CEN22FA151 · Robinson Helicopter R44

**This report was modified on April 29, 2024. Please see the docket for the original report.**

According to the operator, the lesson syllabus for the instructional helicopter flight included emergency procedures, equipment malfunctions, and vortex ring state (VRS) recognition and recovery. Flight track data, video, and a witness statement indicated that the helicopter was maneuvering at slow speeds about 2,000 ft mean sea level in the minute before the accident and shortly before a 4-ft section of the tailboom separated and the helicopter entered a spiraling descent to the ground. The witness stated that the helicopter appeared to hover when the tail boom separated.

The 4-ft section of the tailboom which included the tail rotor came to rest on the roof of a commercial building about 300 ft from the main wreckage. Examination of the helicopter revealed that the main rotor elastomeric teeter stops were severely damaged, and the brackets were bent. The main rotor drive shaft displayed scuff marks where the teeter stops were damaged, consistent with extreme teetering of the main rotor. Main rotor blade contact marks and dents were consistent with the main rotor blades contacting the tailboom in flight, resulting in its separation. Examination of the helicopter and engine did not reveal any preaccident anomalies with the helicopter that would have precluded normal operation. The syllabus for the accident flight included an introduction to VRS and given the flight track information and witness statement, it is possible that the flight instructor was demonstrating, or the pilot receiving instruction was performing, a VRS entry/recovery when the accident occurred. However, since detailed information regarding the helicopter’s flight control and engine parameters was not available, the exact maneuver being conducted at the time of the tail boom separation could not be determined. The main rotor’s contact with the tailboom is consistent with improper flight control inputs or low rotor RPM. Toxicology testing of the flight instructor revealed the presence of bupropion, an antidepressant medication. Based on the available information, it could not be determined whether effects of the flight instructor’s bupropion use or an associated condition contributed to the accident. Toxicological testing of the pilot receiving instruction revealed the presence of cetirizine, an antihistamine. It is unlikely that the effects of this medication contributed to the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset