The Boeing X-36, the second in a line of state-of-the-art fighter jets, pioneered the tailless approach. Boeing Phantom Works, formerly McDonnell Douglas, joined in a collaborative effort with NASA’s Ames Research Center to come up with an aircraft called the X-36 Tailless Fighter Agility Research Aircraft, which would make a revolutionary change in the future makeup of aerial combat.
The X-36 was a 28-percent scale model of a conjectural advanced fighter that made its first flight over the Mojave Desert in May 1997. This remotely piloted aircraft flew 31 successful research missions from May to November 1997, accumulating more than 15 hours of flight time with a radically different design. Its agility was thoroughly checked out at low and high speeds; the Vehicle flew as fast as 234 mph and reached 20,200 feet in altitude.
One of the most striking features of the X-36 was that there were no regular tail surfaces. It had, instead, a canard forward of the wing, with split ailerons, and an advanced thrust-vectoring nozzle for directional control. This resultant design was expected to have improved maneuverability and survivability during combat. This stability in the aircraft was to be controlled through an advanced single-channel digital fly-by-wire control system, which was important due to its indigenous instability in both pitch and yaw axes.
The pilot on the ground remotely controlled the X-36 from a so-called virtual cockpit with a conventional, fighter-type head-up display and a moving-map presentation of the position of the aircraft. This ensured excellent situational awareness without the need for complex autonomous flight control systems.
The aircraft’s performance specifications were modest by full-scale fighter standards. It was 19 feet long, with a span of just over 10 feet, and tipped the scales at about 1,250 pounds when fully fueled. The aircraft was powered by one Williams International F112 turbofan engine, providing about 700 pounds of thrust. Though very tiny, it proved quite stable and maneuverable: it flew steadily at a 40-degree angle of attack and did 360-degree rolls at 15 15-degree angle of attack.
Further testing of the ability to adapt was done by the Air Force Research Laboratory at Wright-Patterson Air Force Base, which contracted with Boeing in 1998 to add on to the NASA tests. In December of that year, the aircraft demonstrated the RESTORE software of the AFRL, which uses neural network algorithms to adjust during flight for control-surface damage or malfunction. This approach was shown to be feasible by two successful test flights.
Tests conducted under the X-36 program delivered experience and data of inestimable value, likely to influence future designs—not least of which is Boeing’s X-45A Unmanned Combat Aerial Vehicle demonstrator. The experiences learned from this pioneering aircraft find application today in modern concepts in the creation of next-generation fighter jets, expanding potential air combat technologies.