Incident Details
On May 29, 2011, at 1508 eastern daylight time, a Robinson R22 Mariner, registration N8313E, conducted a precautionary landing into a driveway near Redding, Connecticut. The certified private pilot and passenger were not injured, and the helicopter was not damaged. The flight was operated under 14 CFR Part 91 as a personal flight in visual meteorological conditions. No flight plan was filed. The flight originated from Kingston-Ulster Airport (20N) in Kingston, New York, around 1330, with an intended destination of Brookhaven Airport (HWV) in Shirley, New York.
Pilot Actions
The pilot reported being at approximately 2,700 feet over Danbury Municipal Airport (DXR) in Danbury, Connecticut, when he heard a slight noise and felt a vibration. He immediately performed a precautionary landing in a driveway near a residence in Redding, about 4 miles southeast of the airport. After landing, he exited the helicopter while it was still running to investigate the vibration source. Upon inspecting the tail rotor section, he heard a "click, click, click" noise and discovered that the tail rotor teeter hinge bolt was sheared and exhibited rotational scoring.
Inspection Findings
A post-incident inspection by a Federal Aviation Administration (FAA) inspector revealed that one part of the tail rotor teeter hinge bolt could be rotated by hand. Photographs taken on the day of the incident showed no torque stripes on the bolt. Examination of the bolt by the NTSB Materials Laboratory found corrosion and wear on the bolt shank between the spacers, as well as wear on the opposed end faces of the spacers. Magnified examinations of the fracture revealed traces and arrest lines consistent with fatigue progression through approximately half of the shank diameter.
Maintenance History
According to FAA records, the helicopter was manufactured in 1994. The most recent annual inspection was completed on May 1, 2011, in accordance with the Robinson R22 service manual checklist, at which time the helicopter had accumulated approximately 2,200 total flight hours. The most recent maintenance overhaul of the tail rotor section was about five years prior to the incident. The pilot stated that the tail rotor teeter hinge bolt was replaced about 800 flight hours before the incident.
Preflight Procedures
The pilot reported that he received a biennial flight review in August 2010. During that review, the flight instructor indicated a problem with the tail rotor teeter hinge bolt. The pilot asked two mechanics to examine the bolt, and both stated it looked normal. The pilot noted that he did not usually use a checklist during preflight inspections, but kept one in the helicopter for reference. He checked "all screws for any suspicious items that might affect the flight" but sometimes could not determine what parts "should be tight and what should be loose." On the day of the incident, he performed a normal preflight inspection and found everything "normal." The Robinson R22 Preflight Checklist states that when checking the teeter bearing bolt, verify it "does not rotate."