ERA19LA156

The pilot landed the seaplane into an easterly wind, then noticed that the surface wind was greater than forecast. Unable to taxi to the beaching location, he elected to return to his destination. He maneuvered the airplane into the wind and applied takeoff power. He described the takeoff run as "bumpy" and the water conditions as "rough." The pilot reported that the left float departed the airplane at rotation speed, and the airplane subsequently nosed into the water. The pilot and passengers were assisted by a nearby vessel and the airplane subsequently sank into 50 ft of water. Inclement sea and wind conditions prevented recovery of the wreckage for 52 days, and the wreckage was stored outside for an additional 13 days before recovery by the salvage company. Extensive saltwater corrosion prevented metallurgical examination of the landing gear components; however, no indication of a preexisting mechanical malfunction or failure was found.

On April 23, 2019, about 1200 eastern daylight time, a Cessna 208 amphibious airplane, N366TA, was substantially damaged during takeoff from Dry Tortugas National Park, about 58 miles west of Key West, Florida. The airline transport pilot and four passengers were not injured. The flight was operated by a private corporation as a Title 14 Code of Federal Regulations Part 91 personal flight. Day, visual meteorological conditions prevailed near the accident site, and no flight plan was filed. The flight was originating at the time of the accident. According to the pilot, he landed into an easterly wind, north of the island. After landing, he noticed that the wind was greater than forecast, and he was unable to taxi to the beaching location. He elected to return to Key West International Airport (EYW). He maneuvered the airplane into the wind and applied takeoff power. He described the takeoff run as "bumpy." As the airplane reached rotation speed, the left float departed the airplane. The airplane then nosed into the water. The pilot assisted the passengers out of the airplane and into a life raft. The airplane sank about 30 seconds later. A National Park Service (NPS) vessel responded and assisted the pilot and passengers. In the NTSB Form 6120.1, Pilot/Operator Aircraft Accident Report, the pilot described the water conditions as "rough." The wreckage came to rest in about 50 ft of sea water. Examination of underwater photos provided by the NPS revealed that both landing gear floats were separated from their mounting structure; however, they were both located with the fuselage, partially attached by cables and broken structure. The upper surfaces of both floats exhibited structural deformation and tearing. Due to inclement sea and wind conditions, the wreckage remained on the sea floor for 52 days before it was recovered. After recovery, the wreckage was stored outside for 13 more days prior to being moved to a wreckage storage facility. Because of saltwater corrosion damage, failure analysis of the landing gear structural components could not be performed. Federal Aviation Administration Handbook 8083-23, Seaplane, Skiplane, and Float/Ski Equipped Helicopter Operations, addresses water effects on operations: "Even relatively small waves and swell can complicate seaplane operations. Takeoffs on rough water can subject the floats to hard pounding as they strike consecutive wave crests. Operating on the surface in rough conditions exposes the seaplane to forces that can potentially cause damage or, in some cases, overturn the seaplane."