First prototype Martin XP6M-1 Seamaster, BuNo 138821, c/n XP-1, first flown July 14, 1955, disintegrates in flight at 5000 feet due to horizontal tail going to full up in control malfunction, subjecting airframe to 9 G stress as it began an outside loop, crashing into Potomac River near junction of St. Mary's River, killing four crew, pilot Navy Lieutenant Commander Utgoff, and Martin employees, Morris Bernhard, assistant pilot, Herbert Scudder, flight engineer, and H.B. Coulon, flight test engineer.