Bell 212HP N911KW accident near Weed, California

Probable cause

The pilot’s failure to maintain altitude during an approach to a lake. Contributing to the accident was the pilot’s failure to release the full water bucket as the helicopter was settling, which reduced the helicopter’s out-of-ground-effect performance.

NTSB analysis

The flight was on an approach to a lake to retrieve water for a water bucket drop operation. During the approach, the instruments scanned normal, and the radar altimeter was set to 200 ft above ground level to provide a buffer between the bucket and terrain. When the helicopter crossed the shoreline, the pilot visually confirmed that the 100-ft long line and bucket were slightly trailing the helicopter and had not dipped in the water. Shortly afterward, he felt a “sudden onset of a significant vibration.” The pilot aborted the water retrieval and noticed that helicopter lost altitude. He applied forward cyclic and raised the collective, but the helicopter continued to descend. The pilot realized that he would not be able to fly out of the descent, so he decided to make a forced water landing. The pilot did not jettison the long line and bucket. After he leveled the helicopter and the skids touched down on the water, he made another attempt to take off, but the helicopter settled into the lake. The pilot reduced both throttle settings to idle in preparation to ditch the helicopter and applied right cyclic as the main rotors slowed. The helicopter rolled right, and the main rotor blades struck the water, which resulted in substantial damage to the fuselage, rotor, and drive systems.

Postaccident examination of the engine revealed no preimpact mechanical anomalies. The airframe examination revealed an out-of-tolerance condition of both pylon damper rod end bearings that likely caused the vibration reported by the pilot. It is likely that, after the lateral vibration, the pilot allowed the helicopter to descend while he tried to determine the source of the vibration. As the helicopter settled into the lake, the bucket filled with water. The resulting increased weight, combined with the pilot’s failure to release the water bucket, decreased the helicopter’s out-of-ground-effect performance.

Text from the NTSB. Open the NTSB docket for WPR21LA268 for the full record.