The AC-130 gunship has earned its stripes in a range of conflicts in the past few decades—from Vietnam up to recent operations against insurgents in Fallujah, Iraq. Over the years the gunships have provided armed reconnaissance, interdiction and direct support of ground troops engaged with enemy forces.

Despite its devastating firepower, however, the venerable platform—currently operating as the AC-130H (Spectre) and AC-130U (Spooky)—has a number of drawbacks due to its origins as a slow, heavy transport airframe, the C-130 Hercules.

Air Force Special Operations Command (AFSOC), which deploys 21 AC-130H/Us, is working to improve the aircraft for continued service, while at the same time looking ahead to a replacement system to undertake the gunship role in the future.

The latest version, the AC-130U, entered service with AFSOC in 1994. It represents the third generation of C-130-based gunships, joining the still-in-service second-generation AC-130H. The AC-130U is one of the most complex aircraft flying; its computers and avionics have 609,000 lines of programming.

The AC-130’s operations in Afghanistan were highlighted by cooperation with the Predator unmanned aerial vehicle (UAV). Predators reconnoitered targets and transmitted this data directly to AC-130s for attack, allowing the latter to operate at stand-off distances. In Iraq, the AC-130U has undertaken close air support (CAS) alongside aircraft such as the Marine Corps’ AV-8B Harrier II and the Air Force’s A-10.

The AC-130 has been effective in its missions of armed reconnaissance, CAS, interdiction and direct action in these recent operations, according to AFSOC spokesman Captain Thomas R.A. Montgomery. “Current operations have again validated the flexibility and utility of this special operations aircraft,” he said.

Although AFSOC has not revealed any shortcomings of the aircraft observed in recent operations, Montgomery added, “We are constantly evaluating options for the future of global engagement and how our weapons systems might be more effective.”

With the experience of recent operations, upgrades were planned and introduced for the gunships. These included replacement of the All-Light Level TV with a night-capable, multi-spectrum system with a 360-degree field of view, and the fitting of AC-130H wingtip tanks in lieu of the previous underwing tanks. Over all, AC-130 communications have been improved, weight decreased and defensive capabilities boosted.

Boeing was contracted to convert four AC-130Hs into AC-130Us. AC-130s further will eventually undergo the same C-130 avionics modernization program as the rest of the C-130 fleet. The new open architecture will allow the aircraft to integrate modern systems. In addition, four new AC-130s are scheduled to enter service in February-June 2006.

An early program to renew the gunship capability was the AC-X advanced concept technology demonstration. AC-X was envisaged as being either an upgrade of the AC-130U or a completely new aircraft. Special forces required the aircraft to have a small size and crew, stealth, high speed, maneuverability, and the ability to carry directed-energy and non-lethal weapons.

Operation Enduring Freedom provided further guidance for the longer-term gunship replacement requirement, and saw a year-long AFSOC Next Generation Gunship (NGG) analysis of alternatives (AOA). This itself was a follow-on to an Air Force Materiel Command Air Armament Center multi-disciplinary Task Force Warlord study, in which aircraft, armament, sensors and data links were all considered. Warlord produced numerous concepts for the NGG AOA, of which 70 of these were for the period 2005 to 2010 and 87 for post-2010.

From the AOA, the Joint Staff was able to produce the Persistent Surface Attack System-of-Systems (PSAS) initial capabilities document (ICD). The Joint Requirements Oversight Council approved the ICD in September 2004. PSAS is now undergoing concept refinement under the Joint Capabilities Integration and Development System.

With respect to future gunship-type operations, Montgomery said, “AFSOC currently has two potential visions of the future: (1) a viable manned platform that’s more difficult to detect and target; or (2) a family of unmanned platforms that provide the same capability.” AFSOC wants a future platform to have “greatly increased survivability, persistence and the ability to apply combat power rapidly, precisely and discriminately,” he continued.

Development at the outset would be in three areas: a precision-guided weapon, an organic UAV to increase stand-off range and provide electro-optical coverage under weather or down urban canyons, and a common operation picture and control to reduce the number of operators required to operate the system and to tie all systems, sensors and platform to the Global Information Grid. With regards to the organic UAV, the AOA listed eight-hour endurance and all-weather and multi-spectral imaging among other requirements.

Although the gunships have again proved their worth in recent combat, the fleet is small and is likely to remain that way as long as the existing framework of air power—in which the gunship role is not as emphasized as much as other attack and combat missions—continues. Any aircraft designed from the outset solely for the gunship role might prove to be the most effective design possible, but would be prohibitively expensive given the small numbers required.

