Scorpion Gunship

The AT-99 “Scorpion” Gunship is a highly maneuverable Mosquito-class missile platform. It is a late twenty first century airframe, developed in a period when UCAV’s were being phased out due to EMP ground-to-air weaponry falling into the hands of insurgents and terrorists, which required human pilots to be re-instated into combat aircraft after eight decades of Unmanned Aerial Combat Vehicles. Because all vehicles used on Pandora are manufactured in situ using stereolithography production techniques, it was necessary to choose vehicles from amongst 21st century designs that did not require the exotic materials technology of the mid-22nd century warfighting airframes.
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The AT-99 "Scorpion" Gunship is a twin turbine, tiltrotor VTOL vehicle. It carries some light ballistic composite armor around the cockpit, and has a canopy formed of a ballistic laminate of optically clear aluminum oxynitride and polycarbonate. Weapons are controlled by a standard on-board targeting computer with pilot override for Manual Flight Mode in high EMF conditions. The pilot’s display is a wrap-around Immersive HUD.

Weapons fire is constrained by an IFF (Identification Friend/Foe) Lockout system, which prevents friendly fire incidents in complex engagements with multiple aircraft and targets. Essentially the gun refuses to fire if the projected probability cone of a friendly vehicle’s flight path will put it in the trajectory of the bullet downrange. All air vehicles in Pandoran service can track each other in a battle theater in real time, using IFF beacons, and this data is integrated into the weapons systems via IFF Lockout.

Four gimbal-mounted .50 caliber guns with 700 rounds per minute cyclic rate of fire The Scorpion has two pair of stub-wing pylons to carry its armament. Scorpion carries 150 TK-411 WAFAR (Wrap-Around Fin Aerial Rocket) in ten 15-tube rocket launchers. The use of the rocket varies according to the warhead that can range from tactical applications to impact-based sensor systems. Eight Hawkeye HELLFIRE (Helicopter Launched Fire-and-forget) are used to engage air-to-air targets in conjunction with the nose-mounted sensor suite.

The Scorpion cockpit is fully sealed and runs at a slight positive pressure to prevent leak-in of the highly toxic Pandoran atmosphere. The corrosive effects of the hydrogen sulphide in the atmosphere requires very short maintenance cycles on all vehicles in Pandoran service, although the Scorpions with their ceramic turbines and drive motors are more resistant than their predecessors, even though those were actually more advanced and recent designs.

There is no ejection seat, as inertial auto-rotation is the preferred method of surviving a power-out scenario. These aircraft, as with all late 21st century rotorcraft, have one serious flaw. If the rotor system is damaged enough to cause eccentric failure at the rotor hub, or blade ejection, the aircraft will have serious structural damage as a result of centrifugal forces sending debris into the airframe. This is followed instantly by asymmetric lift which induces an uncontrolled axial roll, followed by total loss of the vehicle.

This tendency is mitigated by the use of ballistic ceramics and carbon-nanotube composites in the rotor duct-rings that protect the rotors. These ducts are quite robust, and can withstand significant impacts. They also prevent the rotor blade tips from contacting obstacles when the aircraft is operating in complex environments. This makes the aircraft ideal for flight ops amongst the dangling vines of the Pandoran rainforest and amongst the floating mountains. Special “vine-strike” cutters have been added to the leading edges of the airframe and the rotor ducts. These guide any impacting vines into a cutting notch, much like the wire-strike kits which have been employed on rotorcraft on Earth for two centuries.

General Specifications and Flight Dynamics:
The Scorpion was designed to fly in Earth atmosphere, but is easily adapted to operate in Pandoran air, due to its high oxygen content. The Scorpion’s twin vertical lift tiltrotors operate much like any standard rotorcraft from mid-21st century to present. The top speed of the Scorpion is 190 knots on Earth, but on Pandora it is just under 140 knots, (and this can only be achieved in a dive) because of the higher drag of the dense Pandoran air. Its rotor system is rated for 3 Gs positive and 2 Gs negative, with a 200% engineering factor. Maximum rate of climb is 545 meters per minute, with full fuel and ordnance load.

Like the 20th century Bell AH-1 Aircobra Gunship, the Scorpion is a light, maneuverable and adaptable platform. Standard configuration comprises two front-mounted guns, missile racks on the main stub wing pods mid-fuselage, and rocket pods on the lower pylons forward. On Pandora the Scorpion is typically loaded with eight air-to-air Hawkeye missiles and ten air-to-ground TK-411 rockets.

