'Bat' to the Future

The XP-67 helped take McDonnell Aircraft into the airplane manufacturing business

June 02, 2014 in Defense

The XP-67 had a futuristic design and curved airfoil.


Any aircraft known as “Moonbat” has to be a bit different—and the XP-67 certainly was.

Developed in the early years of World War II under a cloak of secrecy by a just-starting-out McDonnell Aircraft Corp., the XP-67 quickly picked up the monikers “Bat” and “Moonbat” because of its futuristic design and smoothly curved airfoil. But it would not be around long enough to get an official name. Only one prototype was built.

Even so, the work engineers did on the prototype provided the company with a wealth of aircraft design and manufacturing experience, opening the door for McDonnell Aircraft to enter the airplane manufacturing business. It would not be long before the McDonnell name was on some of the world’s top jet fighters.

McDonnell Aircraft, a Boeing heritage company, was an aerospace parts maker when it entered a U.S. Army Air Corps competition in 1940 for a high-speed, high-altitude, long-range interceptor that could shoot down enemy bombers and perform other missions. The military wanted an innovative and radical design that could outperform any fighter of the day.

Only a year before, in July 1939, James S. McDonnell had opened his company in St. Louis. It began primarily as a subcontractor for Boeing and Douglas, making subassemblies for their products. But McDonnell wanted to build and sell aircraft of his own design. That opportunity came with the request for proposal issued by the U.S. Army Air Corps.

The company’s initial offering to win the contract was the Model I, similar in concept to the Vultee XP-54, the Curtiss XP-55, and Northrop’s XP-56, with push propellers behind the cockpit. But the McDonnell entry finished near the bottom of some two dozen proposals from various manufacturers. McDonnell engineers continued to modify their design, and in April 1941 submitted a proposal for what would become the XP-67. A month later, the Army Air Corps awarded McDonnell Aircraft a contract to build two prototypes.

With the curved surfaces of the XP-67, the McDonnell team tried to achieve what’s known as laminar flow—the uninterrupted flow of air over an aircraft’s wings or other surfaces. The smoother the airflow, the less drag and the more efficient the aircraft.

The prototype was equipped with two turbo-supercharged Continental XI-1430-17/19s engines. It was 44 feet 9 inches (13.6 meters) long, with a 55-foot (16.8-meter) wingspan. It was designed to cruise at 210 mph (340 kilometers per hour) and a maximum speed of 405 mph (650 kilometers per hour). And it would be heavily armed, with six 37 mm cannons.

But the aircraft proved a major engineering challenge. Wind-tunnel testing uncovered problems, including engine-cooling airflow. Engineers also learned that unless manufacturing tolerances were highly controlled to produce an exceptionally smooth skin finish, the benefits of the laminar-flow airfoil would be lost.

But it was the prototype’s engines that doomed it. They were underpowered, and they overheated. During taxi testing leading up to first flight, the engines caught fire.

McDonnell’s chief test pilot E.E. Elliot took the XP-67 on its first flight on Jan. 6, 1944. Although most of the serious stability and aerodynamic problems found during flight testing were eventually resolved, the engine deficiencies were not. During a Sept. 6, 1944, test flight at Lambert Field in St. Louis, the right engine burst into flames. Elliot managed to land the XP-67 safely, but the prototype was lost. McDonnell wanted the Army Air Corps to provide the money to replace the engines with a different kind. Instead, the program was canceled and the second prototype not completed.

The XP-67 was the only piston-engine airplane McDonnell Aircraft ever produced. Jet-powered aircraft were on the way. But the XP-67 had provided the company just what it needed to become a major player in jet-fighter design and manufacturing, starting with the FH-1 Phantom. It was followed by many others, including the F2H Banshee, F3H Demon, F-101 Voodoo and F-4 Phantom.

Read more stories from the June 2014 issue of Frontiers.