F-31 Wyvern air superiority fighter [WIP; U.R. DSAA product]

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Praxis F-31 Wyvern Air Superiority Fighter
Dominating the Skies. Overwhelming the Threat.

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Introduction - Contents - Design - History - Specifications - Purchase


An F-31 air superiority fighter in the United Republic Air Force's 1st Fighter Squadron based in Al-Aqsa Air Force Base, Merritt.
All credit for the image(s) goes to bagera3005. This image is a modification of the Mitsubishi ATD-X lineart and was used with explicit permission. The above art courtesy of Tippercommon.

- Compass Ghost scheme (1st Fighter Squadron "Freedom Fighters", 325th Fighter Wing, Al-Aqsa Air Force Base)
- Dogfighter scheme (8th Fighter Squadron "Black Aces", 301st Fighter Wing, Holland Air Force Base)

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F-31 Wyvern


U.R. Air Force F-31 fighters from the 1st Fighter Squadron on an
exercise in the northern United Republic.

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Role: Fifth-generation stealth air superiority fighter
National Origin: United Republic of Emmeria
Manufacturers:
• Praxis Defense and Aerospace (prime contractor)
  
• United Aerospace Defense Systems (UNADS)
• Defense Dynamics
First flight: August 7, 2005
Introduction: February 19, 2011
Status: Full-scale operational production, in active service
Primary users:
• United Republic Air Force
• and more; see Operators
Produced: 2005—present
Number built:
• over 648 operational aircraft
• 8 test aircraft
Unit cost:
• USD $170 million (F-31A flyaway cost)
• USD $190 million (F-31A weapon systems cost)
• USD $65 billion (development costs)
Developed from: Praxis YF-31

The Praxis F-31 Wyvern is an Emmerian single-seat, twin-engined fifth-generation stealth air superiority fighter. Designed primarily for air superiority and electronic warfare, the F-31 is capable of performing ground attack and signals intelligence missions.

The YF-31, a prototype version, was designed by an aerospace industry team led by Praxis Defense and Aerospace, UNADS, and Johnson Defense to contend against the YF-30, a fighter produced by Southard (now Southard Eckerman) and Doughbury (now part of Praxis), for the Future Air Dominance (FAD) competition held by the United Republic Air Force in 1996. The objective of the program was to create an advanced fifth-generation air superiority fighter to procure in smaller numbers to complement the smaller, lighter, cheaper F-29 Warrior multirole fighter, whose JDF program progressed around the same time. The Navy and Marine Corps opted out of the FAD program early on, focusing funds instead on the F-29. Left to issue more specialized requirements on its own, the Air Force eventually selected the more agile and maneuverable YF-31 over the speedier and stealthier YF-30, and chose Praxis to become the main contractor for the program.

Due to the extensive costs associated with the research and development of the F-31 and F-29 fighters, the Air Force recycled much of the technology from the F-29 program to integrate it into the F-31. As such, the F-31 Wyvern integrated from its start several highly sophisticated and matured technologies.

Unlike the F-29's Joint Dominance Fighter program, the Future Air Dominance program was closed off to foreign donations and monetary support. Delays caused by cost overruns in the JDF program hampered the progression of the FAD, but as these issues were resolved, the fighter reached initial operating capability (IOC) in 2008 (just two years after the F-29). Full operational capability was reached in 2011. Initially, estimates put the fighter's procurement cost at $170 million, but this number rose to $190 million due to cuts caused by delays. As contract orders were signed and more airframes were ordered, the average weapon systems cost per plane fell back to roughly $150 million by 2012 due to economies of scale.

The aircraft relies on refined all-aspect stealth capability, advanced performance characteristics, cutting-edge sensory systems, and a sophisticated defensive aids system to excel in air-to-air combat. Unlike the F-29, the F-31 does not contain an extensive survivability suite with countless redundancies; instead, it relies solely on superior all-aspect stealth and electronic defensive aids to evade detection.

The United Republic Air Force initially planned to purchase up to 750 fighters, although this number was reduced to 648 in favor of buying larger numbers of F-29s. The F-31 is tightly restricted on the export market due to the sensitivity of technologies in it.

Contents

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• Design
  1. Overview
  2. Engines
  3. Materials and stealth
  4. Cockpit
  5. Sensors and avionics
     1. Radar
     2. EODAS
     3. Electronic warfare
     4. Communications and datalinks
  6. Armament
• History
  • Operational history
• Specifications

• Purchase

[Virana]

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Overview - Engines - Materials and stealth - Cockpit - Sensors and avionics - Armament




The F-31 Wyvern is an advanced 5th generation fighter jet. It integrates an innovative fiber-mat in its structure rather than conventional radar-absorbing materials to reduce maintenance requirements and provide advanced stealth capability, which is significantly augmented by its stealthy design. Relying on a large amount of digitally-controlled flight control surfaces (that can operate in conjunction as an airbrake) and thrust vectoring, the F-31 is a highly maneuverable and agile aircraft, and its powerful engines provide significantly more thrust than previous-generation engines while being less maintenance-intensive and improving fuel efficiency significantly.

