North American T-28B N392W accident near Puyallup, Washington

Probable cause

A nose wheel shimmy during the landing roll for reasons that could not be determined from the available evidence, which led to a loss of directional control.

NTSB analysis

The pilot reported that, after touchdown the nose wheel started to shimmy, and he was not able to steer the airplane. The airplane veered to the left side of the runway as the pilot continued to try and steer away from the edge of the runway using the right brake. When the left main landing gear wheel went off the edge of the runway, he initiated the emergency procedures to retract the landing gear, shut down the engine and open the canopy.

Examination of the wreckage revealed that the nose wheel steering components and the hydraulic shimmy damper appeared to remain intact and attached to their respective mounts. The shimmy damper piston rod was actuated by hand and found to compress and extend normally. No hydraulic fluid leaks were observed on the damper. No evidence of a pre-accident mechanical failure or malfunction was revealed that would have precluded normal operation. The reason for the nose wheel shimmy could not be determined from available evidence.

Text from the NTSB. Open the NTSB docket for WPR21LA318 for the full record.