JAS-27 Rook

Aestrup JA27 Viper
A Royal Acrean Marine Corps JA27NG over the Gulf of Åland, 2022
Role	Multirole fighter
National origin	Acrea Ossoria
Manufacturer	Aestrup ASA
Design group	Aestrup ASA Tionscail Ríoga Aeraspáis
First flight	1 October 1984
Introduction	14 December 1988 (RAMC) 24 March 1993 (RAAF)
Status	In active service
Primary user	Royal Acrean Marine Corps

The Aestrup JA27 Viper is a single-engine, 4.5 generation fighter produced by Aestrup Stridsluftraumsystemet AB for the Royal Acrean Marine Corps and Royal Acrean Air Force. A joint development between Aestrup and Tionscail Ríoga Aeraspáis, the Viper is a product of the Flygsystem 85 program conducted throughout the 1980s.

The JA27 has numerous differences which set it apart from the T-32. When the production Viper debuted in 1987, it was internally and externally different from the Ossorian T-32 which accompanied it. The Viper is slightly larger to accommodate a more powerful engine and increased fuel and payload capacity. It includes different avionics suite, and different onboard systems. The most modern variant is the JA27E, which is fully considered a 4.5 generation fighter and boasts innovations derived from the EFX fighters such as composite construction, full inter-aircraft networking, and sensor-interface integration. The JA27 is named after the Vipir or Vipère, a serpent-like dragon in Acrean mythology.

Development

The Flygsystem 85 (FS85) project began in the late 1970s as a joint program between Acrea and Ossoria to develop a new multirole lightweight fighter. Although the Acrean and Ossorian militaries had different intended roles for the fighter, the initial requirements drawn up were close enough to join together on the project. Development was initially conducted off the back of the successful EF-137 Valkyr which saw service in Acrea and Ruvelka. It's low maintenance requirements, high cost efficiency, and short takeoff and landing characteristics were considered highly desirable, particularly by the RAMC which sought a replacement for the Valkyr for its fixed-wing aircraft corps. These characteristics were to be combined with those of the EF-161 Raven which had entered RAAF service only a few years earlier. The intended result was to be an economical, flexible, highly maneuverable multirole fighter.

Development diverged slightly as early as 1982, as Ossorian requirements drew in the direction for a more economic lightweight fighter whilst Acrean considerations instead wanted more performance out of the aircraft. The result was the concurrent development of two near-identical but different models. As a result of its more demanding requirements, development of the Viper often lagged behind the T-32 by several months. The fighter entered RAMC service in 1988, and began limited service in the RAAF in 1993.

Design

An RAMC JA27C parked in Ruvelka, 2011.

The JA27 Viper is a single engine multirole tactical fighter. It was designed to be lightweight, highly maneuverable cost effective, and easy to maintain. Unlike the earlier EF-161, the Flygsystem 85 was designed to be a multirole fighter from the outset. Although the final product suited Ossorian requirements, it was not considered to be suitable by the RAMC and RAAF. Consequently, the JA27 debuted with substantial changes to enhance its air-to-air performance; it was fitted with the then-brand new EJ-900-91 engine providing 87 kN of thrust in mil power and 142 kN in reheat. Additionally, the aircraft's flight control systems were tinkered with, and its avionics revamped. The radar was replaced and an IRST added, with the fire control systems replaced by Acrean systems adapted from the EF-161. This allowed the aircraft to be compatibly with Acrean helmet mounted cueing systems and allow it to take advantage of the high off-boresight capability of Acrean missiles. The airframe was slightly enlarged, a change that would be adopted by the Ossorian Air Force in the design of the T-32E, and the cockpit slightly raised and the forward upper fuselage modified to increase visibility. The gun was replaced by a 27mm revolver cannon.

Moderate improvements were made to the aircraft over its lifespan in service. The Block CI production lot introduced thrust vectoring with the multi-axis MAVS system, which was integrated with a new flight control system. This modification heavily increased the flight performance of the airframe; in addition to providing it with exceptional low-speed authority, it also enhanced energy performance by utilising both the MAVS system and flight control surfaces to maneuver the aircraft with the least amount of drag.