The composite triple-blade rotors are 5.49 meters in diameter, and are stacked over each other in a coaxial configuration. There are two coaxial rotor systems mounted one on either side, mid-fuselage, on rotor pylons which are fixed at an eight-degree upward angle (the standard dihedral for stability in dual ducted-rotor aircraft.)

Lift is increased or decreased by collective pitch of the rotor system, which is actuated by servos mounted in the annular ring at the outboard ends of each of the six rotor blades. Collective pitch is controlled by a traditional-style collective stick, operated by the pilot’s left hand pushing up or down. The rotors turn at constant RPM, with collective pitch controlling total power delivered to the lifting columns of air. Rotor RPM is maintained automatically by the flight CPU. Throttles are used by the pilot only in Manual Flight Mode, and are generally locked in the cruise detent. In combat or emergency flight conditions, throttles may be positioned at 120% for extra power, but this puts the blade tips near sonic speed in the Pandoran atmosphere, which shortens the life of the rotor system due to vibration.

In hover and at low flight speeds, overall vehicle pitch is induced through cyclic pitch of the rotors, which is actuated by the same servos as the collective pitch, through a muxing algorithm. Pitch attitude is controlled by a joystick in the pilot’s right hand, mounted on the right arm-rest. It higher flight speeds, the horizontal tail planes have enough control authority to induce pitch.

Roll is induced by differential collective pitch in the left and right rotor systems, actuated by the same annular ring servos which induce vehicle pitch and lift. Roll is controlled by leaning the cyclic joystick left or right.

Vehicle yaw is induced through opposed angling of the starboard and port rotor systems around the axes of their respective pylons. This is controlled with foot pedals, a tradition from the earliest rotorcraft.

Fore-aft movement of the aircraft is controlled by angling the port and starboard rotor systems together. This is actuated by servos at the base of each rotor pylon. To accelerate forward, the port and starboard rotorducts are both angled to direct their lifting air columns aft. They are angled the opposite way for deceleration. Each counter-rotating rotor system is torque-neutral, so there is no precession effect when the ducts are angled for yaw, or for forward accel and decel. Fore/aft control is done with the cyclic joystick in the pilot’s right hand, by tilting it forward and back.

There is a slight pendular moment in the lift system, for stability in hover, which causes a characteristic nose-down pitch to the vehicle when it accelerates forward rapidly from a hover, but this characteristic is not seen at higher flight speeds, because of the stabilizing effect of the tail planes.

The power plant consists of two turbine generators rated at 1,970 shp, 1469 kW, feeding to a common distribution bus. From the main bus power is divided to the two annular motors in the ring-ducts, which drive the rotors from their outer ends, rather than the hub. There is an ultracapacitor backup system which can sustain rotor RPM for two minutes, in the event of a full engine failure.

Selection Criteria and Mission:
The mission of the Scorpion is the defense of RDA assets against the various hostile forces of Pandora, which include ground predators, large ground herbivores in territorial attacks, aerial predators, and indigenous Na’vi forces attacking by ground and air. Miners, geologists, survey teams, ground patrols and other base personnel operating outside the perimeter are grateful to have Scorpions flying air-cover. Even Hell’s Gate itself would be vulnerable if not for the 26- hour vigilance of the Scorpion patrol missions.

The Scorpion is a proven “retro” design which functions well in the harsh Pandoran environment. Its ceramic bladed turbines are easily retuned to run in the denser Pandoran atmosphere. Its climb and hover performance are of course higher in the thicker air and lower gravity of Pandora, but its top speed is reduced significantly because of greater drag.

Scorpion gunships can be flown in Pandora’s fluxcons (concentrations of intense magnetic fields), and even into the most intense fluxcon on record, the Flux Vortex of the Hallelujah Mountains. However, it is not recommended because Visual Flight Rules (VFR) must be followed, due to the effects of the flux on instruments. Flying VFR in the floating mountains is hazardous because of prevalent clouds and fog, and floating unobtanium-rich rocks which are constantly moving slowly around the vortex, and therefore cannot be accurately mapped. Weapons systems are also compromised by the flux, requiring line-of-sight targeting, which makes the Scorpions vulnerable to large aerial predators.