The F-31 incorporates one of the most advanced avionics suites in modern fighter jets. Using secure high-capacity datalinks, the fighter is capable of accessing networked information from across several platforms, integrating and fusing them into its unified operational picture as provided by its own sensors. The Wyvern uses a sophisticated active electronically scanned array (AESA) radar and advanced electro-optical distributed aperture system (EODAS) as its primary sensors; the former is optimal for long-distance target acquisition and tracking, and the latter serves as a multipurpose electro-optical/infrared search-and-track system that, when paired with the fighter's sensor fusion engine, provides close-range targeting and threat warning. An array of passive sensors contributes to the plane's capacity for threat warning, allowing onboard systems to employ electronic defensive aids.

An advanced defensive aids system coupled with stealth capability makes it difficult to effectively detect, target, and engage the F-31 with most weapon systems.

When paired with advanced weapon systems, the F-31's capability is further improved. High off-boresight (HOBS) missiles, or missiles that can track targets not directly in front of the aircraft, drastically improve the F-31's dogfighting capacity. Onboard EODAS systems can track threats in all orientations around the plane, and relay this information to Lock-on After Launch (LOAL) missiles. At longer ranges, the F-31's powerful AESA radar has a low probability for intercept (essentially making it difficult to detect), and it can track targets at extremely long ranges to provide targeting information for onboard radar-guided missiles at longer ranges than most previous-generation fighters.

The F-31 contains a capability to perform ground attack missions, although this capability is restricted by the limited space available in the plane's internal bays (which are essential to maintain its low radar cross-section). Bombs in the 1,000 lbs (450 kg) class can fit in the main central bay, allowing the Wyvern to perform long-range precision strike missions.

As a whole, the F-31 serves an essential role in modern United Republic air defense doctrine. Its advanced sensors and datalinks allows it to serve as a force multiplier for the URAF's fleet of 4th and 4.5 generation fighters, allowing them to track and engage targets detected by the Wyvern's sensors without being exposed themselves. The plane's own advanced capabilities, particularly when combined with other electronic warfare elements, makes it a vital component of Emmerian air strategy.

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Figure 2.1: A test of the Bahar & Carter F153
turbofan engine in a wind tunnel. Click to enlarge.

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Figure 2.2: The F-31's engine nozzles. Note the
capability for vectored thrust and low observability.
Click to enlarge.

The F-31 incorporates two Bahar & Carter F153-BC-100 two-axis thrust vectoring turbofan engines. These engines provide superior durability than legacy engines found on previous 4th generation fighters. The high thrust to weight ratio offered by the F153-BC-100 allows for far more efficient supersonic flight without the use of an afterburner. This capability, called supercruise, allows the F-31 to travel farther at higher speeds than previous generation aircraft, producing more thrust without afterburner than most fourth-generation engines with afterburner.

With 40% fewer moving parts than fourth-generation fighter engines, the F153 cuts the support and maintenance requirements in half. This improves strategic mobility, because far less support equipment is required to effectively operate the engines on deployment. In most stages of the engine, the disks and blades are constructed as a single piece to improve efficiency and reduce leakage. Unlike engines in fourth generation fighter aircraft, the fan blades in the F153 are stronger, wider, and shroudless to further maximize efficiency. A unique burn-resistant titanium alloy is used to construct the compressor stators, boosting engine heat tolerance and increasing available thrust. The same alloy is used in the engine nozzles and augmentor to provide advanced heat resistance. Because of these materials, the engine nozzles have a reduced infrared signature as compared to conventional nozzles, making the aircraft more difficult to detect using thermal imaging systems.

All engine components are controlled electronically to maximize efficient use of both engines. They do not produce visible smoke, making it more difficult to detect and track the F-31. Additionally, all line-replaceable units are "one-deep", meaning components are not stacked on top of each other. This eases maintenance requirements for the engine.

Low-observable two-dimensional thrust vectoring nozzles are used. They can direct thrust up to 20 degrees up or down (including with afterburner), drastically enhancing all-round maneuverability and agility. This is a very critical characteristic for dogfights and other close-range engagements, where advanced agility may be required to defeat the threat. Due to digital control of the nozzles, the thrust vectoring feature is integrated into the plane's sophisticated flight control system.

Despite the advent of circular thrust vectoring nozzles that can project thrust in all three dimensions, two-dimensional "slit" shaped nozzles were chosen for the F-31's F153 engine. Two-dimensional thrust vectoring nozzles can be shaped in a design more optimized to reduce both the radar and infrared signature of the rear of the aircraft, particularly due to the chevron shape of the nozzles. The advantage in the reduction of the aircraft's overall signature was considered to be more significant than that provided by three-dimensional vectoring capability; in reality, three-dimensional thrust vectoring does not provide a major advantage over conventional two-dimensional thrust vectoring. Three-dimensional nozzles provide the capability for yaw control through vectored thrust, but yaw is rarely used during air combat maneuvering. The F-31's two-dimensional nozzles can control both roll and pitch of the aircraft, and are mechanically simpler than three-dimensional nozzles like those on the Su-35.