Modern Vipers are made with composites to lower their radar cross section. Radar and sensor systems are largely derived from the EFX fighters, and their sensors and computer systems constitute the most complex and expensive parts of the aircraft's development. The Viper carries an AESA radar, complimented by an IRST equipped with a magnified long-range optical sight to aid in long range identification, an , and a SOL integrated electronic warfare and countermeasure system. SOL contains a SAIRST/DAS consisting of high-resolution infrared sensors directed around the airframe to provide near full spherical coverage. The SAIRST and the aircraft's RWR provide detection of both infrared and radar-guided missile launches, and the SAIRST also directs infrared imaging countermeasure against incoming infrared missiles. The Viper utilises data link to share information gathered through its variety of sensors with both friendly Air Force and Navy aircraft.

Usability and Maintenance

Like the EF-137 it replaced, the JA27 was designed around low-cost operation in austere or ersatz conditions with minimal maintenance requirements, which remains one of its key features. This requirement was directly drawn from its development from the EF-137. The Viper is designed with modularity in mind, meaning that every major component is part of a module which can be rapidly and easily replaced, repaired, or swapped in field conditions. All aircraft are fitted with a Health and Usage Monitoring System (HUMS) that monitors the stress and performance of various aircraft systems and components, and provides information to technicians and maintainers to assist in servicing it.

In the field, the Viper is able to operate with a runway space of 600 meters long, and 12 meters wide. This enables it to be used on ersatz runways constructed from highways and major roads, as well as temporary runways and landing strips. The Viper was designed to be serviced by a small team and have a short turnaround time; during combat operations, a Viper can be refueled, re-armed, and undergo basic inspection and servicing within ten to twenty minutes (depending on mission type) by a team of six maintainers and technicians.

Avionics

RAMC JA27As over Shalum, 1990.

The Viper NG uses the MEGINGJÖRD-DA integrated avionics suite developed from the EF-662 Vampyr, a key aspect of which is its sensor fusion and sensory integration; information gathered through its multitude of sensors and systems are filtered, synthesised, and displayed on the pilot's display to enhance situational awareness and reduce the workload of the pilot. Key sensors on the aircraft are its Kobalt-Zeiss AR/ASM-06S active electronically scanned array (AESA) radar, MDA EK/RMG-11 electronic warfare and countermeasure system, and a Kobalt-Zeiss OS/IRN-D suite which includes the aircraft's infrared search and track sensor slaved to a magnified optical sight, a separate electro-optical targeting system, and its infrared distributed aperture system, and its CNI suite. The avionics of the Viper are designed to communicate with one another to complement roles; the AESA radar provides a component of the electronic warfare system, for instance. They filter, and synthesise the information gathered and present it as a cohesive, comprehensive image of the battlespace to the pilot. The AR/ASM-06S radar is reported to provide a tracking range in excess of 150km, and is complemented by the OS/IRN-D, a component of the Vipers's SOL Combat Avionics Suite. The OS/IRN-D's IRST allows the aircraft to detect airborne targets at a reported range of up to 100km, and surface or sea targets at 10km. Full target tracking and identification is reportedly slightly closer than the maximum detection range of the IRST, while tracking range with necessary quality and precision for weapons guidance is further limited. A primary function of the IRST is use against opposing 5th generation aircraft to allow it to detect, vector onto, and engage said aircraft. It can also use this capability to vector onto and track enemy aircraft without eliciting radar emissions that would reveal its presence. The OS/IRN-D's distributed aperture system consists of several infrared optical sensors arranged around the aircraft that works in conjunction with the RWR of the EK/RMG-11 to provide all-aspect missile launch warnings for both radar-guided and infrared-guided munitions, as well as increased situational awareness. Although the sensors can detect and provide a basic track to the pilot, they are unable to provide adequate tracking for weapons. The pilot's head-mounted display tracking was considered sufficient to provide tracking for the aircraft's high-off boresight M-9 IRSS missiles. In addition to OS/IRN-D, SOL provides conformal electronic countermeasure pods distributed along the wing roots of the aircraft. Networking with the missile warning system provided by the SAIRST, the SOL pods use directed infrared light to attempt to confuse or spoof the seeker of incoming infrared missiles, enhancing survivability especially when combined with other defensive measures like flares and evasive maneuvering. The Viper can rapidly provide information and targeting data to friendly aircraft via datalink, although it does not possess a radar as powerful as dedicated platforms. The deliberate upgradeability designed into the airframe both via software and ease of hardware replacement allows these systems to be easily and efficiently swapped and updated.

