Incident Overview
On 13 October 2021 at about 0436Z, a student pilot and a flight instructor were conducting hover training exercises on the threshold of Runway 35 at Port Elizabeth International Airport in a Robinson 22 Beta II helicopter (registration ZS-RNH). The flight was conducted under Part 141 training operations. Weather conditions were clear.
Sequence of Events
According to the flight instructor, she took control to reposition the helicopter for a takeoff into the wind. After stabilizing in ground effect hover, she instructed the student to take control. Upon handing over controls, the instructor noticed the engine RPM decreasing. She told the student not to hold the throttle tightly as she retook control. The low RPM warning activated, and the helicopter began to sink. The instructor attempted to increase RPM by manipulating the throttle but was unsuccessful. She raised the collective to cushion the landing. The helicopter landed safely, and the engine was shut down. No damage occurred, and no injuries were reported.
Findings
The instructor held a valid Commercial Pilot License and Grade 3 Instructor License. Post-incident inspection revealed that the insert housing the ball in the rod end of the overtravel spring had become loose and separated from the rod end. The last mandatory periodic inspection (MPI) conducted on 25 October 2021 did not involve work on that rod end. The rod end had not been replaced since the aircraft entered the country on 27 November 2008. It was an on-condition part, not life-limited. After the incident, the rod end was replaced with a serviceable part (Part number: A933-3) in accordance with the maintenance manual, and the helicopter was tested and found serviceable.
Probable Cause
The probable cause was loss of engine power during hover exercises due to a loose insert in the rod end of the throttle control overtravel spring.