In 1952, the U.S. Navy wanted a nuclear-capable attack aircraft to replace the AD Skyraider. Douglas Aircraft chief engineer Ed Heinemann was alarmed by the trend toward ever-larger, ever-heavier jets. His team proposed an aircraft with a maximum takeoff weight of 14,250 pounds—barely half the Navy's notional limit. The Navy signed the contract on June 12, 1952. The XA4D-1, Bureau Number 137812, flew for the first time on June 22, 1954. The "Skyhawk" was so small that its 27-foot wingspan eliminated the need for folding wings—a first for a carrier jet since the SBD Dauntless. Its delta wing contained integral fuel tanks. Its landing gear was designed to drop by gravity in a hydraulic failure. In 1955, an A4D-2 set a world speed record of 695.163 mph over a 500-kilometer course. Pilots called it the "Scooter," the "Tinker Toy," and most affectionately, "Heinemann's Hot Rod." The Skyhawk entered fleet service in September 1956 and became the Navy's primary light attack aircraft for the next three decades. In Vietnam, it was the most numerous attack type on carrier decks. Nearly 3,000 were built, and they served in Argentina, Australia, Israel, Kuwait, New Zealand, and Singapore. Vice Admiral James Stockdale and Senator John McCain both flew it—and both were shot down in it. The A-4 proved that a combat aircraft did not need to be large to be lethal. It needed to be right.