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Casualties unknown

Seaplane Collides with Water After Encountering Boat Wake (N6668L)

Sidney, ME, US

On July 21, 1985, a Lake LA-4 (registration N6668L) was involved in an aviation accident near Sidney, ME. Investigators recorded the probable cause as: The pilot's failure to maintain adequate clearance from a boat wake while operating at low altitude, which resulted in loss of control and subsequent collision with the water. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-20Data APIEditorial standards

A seaplane encountered a boat wake while flying low, porpoised multiple times, and collided with the water nose-down at approximately 45 knots. The left pontoon detached during impact.

What happened

The pilot reported that the aircraft was maintaining step flight at an indicated airspeed of approximately 45 knots when it encountered a wake generated by a nearby boat. Following the encounter, the aircraft began to fly erratically and porpoised two or three times before colliding with the water surface. The impact occurred in an estimated nose-down attitude of 10 to 15 degrees, with engine power set to idle.

During the collision sequence, the left pontoon became detached from the airframe. The aircraft immediately began taking on water and sank approximately four minutes after the initial impact, according to pilot accounts.

Findings

  • Airspeed: Indicated 45 knots at time of incident
  • Attitude: Estimated 10 to 15 degrees nose-down upon water contact
  • Power Setting: Engine power was off during the event
  • Damage: Left pontoon detached; aircraft filled with water and sank
  • Contributing Factor: Encounter with a boat wake while flying low over water

Probable cause

The pilot's failure to maintain adequate clearance from a boat wake while operating at low altitude, which resulted in loss of control and subsequent collision with the water.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X37274. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.