Before F-47, There Was X-36! Why Did Boeing Abandon Its Tailless Aircraft That Was Co-Developed With NASA?

President Donald Trump awarded Boeing the Next-Generation Air Dominance (NGAD) contract, marking the biggest milestone in US aviation in over twenty years. The sixth-generation crewed fighter dubbed the ‘F-47,’ is expected to revolutionize air combat.

This development upset the other contender, Lockheed Martin, which also recently withdrew from the US Navy’s F/A-XX next-generation fighter jet contract. Following the announcement, the company’s shares were on a downward spiral. 

The contract’s award to Boeing comes at a time when the company needed it the most. The company struggled the past year due to financial difficulties, technical issues, and cost overruns on fixed-price contracts.

In 2023, it even announced that it would shut down the F/A-18E/F Super Hornet line and partially redirect its operations to advanced combat jets, an indirect reference to the NGAD fighter program.

The NGAD contract was an existential need for the company. Boeing needed a significant profitable franchise to compensate for losses on some earlier projects. This contract would also guarantee that Boeing will retain the engineering expertise required to compete with its rivals. 

The triumph is seen as a ‘comeback’ for Boeing. Earlier, Boeing’s X-32 demonstrator had to concede to Lockheed Martin’s X-35 in the Joint Strike Fighter contest, which led to the development of the F-35 Lightning II.

Boeing will develop the F-47, a crewed sixth-generation air superiority fighter at the center of the NGAD program. The aircraft will operate alongside drones or CCAs in a manned-unmanned teaming (MUMT) configuration. It will eventually replace the Lockheed Martin F-22 Raptor.

File Image: F-47: Artist’s Rendering.

Former US Air Force Secretary Frank Kendall earlier described the initiative, saying, “NGAD must be more than just the next crewed fighter jet. It’s a program that will include a crewed platform teamed with much less expensive autonomous un-crewed combat aircraft, employing a distributed, tailorable mix of sensors, weapons, and other mission equipment operating as a team or formation.”

While the F-47 continues to make headlines and boost Boeing’s shares, it is worth remembering that another tailless aircraft that Boeing developed in collaboration with NASA—the X-36—is currently in US Air Force museums.

What Was The Boeing X-36?

Boeing X-36 Tailless Fighter Agility Research Aircraft was an American stealthy sub-scale prototype jet built sans the conventional empennage (tail assembly) that most traditional aircraft of the time had.

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Plan view of the X-36

The Boeing Phantom Works (the advanced research, development, and prototyping division of Boeing Defense, Space & Security) and NASA constructed two unmanned X-36 Tailless Fighter Agility Research Aircraft in the mid-1990s to develop technology for a small, maneuverable fighter.

The X-36s were about a quarter of the size of a potential future fighter—an aircraft configuration on a scale of 28 percent.

In 1993, McDonnell-Douglas (now Boeing) suggested creating a remotely piloted scale aircraft technology demonstration to assess the advanced technologies in an actual flying environment. The project was an unparalleled accomplishment for a remotely piloted aircraft program. Starting in 1989, Ames and the Phantom Works created the technologies needed for tailless agile flight.

This proposal was based on the successful outcomes of intensive wind tunnel testing and computational fluid dynamics (CFD) analysis.

The aircraft was made to fly without the conventional tail surface. The X-36 had its first flight in May 1997, and the flight test program achieved a remarkable feat by meeting or surpassing all project targets.

“It was designed to fly without the traditional tail surfaces common on most aircraft. Instead, a canard forward of the wing is utilized, in addition to split ailerons and an advanced thrust-vectoring nozzle for directional control. The X-36 is unstable in both the pitch and yaw axes; therefore, an advanced, single-channel digital fly-by-wire control system, developed with some commercially available components, stabilizes the aircraft,” according to NASA.

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X-36 in flight-Wikipedia

“The X-36 project team developed and demonstrated the tailless fighter design using advanced technologies to improve the maneuverability and survivability of possible future fighter aircraft. The X-36 program met or exceeded all project goals,” as per information on the NASA website.

Fully fuelled, the X-36 prototype weighed about 1,250 pounds. It was three feet high, nineteen feet long, and had a wingspan of more than ten feet. It was powered by the Williams International F112 turbofan engine, which produced roughly 700 pounds of thrust.

The X-36 was controlled remotely by a pilot in a virtual cockpit at a ground station using a video camera installed in the nose of the aircraft (together with an onboard microphone).  Pilot situational awareness was enhanced with a regular fighter-type head-up display (HUD) and a moving-map depiction of the vehicle’s position within range. 

This pilot-in-the-loop method removed the need for costly, intricate autonomous flight control systems and the dangers of those systems’ inability to handle unexpected or unknown occurrences while in flight.

A normal research trip took 35 to 45 minutes from takeoff to landing. The aircraft flew for a total of 15 hours and 38 minutes during its 31 successful and safe research flights over the course of 25 weeks, using four distinct versions of flight control software. It had a maximum angle of attack of 40 degrees and a maximum altitude of 20,200 feet.

The X-36 prototype was also tested in 1998 by the US Air Force Research Laboratory (AFRL) using their RESTORE (Reconfigurable Control for Tailless Fighter Aircraft) software.  

The project, which was jointly funded under an approximately 50/50 cost-sharing structure, involved NASA and Boeing as full partners. The two prototype aircraft’s development, construction, and flight testing came at a total program cost of about US$21 million. 

The first X-36 is at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio.

X-36 at the National Museum of the United States Air Force
X-36 at the National Museum of the United States Air Force

Personnel associated with the program autographed the X-36 “cockpit” and forward fuselage areas before Boeing donated the aircraft to the museum. The second X-36 is displayed outside the Air Force Test Flight Center Museum at Edwards Air Force Base in California.

However, despite the remarkable success of the program, the advanced fighter design was not pursued, probably because the costs associated with building a full-scale prototype were deemed too high at the time.