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AFTI F-16

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Imagine a fighter that can fly a low level Close Air Support mission, deliver its weapons on target and then perform a full-on dogfight before returning to base; imagine this level of combat flying without a pilot in the cockpit. A pilotless F-16 Fighting Falcon has become a reality, but not for long. The AFTI F-16 program engineers at Edwards AFB were well on the way to perfecting the pilotless F-16 concept when funding for the program was cancelled.

Even though the program has been cancelled much of the work conducted is nonetheless valuable to current aircraft enhancement programs, and it is applicable to future programs such as the Unmanned Combat Air Vehicle (UCAV). While there are no plans to turn AFTI into a true UCAV, it is being used as the test bed for a purpose-built UCAV.

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The AFTI F-16 is a research aircraft sponsored by Wright Laboratories. The aircraft is part of the USAF inventory but it has flown only 1400 hours, even though it was the sixth pre-production F-16 built. It is probably the most expensive USAF aircraft in service because of the many modifications for trials work and in experimental programs.

A lot of the purpose-built equipment developed for the F-16 is still being used by AFTI and other programs, and much of the high dollar items no longer used in the AFTI program have been modified to support other projects. These include the two FLIR systems and the night vision helmet systems. Work on the aircraft’s digital flight control system and integrated avionics programs have been a forerunner to modifications on the whole F-16 fleet.

The aircraft was also fitted with canards positioned off the engine inlet which gave it a lateral de coupled motion capability. This allowed the engineers to decouple the aircraft’s angle of attack off its actual flight path - something that was, and is still ahead of its time. Other changes have been made to the longitudinal control surfaces, the flaps, and the horizontal tail to allow de-coupled motions.

For example in the air-to-air mode the pilot could fly a track with the nose pointing either off to the side, up or down. This enabled the pilot to point the gun at a target offset from the actual flight path: up to eight degree deflection angle at slow airspeeds was achievable, down to a couple of degrees at higher air speeds.

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Other de-coupled motions allowed the aircraft to perform flat turns, that is, keeping wings level as the aircraft turned. This was very useful in the bombing phase of an air-to-ground mission.

Unconventional flight trials introduced extraordinary stress on the airframe which, at times, was beyond the limits of the original design specifications. The F-16 was fully instrumented so the team on the ground could see what was happening at any given time. The tail was found to be the weakest point since it was not intended to generate the extra load forces.

The next major program phase was to develop an advanced integrated avionics system for the F-16. This led to advanced auto-pilot functions that allowed the aircraft to deliver 5-G lateral bomb tosses, fly in auto air-to-air and engage in auto dogfighting with full 9-G authority. This was the highest authority auto-pilot on an aircraft - and that was introduced 10 years ago.

The bombing system had 5-G authority and a full 180 degrees per second roll rate, but it lacked a forward-looking sensor on the jet. Because the auto-pilot system had such authority, bank angle was not limited. Four antennas for the radar altimeter mounted around the nose of the jet gave altitude above the ground at any attitude.

New datalink systems were also developed. Autonomous operation of the aircraft and weapons systems is possible through the auto-pilots but human confirmation of the target prior to committing lethal force is essential. Even with unmanned aircraft a pilot, remote from the engagement, would still need to decide on the use of lethal force: analysing the data-linked information, making a decision to engage, and then commanding the onboard systems to execute the attack.

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For the next CAS phase the jet was returned to standard configuration. The aim was to counter objections that the trials had been conducted to date on a highly modified F-16. Into this now standard jet the team incorporated their CAS features, auto-pilot functions, and installed a digital terrain system.

The digital terrain database, specific to the area of operations, was used to enhance navigation and terrain following capability. The digital terrain database allowed terrain following without having to project energy forward with a TF radar. The only active sensor was a radar altimeter which can also be made stealthy. For the trials the team flew an F-16 with GPS and a radar altimeter to validate the terrain data.

The AFTI team ended up with a digital terrain system that not only enabled terrain following but also aided development of an auto ground avoidance system. At 200ft AGL doing a 5g lateral bomb toss in an aircraft that can command a 180 degrees per second turn rate, backup safety measures are critical. Lockheed developed an auto ground collision avoidance system based on data from a radar altimeter, but as the program progressed into the digital terrain system phase, it also utilised the digital terrain data.

Some AFTI development work has progressed on to the digital F-111 (before it was withdrawn from service) and much of the work is now being used in the F-22 and F-117 programs. A lot of the design architecture in the F-22 is very similar to that in the F-16 AFTI. Being the very first test bed for DFCS it had a very pronounced effect.

The work carried out under the AFTI project may not have led to a combat ready unmanned F-16 fighter, but the research and development work carried out has had great benefit for current aircraft development programs.


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Last Updated January 9th, 1998


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