Y-junction. Furthermore, because the flight was not intended to be operated from the right seat, the pilots had not performed a specific check of the right-side control's attachment during their pre-flight inspections.
Findings
- The primary cause of the accident was a lack of effective control by both pilots due to a combination of a control input, a breakdown in cockpit communication, and the use of an inappropriate handover procedure learned from different aircraft types.
- The pilot in the right seat was unable to prevent the accident because the right-side joystick handle was not secured to the control column, causing it to detach during an emergency maneuver.
- The pilots failed to establish a specific verbal procedure for the transfer of control for this specific flight, and the pilot in the left seat did not verbally confirm the transfer of control ("your controls").
- The aircraft's high-power setting and full flap configuration limited the ability to climb over obstacles once the bank angle increased.