What happened
During the final stages of a flight, while the aircraft was nearing the end of its downwind leg and before initiating the base turn, it departed from level flight. The aircraft entered an increasingly steep and accelerating descent, which continued until it collided with the terrain at high speed. The impact was not survivable, resulting in fatalities. At the time the descent began, the aircraft was traveling at approximately 78 kt, which was well above the estimated stall speed of 48 kt.
The investigation
Investigators examined the wreckage, flight path data, and the aircraft's mechanical systems. The investigation found no evidence of pre-existing defects in the airframe or engine, nor any evidence of a bird or drone strike. The weather conditions at the time were clear with low winds.
Analysts considered several potential causes for the departure from level flight. A control jam was ruled out as most flight control failures would not produce such a smooth, rapid, and steep descent. The possibility of an accelerated stall was also dismissed, as the recorded data showed no significant changes in altitude or direction that would indicate the necessary banked turn or pitch-up movement.
Investigators also examined the possibility of a seat slide. While damage to the front seat indicated it had slid forward and hit a stop bolt, there was no longitudinal deceleration prior to the descent that would have caused such a movement. Furthermore, a seat slide would not explain the sustained forward pressure required to maintain the descent throughout the flight path.
Findings
- The aircraft's weight and balance were within established limits.
- The sustained forward control yoke movement was the primary driver of the descent.
- The increasing airspeed during the descent would have required the pilot to maintain or even increase the forward pressure on the controls.
- No mechanical failures or external factors, such as weather or wildlife, were identified as the cause of the descent.