What happened
On November 12, 1999, a Piper PA 22-150, registered ZS-DID, was conducting a solo cross-country training flight departing from Grahamstown. Approximately one hour and 40 minutes into the flight, the student pilot detected an unusual vibration through the control column. Upon inspection from the cockpit, the pilot observed that the starboard stabilizer/elevator control surface was fluttering.
As the flight progressed, the intensity of the vibration increased. After roughly ten minutes of managing the unstable controls, the pilot determined that a continued flight was unsafe and initiated a forced landing. The aircraft came down in a heavily vegetated area within the Orchards District of Albany, approximately 10 nautical miles northeast of Grahamstown. While the aircraft sustained substantial damage due to the terrain, there were no injuries reported.
The investigation
The investigation focused on the mechanical failure of the elevator control surface. Investigators utilized electron microscope testing on the failed component to determine the nature of the structural compromise. This analysis was used to establish the physical mechanism that led to the flutter.
Findings
- The primary cause of the flight instability was the failure of the elevator control surface.
- The investigation concluded that the failure was likely due to an overload failure.
- Microscopic examination indicated that the control surface had struck or impacted an object, which directly led to the structural failure and subsequent fluttering.