Anti-Missile Decoys for Civilian Aircraft

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This article is published in AD&D Magazine

Saab Avitronics, Chemring Countermeasures and Naturelink Aviation have joined forces on a roadmap to provide civilian aircraft with self-protection systems to enhance the safety of passengers, cargo and flying personnel.

14 March 2007 will go down in history as the day when civilian aircraft obtained an effective counter-measure against dreaded terrorist attacks using Man Portable Air Defence System (MANPADS).

Amidst clear skies over the Overberg Testing Range (OTB) in Bredasdorp near Cape Town in South Africa, an Embraer 120 provided by Naturelink Aviation took to the air with the Civil Aircraft Missile Protection System (CAMPS) developed by Saab Avitronics fitted with decoys from Chemring Countermeasures.

The installed system comprised the CAMPS unit and, as reference, also the Saab Avitronics military dispensing equipment so as to check the effectiveness of the civilian counter-measure when compared against more established military decoy incendiary applications.

The tests were carried out flawlessly and Björn Erman, President of Saab Avitronics, was effusive in his comments afterwards.

“This demonstration is an important milestone in our CAMPS program. The system is designed to be an integral part of the aircraft to effectively counter the Man Portable Air Defence System (MANPADS) threat against civilian airline, transport and VIP aircraft.”

“Based on successful trials the system can potentially be operational on Naturelink platforms by the middle of 2008,” he added. “We have just started the process of getting CAMPS certified for civilian applications through the European Aviation Safety Agency (EASA).”

Infrared imageries show the heat signature of the aircraft is reduced tremendously aftre the decoy flares are dispensed, almost completely masking the aircraft © - AD&D Magazine

The CAMPS unit was specially designed to meet the requirements for civilian, VIP as well as Special Mission aircraft. This includes system safety, costs and operational aspects of this type of system which are more pronounced than for the military environment.
Such features are especially important as a civilian aircraft cannot do any evasive maneuvers to avoid a missile attack as a fighter jet can. Further, such a violent evasive manoeuvre would violate the procedures for take off and landing around an airport and could cause other risks.

Core system

At its heart, CAMPS consists of the MAW 300 ultra violet based Missile Approach Warner, a central electronic unit and the BOA dispensers. BOA is an electromechanical dispenser designed to dispense a new, non pyrotechnical type of IR decoy developed by Chemring Countermeasures which overcomes all the safety issues associated with pyrotechnical decoys.

The system is switched on when the aircraft is below 15,000 feet, which is the threat envelope of a MANPADS today. The pilot is not in the loop as the whole sequence from the firing of the missile to impact takes only about seven seconds. The missile is detected by the UV sensors and the countermeasure are initiated automatically within that time.

MAW-300 installation © - AD&D Magazine

Specifically, the MAW sensors detect the UV-light emitted by a missile´s burning propellant, both when it is launched and in flight. The range of a MANPADS varies depending of the missile type, but traditionally it is about 5,000 m and a missile attack can be detected at that distance.

This sensor has a unique optical design, incorporating state-of-the-art filter technology, with purpose-built image-intensifier tubes and photon-counting focal-plane array processors that ensure high sensitivity and a long detection range.

The basic aircraft self-protection suite has two sensors to cover the aft to beam sector of the aircraft and one Dispenser System (BOA CMDS) per engine. To achieve 360-degree coverage, the system uses a total of four sensors.

Using a distributed, hierarchical data-processing architecture to ensure optimal utilization of information in real-time, each MAW-300 sensor’s data is transferred to a digital signal processor, where equalisation, segmentation and feature extraction operations are executed.

Each sensor processor can track and process several potential threats, passing the data to a controller, where it is integrated with real-time INS information to compensate for platform movement, attitude and altitude.

Rapid real-time processing results in the system deducting if the missile is directed towards the aircraft or have a flight path directed otherwise.The controller uses neural net pattern recognition algorithms to ensure accurate operation with exceedingly low false alarm rates.

Saab lays claim to have implemented the neural-net based classifier – which to their knowledge, the only manufacturer to have done that.

A neural net, trained on valid real measured missile and clutter data, achieves superior performance over conventional “rule-based” classifiers. The neural-net based classifier recognizes missile-like behaving-events or patterns without necessarily having seen that specific missile threat before or the conditions in which it occurred.

Decoy deployment

Once a threat is identified, the BOA Counter Measure Dispenser System (BOA CMDS) is triggered. On the cockpit panel, the pilot will get an indication that the system has been activated, but he is not suppose to (and cannot) intervene in the program. The BOA CMDS is an electro-mechanical dispenser for safe, non-visible and effective pyrophoric IR decoys as covert pyrophoric decoys are foreseen as a prerequisite to counter proliferated MANPADS threats against civil airliner and VIP aircraft applications.

The featured photos taken during the testing demonstration were that of a conventional pyrotechnical dispenser on the aircraft dispensing conventional Magnesium Teflon flares – used to allow for better visibility during the test. © - AD&D Magazine

The BOA CMDS is a derivative of the mature BOL technology of electro-mechanical dispensers, a Saab Avitronics specialty since the mid 1950´s which has proven its supreme effectiveness on platforms such as the F-15, F-14, Tornado, Eurofighter and JAS 39 Gripen.

The dispensers are loaded with plastic or biodegradable packs containing leaves of pyrophoric material, with the decoy packs dispensed sideways into the free airstream. The packs are opened just after dispense and the dispersion of the leaves is augmented by the wing vortices.

The pyrophoric material can be tailored to achieve a suitable grey body IR signature. These characteristics make it possible to defeat advanced IR threats by the means of reactive dispense.

The dispense sequence is defined by data parameters including number of decoys to be dispensed and timing parameters within that sequence in order to optimize decoy response to a threat detected by the MAW-300 system.

