What happened
On March 16, 2019, at 17:52 UTC, a Sportcruiser UL, registration CS-UPL, operated by Aero Clube de Bragança, experienced a catastrophic structural failure while operating near Bragança Aerodrome (LPBG), Portugal. During the flight, the right main wing spar suffered a sudden and complete failure, leading to the loss of structural integrity of the aircraft.
The investigation
The GPIAAF investigation focused on the detailed examination of the wreckage, specifically the right main wing spar. The investigation analyzed the aircraft's mass and balance, the flight envelope limitations, and the impact of onboard modifications. Investigators performed theoretical calculations and physical tests to evaluate the structural loads experienced during the flight. The probe also examined the regulatory framework governing light sport aircraft in Portugal, noting that the aircraft's actual mass differed from the mass declared for licensing (which was limited to 450 kg). Additionally, the investigation reviewed the aircraft's instrumentation, noting a modification to the airspeed indicator where a red arc was added to mark the Never Exceed Speed (Vne) instead of a single point.
Findings
- The primary cause of the accident was the catastrophic structural failure of the right wing spar.
- The actual mass of the aircraft was a significant contributory factor, as the weight exceeded the declared licensing limit of 450 kg, potentially subjecting the structure to loads beyond its design capabilities during maneuvers.
- There was a discrepancy between the aircraft's design standards and the national regulatory requirements for ultralight aircraft.
- Modifications to the airspeed indicator (adding a red arc) indicated a lack of standardized training or oversight regarding instrument markings.
- The manufacturer had previously declared that the aircraft did not comply with certain initial approval requirements.