Mystery of Missing Bolt in Cessna 172 Unsolved

It was a soft field landing by the pilot of Cessna 172 on a grass runway in William, Georgia.

The initial touchdown was perfect on the main wheels in a nose-up attitude. The pilot lowered the nose wheels as the aircraft started to slow down.

A significant shimmy was felt as the nose wheel touched the runway.

Shimmy damper failure, pilot thought, so to minimize the weight on the nose wheel he applied back pressure on the control wheel.

The nose was lowered again as the aircraft continue to decelerate. This time vibration was more prominent. The pilot repeated his action, raising the nose wheel as much he could.

The speed of the Cessna 172 aircraft reached a point where it was not possible to keep the nose wheel off the ground.

But than the nose wheel separated from the airplane as it touched down again.

When the Cessna 172 aircraft was examined it revealed that a bolt and nut and associated washer that connects nose wheel steering arms assembly with the upper torque assembly was missing, and it was not found.

According to pilot, during the pre-flight inspection he had seen the bolt. How the bolt separated from the nose wheel could not be determined.

According to the aircraft manufacturer, without this bolt, the shock strut tube assembly will caster freely on the lower shock strut assembly of the nose wheel. It will cause significant shimmy and because of this reason there can be significant reduction in nose wheel steering control.

When the torque assembly is not attached, the effect of shimmy dampener will be reduced significantly, and may also be nonexistent.

When the logbooks of aircraft maintenance were analyzed, the nose wheel had not undergone any maintenance recently. Analysis of the fractured surfaces of the broken nose wheel revealed failure of the part due to overload forces during landing.

No problem was found before the impact that could hamper safe operation of the Cessna 172 aircraft.

The reason why and how the bolt got detached from the nose wheel still remain unsolved.

Probable cause: The nose wheel separated after landing. The bolt that attach nose wheel steering arm assembly with the upper torque assembly was found missing. How and when the bolt separated remains unsolved.

NTSB Identification: ERA15LA160

This aircraft accident report was published on the website of the National Transportation Safety Board. This article is written for educational purpose and to make pilots and student pilots aware of what all could happen in flying and to learn from the misfortunes of others.

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