One unique characteristic of the F153 engine that visually differentiates it from engines on fourth-generation fighter aircraft is the color of its exhaust. Due to significantly superior efficiency and higher internal temperatures, the F153 engine's exhaust is red-blue, unlike the red-orange exhaust of previous aircraft.

The F153-BC-100 engines provide 110 kN (24,730 lbf) of dry thrust each. The wet thrust is classified, but common estimations place the number at around 165 kN (37,100 lbf) each.




The F-31's design phase involved the integration of cutting edge material technologies to aggrandize the jet's performance characteristics. The extensive use of composites and titanium are stronger than legacy materials used on airframes of fourth-generation fighters, and their improved temperature and corrosion resistance properties make them optimal for use on the F-31.

37% of all materials by weight in the F-31's structural airframe are composed of Titanium-64 alloy. 13% of materials in the airframe are conventional steel and aluminum, much like that used in previous generation fighters. The fighter features a massive 42% advanced structural composites, including a unique stealth fiber mat that replaces the need for separate radar-absorbing metallic paint. A complete list of materials in the F-31's structural airframe, listed by percent weight distribution, can be found in Table 3.1.

Table 3.1: List of materials in structural airframe of F-31 by weight distribution

Material	Percentage weight distribution
Titanium-64	37%
Thermoset polymers and composites	42%
Aluminum	7%
Steel	5%
Titanium-62222	3%
Thermoplastic composites	>1%
Other (aircraft parts, and auxiliary materials etc.)	5%

Significant effort was put towards reducing the aircraft's Radar Cross Section (RCS). Rather than conventional radar-absorbing metallic paint such as that used on the American F-22 Raptor, the F-31 utilizes a new fiber mat integrated into the structural composite in a similar style to the F-35 Lightning II. This technology was developed for the Emmerian F-29 Warrior stealth multirole fighter, and it was integrated into the F-31 when the Air Force rolled matured technologies from the F-29 development program into the F-31 as a cost-saving measure and a technological breakthrough. The fiber mat requires far less maintenance than previous RAM, and it weighs significantly less.

The airframe must be produced with special care to maintain its outer mold line in order to maintain stealthy characteristics from all angles. Unlike the F-29, which was designed primarily for frontal-aspect stealth, the F-31 was designed to be difficult to detect from any aspect. One of the key aspects of proper stealth airframes is the minimization of surfaces directly perpendicular to the aspect where radar waves are expect to impact the aircraft from, which is usually from the front. Not only does the F-31's design reduce the amount of surfaces altogether, but also through the use of surfaces that face directions other than the front at angles parallel to other surfaces. The radar waves then get redirected in a single direction, decreasing the chances of indirect detection. The design incorporates parallel lines and avoids the use of curves, which compromise stealth. This is illustrated in Figure 3.2. Surfaces with a higher chance of being detected, particularly from the sides, receive more extensive amounts of radar-absorbent fiber mat composite to aid in reducing their overall cross section.

Figure 3.2: Illustration of the F-31's use of parallel edges to reflect radar waves away from their source. Click to enlarge.

A proper stealthy design must expand the use of parallel edges on areas where multiple parts connect to each other, because it is necessary to avoid high-return shapes and attitude angles. The F-31, as with many fighters, uses a "sawtooth" serrated edge design on panels that employs a staggered line, as visible in Figure 3.3, on connecting edges that would otherwise be perpendicular to the front of the aircraft.

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Figure 3.3: A photograph of the F-31's internal
weapons bay. Note the jagged construction at the
front and rear. Click to enlarge.

In order to provide advanced aerodynamics concurrent with a stealthy design, the F-31 relies on planform shaping and faceting with blended boundaries. Due to the extremely low level to which the RCS is reduced, otherwise trivial details become vital. For example, the F-31 must rely on serrated edges for access panels and doors, because otherwise, they would become significant sources for the enlargement of the aircraft's radar cross section.

Another area that increases overall radar cross section is the cockpit, where the pilot and internal bulkheads normally increase the aircraft's vulnerability to radar. In order to negate these shortcomings, the F-31 uses a carefully designed external set up that optimizes stealth characteristics, eliminates the use of a support frame (using a frameless canopy), and coats the glass in a material similar to that used for temperature control in commercial buildings. When active, this produces a gold hue from the canopy.

