Military

X-62A / NF-16D VISTA (Variable In-flight Simulator Aircraft)

The NF-16D Variable In-flight Simulator Aircraft (VISTA) has been redesignated as the X-62A, effective June 14, 2021. The X designation denotes aircraft that are designed for testing configurations of a radical nature. X aircraft are not normally intended for use as tactical aircraft. Following its redesignation to X-62A, VISTA now joins a storied family of aircraft such as the Bell X-1, the first airplane to break the sound barrier, and the hypersonic, rocket-powered North American X-15, which holds the record as the fastest piloted aircraft.

The F-16 Multi-Axis Thrust-Vectoring (MATV) program originally began as a joint General Electric/General Dynamics privately-funded program for a thrust-vectored version of the Fighting Falcon. The USAF initially declined to support the program, so the two companies agreed to collaborate with the Israel Defense Force/Air Force, which was interested in the program for its own F-16s. Wright Labs bought the aircraft in 1988 and from 1988 until 1992, the VISTA/F-16 program was accomplished. There was no connection between thrust vectoring and VISTA/F-16 at this time. The VISTA F-16D was redesignated NF-16D, the N prefix meaning that the aircraft had a special test status and that the modifications were sufficiently drastic that it would be impractical to restore the plane to its original condition.

The VISTA, which is operated by the Air Force Test Pilot School with the support of Calspan and Lockheed Martin, first flew in 1992 and has been a staple of the TPS curriculum. It has provided TPS students the ability to experience various flying conditions including simulation of other aircrafts’ characteristics.

VISTA could be configured to emulate the performance of other modern fighter aircraft. The model of the aircraft to be simulated is programmed on the in-flight simulator's computers. When the evaluation pilot flies from the cockpit, the in-flight simulator responds like the model. The NF-16D has been used to support the development of the F-22 and the Light Combat Aircraft (India).

This unique research aircraft performed a multitude of missions to evaluate flight characteristics of new aircraft that have not yet flown, to perform research in the areas of flying qualities, flight control design, pilot vehicle interface, weapons and avionics integration, and to train test pilots and engineers.

In-flight simulation and the VISTA research support functions are made possible (and affordable) by the addition of a second flight control system called the Variable Stability System (VSS), which operates in parallel with the normal F-16 control laws. The VSS is hosted in three Rolm Hawk 32 ruggedized airborne digital computers. The VSS is engaged once the VISTA is in the air and commands, with essentially full-authority, the NF-16D left and right horizontal stabilizer, ailerons, thrust, rudder, and trailing edge flaps. The front seat pilot flew the F-16 through the second control system and will feel like he was flying the simulated aircraft or experimental control laws. The back seat pilot was the safety pilot and can take-over control of the VISTA at any time. This concept allows experimental configurations to be tested with safely and without extensive software validation and verification.

The VISTA was upgraded in the mid-1990s to enhance its simulation fidelity and its research capabilities through the addition of a programmable helmet mounted display HMD and head up display HUD in the front cockpit. The programmable helmet mounted display system consists of a GEC Marconi Avionics Viper 2 Helmet Mounted Optics Module integrated with a modified Helmet Integrated Systems Limited HISL HGU-86P helmet, the Honeywell Advanced Metal Tolerant tracker, and a GEC Marconi Avionics Programmable Display Generator. The monocular HMD system is designed for growth to stroke on video, binocular capability.

“For more than two decades VISTA has been a vital asset for the USAF TPS and the embodiment of our goal to be part of the cutting edge of flight test and aerospace technology,” said William Gray, VISTA and TPS chief test pilot. “It has given almost a thousand students and staff members the opportunity to practice testing aircraft with dangerously poor flying qualities, and to execute risk-reduction flight test programs for advanced technologies.”

One of the first hurdles that was encountered was the lack of definitive system and performance requirements. System requirements could not be defined a priori but evolved in the course of source selection because the budget was essentially the only requirement. An "off-the-shelf" system procurement was clearly essential. The cost and availability of these systems dictated the vast majority of the requirements. Requirements evolution of this sort was not necessarily a problem - it was a recognized fact - but it did invoke a substantial amount of consternation and continual re-evaluation of goals, missions, issues and the like for people who were unaccustomed to dealing with this type of procurement. By 2021 the VISTA was in the midst of an upgrade program which will fully replace the VISTA Simulation System (VSS). The upgrade program will also add a new system called the System for Autonomous Control of Simulation (SACS) to support autonomy testing for the Air Force Research Laboratory’s Skyborg program.

“The redesignation reflects the research done on the aircraft over the past almost 30 years, as well as acknowledges the major upgrade program that is ongoing to support future USAF autonomy testing,” said Dr. Chris Cotting, USAF TPS director of research.

Skyborg is an autonomy-focused capability that will enable the Air Force to operate and sustain low-cost, teamed aircraft that can thwart adversaries with quick, decisive actions in contested environments. The program will enable airborne combat mass by building a transferable autonomy foundation for a family of layered, unmanned air vehicles. This foundation will deliver unmatched combat capability per dollar by lowering the barriers to entry for industry and allowing continuous hardware and software innovation in acquisition, fielding and sustainment of critical mission systems. During this effort, AFRL will prototype a suite of autonomy and unmanned system technologies equipped with capabilities that can support a range of Air Force missions.

Skyborg will not replace human pilots. Instead, it will provide them with key data to support rapid, informed decisions. In this manner, Skyborg will provide manned teammates with greater situational awareness and survivability during combat missions.

The VISTA started life as a Block 30 F-16D. Throughout its life, it has received numerous upgrades and modifications. VISTA was originally given the N prefix to denote its status as Special Test, Permanent. The N prefix indicates aircraft on a special test program whose configuration is so drastically changed that return to its original configuration or conversion to standard operational configuration is beyond practicable or economic limits.

“We have found ways to use VISTA that were not envisioned by the original designers, so we were running into frustrating limitations,” Gray said. “The modifications will address these limitations and profoundly improve our ability to quickly and safely test an almost unlimited variety of radical control law configurations. Even so, the X-62A will continue to serve as a curriculum aircraft, and will be an even brighter symbol of our aspirations.”

“VISTA will serve as one of the main assets of the newly-created Research Division at USAF TPS,” Cotting said. “As part of the upgrade program, VISTA has been redesignated from the NF-16D VISTA to the X-62A VISTA, making USAF TPS the only test pilot school with an active X plane supporting its curriculum.”