Instead, a future manned gunship will be a derivative of an existing or future type, very likely a transport. The Air Force wants to introduce a family of stealthy transport and special mission aircraft from around 2015-2020; roles would be transport, air-to-air refueling tanker, special forces insertion and gunship. The aircraft’s size would be between that of the C-130 and the Boeing C-17. Industry has responded with designs to fulfill this requirement.

Lockheed Martin Skunk Works has developed the concept of a modular large-body aircraft to undertake the range of roles listed. This aircraft, designated MACK, will be capable in M-X (special forces insertion), A-X (gunship), C-X (transport) and K-X (tanker) roles. Interchangeable modules can be fitted depending on the requirement.

MACK would have a tailless compound delta wing, with roughly the outer third bent upwards. Multi-spectral stealth characteristics would make it capable against both early warning and fire control radars. Its two engines would be installed inside the airframe. They would be high-bypass types, making them quieter and cooler.

The airframe itself would be made primarily of composite material, although existing composites would be employed in order to reduce costs. Like today’s dedicated strike/interdictor aircraft, MACK would be capable of terrain-following and terrain avoidance flight. It would also be fitted with both offensive and defensive self-protection systems. Aircrew would include pilot, co-pilot and navigator. Gross take-off weight would be 230,000 pounds to 240,000 pounds The engines would each provide 63,000 pounds of thrust, and field length with a 22,000 pound payload would be 1,500 feet.

The A-X itself would have two retractable guns in turrets, one installed above and one below the fuselage. With these guns, the aircraft would avoid the need for a racetrack flight pattern as used by the AC-130, which because it has guns on only one side must continually circle the target.

More recently, Lockheed Martin has evolved the MACK into a bomber model labeled BMACK. The completely new MACK/BMACK aircraft would be operational about 2020.

Boeing Phantom Works has developed the Advanced Theater Transport (ATT) design. Also known as the Superfrog, the aircraft originated in company studies for a short take-off and landing (STOL) transport able to use a 1,000-foot runway. The ATT is a tilt-wing aircraft, which allows a much reduced runway length. The aircraft can use runways as short as 650 feet.

Also it can carry up to twice the payload with a rolling takeoff, as opposed to a vertical take-off. Further, removing the tail enhances low-speed flight for short landings in addition to reducing radar signature. The ATT would have four turboprop engines and the tilt-wing would be swept forward. Fuselage cross-section would be comparable to that of the C-17. Its payload of 80,000 pounds would be nearly twice that of the C-130J.

Still, the aircraft is smaller than the C-X Air Force family requirement. Range and endurance for the gunship mission are concerns as well.

Boeing is taking its YC-15 STOL transport aircraft fuselage, which is almost 20 years old, out of storage and converting it into a demonstrator for the ATT. It will be configured as a stealthy tilt-wing, tailless aircraft. The four jet engines will be replaced by four turboprops, four engines being deemed safer and more cost-effective than two. The new tilt-wing will be able to rotate 20 degrees from the horizontal. The aircraft will have a payload of 80 tons and be able to operate from a 750-foot runway.

Phantom Works is also developing the blended wing body (BWB) concept, not dissimilar to the flying wing configuration as seen in the B-2A bomber. It is a tailless delta type with engines mounted on the top of the rear fuselage.

The BWB has a simpler structure than conventional designs and a better lift-to-drag ratio. It can also be modular—various sizes of aircraft are possible by adding sections to the middle of the fuselage. NASA has been involved in the research for a number of years.

Boeing has flown a scaled-down model and is also working with Cranfield Aerospace in Britain on another. NASA Langley Research Center has also been developing a model. The BWB design is suitable for a number of roles, including heavy bomber, intelligence-gathering, transport, tanker and gunship, with many common systems in the different versions.

Bell Helicopter, meanwhile, has scaled up the Bell-Boeing V-22 Osprey tilt-rotor design into a four engine aircraft, the Quad Tilt-Rotor (QTR), comparable in size to the C-130. Payload would be 10-20 tons and speed greater than 300 miles per hour, with a range of between 1,000 and 2,000 miles. It would be capable of vertical landing and rolling take-offs and of operating from aircraft carriers and amphibious vessels. More than half of the QTR’s systems would be from the V-22, reducing its cost.

The cheapest route to a new generation gunship though would be modifying an existing aircraft. The U.S. military’s two new-generation transports, the C-130J and C-17, could be so evolved. Lockheed Martin has proposed the idea of an AC-130J “arsenal ship,” which could deploy 8-12 cruise missiles, such as the CALCM, JASSM, JASSM-ER and MALD jammer.

With regard to the unmanned component, possibilities include a large unmanned combat air vehicle (UCAV), or groups of UCAVs. Boeing is studying a survivable, long-duration unmanned gunship concept, which could develop out of the X-45 UCAV that the company is currently working on.