Because of the necessity to maintain stealth, the F-31 relies primarily on internal weapons bays for storage of armaments rather than placing them on external pylons. While four optional pylons are available, particularly for operations where a high mission weapons load is more important than stealth, they are rarely used; because the F-31 is focused on being a stealth air superiority fighter, its limited ground attack missions are conducted using internally mounted 1000 lbs (450 kg) class bombs. The pylons are utilized when the plane is flying for strategic transportation to an operational theater (ferrying), where it mounts two external fuel tanks and can also carry additional missiles.

The drawbacks to using internal weapons bays as the primary storage area is relatively significant. The bays are extremely limited in volume, and can only support a small number of weapon systems. Missiles and bombs with infrared seekers, which would otherwise require their seeker head to acquire a lock, cannot obtain a lock while inside the bay unless the bay is temporarily opened (thus eliminating the stealth advantage). The most common solution is the utilization of missiles capable of Lock On After Launch (LOAL), whereby the aircraft's own infrared sensors receive a lock and, after firing, guide a missile in the direction of its target; the missile, now launched, is then capable of acquiring a lock on its target.

The F-31 is classified as a Very Low Observable aircraft by the United Republic Air Force, with a radar cross section often cited as equivalent to that of a "metal marble". However, this is a generalization; in reality, any given aircraft's radar cross section depends on a significant amount of variables, such as incident angle, reflected angle, polarization of transmitted and received radiation in relation to the target, and other factors. It is believed that the Air Force's "metal marble" references the radar cross section from directly in front of the aircraft.

The reduction of infrared observability is also an important facet of the F-31's design. The two most common sources of infrared radiation on fighter jets are jet wakes and hot parts. It is critical to note that surfaces that emit less infrared energy may reflect more internal heat, requiring a compromised surface design for engine parts. The engines produce far less carbon, a very high emissivity material, and employ emissivity control to reduce its capacity for producing infrared radiation. The F-31 uses a combination of temperature control/reduction and masking to decrease the plane's visibility under thermal imaging. A special topcoat produced by UNADS further reduces the plane's vulnerability to infrared, and only marginally increases the plane's weight.

Despite the reduced vulnerability of the F-31 to infrared, its engines still may produce enough heat to allow most infrared missiles to lock onto it, and the heat produced by air resistance can be detected by infrared focal plane array (FPA) seekers found in the latest infrared air-to-air missiles, which employ imaging infrared (IIR) and a smart seeker to optimize their guidance system.

The low observability design of the F-31 relies on a culmination of advanced design and shaping techniques, selection of sophisticated materials, and careful attention to minute details. Through the use of advanced computer-aided drafting programs, extensive knowledge on stealth fundamentals, and advances in material technology, the F-31 is a low-observable fighter that is difficult to detect and track across the spectrum.

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Figure 4.1: The 4th generation F-16 Fighting
Falcon's cockpit displays (top) compared to the F-31
Wyvern's panoramic cockpit display (above). Click to
enlarge.

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Figure 4.2: Various configurations of the Panoramic
Cockpit Display. Click to enlarge.

Like the F-29 Warrior, the F-31 contains a full-width 50x20 cm Panoramic Cockpit Display (PCD), opting for a minimalist cockpit controls approach to ease overall burden on the fighter pilot. Because the touchscreen display is a single screen, the configuration of the display can be modified to fit operational requirements in a concept reminiscent of common computer operating systems as visible in Figure 4.2. The PCD, by default, displays all vital flight information, and by design serves the objective of reducing the pilot's burden, allowing the pilot to make rapid tactical decisions on the battlefield. A comparison of the F-31's PCD with the F-16's various displays and control systems can be seen in Figure 4.1.

To control the aircraft, the pilot has access to a right-side control stick and left-side throttle in hands-on-throttle-and-stick (HOTAS) configuration. This means that the pilot can access almost all basic flight controls without removing his hands from the stick and throttle, allowing for advanced aircraft control during complex maneuvers. Many functions that do not need to be conducted in the heat of combat—particularly minor functions such as maintenance—can be conducted using voice control.

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Figure 4.3: A demonstration
of the JACES helmet. Click to
enlarge.

The F-31 shares the F-29's Joint Aviator Combat Engagement System (JACES), an integrated flight suit and helmet-mounted display (HMD) ensemble produced by Vizispace. The G-suit allows resistance to G-forces up to 9 g, allowing pilots to perform advanced maneuvers involving tight turns. The helmet-mounted display is an advanced helmet that can project vital flight data into the helmet. Although the Wyvern was originally intended to contain a basic heads-up display (HUD) such as that found on most fighter aircraft, the success of the JACES helmet on prototypes for the F-29 development program caused it to become one of the many shared components between the two fighters. So, the F-31 was constructed without a HUD by default, but it contains the capability for one to be mounted in last resort.

