The F-16XL

42 years ago, on Jul. 3, 1982 the F-16XL, a unique prototype fighter jet that never quite reached its full potential, performed its maiden flight.

The F-16XL was developed by General Dynamics as a variant of the iconic F-16 Fighting Falcon and it featured a distinctive “cranked-arrow” delta wing design promising increased range and improved ground attack capabilities.

Did you know the USAF asked General Dynamics to keep the F-16XL supercruise ability quiet to avoid impacting the Advanced Tactical Fighter program?
A high angle 3/4 right front view of a parked F-16XL Fighting Falcon aircraft armed with AIM-9 Sidewinder missiles.

As explained by Albert C. Piccirillo in the NASA’s book Elegance in flight: a comprehensive history of the F-16XL experimental prototype and its role in NASA flight research, General Dynamics (GD) ‘recognized that the standard F-16 increasingly was being committed by the Air Force to a multirole mission that the aircraft had never been intended for. Originally designed as a lightweight air combat fighter, the aircraft was more and more often being tasked to perform ground attack missions. The F-16 was far from optimal for that role. Weight and drag penalties, imposed by air-to-ground ordnance and related targeting sensors, severely reduced its speed and range capabilities. The aircraft was also seriously limited in the number of weapons that it could carry compared to a larger aircraft.

‘Initially known as Supersonic Cruise and Maneuver Prototype (SCAMP), the GD initiative was also intended to address emerging Air Force interest in supersonic combat capability. By independently developing an experimental prototype that would inexpensively validate the concept of transonic/supersonic cruise and maneuverability along with improved air-to-ground capabilities, GD hoped to interest the Air Force in supporting development and production of what was essentially a new aircraft, but one that shared much in common with the basic F-16.

Not in competition with the F-15E

Did you know the USAF asked General Dynamics to keep the F-16XL supercruise ability quiet to avoid impacting the Advanced Tactical Fighter program?
General Dynamics F-16XL (S/N 75-0749 and 75-0747) banking in flight. Note the unusual paint scheme on the lower aircraft and weapons loading on 18 of 19 mount points on the upper aircraft (two wingtip Sidewinders, four inboard Sparrows and 12 bombs).

‘The company was able to obtain Air Force support and partial funding for a flight demonstration program. Early on, this evolved into a competitive evaluation with the aircraft that the senior leadership within the Air Force really wanted—an air-to-ground version of the F-15 Eagle air superiority fighter known as the F-15E. General Dynamics attempted to convince the Air Force that a production variant of the F-16XL was complementary to the standard F-16 and did not need to be in competition with the larger F-15. However, Congress directed that only one of these aircraft was to be funded for production as what the Air Force termed its Dual-Role Fighter (DRF).’

Thus, the USAF chose the F-15E.

As noted by Alert 5, to delve deeper into the story of this intriguing aircraft, we can turn to the book “General Dynamics F-16XL Dual-Role Fighter: An Illustrated History” by Tony R. Landis. The book has been written from the perspective of the US Air Force Materiel Command History Office, offers a comprehensive look at the F-16XL’s design, the early days under the SCAMP program, test program, research with NASA, and eventual retirement and display in museums.

Did you know the USAF asked General Dynamics to keep the F-16XL supercruise ability quiet to avoid impacting the Advanced Tactical Fighter program?
An air to air left underside view of an F-16XL.

Some interesting trivia about the F-16XL are also unveiled by Landis in his books. Both prototypes featured a unique “throttle bump” on the left side of the forward fuselage. The throttle rotation connection was accommodated in this bump, something standard F-16s didn’t need due to their different wing design.

F-16XL supercruise ability

According to the book, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin had the opportunity to sign their names on the aircraft during separate tours of the F-16XL at NASA Dryden.

The supercruise ability of the F-16XL is only mentioned in the book. A significant modification involved swapping the standard inlet with the Large Normal Shock Inlet (LNSI) that increased engine air intake by 8 percent in order to achieve the feat. The F110-GE-129 engine combined with this tweak, allowed the F-16XL to achieve “supercruise,” sustained supersonic flight without using the afterburner. As told by Alert 5, Landis pointed out that the USAF requested General Dynamics to keep this information quiet to avoid impacting the Advanced Tactical Fighter program (for which the candidates were the YF-22 and YF-23). The F-16XL received a new paint job with a distinct gray stripe on the air intake to signify the alteration following this modification.

Did you know the USAF asked General Dynamics to keep the F-16XL supercruise ability quiet to avoid impacting the Advanced Tactical Fighter program?
F-16XL #1, NASA 849 and SR-71A, NASA 844 during one of the flights in the sonic boom research program.

Variants that never were

Landis also describes F-16XL variants that have never been developed, such as Wild Weasel F-16XL designed to suppress enemy air defenses. This variant would have featured a dorsal fairing to house the APR-83 avionics suite for radar detection and jamming along with a dedicated launch computer for the AGM-88 HARM anti-radiation missile.

The advanced Interceptor variant conceived for long-range air-to-air combat was even odder. This variant of the F-16XL would have featured Infrared Search and Track (IRST) sensors and likely Radar Frequency (RF) sensors embedded in the leading edge of the wing for enemy detection. A significant load of long-range air-to-air missiles, resembling the AIM-54 Phoenix but without rear control fins, hinting at the possibility of a next-generation weapon, would have been carried by the aircraft.

US Navy EA-18G pilot explains why Ukraine should use F-16s just for SEAD missions and not for air-to-air missions
This print is available in multiple sizes from – CLICK HERE TO GET YOURS. F-16CM Fighting Falcon – Wild Weasel 50th Anniversary, 2015

Two specialized cameras – KS-87D oblique cameras with various focal lengths for detailed images and a tri-lens wide-angle camera for broader coverage, would have been carried by a two-seat Reconnaissance variant prioritized battlefield recon. As highlighted by Alert 5, these cameras would likely have been housed in separate pods for optimal placement. A data link pod atop the vertical stabilizer suggests real-time transmission of reconnaissance data. Notably, the removal of the gun port signifies a complete shift towards gathering intel.

The legacy

The F-16XL legacy lives on event though it never entered production. Today both the F-16XL aircraft are at the Air Force Flight Center Museum, at Edwards AFB (75-0747 is on display at the Museum Air Park while 75-0749 is in storage). Both of them served as a testament to the innovative design and potential of this aircraft. Landis concludes his book by expressing his hope that these “elegant machines” will find proper display to preserve the legacy of those involved in their creation.

F-16 model
This model is available from AirModels – CLICK HERE TO GET YOURS.

Photo credit: U.S. Air Force, General Dynamics and NASA