The Storm Eagle is a Forge World product, created to beef up the Space Marines' section of Imperial Armour Aeronautica (as if the Marines didn't have enough toys already), and to give some non-Apocalypse aerial transport to those Chapters that aren't Blood Angels or Grey Knights (including Chaos Space Marines). The Space Marines apparently used loads of them during the Great Crusade, but the forge worlds that made them were destroyed during the Horus Heresy. This meant that the only Storm Eagles in use were those left over at the end of the Heresy, so you had to be from the First or Second Foundings to even have them and even then they were only seldom deployed, but those chapters who are friends of the Adeptus Mechanicus seem to be using theirs a lot more frequently, almost as if they're being made again...
The Storm Eagle Assault Gunship is the Largest Non-Lord-of-War transport of the Space Marines, carrying a full twenty Marines as opposed to the Stormraven's twelve-plus-Dreadnought or the Land Raider Crusader's sixteen.
As for weapon loadouts, the Storm Raven carries a twin Heavy Bolter which can be swapped for a Typhoon Missile Launcher or twin Multi-melta, two Twin Hellstrike Missile Launchers which can be traded for a pair of twin Lascannons, and a Vengeance Missile Battery.
The Storm Eagle is an 18 Power, 14 Wound, Toughness 7 flyer with a 3+ save for your SPEHSS MEHREENS.
The Storm Eagle Assault Gunship is just that, an assault gunship, designed to carry your power armored super human killing machines, straight into the enemy, blast apart any heavy resistance, then airdrop your demigods of destruction onto whatever dazed and shocked enemies are still standing. With its twenty model capacity (with JUMP and TERMINATOR models counting as two models and CENTURION models counting as 3) the Storm Eagle can drop an absolute boatload of marines on whatever poor souls happen to be in your way.
With 8th Edition allowing various units to pile into a single transport, the Storm Eagle can carry a devastating assault package. You want 3 assault Centurions backing up your 5 Hammernators with a Captain to give them all rerolling 1s to hit? You got it!
Also the Storm Eagle is considerably more resilient than its 7th edition incarnation. Not only is it no longer blowing up in your face on an "Explodes!" roll on the damage chart, but the Hard to hit rule means that opposing gunners will have a harder time actually landing shots on your space plane. Just be aware if you drop into hover mode you lose this rule.
A rare and precious variant utilised exclusively by the Raven Guard Legion during the Great Crusade and Horus Heresy eras of the 30th and early 31st Millennia. This variant Storm Eagle pattern was fitted with a range of highly prized and barely understood systems, from its rad-shrouded armour to its quantum field repellors. These additional systems required a higher degree of maintenance and some interior space was sacrificed to make room for them, meaning the vessel had a slightly reduced troop-carrying capacity. Given that the Darkwing pattern was often utilised to insert small units of elite warriors such as the Mor Deythan deep into enemy-held territory, this was no great loss. Each Chapter within the XIX Legion maintained a stock of these highly-prized gunships. It is not known if the Raven Guard still utilises this rare pattern of Storm Eagle in the late 41st Millennium.
The Nighthawk Pattern is a specialised variant of the Storm Eagle that was developed at the dawn of the 31st Millennium by the illustrious Sabik Wayland, an Iron Father of the Iron Hands Legion. The Nighthawk Pattern was equipped with a multi-spectrum camouflage field which greatly increased the vessel's stealth capacities. The Nighthawk Pattern was also noted to be far more agile than the average Storm Eagle and was equipped with decoy launchers able to confuse incoming missiles. The Nighthawk Pattern was still undergoing tests at the time time of the outbreak of the Horus Heresy, its construction plans having not been sanctioned by the Mechanicum for mass-production. In fact, the only Nighthawk Pattern known to have effectively flown was Wayland's own personal gunship which undoubtedly proved its efficiency on the many covert missions led by Wayland and the valiant crew of the Strike Cruiser Sisypheum. If and to what extent the Nighthawk Pattern was indeed commissioned for regular duty remains unclear.
The Roc Pattern is unique to the Minotaurs Chapter; a variant of the the standard pattern Storm Eagle is the Roc Pattern Storm Eagle, which is intended to serve as a dedicated tank-destroyer. Although outwardly indistinguishable from the standard pattern of the aircraft, the Roc Pattern Storm Eagle forgoes a proportion of its transport capacity for added specialized anti-armour munitions and on-board fuel reserves for its attitudinal thrusters to enhance its ability to carry out ground attacks. It loses six seats to hold the aforementioned additional fuel and ammunition. Beyond the original Storm Eagle's loadout, the Roc Pattern comes with lascannons standard and replaces the Heavy 2 5" blast missile launcher with a Heavy 4 twin-linked krak launcher It also gets a BS boost for attacking ground targets.
An Inquisitorial spin on the Storm Eagle, notably used by Erasmus Crowl on Terra, when an investigation took him into orbit. Sacrifices much of its armament for stealth systems unlike the Darkwing and Nighthawk. This wouldn't be the first time that Space Marine had superior tech compared to the Inquisition.