What happened
On July 30, 2020, an AS-350 B2 helicopter, registration PR-MJX, was performing an emergency mission to provide medical assistance to a victim of cardiac arrest in the Administrative Region of Vicente Pires, Brasília. The aircraft, operated by the Corpo de Bombeiros Militar do Distrito Federal (CBMDF), was attempting to land in an unregistered area—a college parking lot.
During the final approach, the helicopter's main rotor blades collided with the facade of a building located to the left of the landing zone. The impact caused substantial damage to the aircraft and also damaged a nearby vehicle and a window of an adjacent building. The five crew members on board sustained minor injuries.
The investigation
CENIPA's investigation focused on the environmental conditions and the landing site characteristics. The investigation established that the landing area, a concrete parking lot, was covered in a significant layer of dust, sand, and gravel due to a prolonged drought in the region.
Investigators examined the aircraft's maintenance records, finding the airframe and engine logbooks up to date and no mechanical failures contributing to the crash. Meteorological reports confirmed VFR conditions, but noted that the downwash from the rotors was likely to disturb the loose surface material. The investigation also reviewed the crew's flight experience and the operator's Standard Operating Procedures (SOP) regarding landings in unregistered areas.
Findings
- The primary cause of the accident was a brownout phenomenon, where the downwash from the main rotor blades caused a large cloud of dust and debris to rise, obscuring the pilot's vision.
- The landing site was surrounded by obstacles, including fences, bleachers, and buildings, which prevented the effective dispersion of the raised dust.
- The prolonged dry season had left the concrete surface of the parking lot covered in loose, fine-grained material, increasing the risk of visual degradation.
- The crew's assessment of the landing site failed to sufficiently account for the potential for non-visual flight conditions caused by the dust suspension.