The JACES HMD provides several advanced functions. Its primary function is to display flight symbology and aircraft flight characteristics for the pilot. Because this is mounted in the helmet rather than on a separate display, it is visible to the pilot when looking in any direction. The HMD's second function is to serve as a helmet-mounted cueing system; it contains a reticle that can be used to target aircraft at almost any orientation around the F-31. This cues the aircraft's weapon systems and sensors to track that specific threat and obtain a weapon lock from an onboard weapon of the pilot's choice. The novelty of this is that the F-31 does not need to be pointing at its target for successful guided weapon deployment; instead, the pilot is capable of cueing the plane's infrared search-and-track (IRST) systems to lock onto the aircraft, then launch a high off-boresight (HOBS) missile that is guided in the direction of the target. The missile then obtains a lock, and enters the normal engagement cycle. This allows the pilot to aggressively engage enemy aircraft from almost any angle, providing a significant advantage in close-range dogfights. The situational awareness IRST (SAIRST), combined with other sensors, constantly tracks all known threats around the F-31, providing the pilot with early warning and rapid threat identification.

The final objective of the HMD is to serve as a multipurpose day/night sight to provide advanced precision visibility to the pilot. The Wyvern's IRST system, called EODAS (electro-optical distributed aperture system), consists of electro-optical/infrared sensors around the aircraft that provide a "sphere" of vision for the pilot in all directions around the plane. Using the day/night sight functionality, the pilot can view high-resolution video in any direction, including directly downwards (if the pilot were to look directly down while the functionality is turned on, he would see the ground far beneath his aircraft rather than the inside of the cockpit). These images are projected onto the HMD in real time with little lag time, providing unprecedented optical clarity and precision visibility through the fusion of electro-optical and infrared sensors. Projection of vital flight symbology is another feature integrated into the helmet, which can display maps, radar, and virtual "airborne highways" that aid the pilot in flying the aircraft, especially under difficult conditions.

The helmet, in order to reduce weight and ensure compatibility with the Laertes IV ejection seat, is constructed from a metal matrix composite chassis with a carbon fiber polymer shell, and features lightweight polymer foam on the inside for shock absorbance. The helmet is connected via a short tube to the Laertes IV's suspended headrest, which in turn links with the seat's oxygen supply that is connected to the aircraft's facilities. This further reduces the weight load on the pilot's head to enhance endurance with high-g maneuvers.

The F-31 features an advanced fourth-generation Symmetriad Laertes IV ejection seat produced under license in the United Republic by Universal Air Systems (UAS). It is designated the SJU-20/A and is the same ejection seat used in some of the world's most advanced fighter jets, such as the Lyran LY910 Shadowhawk, Libertarian Chimera ATF, and Gemballa GM-25 Cuirassier. Unlike most systems utilizing the Laertes IV, the F-31 and F-29 do not utilize its integrated G-suit and helmet, instead opting for the JACES system with full compatibility.

The SJU-20/A Laertes IV incorporates numerous innovative features not found in third-generation ejection seats found on legacy fighter jets and aircraft. It utilizes rockets instead of explosives, providing precision thrust and direction control to allow for ejection under numerous circumstances, including when the aircraft is upside-down or in shallow water. The controlled ejection from the rockets places less stress on the pilot by limiting acceleration, preventing many injuries that often end aviator careers. Crew endurance is extended by up to 50-100% due to the seat's enhanced ergonomic package, which includes full adjustment, assisted movement, and active vibration absorption. Because the JACES G-suit and helmet are modified specifically for use with the Laertes IV, the suit's characteristics provide multi-point support under G-forces. An independent computer system in the seat, linked to the aircraft's sensors, can automatically eject the pilot if the F-31's destruction is imminent. The zero/zero ejection seat can be used both at high speeds and at standstill with zero altitude.

In order to maximize the pilot's field of view, the F-31 incorporates a frameless canopy, maintaining canopy strength using a tapered thickness for resistance to bird strikes, atmospheric conditions, and limited hostile fire. Unlike the F-29's forward-opening canopy, the F-31's canopy uses a conventional rear-opening design. It is coated in liquid glass and tinted in a similar manner as that used for internal temperature control in commercial buildings to preserve the aircraft's low radar and infrared signatures as well as protecting the pilot from laser dazzles and the sun.

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Figure 4.1: A common integrated processor with
many of its module slots empty. These slots can be
filled and modules can be replaced. Click to
enlarge.

The F-31 features an advanced integrated avionics suite centered around common integrated processors that combine sensory information, battlespace analysis from friendlies, and friendly status updates to provide a unified operational picture from a single source. The processor systems are networked computers integrating radar, electronic warfare capabilities, sensor data, communications, weapons, navigation, and systems data fused together under the same computer for coherent display to the pilot. Processing resources for the plane's entire avionics architecture are provided by the two common processor computers, which contain 66 module slots each that can undergo electronic reprogramming to assume the role of other modules should one or more malfunction and can be upgraded or modified without replacing the entire system. Each aircraft contains room for a third processor to be installed should future avionics upgrades require increased resources. Currently, an F-31's computers operate at 20 billion instructions per second and contain over 32 GB random access memory and 5 TB internal storage.

