Incident Description
On June 23, 2010, at approximately 1425 eastern daylight time, an experimental, amateur-built SeaWind 3000 amphibian airplane, registration N79DJ, was substantially damaged during descent near Sanibel Island, Florida. The aircraft was operated by an airline transport pilot (ATP) under 14 Code of Federal Regulations Part 91 for a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from Key West International Airport (EYW) at about 1345, with a planned destination of Sarasota/Bradenton International Airport (SRQ).
The pilot reported that while descending through 6,000 feet mean sea level over the Gulf of Mexico, approximately 40 miles west of Southwest Florida International Airport (RSW), a vibration developed in the elevator control. Reducing engine power decreased the vibration, but increasing power caused it to intensify, eventually requiring the pilot to reduce power to a level where altitude could not be maintained. The pilot then executed a forced landing to water about 200 feet offshore of Sanibel Island. The landing was hard, resulting in damage to the engine nacelle and empennage.
Postaccident Examination
A Federal Aviation Administration inspector examined the airplane and found that a portion of the elevator had separated in-flight. The pilot attributed the initial vibration to a separated elevator balance horn, with increasing vibration leading to the separation of the second balance horn, then three-fourths of the elevator, causing the airplane to shake. The separated elevator and balance horns were not recovered. The remaining one-fourth of the elevator was sent to the NTSB Materials Laboratory for metallurgical examination. The examination revealed that the adhesive in areas where skin was missing had remnants of carbon fibers still bonded, consistent with an overload failure rather than adhesive failure. The bottom surface of the elevator trim tab was missing its entire skin panel, consistent with the elevator failing in the downward direction as outboard portions departed.
Aircraft Details
The four-seat, high-wing amphibian, serial number 48, was equipped with a Lycoming IO-540-EXP, 400-horsepower engine. The pilot, who was also the owner/builder, completed construction on June 4, 2010, and the airplane had accrued 43 total hours since completion. The empennage was manufactured by Precision Design. The pilot reported that Precision Design offered an empennage with increased performance at lower cost than the SeaWind-manufactured version. The owner of Precision Design stated that the company had not manufactured parts for SeaWinds in about 10 years prior to the accident and had produced about 20 SeaWind empennage sections in total. The owner of SeaWind noted that Precision Design stopped producing empennage sections around 2002 and that the Precision Design empennage was 49 percent larger than the SeaWind version, adding significant surface area and increased gust loads without compensating engineering. The SeaWind owner believed about 10 Precision Design empennage sections were on the market and was aware of three (including the accident airplane) that experienced flutter. He also noted that the maximum recommended engine for the airplane was 300 horsepower, while the accident airplane had a 400-horsepower engine.
Meteorological Information
Southwest Florida International Airport (RSW) was about 20 miles east of Sanibel Island. The reported weather at RSW at 1453 included wind from 060 degrees at 14 knots gusting to 19 knots, visibility 10 miles, few clouds at 5,000 feet, temperature 35°C, dew point 22°C, and altimeter 30.05 inches of mercury. Review of radar data showed the accident airplane traveling at a groundspeed of approximately 200 knots in the vicinity of convective activity.