Versatile, reliable and economical: it’s easy to understand what makes the Lockheed Martin C-130 Hercules the most successful military transport of all time. But for the AC-130 “gunship” version of this four-engined beast another word comes to mind: lethal. The origins of the U.S. Air Force (USAF) gunship program go back to 1965 in Vietnam, when vintage Douglas C-47 Skytrains of the 4th Air Commando Squadron were fitted with three 7.62mm Gatling-type miniguns firing through side windows and the cargo door. Operating at night at low altitudes, these crude gunships delivered such an overwhelming volume of fire that they often saved outposts and villages from being overrun by North Vietnamese and Vietcong attacks. The early AC-47s relied on parachute flares to see its targets, but were gradually upgraded by successive generations of electro-optical night-vision devices. The rifle-caliber mini-guns were supplemented by 20 mm VulcanGatling and 40 mm Bofors L/60 automatic cannon, and even a low-recoil version of the Army’s 105 mm howitzer.
Eventually the elderly C-47s were replaced by newer airframes: the Fairchild C-119 and finally the C-130. The ground troops’ affectionate nickname, “Spooky” endured, however, with the AC-130U. The AC-130H bears the official USAF name of “Spectre.” The “J” model C-130, but for its characteristic six-bladed propellers, is externally similar to previous models, but on the inside it is very much a 21st century aircraft. On the flight deck a “glass cockpit” replaces the banks of analog mechanical instruments that engineers today jokingly call “steam gauges.” The many digital systems allow reduction of the flight crew to just a pilot, co-pilot and loadmaster, eliminating the need for flight engineer or navigator. New Rolls-Royce AE-2100 turboprop engines drive the advanced six-bladed composite propellers. With over 180 delivered so far, the Air Force has chosen the C-130J as the platform for the next generation of the gunship.
The nature of war has changed, and America’s overwhelming firepower sometimes seems to create more problems than it solves. America’s enemies have learned to hide among innocent noncombatants and to propagandize the inevitable collateral damage that results from our close air support attacks. Rather than more devastating weapons, senior commanders are now urgently demanding far more precise weapons that create vastly less destruction. The solution is a new generation of small guided missiles that will equip the AC-130J. Mounted in groups on wing pylons, or dispensed from a launcher installed in the plane’s cargo ramp, two new munitions, Griffin and Viper Strike, will allow operators to make pin-point attacks from a greater stand-off range, with less risk of collateral damage to civilians. Developed by Raytheon, Griffin is a tube-launched missile with a semi-active laser seeker. This means that a laser designator, either on the ground or in the air, must “paint” the target with coded pulses of invisible coherent light. The seeker head in the missile detects the laser spot, recognizes the code pattern and homes in on the target. Originally intended as a lightweight weapon for the MQ-1 Predator drone, Griffin uses proven components from the FGM-148 Javelin anti-tank and AIM-9X Sidewinder missiles. A Predator can carry three Griffins in place of one heavy (100 pounds/45.5 kg) Hellfire missile, allowing more targets to be struck in a single sortie. In November 2008, U.S. Special Operations Command ordered 130 Griffins, with an option for an additional 200.
Northrop Grumman developed the GBU-44 Viper Strike glide bomb in 2002, using technology derived from the Army’s cancelled Brilliant Anti-Tank (BAT) submunition. In place of the BAT’s acoustic sensor of (intended to home on the sound of vehicle engines) Viper Strike combines GPS-aided guidance with semi-active laser homing. It can use the same wide range of airborne and ground-based laser target designators as Griffin, and many other precision munitions. In late 2004 it was field-tested in Iraq onboard the Army’s MQ-5 Hunter UAV. As an unpowered glide bomb, Viper Strike’s range depends on the release altitude, as well environmental factors; but a nominal glide ratio of 10:1 suggests that from an altitude of 6,000 feet it could potentially strike a target over ten miles distant. The AC-130J will also pack a powerful gun: the ATK Mk. 44 Bushmaster 30 mm automatic cannon. This weapon fires up to 250 rounds per minute, using a chain drive powered by a one-horsepower electric motor. A dual-feed selector allows rapid switching between two kinds of ammunition; typically high explosive incendiary (HEI), or high explosive dual purpose (HEDP), which can penetrate light armor. Effective range of the gun is about 3,000 meters (9,800 feet). Plans announced in April 2010 are for AFSOC to acquire 15 of the new AC-130Js, based on new production airframes from Lockheed Martin. In addition, AFSOC will retain their remaining AC-130U Spectres, while retiring older gunships based on earlier Hercules models. This should give AFSOC a credible gunship force well into the 21st century.