|This article, AD66 Heron Attack Dropship, is currently under active construction.|
Older than the D77 Pelican family of dropships, the D66 Heron preceded the Pelican by three decades, filling a requirement for the UNSC Navy and Marine Corps for an atmospheric/orbital transport. After forty years of service, most of the Herons were replaced by the newer, more advanced Pelicans, with most decommissioned or converted into trainer craft. A number entered the black market, inconspicuously entering use among a variety of Insurrectionist groups, while a small number of combat units still use it as a dedicated attack dropship, supplementing the Pelicans, Vultures and Sparrowhawks that would normally fill the role.
For most of the UNSCDF's existence, humanity hasn't fought an actual full-scale war. Since the end of the Interplanetary War, the most the UNSC was forced to deal with was the occasional pirate group, which were dealt with relatively quickly by Naval battlegroups. As discontent among the Outer Colonies began to increase, however, FLEETCOM decided that a modification of existing battle doctrine was required. Emphasis was to be placed on mobility, including flexibility and rapid deployment, rather than sheer firepower; it is a doctrine the Marines still embody today, and there seems to be no signs of change. As part of this, the Navy and Marine Corps requested a dropship enabling them to meet their requirements.
A number of private corporations submitted proposals, but it was Misriah's XD66that caught the Navy's eye. Previously, dropships had been dedicated troop transports protected by fighter or gunship escorts. The design for the XD66 included hard points for rocket and missile pods, and was to include a 50mm chaingun; the incorporation of heavy weapons onto a dropship was unprecedented, and would allow the XD66 considerably mission flexibility, as well as close air support and tactical strike capability, filling the roles of dropship and gunship simultaneously. When the Navy adopted it, the only alteration was that the autocannon was replaced with a 30mm design, already in use, to reduce maintenance costs.
Production was started in 2479 at the Misriah Armouries factory assemblies on Mars. The first pre-production models were extensively tested by the Navy and Marine Corps for a year - environmental and temperature factors were taken into account, as well as the mano9euvres it was expected to perform in its ccombat duties. Orbital reentry was extensively performed to see the effect of repeated reentries on the craft, and modifications were made to later models to allow docking with most warships. When Misriah began full scale production, the XD66 was already gaining popularity amog the Sailors and Marines expected to receive them. When Reach was established as the UNSC's primary military headquarters, the first production line craft produced by Misriahs new Elysium division was the D66, and is arguably the first craft produced on Reach.
The D66 would see extensive use throughout the various brushfire conflicts among the Outer Colonies, deploying Marines were needed, and supporting them from the air. The Herons also allowed the Marine Corps unparalleled armoured mobility - the Heron was the first dropship designed to airlift vehicles to the frontline, vastly improving their mobility, providing an edge that the early Insurrectionists found difficult to match. By the time the Insurrection had begun in earnest, the Heron had already gained a level of reverence and respect by its pilots that few other craft matched.
The Herons would also be used extensively in Operation: TREBUCHET, deploying Marines on Reach, Tribute, Circumstance and Beta Gabriel. As conflict broke out in a dozen other star systems, Herons saw service across more UNSC territory. A number of squadrons created dedicated gunship variants, trading passenger capacity for fuel and armaments. Others were converted into heavy lift variants, dedicated vehicle carriers; but for the most part, the Herons served quite adequately as troop carriers. The gunship variant, specialising in close air support and ground attack, was designated the AD66.
By the time conflict erupted with the Covenant, the Heron had begun show a number of vulnerabilities. Older models were beginning to show their age, the constant reentry operations taking a toll on their structural integrity. The introduction of the Scorpion IV rockets and Anvil II missiles rendered their predecessors obsolete - the one major flaw with the Heron was that it was specifically designed for the replaced weapons, which had at the time been expected to remain in service for considerably longer. Retrofitting the entire Heron fleet allowed them to be compatible with the new armaments, but there were problems with blowback and firing mechanism - the Scorpion IV relied much more heavily on electronic activation than its predecessor, which required still more upgrades to the Herons' electronics. The adoption of the M12 Warthog and M808B Scorpion required upgrades to the vehicle carry capacity - the Scorpion MBT only barely fitted, even in the improved compartment. As the list grew, it was decided that the D77 Pelican, then a relative newcomer to UNSC service, was a better contender for the role of the Navy and Marine Corps dropship.
As the war drew on, more and more Pelicans were introduced into roles once held by Herons. The majority of their troop transport and air cavalry units had made the transition by early 2534, but Heron gunships continued to see service until the end of the war. For the most part, they were sold to the UNSC Army as a cheaper alternative to the newer Hawk gunship, or to the Colonial Militia to provide rudimentary transportation and medivac capabilities. A small number were stripped of military equipment and sold to the private sector, used as private corporate shuttles, but even these were replaced by newer, more effective models. By 2549, the only frontline operators were a small number of Terran, Martian and Reach Colonial Militia units - the Marine Corps and Navy continued to operate a small number as advanced trainers for more advanced craft. In 2550, CENTCOM decided to recommission and modernise the Herons as dedicated hybrid gunship transports, the Pelicans having proved to show mixed results - while robust and flexible, it was ill-suited to heavy weapons loadouts, specialising in transport and airlift duties. The Heron was intended as a cheap, effective supplement to the existing complement of UNSC gunships and ground attack craft, replenishing the ranks of the much battered Marine Corps and Navy air squadrons, and in 2551 the first of the new and improved Herons, the AD66B, entered service, seeing their first combat duty during in Operation: HOT GATES. They would see service throughout the rest of the war, and were finally withdrawn from service in 2553.