A 64-year-old Arvada experimental airplane maker died during the first test flight of an aircraft as his son and a client watched Sunday morning, the Weld County coroner said.Ib Christian R. Hansen was killed during a fiery crash into a field soon after taking off from Erie Municipal Airport, said Deputy Coroner Chris Robilliard.He was flying a Cassut III M Racer, a tiny single-seat racing and acrobatic airplane, that made him famous among kit-plane enthusiasts. Hansen and his son had built the ill-fated plane for the client, Robillard said.A veteran Formula 1 airplane racer, Hansen sold kits and design plans for the Cassutt from his Arvada business, National Aeronautics Company.Witnesses told authorities something went terribly wrong minutes after he took off."They said the plane got to about 300 feet and then it started acting funny," Robillard said."He had a parachute on. But, of course, he didn't have enough altitude to get out of the plane," Robillard said.The initial identification was based on the statement's of Hansen's son, who was watching from the ground, and the client, who was following Hansen in a chase plane, Robillard said.A native of Sweden, Hansen's flying career hearkened back to the barnstorming days of early aviation."(Hansen) learned to fly in Liberia, went through and survived the revolution, (and) with only 300 hours (experience) flew a small single-engine plane across the Mediterranean Sea to visit relatives in Sweden," according to a 2009 newsletter for the Antique Airplane Association of Colorado.Hansen then came to the United States where he flew in several National Championship Air Races in Reno.The National Transportation Safety Board will investigate the cause of the crash, police said.