Seaplane Collides with Bridge Abutment Following Aborted Takeoff Due to Float Damage

Casualties unknown • Williston, ND, US

A seaplane collided with a concrete railroad bridge abutment during an aborted takeoff. The incident occurred after the pilot failed to detect severe leaks in the floats caused by freezing water damage while the aircraft was stored.

What happened

The aircraft experienced a collision with a structure during the initial phase of flight operations. Specifically, the pilot initiated a takeoff taxi but was unable to achieve lift-off before running out of usable runway or waterway distance. Upon realizing the situation could not be resolved, the pilot attempted to abort the maneuver. However, the aircraft failed to decelerate sufficiently to avoid impact with a nearby railroad bridge abutment constructed of concrete.

The investigation

Post-incident examination revealed significant mechanical issues related to the aircraft's flotation devices. The pilot reported that the seaplane had been exposed to sub-freezing temperatures while stored, resulting in water remaining inside the pontoons. This water froze and expanded, causing structural compromise to the floats. The swelling ice led to severe leaks within the float compartments.

The pilot noted that the aircraft remained afloat for approximately two weeks after being left unattended because it was grounded on land rather than floating freely. When the pilot prepared the aircraft for operation again, he pumped out the water, stating that no ice remained inside at that time. Crucially, the pilot did not perform any further pre-flight inspections to verify the integrity of the floats before commencing the takeoff taxi.

Findings

The primary factor contributing to the accident was the failure of the flotation system. The severe leaks in the floats were directly caused by damage from freezing water that had swollen inside the pontoons during storage. The lack of a thorough pre-flight inspection allowed the pilot to launch the aircraft without detecting these critical defects, leading to the inability to stop or gain altitude before striking the bridge abutment.

Probable cause

The pilot's failure to inspect the floats for damage prior to flight, which resulted from water freezing inside the pontoons during storage and causing severe leaks.

Frequently asked questions

What happened in the 1984-11-08 Cessna 185C accident near Williston, ND?

A seaplane collided with a concrete railroad bridge abutment during an aborted takeoff. The incident occurred after the pilot failed to detect severe leaks in the floats caused by freezing water damage while the aircraft was stored.

What aircraft was involved and where did it happen?

The accident on 1984-11-08 involved a Cessna 185C, registration N5831T, at Williston, ND.

What was the probable cause of the accident?

The pilot's failure to inspect the floats for damage prior to flight, which resulted from water freezing inside the pontoons during storage and causing severe leaks.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X41556. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.

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