Aircraft: RV-6A. Injuries: 1 Fatal. Location: West Jordan, Utah. Aircraft damage: Destroyed.
What reportedly happened: The accident happened at the end of a four-hour flight. The pilot, who had an estimated 810 hours in the RV-6A, transmitted his intentions to join the traffic pattern at the airport. A short time later, an indiscernible distress transmission was made over the frequency and the RV-6A was seen spiraling to the ground.
GPS data recovered from the airplane revealed that it was traveling at an appropriate airspeed for entry into the downwind leg of the traffic pattern with a sufficient margin above the stall speed to maintain flight. It then made an abrupt left turn, resulting in a spiral dive, which progressed into a spin without sufficient altitude to recover.
The post-accident examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
The pilot’s abrupt maneuver during the approach was consistent with an avoidance maneuver. The maneuver, which was calculated to be a 65° angle of bank to the left, most likely placed the airplane into an accelerated stall condition, which developed into a spin. In addition, the airplane was loaded toward its aft center of gravity limit, which could have increased its pitch sensitivity, thereby exacerbating the turn. A successful recovery from an unintentional stall-spin at pattern altitude is extremely unlikely.
Radar data revealed that the airplane passed through a cluster of primary targets (with no altitude information) at the time of the accident. Such primary targets could potentially be radar system anomalies, thermal air currents, or bird reflections. According to a bird mitigation specialist, large birds, or flocks of smaller birds, are often present at that time of year, and such birds typically fly circling patterns in thermal air currents at traffic pattern altitudes.
Probable cause: The pilot’s execution of an abrupt maneuver, likely to avoid birds, which resulted in a stall and spin.
NTSB Identification: WPR11FA450
This September 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.