The F-31 employs a fly-by-optics system rather than the fly-by-wire used on legacy aircraft, using fiber optic cables instead of traditional wires to link computer systems. Fiber optics allow for faster and more efficient transfer of information, reduce overall internal weight, and are more resistant to jamming and interference. A similar fly-by-optics system was originally developed for the F-29, and later integrated into the F-31.

The advanced computers are powered by the F-31's integrated powerpack, and direct power-by-wire control to flight control surfaces using double-redundant electrohydrostatic actuators (EHAs) rather than traditional hydraulics. EHAs utilize power through electrical wires rather than an external hydraulic power supply, drastically reducing moving parts and weight. Because redundancy can be provided by utilizing extra power/control units per surface, the vast reduction in complexity eases maintenance and support requirements.

One of the key aspects of the F-31's computer systems is their powerful sensor fusion capacity. By combining data acquired through secure datalinks, from onboard sensors, and transmitted from friendly aircraft, a group of F-31s can constantly maintain an advanced and clear picture of the entire battlespace for unprecedented situational awareness.

AN/APG-94 Ghost Eye AESA radar

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Figure 4.2: The APG-94v2 being mounted onto an
F-31 Block 20. Click to enlarge.

The primary sensor system on the F-31 is the Southard Eckerman AN/APG-94 Ghost Eye AESA radar, a highly sophisticated active electronically-scanned array radar focused on air superiority. It is a phased array radar provides numerous capabilities to support the F-31's air dominance mission, instantaneously scanning 120° of airspace by electronically forming multiple beams and utilizing agile beam steering to simultaneously detect multiple threats and track priority targets. It eliminates all mechanical control parts due to its use of electronic scanning. As a low-probability of intercept (LPI) radar, the APG-94 complements the F-31's low-observability and stealth characteristics, defeating most radar warning receivers and electronic warfare systems. This is accomplished through the emission of low energy pulses over a wide frequency band, after which the signals processor combines multiple echoes to track targets. Each pulse contains far less energy than that on conventional radars and breaks conventional modulation patterns, making it astronomically more difficult for radar warning systems to detect. In terms of overall power, the APG-94 contains 1500-2000 transmit/receive modules. Using a target recognition system that analyzes Doppler shifts in the target's maneuvering in a high-resolution radar image, the F-31 is capable of determining the type of target by formulating a 3D map of the target and comparing it to known images in its database.

A subsequent upgrade to the radar, APG-94v2, integrates multimode capability, and it was developed from the F-29's APG-90 radar. It can perform simultaneous tracking of air and ground targets through the use of high-resolution synthetic aperture array mapping, automatic cueing and recognition, ground moving target indication tracking and targeting, and other methods. Rather than just a single array in the nose, the APG-94v2 integrates side-looking radar arrays in the cheeks as well, providing nearly 360° radar coverage. All Block 20+ F-31s contain the APG-94v2, and previous lots are scheduled to undergo upgrades to bring them to Block 20 specifications.

In terms of air-to-air capability, the APG-94 provides "look down-shoot down" capability, essentially allowing the plane to fire at targets beyond the horizon. Estimates place the APG-94's range for detecting targets at around 200-240 km (120-150 mi) against 1 m² RCS targets. This is comparable to several modern active electronically scanned arrays, as demonstrated in Figure 4.3.

Figure 4.3: An analysis of contemporary AESA radars and their reported detection ranges for various types of targets.

AN/AAQ-144 Electro-optical distributed aperture system

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Figure 4.4: A mockup of an electro-optical sensor
from EODAS at the North Star Expo, 2006. Click to
enlarge.

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Figure 4.5: A view of the ground through the F-31's
AAQ-144 EODAS. Click to enlarge.

The AN/AAQ-144 Electro-optical Distributed Aperture System (EODAS) serves as the F-31's multipurpose day/night camera, situational awareness infrared search-and-track, and missile launch detection system. EODAS consists of seven advanced electro-optical sensors placed in strategic areas on the Wyvern's airframe that combine to provide a "sphere" of constant infrared surveillance around the aircraft. EODAS accomplishes a number of goals on a stealthy, integrated system that legacy aircraft required external pods for. It forms an integral part of the F-31's passive sensor suite, meaning that it does not emit radiation to detect targets.

Firstly, EODAS serves as a situational awareness infrared search-and-track (SAIRST) system, constantly tracking potential threats, allied aircraft and friendlies, and other points of interest in the air. In doing so, the F-31's pilot constantly knows the exact location of enemy aircraft, and thus has a competitive edge in performing aerial maneuvers over most other aircraft. As a combined system, EODAS serves a guidance role for onboard weaponry; the pilot can track threats through EODAS in any orientation around the plane and cue infrared-guided missiles to pursue the target. Because the missiles are normally stored inside the Wyvern's internal bays, their infrared seeker cannot obtain a lock until the missile has been launched. Thus, it is necessary to use mid-flight course correction on IR-guided missiles with Lock On After Launch (LOAL) capability to attack targets at close range. Other weapon systems, such as the onboard cannon, can be slaved to the EODAS for a similar purpose. Although the cannon itself is incapable of traversing, it can be set to automatically fire once the target (who is being tracked via EODAS) approaches the gun's line-of-sight.

