A 54-year-old pilot was killed when a plane he had built himself crashed south of the Vineyard on Saturday afternoon. Timothy L. Crawford of Idaho Falls, Ida., was piloting a single-engined, two-seater Long-EZ aircraft from Barnstable Municipal Airport when for no known reason the plane crashed about four miles south of Long Point, West Tisbury.

State police Sgt. Robert Moore said a call came into the communication center that another pilot had observed floating debris south of the Island at approximately 3 p.m. "The plane was floating in the water, full of Styrofoam," the sergeant said.

U.S. Coast Guard were dispatched. Joining in the search was state environmental police Sgt. William L. Searle. The county sheriff's department also assisted.

"Bill Searle was the first on the scene and he found the gentleman dead, floating in the water," Sergeant Moore said. An empty life raft was reportedly floating nearby.

The body was transported to North Wharf in Edgartown.

There was a light breeze. Waters south of the Vineyard were relatively calm at the time of the accident, and visibility was clear.

Sergeant Moore said his office is in direct contact with the National Transportation Safety Board, which is leading the investigation into the accident. The Massachusetts Aeronautics Commission is also involved. "The plane was pretty much intact when we got there," the sergeant said. "The plane is still buoyed off South Beach," he said. Efforts are under way to have the plane salvaged. "There might be some flight data on the plane to help determine the cause of the crash."

Yesterday, Sergeant Moore said his office had heard reports that pieces of the plane were washing ashore.

An autopsy has been scheduled for today at the state medical examiner's office in Pocasset.

State trooper Jeffrey Stone from the district attorney's office is working on the investigation.

Mr. Crawford, the pilot, was a respected scientist with the National Oceanic and Atmospheric Administration. He was director of the field research division with the NOAA Air Resources Laboratory in Idaho Falls, married and the father of two daughters. He was known as an experienced pilot and an expert on the weather. According to his resume, posted on the Internet, he was an instrument-rated pilot with 3,000 flight hours. He owned two planes and was an avid aircraft builder, having constructed five. He was also a published scientist and a respected researcher on the changes being brought by global warming.

The Long-EZ airplane is a composite fiberglass/foam plane that weighs 950 pounds and is run by a 160-horsepower engine driving a pusher prop. Mr. Crawford had posted information on his airplane on the Internet, noting that it contained highly sophisticated air measuring gear including sensors for water vapor, carbon dioxide and dew point sensors.

"When fully instrumented, the rear seat is occupied with a computer and instruments. With only the pilot aboard to fly the airplane and collect data, the system is highly automated," he wrote.

In an article about his airplane on the Internet, Mr. Crawford wrote: "Although single-engined, the airplane has many important safety features. . . . The forward lifting surface (called a canard) prevents stall and spin. A ballistic parachute can be deployed in 0.9 seconds for emergency recovery of the pilot, airplane and instrumentation. Should the emergency occur over water, the solid foam-core airframe floats."

Sergeant Searle said yesterday that credit for the search goes to four civilian pilots working ou of Katama Airpark and one from Martha's Vineyard Airport. "They were able to quickly identify the site, location of the debris and the missing pilot," he said.

The 120-foot research vessel Cape Henlopen from the University of Delaware arrived on the scene and assisted in the search. They were able to identify the location of what was sighted from above by the assisting planes.

The plane was floating right side up. The raft was deployed right next to the plane and was upside down, Mr. Searle said.