What happened
On October 15, 2013, a BK 117 C-2 helicopter, registration PR-EKN, was performing a landing at a soccer field in Itapipoca, Ceará, Brazil. The aircraft had departed from Fortaleza to transport one pilot and eight passengers. During the transition from the approach to the landing, the downwash from the main rotor disturbed the loose sand and dust on the field, creating a dense cloud of debris. This phenomenon, known as brownout, caused a momentary loss of visual ground references. As the pilot continued the landing without clear visual cues, the aircraft maintained an excessive nose-up attitude, resulting in the tail rotor guard and the left side of the vertical stabilizer striking the ground. All nine occupants escaped the incident without injury, and the aircraft sustained only light damage.
The investigation
CENIPA's investigation focused on the environmental conditions and the pilot's decision-making process. Investigators established that while the pilot had experience operating in this specific location with different, lower-powered helicopters, this was his first operation at the site using the BK 117 C-2. The investigation examined the aircraft's technical status, finding that the airworthiness certificate was valid, the weight and balance were within limits, and all maintenance logs were up to be date. The investigation also analyzed the impact of the brownout phenomenon on situational awareness and the pilot's ability to maintain directional control near the ground.
Findings
- Brownout phenomenon: The primary cause was the loss of visual references due to dust and sand kicked up by the rotor wash, which significantly reduced the crew's situational awareness.
- Inadequate pilot judgment: The pilot failed to account for how the higher engine power and greater downwash of the BK 117 C-2 compared to his previous aircraft would increase the risk of a brownout at this specific location.
- Limited type experience: The pilot had relatively low experience with this specific model, having flown only approximately 43 hours in the BK 117 C-2 at the time of the accident.
- Environmental factors: The presence of loose soil at the landing site directly contributed to the formation of the dust cloud.