Scorpion pilots have many stories of fatal and near-miss attacks by Pandoran aerial predators, including the large mountain banshees, the Medusa aerocoelenterates, and even rare but extremely dangerous encounters with the king predator of the air, the Great Leonopteryx. The occasional attacks by banshee-mounted Na’vi are sporadic and uncoordinated, and pose little threat to Scorpions flying in small formations of two or three aircraft. The Scorpion’s light armor and canopy can withstand the impact of a Na’vi arrow, despite its formidable mass and speed. However, it is rumored that a Na’vi firing in a vertical attack dive can generate enough combined velocity (between the 40-meter-per-second release-velocity of the arrow from the bow, and the 120 knot dive speed) that the two-meter -ong arrow can hit with sufficient kinetic energy to penetrate the Scorpion canopy if fired at close range. There are no pilots who have survived such an attack to directly confirm this, and the RDA does not, as a policy, invest time and resources in crash site investigations, so there is no forensic data available.

The Scorpion, like all the aircraft used by the RDA on Pandora, looks like an antique by mid-22nd century standards, although ironically it operates far better than more recent gunship designs which were tried in the early years of the RDA presence on Pandora.

Though long retired from service on Earth, the Scorpion is a reliable and valuable asset in the dangerous environment of Pandora. Its robustness, and ease of service in the field make it the right choice, as opposed to the newer generations of robotic and piloted combat aircraft used on Earth, which employ exotic materials in their construction (self-healing variable geometry nanocomposites), and rely on quantum electronics that cannot be serviced in situ and are sensitive to the EMF effects of the fluxcons. Also, the Scorpion is a product of an era of warfare in which EMP (electromagnetic pulse) weaponry was employed extensively, so its EMP-hardened fly-by-light flight controls and shielded propulsion system are ideal for use in the powerful magnetic fields of Pandora. Because of its small size, it does however lack AES (Active EMF Shielding), which makes it vulnerable in powerful fluxcons like the Hallelujah Flux Vortex.

Pandora attracts pilots who long for the romantic past of flying “seat of the pants”, and for the kind of aerial combat not seen since World War Two. After almost two centuries of killing over-the-horizon with advanced missile targeting and “smart” weapons, the conditions on Pandora appeal to a certain type of pilot who wants to “see the whites of their eyes” in an old school dogfight, despite the added risk to themselves.

Pilot Comments (from an interview with Colonel James “Asia” Ardmore, RDA Secops, formerly Captain USN, conducted by Freemedia Officer Marcia De Los Santos, January 4, 2149):

“Flying gunship sorties on Pandora, you’ve gotta have eyes in the back of your head. Those banshees are big bastards and they’re batshit squirrelly. They can hit speeds over 140 knots in full delta attack dive, which is usually coming out of the sun or overhead cloud cover. And they don’t know what a rotor system is, so they’ll get their damn wings sucked right through your blades if they get on top of you, then you lose the rotor and you’re going in. Of course the banshee doesn’t do too well in that deal either, but it’s cold comfort to the pilot.

“You’ve got to keep your head on a swivel if you want to live out your tour. Also, whoever spec’ed this Fang-7 gun system should be taken out and horsewhipped. They’re a close-air-support weapon, not an air-to-air weapon, so they’re set up for shooting at the ground. They’re the wrong tool for the job. They angle down and traverse great, but they only elevate about fifteen degrees. When you’re turning in on an aerial target, it’s hard to get the angle if you’re steeply banked. The banshees can turn inside us, which makes them hard to hit in a close fight. Obviously we’ve got the speed over them, except in a dive, because our VNE (Velocity Not-to Exceed) in this soup they call air here is only about 140. We’ll pull our rotors off if we try to match them in a dive. Also… never, ever, take on a Leo. Those big sons of bitches come out of the sun, and I’ve seen them tear apart a Samson and eat the crew like peanuts. Best choice is to outrun them straight and level. They can’t catch us at full boost, but they’ll sure catch you in a dive. Usually they hit from above, out of the sun, like those old German Stukas. If you feel that shadow on you, you’ve got about two seconds to react or you’re lunch. And there’s no warning screech. They screech after they’ve hit you, and it’s the last sound you’re gonna hear.”

Editor’s note: Colonel Ardmore was killed in action on Pandora. His remains were never recovered.