Fixed- and rotary-wing aircraft face a plethora of Surface-to-Air and Air-to-Air Missile (SAM/AAM) threats employing radar, infrared and laser guidance. Integrated Self-Protection Systems (ISPS) provide a means of addressing these threats via pods, which can be mounted on aircraft and internal systems.
The dominant threat faced by aircraft assisting Operation INHERENT RESOLVE, the US-led air campaign against the Islamic State of Iraq and Syria (ISIS) insurgent group operating in these two countries is the danger of attack from Man-Portable Air Defence Systems (MANPADS). Several attacks have been witnessed by MANPADS. For example, on 5 April a Syrian Air Force (SAF) Sukhoi Su-22 fighter was reportedly lost to a MANPADS of an unknown type fired by Al-Qaeda insurgents near Aleppo, northern Syria. At the other end of the spectrum, Active- and Semi-Active Radar Homing (ARL/SARL) SAMs continue to pose a threat. This was brought sharply into focus in late November 2015 with the deployment of an Almaz-Antey S-400 Triumpf SAM battery by the Russian Air Force (RuAF) into Syria, following the downing of an RuAF Sukhoi Su-24 ground attack aircraft on 24 November by Türk Hava Kuvvetleri (Turkish Air Force) General Dynamics/Lockheed Martin F-16C/D fighters using Raytheon AIM-9X Sidewinder AAMs.
While MANPADS are generally employed for Short Range Air Defence, and larger strategic systems such as the S-400 providing theatre air defence thanks to the 215.9 nautical mile/nm (400 kilometre) range of its 40N6 missiles, military aircraft also face threats from systems such as the Almaz-Antey 9K37 Buk missile system capable of engaging targets at ranges of up to 13nm (25km) using its 9M317ME SAMs. Although a Russian 9K37 Buk battery shot down a civilian Boeing 777-200ER airliner belonging to Malaysian Airlines on 17 July 2014 over eastern Ukraine, an aircraft not carrying any form of self-protection systems, such weapons have claimed military aircraft in recent years. For example, during the 2008 South Ossetia conflict, Georgian 9K37 Buk-1M batteries were believed to have shot down a Tupolev Tu-22M strategic bomber, and three Sukhoi Su-25 ground attack aircraft belonging to the RuAF.
Nevertheless, it is not only SAM systems which pose a clear and present threat to military aircraft, AAMs constitute a similar danger. Air-to-air kills are less frequent in the contemporary operating environment with the notable exception of the SAF and RuAF losses discussed above. However, the continued threat posed by advanced AAMs such as the Russian Vympel R-77 ARH cannot be discounted, and hence ISPSs have to be configured to protect aircraft to this end.
Broadly speaking ISPS are available either installed at the factory level on new build, or upgraded military aircraft, or are available in a podded configuration which can be mounted to an aircraft’s hardpoints to provide self-protection. These systems can contain Radar Warning Receivers (RWRs) to alert the crew as to the presence of incoming ARH/SARH weapons, a Missile Approach Warning System (MAWS) which can detect the infrared (IR) heat signature of an incoming missile, regardless of its guidance system, by detecting the missile’s hot exhaust. A Laser Warning System can also be included to alert the crew that their aircraft has been illuminated by a laser threat such as a beam-riding missile. Meanwhile, an ISPS may also include chaff and flares which can be dispersed to present a more attractive target for an IR or ARH/SARH SAM/AAM, or a directional IR countermeasure to perform a similar function by blinding an IR-guided missile. In addition, the ISPS will include the accompanying computer hardware and software to detect incoming threats, to trigger countermeasures, and also to connect the ISPS to the aircraft’s avionics, allowing its control by the crew.
Design Considerations
During a presentation by RUAG at this year’s Electronic Warfare (EW) Europe conference held in Rotterdam, the Netherlands, between 10 and 11 May, representatives from the company outlined the fundamental design requirements for ISPSs. The company noted that these comprise sensors to see the threat, and countermeasures to neutralise it. The firm added that podded ISPSs have several attractions for military fleets: Firstly, pods can be swapped between aircraft which have been configured them. As an air force, army or navy may not always be flying all of their aircraft in harm’s way all of the time, it is possible to purchase a number of ISPSs and to swap them across a fleet as and when they are required. “One advantage of the pod is that you don’t need one pod per aircraft, just enough pods to equip aircraft performing missions,” the company representative noted during their presentation. Secondly, it may be less expensive for operators to employ a podded solution on a hardpoint rather than taking an aircraft out of service and paying for the time and effort of performing a full ISPS installation. The RUAG presentation argued that the installation of an ISPS within a combat aircraft could cost up to $2 million whereas a podded ISPS could cost circa $1.5 million, with the installation of the necessary wiring to accommodate the pod and changes to the aircraft avionics costing circa $100,000. Thirdly, local civil aviation requirements may prevent military aircraft from landing at certain airports if they are carrying pyrotechnics such as IR flares. A podded configuration means that the ISPS can be removed from the aircraft allowing it to fly into airports which otherwise may be denied. Ultimately, podded ISPSs “are a potential solution in the face of reducing defence budgets,” the company representative noted. RUAG’s podded ISPSs include its ISSYS offering which has been developed in co-operation with Saab (see below).
