Synthetic vision system Flying the Northrop YF-23

A synthetic vision system (SVS) is a computer-mediated reality system for aerial vehicles, that uses 3D to provide pilots with clear and intuitive means of understanding their flying environment.

Synthetic vision is also a generic term, which may pertain to computer vision systems using artificial intelligence methods for visual learning, see “Synthetic Vision using Volume Learning and Visual DNA”.

Synthetic vision provides situational awareness to the operators by using terrain, obstacle, geo-political, hydrological and other databases. A typical SVS application uses a set of databases stored on board the aircraft, an image generator computer, and a display. Navigation solution is obtained through the use of GPS and inertial reference systems.

Highway In The Sky (HITS), or Path-In-The-Sky, is often used to depict the projected path of the aircraft in perspective view. Pilots acquire instantaneous understanding of the current as well as the future state of the aircraft with respect to the terrain, towers, buildings and other environment features.

In 2005 a synthetic vision system was installed on a Gulfstream V test aircraft as part of NASA’s “Turning Goals Into Reality” program. Much of the experience gained during that program led directly to the introduction of certified SVS on future aircraft. NASA initiated industry involvement in early 2000 with major avionics manufacturers.

Eric Theunissen, a researcher at Delft University of Technology in the Netherlands, contributed to the development of SVS technology.

At the end of 2007 and early 2008, the FAA certified the Gulfstream Synthetic Vision-Primary flight display (SV-PFD) system for the G350/G450 and G500/G550 business jet aircraft, displaying 3D color terrain images from the Honeywell EGPWS data overlaid with the PFD symbology. It replaces the traditional blue-over-brown artificial horizon.

In 2017, Avidyne Corporation certified Synthetic Vision capability for its air navigation avionics. Other glass cockpit systems such as the Garmin G1000 and the Rockwell Collins Pro Line Fusion offer synthetic terrain.

Lower-cost, non-certified avionics offer synthetic vision like apps available for Android or iPad tablet computers from ForeFlight, Garmin, or Hilton Software

The Northrop/McDonnell Douglas YF-23 is an American single-seat, twin-engine stealth fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF’s Advanced Tactical Fighter (ATF) competition, battling the Lockheed YF-22 for a production contract. Two YF-23 prototypes were built, nicknamed “Black Widow II” and “Gray Ghost”.

In the 1980s, the USAF began looking for a replacement for its fighter aircraft, especially to counter the USSR’s advanced Sukhoi Su-27 and Mikoyan MiG-29. Several companies submitted design proposals; the USAF selected proposals from Northrop and Lockheed. Northrop teamed with McDonnell Douglas to develop the YF-23, while Lockheed, Boeing and General Dynamics developed the YF-22.

The YF-23 was stealthier and faster, but less agile than its competitor. After a four-year development and evaluation process, the YF-22 was announced the winner in 1991 and entered production as the Lockheed Martin F-22 Raptor. The U.S. Navy considered using the production version of the ATF as the basis for a replacement to the F-14, but these plans were later cancelled. The two YF-23 prototypes were museum exhibits as of 2010.

American reconnaissance satellites first spotted the advanced Soviet Su-27 and MiG-29 fighter prototypes in 1978, which caused concern in the U.S. Both Soviet models were expected to reduce the maneuverability advantage of contemporary US fighter aircraft.[1] In 1981, the USAF requested information from several aerospace companies on possible features for an Advanced Tactical Fighter (ATF) to replace the F-15 Eagle. After discussions with aerospace companies, the USAF made air-to-air combat the primary role for the ATF.[2] The ATF was to take advantage of emerging technologies, including composite materials, lightweight alloys, advanced flight-control systems, more powerful propulsion systems, and stealth technology.[3] In October 1985, the USAF issued a request for proposal (RFP) to several aircraft manufacturers. The RFP was modified in May 1986 to include evaluation of prototype air vehicles from the two finalists. At the same time, the U.S. Navy, under the Navalized Advanced Tactical Fighter (NATF) program, announced that it would use a derivative of the ATF winner to replace its F-14 Tomcat. The NATF program called for procurement of 546 aircraft along with the USAF’s planned procurement of 750 aircraft.[4]

Top view of the YF-23, showing the trapezoidal wings and separation between the forward fuselage and engine nacelles

In July 1986, proposals were submitted by Lockheed, Boeing, General Dynamics, McDonnell Douglas, Northrop, Grumman and Rockwell. The latter two dropped out of competition shortly thereafter.[5] Following proposal submissions, Lockheed, Boeing, and General Dynamics formed a team to develop whichever of their proposed designs was selected, if any. Northrop and McDonnell Douglas formed a team with a similar agreement.[6] The Lockheed and Northrop proposals were selected as finalists on 31 October 1986. Both teams were given 50 months to build and flight-test their prototypes, and they were successful, producing the Lockheed YF-22 and the Northrop YF-23.

The YF-23 was designed to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance. Supercruise requirements called for prolonged supersonic flight without the use of afterburners.[9] Northrop drew on its experience with the B-2 Spirit and F/A-18 Hornet to reduce the model’s susceptibility to radar and infrared detection. The USAF initially required the aircraft to land and stop within 2,000 feet (610 m), which meant the use of thrust reversers on their engines. In 1987, the USAF changed the runway length requirement to 3,000 feet (910 m), so thrust reversers were no longer needed. This allowed the aircraft to have smaller engine nacelle housings. The nacelles were not downsized on the prototypes.

The first YF-23 (serial number 87-0800), Prototype Air Vehicle 1 (PAV-1), was rolled out on 22 June 1990;[13] PAV-1 took its 50-minute maiden flight on 27 August with Alfred “Paul” Metz at the controls.[14] The second YF-23 (serial number 87-0801, PAV-2) made its first flight on 26 October, piloted by Jim Sandberg. The first YF-23 was painted charcoal gray and was nicknamed “Black Widow II”, after the Northrop P-61 Black Widow of World War II. It briefly had a red hourglass marking resembling the marking on the underside of the black widow spider before Northrop management had it removed.] The second prototype was painted in two shades of gray and nicknamed “Spider” and “Gray Ghost”.