One of the advantages with a decoy system is that it is effective regardless of how many missiles are launched simultaneously – it can handle many missiles at the same time, which all react to the decoys. A DIRCM (Directed IR CounterMeasure system) can only handle one missile at the time.

Also, it does not matter if the missile attacks come from the front, the decoys will deceive the target seeker anyway. And if the perceived threat is false, the system will initiate the decoys anyway – but Saab claims such instances will be rare with the use off the neural net-based classifier that can identify and ignore typical nuisances at airports like birds in flight.

Safety features

The dispensers are all characterized by excellent reliability, easy integration and outstanding performance – designed to suit civil airliner operations and the requirements for operation on civil airports, with focus on safety, reliability and operating costs.
CAMPS is totally modular and can be adapted according to aircraft size or operational requirements. CAMPS is easy to install, also as a retrofit, with low procurement and operational costs. The BOA CMDS is mounted internally in the engine pylons or conformal to the fuselage or inside the fuselage, depending on which aircraft is to be protected.

BOA CMDS in a conformal housing on an Airbus A320 engine pylon. © - AD&D Magazine

Mounting the dispensers close to the engine IR signature increases the decoy effectiveness. The number of dispensers varies with the engine configuration of the particular aircraft to be protected, but generally one dispenser per engine or less is sufficient.
Saab also states that the electro-mechanical dispensers are inherently safe. No pyrotechnic squibs are used and the pyrophoric decoys are non-explosive.

The pyrophoric decoy material has been developed by Chemring Group – the world leader in advanced countermeasure technology. The Combustible Area Decoy (CAD) is non-explosive, non-pyrotechnic and burns at a relatively low temperature.
The probability for inadvertent dispense is extremely low and furthermore, the effect of an inadvertent dispense is also very low due to the low dispensing velocity (1-2 m/s), the low mass of the decoys (order of a magnitude lower than a pyrotechnical flare) and the low burn temperature featured by the use of covert pyrophoric decoys.

The pyrophoric decoys in conjunction with the electromechanical dispensing features of the BOA CMDS enables a non-pyrotechnical system, eradicating the risks involved with pyrotechnic dispensing and ensuring safe handling and operation.
The pyrophoric decoys also release virtually all its energy in the IR spectrum, i.e. at lower temperatures than traditional flares, which mitigates the risk for collateral damage and makes the decoys virtually invisible to the human eye.

Installation of BOA CMDS in the engine pylon of a Boeing aircraft. The packs are dispensed sideways into the air stream. © - AD&D Magazine

Due to its pyrophoric nature and clever package design, the material is safe to load and unload, and requires no special training or protective measures to handle it. The covert decoys are placed inside a sealed package and are opened and activated only after being dispensed into a fast airstream, which is needed to open up the decoy pack.

Electromechanical dispensers are also silent: no sound can be detected inside the aircraft when decoys are dispensed.
The decoy cassetes are designed to house decoys for two separate attempts – one at start and one at landing. The number of decoys per missile attack depends on aircraft type. Once the cassettes have been initiated the maintenance personnel have to change the cassettes.

The decoys can be handled without special facilities or training; the handling and loading is simple. CAMPS is installed flush with the aircraft skin and does not add drag to the aircraft, and has minimal weight implications.

The CAD material has been designed so that it burns almost completely to leave no solid matter as a residue following combustion. This means that after dispensing there is virtually no evidence that decoys have been ejected.

360° warning coverage system. © - AD&D Magazine

The consequence of this is that the material can be safely dispensed in sensitive areas, such as those surrounding civilian airports. Unlike with conventional flare decoys, the possibility that burning material could reach the ground has now been eliminated.

Saab Avitronics offers technology, products and services within Electronic Warfare as well as airborne mission and utility sub-systems to defence forces and industries worldwide. It serves the global market with world-leading products, services and solutions ranging from military defence to civil security and is a leading supplier of Avionics and Electronic Warfare Systems on the international market.

The company offers a full range of Electronic Warfare assets, with focus on systems, equipment and in-service support for self-protection, ESM and Electronic Attack. Key elements are radar, UV and laser sensors as well as jammers, decoys and counter-measures dispenser systems. Complete EW systems are available for airborne, naval and ground vehicle applications.

Its Avionics range include airborne mission and utility systems, health and usage monitoring systems (HUMS), reconnaissance systems and flight control equipment. Key competence areas are safety critical systems and software, modular avionics, video and graphics processing, digital map systems and sensor integration.

Saab Avitronics has some 1200 employees in Sweden (Järfälla, Kista, Linköping, Jönköping and Gothenburg) and in South Africa (Centurion, Midrand and Cape Town).

CAMPS in a nutshell

The MAW-300, provides for:
• 110° conical Field-of-View per sensor.
• Seamless handover between sensors.
• Accurate and rapid detection and tracking of approaching missiles.
• Multiple target tracking capability (up to 8 targets simultaneously).

The Electronic Controller Unit (ECU):
• Processes the sensor information.
• Determines missile Angle of Arrival and calculates Time To Impact (TTI).
• Initiates BOA decoy dispensing at optimized time.

The BOA CMDS is loaded by exchanging a preloaded magazine containing the decoys packs. When loaded in the magazines, double barriers protect the packs from air. The maintenance of the dispensers and replacement of decoy magazines can be kept to the aircraft regular maintenance at intervals of one year or more. No flight-line maintenance and very low preventive maintenance is required.
• Payload Capacity ~30 packs
• Control Signals RS-485 serial data link,
• MIL-1553B data bus, discretes
• Power Supply 115 VAC, 400 Hz or 28 VDC
• Mass fully loaded 7.5 kg

Source & copyrights: AD&D Magazine

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