Like RUAG, companies involved in the provision of aircraft self-protection systems are detecting a trend towards the increased adoption of comprehensive ISPS suites for combat aircraft. Mike Doyle, capability manager for defensive aids subsystems at Leonardo’s (formerly Finmeccanica) airborne space and systems division noted, “The outdated view that adequate platform protection can be provided by fitting individual means of countering individual threats (such as an RWR linked to a chaff dispenser or a MAWS linked to a flare dispenser for IR threats) is gradually being replaced by a recognition around the world of the necessity of fielding properly integrated self-protection system.” Leonardo is heavily involved in ISPS provision with its flagship products, including the Praetorian Defensive Aids Subsystem which is used onboard the Eurofighter Typhoon family of fighters produced by the EuroDASS consortium, of which the company is a member alongside Airbus, BAE Systems, Elettronica and Indra. Mr. Doyle continues that Leonardo places a premium on ‘future proofing’ their ISPS products. He stressed that the products are “scalable and flexible” and that this approach “not only allows the solution to be readily tailored to the platform operational requirements but also to be upgraded in the future.”
Size Matters
As well as scalability being an increasingly important issue in ISPS design, size and weight is an important consideration. Available real estate is limited on any military aircraft and therefore ensuring that an ISPS is as physically non-intrusive as possible without suffering degradation in performance remains important. Elbit Systems’s All-in-Small ISPS has taken this approach, offering a self-protection system contained in a single line replacement unit which consists of a digital RWR, IR-based MAWS, advanced laser warning system and an integrated chaff and flare launcher, the company told AMR via a written statement.
Elbit Systems is joined by Israel Aerospace Industries’ ELTA systems division. Ravi Navon, the company’s EW systems marketing and projects manager states that the firm provides a number of ISPS. These include the EL/L-8206 which has a modular design letting the customer determine the subsystems they wish to use in their ISPS. Mr. Navon states that a RWR and radar geolocation device, alongside an EW controller, equips the EL/L-8206 as standard. These sensors can be combined with a MAWS and a third-party laser warning system, plus chaff and flare dispensers, a towed RF (Radio Frequency) decoy for countering ARH/SARH SAMs/AAMs and the firms’ own Directional IR Countermeasure. IAI’s EL/L-8264 product meanwhile comprises an RWR and provides radar geolocation.
Like the majority of RWRs equipping contemporary ISPSs, IAI’s RWR technology covers the two to 18 gigehertz (GHz) frequency bands. This allows it to detect a wide range of threats including ground-based air surveillance radars operating in S-band (2.3-2.5/2.7-3.7 Gigahertz/GHz) and C-band (5.25-5.925GHz) plus the X-band (8.5-10.68GHz) radars which are typically used by SAM fire control radars and fighter aircraft radars. Further up the radar spectrum, the RWR’s frequency range allows the detection of Ku-band (13.4-14/15.7-17.7GHz) radars that can be used for target tracking to support SAM batteries. Mr. Navon also states that the firm’s RWRs can be extended in frequency coverage downwards to 0.5GHz, allowing them to detect emissions from high-band Ultra High Frequency (890-942 megahertz/MHz) and L-band (1.215-1.4GHz) radars which are increasingly used for air surveillance given their ability to detect targets with a low Radar Cross Section (RCS). It should be noted that while such radars do not yet have the ability to provide a target position of an accuracy which can be used for guiding a SAM, they can denote an area of sky where a low RCS target maybe located.
Regarding podded systems IAI provides the EL/L-8212 and EL/L-8222 products. The principal difference between these includes their physical size, with the EL/L-8212 being designed for relatively small fighter aircraft such as the F-16 family, and the EL/L-8222 optimised for larger platforms such as the McDonnell Douglas/Boeing F-15 Eagle fighter family. Like other ISPSs discussed in this article, the EL/L-8212 and EL/L-8222 can be accommodated on weapons stations capable of carrying AIM-9 and AIM-120 family weapons, alongside Raytheon’s AIM-7M Sparrow AAM.