As a form of IRST, EODAS also serves a critical role in providing the pilot with integral Battle Damage Assessment (BDA) capability. When prioritizing or firing weapons at a given target (either in the air or on the ground), the pilot can set a display in the cockpit to follow the target in question. This allows the pilot to maintain constant target surveillance of the target and confirm the impact of weapons fired at the it.

Secondly, EODAS operates as an integrated threat launch detection and warning system. In conjunction with other passive sensors in the F-31's electronic warfare suite, EODAS can detect and locate missile launch from hostile aircraft or ground-based air defenses, and the aircraft's electronic warfare systems can respond with passive or active countermeasures to subdue or redirect the threat. EODAS has demonstrated successful detection and location of ballistic missile launches, artillery and tank fire, and other forms of hostile fire that represent a threat to allied forces. In the event of missile attacks on the F-31, the EODAS constantly tracks the missiles in any direction around the aircraft, allowing the pilot to maneuver the plane to evade the missile effectively.

Thirdly, EODAS provides spherical day/night infrared vision to the pilot. This is a critical characteristic for difficult visual conditions, such as bad weather or night operations. In previous generations, night fighter operations required the pilot to use separate night vision goggles. This was the provisional solution utilized in the F-31 until the plane's helmet-mounted display was perfected; the F-31's canopy was never designed with enough headroom to allow for use of night vision goggles, which caused numerous difficulties until the HMD was finalized. With EODAS, the pilot has access to spherical infrared vision in any direction. The helmet employs advanced optical head tracking techniques to determine the direction the pilot is facing, and the view through EODAS sensors in that direction can be projected to the helmet-mounted display.

All of the EODAS's functions are performed simultaneously at all times.

Electronic warfare system

The F-31 contains a sophisticated electronic warfare suite consisting of two distinct branches: detection systems and countermeasures. The system is termed the Southard Eckerman AN/ASQ-45 Electronic Warfare System (EWS), which operates as a versatile integrated system that improves the F-31's survivability in both aerial combat and strike missions. It employs a variety of methods to passively or actively detect, jam, or redirect guided munitions.

The system integrates a passive sensor suite, consisting primarily of systems that detect emissions. The primary sensor utilized by the ASQ-45 is the plane's EODAS system, which detects missile launches and tracks enemy aircraft and missiles around the Wyvern. Its capacity for angular localization and missile range tracking allows for compatibility with more unique countermeasures, such directional infrared countermeasures (DIRCM). Secondary sensors integrated in the ASQ-45 include sophisticated radar and laser warning receiver antennas and in the wings and stabilizers, which identify radar and laser emissions locking on to the Wyvern from any direction.

The other branch in the ASQ-45 is the universal countermeasures suite. The system can utilize the F-31's advanced APG-94 AESA radar to jam hostile radar systems. Additionally, the ASQ-45 contains an AN/VLE-12 active radar cancellation system; by sampling and analyzing incoming radar emissions, the system releases emissions of the same wavelength and amplitude with opposite phase in order to cancel out incoming emissions through destructive interference. Although these systems need to be activated, both methods are computer-controlled due to their extreme complexity.

Additionally, the ASQ-45 integrates a standardized Vehicle Countermeasure Package (VCP). It features AN/VLE-10 laser dazzlers that deploy decoy laser beams; AN/VLQ-11 directional infrared countermeasures that emit modulating dazzling laser beams; and AN/VLE-13 decoy launchers that can deploy high-powered infrared flares, ion flares, radar-defeating smoke generators, and chaffs.

Due to its integration with the F-31's cutting edge sensor fusion engine, the ASQ-45 provides advanced capabilities that drastically enhance the F-31's survivability and enhance its overall situational awareness. The fighter alerts the pilot of threats (such as a missile launch) and their location (both through symbology on the HMD and through an auditory voice cue), and relays this information through datalinks to other allied units (including other F-31s) in the vicinity. The fusion engine then combines the array of sensory information to easily triangulate the launch point for the threat, attempts to determine the nature of the threat (IR missile, SAM, etc.), and provides the pilot with a recommended solution to evade the threat as well as deploying countermeasures (such as infrared dazzlers and flares for IR-guided missiles or employment of active cancellation and chaffs for radar-guided missiles). The goal is to simplify the information that must be processed by the pilot by attempting to perform a significant portion of the processing (such as combination of SAIRST tracking, triangulation of missile launch points, and deployment of countermeasures) through computer systems and providing the pilot with the output. The result is a significantly-reduced workload for the pilot, allowing him to commit mental resources to making difficult tactical decisions on a fast-paced battlefield.

