What happened
On October 13, 2016, a Robinson R44 helicopter, registration PR-DYD, departed from Eldorado do Sul, RS, bound for a landing near the Hotel Pampas in Canela, RS. The aircraft was carrying one pilot and two passengers. During the approach to the intended landing site, the pilot reported a drop in rotor RPM. In an attempt to manage the situation, the pilot diverted the aircraft toward the Canela Aerodrome (SSCN).
During the diversion, the helicopter was unable to maintain controlled flight and collided with the ground approximately 100 meters from the runway. The impact resulted in substantial damage to the aircraft. The pilot sustained light injuries, one passenger was uninjured, and the second passenger suffered serious injuries.
The investigation
CENIPA investigators examined the Lycoming O-540-F1B5 engine, which was inspected by DCTA. The technical analysis found no mechanical abnormalities, failures, or defects in the engine components, cylinders, or lubrication system that could have caused a loss of power.
Investigators explored two primary hypotheses for the RPM decay. The first suggested carburetor icing, noting that the carburetor heat switch was found in the closed position and meteorological data indicated high humidity and a small dew point spread, creating conditions highly conducive to icing. The second hypothesis suggested that the pilot's flight maneuvers—specifically adjusting the cyclic and collective to enter the traffic pattern while facing a tailwind at high density altitude—may have increased drag beyond the engine's ability to maintain RPM.
Crucially, video footage from a passenger's recording showed that after the low RPM horn and caution light activated, the pilot did not immediately follow the manufacturer's emergency procedures, which mandate increasing throttle and lowering the collective to recover RPM.
Findings
- Improper use of flight controls: The pilot's maneuvers during the approach contributed to the loss of rotor RPM.
- Pilot judgment: The pilot failed to execute the required emergency recovery procedures (lowering the collective) immediately upon hearing the low RPM warning, which was the decisive factor in the severity of the crash.