Cockpit

The cockpit of a Viper E in a simulator.

The Viper NG's upgraded cockpit in a simulator.

The Viper uses a full glass cockpit and all-digital flight instruments. The head's up display (HUD) is used as the primary flight instrument, with symbology and information for various flight modes displayed for the pilot. was displayed originally on three large liquid-crystal multi-function Head's Down Displays (HDDs) arranged in the cockpit. This cockpit design was changed slightly for the Viper NG. The three LCD MFD displays were replaced by a single large LCD touchscreen multi-function wide area display with further improved fidelity and resolution, complimented by two additional smaller displays on either side of the cockpit in a similar arrangement to the EF-650 Striga. Despite the addition of touchscreen capability, tactile buttons for manipulating the MFDs were retained by demand of pilots. The cockpit displays underwent additional updates in 2015. The Viper NG also implemented a new helmet-mounted display system (HMDS), allowing pilots to display all flight and combat information, usually displayed on the HUD, in their visors. As a result of this, the Viper's traditional HUD frame was replaced with a more discrete, thinner framed display.

Operational History

Zemplen War

Acrean JA27Cs were deployed in Ruvelka to provide point air defence and close air support during the Zemplen War. One fighter group consisting of three squadrons- VF-64, VF-59, and VF-76- was distributed across multiple airfields in Ruvelka. Compared to other Acrean airframes, they accounted for relatively few combat victories, achieving a combined total of 15 shoot-downs of enemy aircraft of various types over the course of their deployment.

Midsummer War

The Viper accounted for the most numerous fighter airframe deployed by the RAAF during the Midsummer War, with two fighter groups deployed in Shalum at the outbreak of hostilities. Due to the success of Coalition air operations, however, the Vipers did not see much use as their primary responsibility was the defence of Shalumite airspace.

Variants

• JA27A: First series aircraft introduced in 1988.
• JA27C:
• JA27E: The Viper E, introduced into service with the RAMC in 2009, includes a more advanced AESA radar, new electronic warfare systems, as well as a fully redesigned internal cockpit eliminating old instruments and replacing them fully with high-resolution LCD displays, and using improved sensor and system integration derived from the EF-662 program and EF-165 modernisation program.
• JA27NG: Introduced in 2014, incorporates several avionics and interface changes.

Operators

Current Operators

• Royal Acrean Marine Corps
• Royal Acrean Air Force

Specifications (JA27NG)

General Characteristics

• Crew: 1
• Length: 15.5 m
• Wingspan: 8.8 m
• Height: 4.5 m
• Wing Area: 31 m²
• Empty Weight: 7,800 kg (17,200 lbs)
• Max Takeoff Weight: 16,500 kg (37,000 lbs)
• Powerplant: 1x MDA EJ-900-5 afterburning turbofan, 90 kN (20,233 lbf) dry thrust, 145 kN (32,500 lbf) reheat
• Fuel Capacity: 3,500 kg (7,700 lbs) internal

Performance

• Maximum Speed: Mach 2.05 at altitude
• Mach 1.25 at sea level
• Mach 1.2 supercruise at altitude
• Service Ceiling: 58,000 ft

Armament

• Guns: 1 x 27mm revolver cannon with 220 rounds
• Payload: 10 hardpoints (9 weapons-capable, 3 external tank-capable, 1 designated for FLIR/TGT/EW pod) with capacity of up to 7,200 kg of stores
  • Example Air-to-Air Configuration: x2 M-9 IRSS, x10 M-13 MSRA (8 on twin store racks), x1 external fuel tank