LAX03IA252

The commercial helicopter pilot reported that while in cruise flight, the helicopter developed a severe vibration. The vibration was so extreme that he was not able to read any of his flight instruments. He declared an emergency, started a slow descent, and made a run-on landing to a dirt field. A post-incident inspection revealed that the right forward transmission lift link had failed at the lower rod end assembly. The failure point was in the threaded area of the rod end. The total time on the failed part (p/n 222-331-626-105) was 3,890.8 hours total time since new. The lift link assembly was the original part installed on the incident helicopter. The lift link assembly was shipped to the National Transportation Safety Board, Materials Laboratory and forwarded to Bell Helicopters for further analysis. It was determined that the link fracture was a result of fatigue in a thread root of the lower elastometric rod end bearing housing. No material discrepancies or deficiencies were found in the rod end bearing housing.

History of flight

On July 30, 2003, at 1056 Pacific daylight time, a Bell 222, N29KH, made an emergency off airport landing near Salinas, California. California Shock Trauma Air Rescue (CALSTAR) was operating the helicopter under the provisions of 14 CFR Part 135. The commercial pilot, and 3 passengers were not injured; the helicopter sustained no damage. The cross-country air medical transport flight departed Hollister, California, about 1050 en route to Salinas Municipal Airport (SNS) Salinas, California. Day visual meteorological conditions prevailed; a visual flight rules (VFR) flight plan had been filed. The primary wreckage was at 36 degrees 41 minutes north latitude and 121 degrees 34 minutes west longitude.

The pilot reported that while in cruise, during an aero medical transport flight, he experienced a severe vibration. The vibration was so extreme that he was not able to read any of his flight instruments. The pilot was in communication with SNS tower, he declared an emergency and started a slow decent. Upon slowing the helicopter down the vibration decreased. The pilot elected to make a run-on landing to a dirt field 2 ½ miles northeast of SNS.

An inspection of the helicopter after landing revealed that the right forward lift link had failed at the lower rod end assembly. The failure point was in the treaded area of the rod end. The rod end part number was 222-331-626-105 and the serial number BW434. The total time on the failed part was 3,890.8 hours total time since new. The lift link assembly was the original part installed on the incident helicopter.

A review of the maintenance records indicated that during the last 118.7 hours the helicopter had been tracked and balanced on 3 separate occasions. Included in the same 118.7 hour duration was a cracked outboard trim tab on the main rotor blade, a cracked frame dampener and the frame dampener support.

The last track and balance of the main rotor system was completed 2.1 flight hours prior to the lift link assembly failing.

The lift link assembly was shipped to the National Transportation Safety Board, Materials Laboratory and forwarded to Bell Helicopters for further analysis.

The results of the examination were as follows:

The fracturing of the link was a result of fatigue originating in a thread root of the lower elastometric rod end bearing housing. No material discrepancies or deficiencies were found in the rod end bearing housing.

The elastomer in the elastomeric bearing on the fractured end had extruded and/or worn away from the metal shims allowing the shims to move out of position. Metal-to-metal wear had occurred between the center inner member and the shims. The wear and missing elastomer allowed the bearing center to shift 0.3 inch (8mm) toward the lower end of the link.

Inspection revealed the elastomer in the upper elastomeric bearing had some deterioration. However, the upper elastomeric bearing was considered serviceable when inspected to the requirements of the Model 222 component Repair and Overhaul (CR&O).