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Lieutenant Commander Michael Pomare, Office of Naval Intelligence, UNSCDF Navy
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AC-173 Eidolon Gunship
Production information

Sierra Space Systems

  • AC-173A "Red Cobra"
  • AC-173B "Blue Eagle"
  • AC-173C "Black Owl"

Atmospheric Gunship

Technical specifications
  • LRS-224 Electronic Warfare Suite
  • 2 x 7.62x51mm Minigun
  • 2 x 12.7x99mm AIE-A Heavy Machine Gun
  • 1 x DEW-1A
Year introduced


  • Close Air Support
  • Air Interdiction
  • Force Protection
  • Colonisation
  • Insurrection
  • Human-Covenant War

The role of a gunship is nothing new to warfare - first fielded in limited numbers during the various conflicts of the mid 20th Century, i.e.; the Korean and Vietnam wars, even the earliest gunships had adopted profiles that would be recognisable hundreds of years later - either VTOL-capable helicopter gunships, capable of striking targets at comparatively close range using their agility and mobility to their advantage, or larger airplane gunships that engaged at considerably longer range, circling an area to provide heavy machine gun and howitzer support against enemy forces. By the Vietnam war, the US Air Force had perfected the process, producing the AH1 Cobra attack helicopter and the AC-47 Spooky Gunship. The Gulf War and War on Terror would see their replacement in most circles with a variety of helicopter gunships produced by various companies, thought he AC-130 Specter/Spooky II Gunships would continue to fill the latter role for a considerable time almost unopposed well into the 21st Century.

In this regard, the AC-173 may be regarded as the spiritual successor of the Specter gunship of the US Air Force. A dedicated ground attack aircraft, the Eidolon is designed to carry a variety of weapons packages for engaging hostile ground targets, ranging from infantry units to vehicle formations to enemy bases of operations, providing ground troops and battle commanders with various forms of signals intelligence, and to operate at extreme long range, well out of the line of sight and range of fire of enemy hostiles. Introduced in 2483, the Eidolon has the dubious honour of being the first UNSC combat aircraft to be equipped with a directed energy weapon, the now infamous DEW-1A, and would serve throughout the Insurrection. The introduction of the AC-220 Vulture Gunship was intended to replace the Eidolon, though many CMA units preferred the older craft due to its reliability and effectiveness. When the CMA was disbanded, many of these units were appropriated by the UNSC Air Force, and would continue to support UNSC Army and Marine ground troops in combat operations until 2536, when the last of them were retired from active duty.


During the Interplanetary War, a number of glaring flaws in the nature of gunship warfare had been revealed to the fledgling UNSC. While military forces would come to rely on the AC-163 gunships that operated on Earth, their notable absence on Mars was a concern that no military commander had expected. The environmental conditions of another planet meant that the gunship simply couldn't operate in such conditions - suggestions that gunships should be ferried over to the red planet were regarded with humour among UNSC astronavigators, who pointed out that the differences in gravity and air pressure meant that designs that were perfectly aerodymanic on Earth simply wouldn't work on Mars. The Argyre Planitia Campaigns were a lesson that the UNSC took to heart, and gunship roles would continue to be filled by adaptable VTOL craft that could be modified to operate under most atmospheric and gravitational conditions.

By 2483, however, the UNSC had managed to smooth out many of the problems it had faced two hundred years earlier, and began looking for a contractor to produce the next generation of UNSC Air Force gunship. Increases in Insurrectionist activity, and their effective of asymmetrical warfare tactics, rendered conventional helicopter and dropship gunships ineffective in the roles they had once held, and the Air Force brass deemed the time ripe for a return to the gunships of old, like the famous Spectre. Misriah Armories and Bellum Aerospace Industries both offered designs, with Misriah's XAC-200 eventually to form the basis for the AC-220 Vulture, but it was the proposal of Sierra Space Systems that eventually won the Air Force's confidence, and was put into production.

During the era of colonisation, most offworld territories were extremely inhospitable, regardless of how well suited they were to colonisation. Continued terraforming had mitigated this somewhat - worlds like Harvest and Reach were practically Earth-like in all the factors needed for flight, and they were not the only colonies to fit the criteria. Seventeen colonies supported Earth-like environments by 2468, and almost a hundred more were well on their way to full habitability - while this was regarded as an achievement in and of itself, it also opened up new, and old, lines of military thought.

The introduction of the AV-14 Hornet was meant to provide UNSC Marine and Army troops on the ground with a visible and effective force in the sky, able to carry a variable payload, conduct special forces insertion missions, aerial reconnaissance, and so forth, and do so in numbers that were difficult for Insurrectionists to counter. But outside of modifying a number of Pelican dropships, the UNSC maintained no true gunship presence in the skies of worlds like Eridanus II and Tribute, notable hotspots of Insurrectionist activity, where UNSC counter terrorist forces needed the fire support they would have provided. In 2481, the Colonial Military Authority began looking for a craft to fill this role.

The first criteria they put forth was that any proposal necessarily needed a significant loiter time, with the possibility of extending this further with aerial refueling. The second was that it needed to be capable of being deployed from orbit - the nature of interstellar empire policing means that transport of aerial assets needs to be by secure starships, deployed on a planet, and unpacked for operation. Unfortunately, the actions of the Insurrection left the CMA and UNSC with little in the way of reaction time, and it was decided that any gunship adopted would need rapid deployment capability from an orbiting frigate/cruiser/carrier. A third requirement, that of an advanced directed energy weapon, was added at the last minute by CAA advisors, for two reasons - for one thing, the technology would be perceived well by Earth loyal civilians, providing a perceived technological edge to the CMA; and for another, defence contractors lobbied the CAA hard to have it included, hoping that it would open up a whole new chapter in defence technology, and in turn new profits. At the forefront of the lobbyists was Sierra Space Systems, which had developed the DEW-1X, a hydrogen-fluoride chemical laser that had been in development for three decades, and the company believed was ready for testing and deployment.