US suppliers of ISPS include Harris which, following the award of a contract by the US Navy on 21 March worth $88.3 million, is equipping that service with 48 AN/ALQ-214(V)4/5 radio frequency jamming systems. This latest order follows an earlier July 2015 award for 46 examples. The March contract is expected to be completed in December 2017. These 48 new systems will be used to protect existing McDonnell Douglas/Boeing F/A-18C/D/E/F Hornet and Super Hornet fighters. The AN/ALQ-214(V)4/5 forms part of the company’s AN/ALQ-214 Integrated Defensive Electronic Countermeasures (IDECM) family. Regarding these two variants, the AN/ALQ-214(V)4 outfits the F/A-18E/F while the AN/ALQ-214(V)5 equips the legacy F/A-18C/D, the principal differences between the two systems focusing on the mounting equipment used to install the self-defence system inside the respective aircraft. The architecture of the AN/ALQ-214 combines an RF generator, onboard RF transmitters and a towed decoy. The generator produces an RF signal designed to spoof or disrupt potentially hostile radar and radar-guided SAMs and AAMs. It also has a modular and programmable design to counter emerging RF threats. Compared to earlier versions of the AN/ALQ-214 which commenced delivery in 1997, the AN/ALQ-214(V)4/5 has a weight saving of 100 pounds (45 kilograms) and has important updates to its hardware and software architecture allowing the AN/ALQ-214(V)4/5 to take emerging radar threats into account as and when they appear.
Architecture
Beyond the considerations of size, weight and power consumption, and the need to employ scalability and flexibility in ISPS design, the architecture of an ISPS has to be carefully considered. This is particularly pertinent regarding the systems equipping fighters, a written statement from Saab to AMR noted. “The environment on a fighter regarding vibration and temperature (for example) is very challenging when it comes to (electronic warfare) equipment.” These challenges are increasingly being met, the company notes, via the use of digital receiver and exciter technology, which enjoy a higher performance and are easier to upgrade than their analogue counterparts. Regarding the transmitters which may be employed in ISPSs to broadcast jamming signals, travelling wave tubes which are used to amplify RF signals are progressively being replaced by solid state transmitters employing Gallium Nitride (GaN) technology. GaN, meanwhile, is increasingly used in the manufacture of semiconductors is it can tolerate high operating temperatures and hence high power levels, thus enabling Radio Frequency (RF) jamming transmitters to perform high powered jamming against RF threats.
Allied to this is the incorporation of Active Electronically Scanned Array (AESA) technology in RF jamming. The military radar domain has embraced AESA technology due to its ability to employ multitudes of Transmit/Receive (T/R) modules on a single antenna. Each T/R module effectively acts as its own miniature radar, generating an RF pulse, transmitting it, and processing the pulse’s echo. This enables the radar to rapidly change between modes such as air-to-air or air-to-ground tracking, to electronically steer their beams using the process of constructive interference (in a similar fashion to how two magnets with the same polarity will repel each other) thus reducing the number of moving parts which a radar requires. AESA technology has similar potential benefits for aircraft self protection in that it allows several RF threats to be engaged at once, and for threats to be jammed without necessarily needing to physically steer the antenna. Saab is employing this technology in the evolution of the self-protection system which it employs in its JAS-39C/D Gripen fighter, and which will adorn its future JAS-39E Gripen variant, unveiled in May.
Supplementing the JAS-39C/D/E ISPS is the firm’s ESTL (Enhanced Survivability Technology) podded ISPS. The ESTL can outfit any Raytheon AIM-9 Sidewinder family or AIM-120 (Advanced Medium Range AAM) weapons station, with the ensemble incorporating a MAWS, the firm’s BOP pyrotechnics dispenser an EW controller and a BOL chaff and flare dispenser. Flight testing of the ESTL has been performed using the JAS-39C/D and the ESTL is available in two versions: the ESTL-300 and ESTL-400. The discriminating factor between these two versions is the provision of an additional MAWS on the rear of the ESTL-400, and the replacement of the BOL subsystem on the aft of the ESTL-300 with an additional BOP subsystem on the ESTL-400. The company’s written statement adds that two ESTL-300s will provide full lower hemispherical coverage for an aircraft, which can also be provided with a single ESTL-400. Full hemispherical coverage can be provided by two ESTL-400s. Saab’s BOZ-EC ISPS has been designed with fighters in mind and equips the Aeronautica Militaire’s (Italian Air Force) Panavia Tornado IDS ground-attack fighters and Tornado-ECR suppression of enemy air defence aircraft.
Future Shock
One of the vexing aspects of ISPS design is that systems have to be developed with both contemporary and future threats in mind. Mr. Doyle states that future requirements for ISPS could include hostile fire indicators. The experience of the US-led coalition during the recent interventions in Iraq and Afghanistan have underscored the danger that conventional small arms fire can pose to military aircraft, particularly ‘low and slow’ platforms such as helicopters. To paraphrase Rudyard Kipling who observed in his 1886 poem Arithmetic on the Frontier that a low-cost Jezail muzzle-loading weapon much used by contemporary Afghan warriors was sufficient to kill an expensively trained British soldier, a well-placed rifle shot can bring down a helicopter. Therefore, the means of acoustically detecting small arms fire, or using optronics sensors to detect muzzle flash, could provide a means of determining the origin of a shot, allowing the pilot to perform evasive action to avoid the shot and also to determine its point of origin to give retaliatory fire.