Communications and datalinks

The F-31 features a very robust communications arrangement to allow it to interface with other friendly fighters and other military units. This allows the distribution of immense amounts of data over an interconnected network, effectively synchronizing the operational picture available to all friendly units. With access to secure communications, pilots are able to ensure accurate updates of potential targets are both sent to and received from other allies.

The Advanced Multipurpose Datalink (AMDL) is an advanced data waveform used to broadcast secure information to friendly aircraft and other receiving terminals. Information about enemy targets, aircraft status, and tactics can be disseminated to other aircraft or sent by a centralized mission command system. The primary objective in practice, however, is to make each aircraft more self-sufficient and decentralize the overall mission profile. With ready access to information about friendly forces—hostiles detected or being targeted by allies, potential threats identified by external sensors, and vast amounts of other information—the pilots individually are able to operate in a far more autonomous capacity, and flights are able to coordinate (within themselves and with other flights) advanced aerial tactics. These communications are secured through tightly directed radio signals in the K_u band, and it utilizes frequency hopping and inherent anti-jamming capability to avoid interception. All signal and data processing resources are acquired from the F-31's central integrated processor. AMDL is capable of transferring data at a speed of 548 megabits per second, which far exceeds Link-16's 1 megabit per second.

Initially developed specifically for use with fifth-generation fighters, upgrades to existing receiver terminals utilizing legacy Link-16 datalinks can allow the terminals to interface with AMDL. These modifications usually require other avionics upgrades to function effectively, but they can provide 4th and 4.5 generation fighters to communicate over similar channels with similar capabilities. Because the F-31 employs both AMDL and Link-16, allied fighters without the capacity to utilize AMDL can still receive information from the F-31 and other 5th generation fighters.

[Virana]

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[Virana]

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General Characteristics

• Crew: 1 (1 pilot)
• Length: 18.85 m (61.84 ft)
• Wingspan: 12.71 m (41.7 ft)
• Height: 5.1 m (16.73 ft)
• Wing area: 75.2 m² (809.45 sq ft²)
• Empty weight: 19,800 kg (43,650 lbs)
• Loaded weight: 29,400 kg (64,820 lbs)
• Maximum takeoff weight: 37,000 kg (81,570 lbs)
• Powerplant: 2× Bahar & Carter F153-BC-100 two-axis thrust vectoring turbofans
  • Dry thrust: 110 kN (24,730 lbf) each
  • Thrust with afterburner: 165 kN (37,100 lbf) each

Performance

• Maximum speed:
  • At altitude: Mach 2.27 (2,780 km/h; 1,730 mph) (tested to Mach 2.31)
  • Supercruise: Mach 1.81 (2,220 km/h; 1,380 mph)
• Range: 3,055 km (1,650 nmi) with two external fuel tanks
• Combat radius: 730 km (395 nmi) on internal fuel
• Rate of climb: estimated ~305 m/s (68,000 ft/min)
• Wing loading: 391 kg/m² (80.1 lb/ft²)
• Thrust/weight: 1.133 (1.27 with loaded weight and 50% fuel)
• Maximum design g-load: -3.0/+9.0 g

Armament

• Guns:
  • M61A2 Vulcan 20 mm 6-barreled rotary cannon (480 rounds)
• Hardpoints:
  • 4× under-wing optional hardpoints (2 per wing) (WARNING: use compromises stealth)
    • 2× AA/AS hardpoints (wet; 1 per wing) rated for 2300 kg
    • 2× AA/AS hardpoints (1 per wing) rated for 1150 kg
  • 1× central bay
    • 2× roof-mounted hardpoint per bay, rated for 1150 kg
    • 4× roof-mounted hardpoint per bay, rated for 300 kg
  • 2× auxiliary bays (one on each side of fuselage)
    • 1× single-load hardpoint per bay, rated for 150 kg
• Missiles
  • Air-to-air missiles
    • AIM-120 AMRAAM
    • AIM-9X Sidewinder
    • IRIS-T
    • MBDA Meteor
    • Joint Weapons Program - AAMs
      • AIM-11X Python XSRM
      • AIM-145C Medusa XMRM
      • AIM-160 Golden Eagle XLRM
  • Air-to-surface missiles (only external)
    • AGM-154 JSOW
    • AGM-158 JASSM
    • Brimstone/MBDA SPEAR
    • Joint Air-to-ground Missile
    • Storm Shadow
    • SOM
    • Joint Strike Missile

Avionics

• Rayzero AN/APG-92 SCAN AESA radar and RWR (240 km against 1 m² targets for radar; 470 km for RWR)
• Southard-Ackerman AN/ALQ-43 SPECTRA defensive aids system
  • AN/AAQ-38 electro-optical Distributed Aperture System missile warning and situational awareness system
  • Radar and laser warning receivers
  • Southard-Ackerman AN/ASQ-392 electronic warfare system

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