Protecting aircraft against IR guided missiles depends in most cases firstly on reliable detection and warning of missiles and secondly on applying effective ECM. An exception to this are omni-directional IR jammers which do not make use of missile warning at all, as they simply radiate modulated IR energy for as long as they are switched on. These jammers have been around since the 1970s and when the correct jamming modulation techniques were applied, were reasonably effective against 1st-generation amplitude-modulated MANPADS, which operated in the near-IR band (1 to 2
micrometres (μm)). The arrival of 2nd- and 3rd-generation MANPADS changed that. They operate in the mid-IR band (3 to 5 μm) and use more advanced modulation techniques (for example frequency modulation). Instead of jamming these missiles, the omni-directional IR jammer became a source for the missiles to home in.
Functional requirements Providing timely warning against IR MANPADS is a challenge. They give no warning of their presence prior to launch, they do not rely on active IR, radar guidance or a laser designator, which would possibly emit a detectable radiation. They are typically fire-and-forget and can lock on and engage a target, speed to the target and destroy it in seconds. They have a small but visible radar signature and also a propellant which burns – depending on the platform, typically for a very short duration. MANPADS are relatively short-range weapons, typically up to about five kilometers with the heart of the kill envelope one to three kilometers. They therefore allow very little margin for error to effectively counter them as the time to impact (TTI) on a target at one kilometer, is only about three seconds. The TTI for targets at three and five kilometers is also relatively short – only seven to a little over eleven seconds respectively. The MAW must provide reliable and timely warning to allow appropriate counter measure responses. Near 100% probability of warning (POW) and very fast reaction times to counter nearby missile launches (in the order of one second) are essential. Air crew will rely on the system only if they have high confidence in it. The MAW must also have sufficiently low
false alarm rates (FAR), even when illuminated by multiple sources (which may include threats) from different directions. Quick response times and low FAR are inherently conflicting requirements. An acceptable solution requires a balanced approach to provide the most successful end result without compromising the POW. Since a longer time-to-impact (TTI) warning is almost invariably desirable, this leads to the conclusion that there is something like a too-low FAR: all warning systems gather data, and then make decisions when some confidence level is reached. False alarms represent decision errors, which (assuming optimal processing) can be reduced only by gathering more information, which means taking more time, inevitably resulting in a reduced time-to-impact. Most users would tolerate an increased FAR (up to some point where it starts limiting operations) instead of a reduced TTI, because their probability of survival depends fairly directly on the TTI, which represents the time in which countermeasures can be deployed. Accurate azimuth and elevation angle of attack (AOA) information can be another very important requirement.
Directional IR counter measures (DIRCM) systems depend on MAW systems for accurate enough initial pointing (about two degrees) to ensure that the DIRCM acquires and engages incoming missiles timely and successfully. Accurate AOA is also important in deciding the dispensing direction of the counter measure decoys (flares). It is vital to avoid the situation where the platform and the dispensed decoys both remain within the instantaneous field of view (IFoV) of incoming missiles. In situations like that missiles could very well, once they pass the decoys, still hit the platform. This is of particular importance where separation between the decoys and the platform takes too long as is the case with slow flying aircraft. Accurate AOA is further important where the platform should preferably maneuver when dispensing decoys to increase the miss distance. This is more applicable to fast jets where their high speed tends to negate the separation caused by the decoy's ejection velocity. A turn towards approaching missiles to establish/increase the angle between the decoy and the platform is especially important in cases where a missile approaches from the rear between the five or seven 'o clock sectors. If the AOA is not accurate enough, the pilot could very well turn in the wrong direction and set himself up for the situation as described above. The system must also be fully automated as the human reaction time in relevant cases (short range launches) is too long.
Physical requirements Light aircraft, helicopters, and fighters usually have limited space and mass capacity for additional equipment. The system may also cause adverse aerodynamic drag which demands minimal physical size and number of boxes. The power consumption must further be kept within the capacity of the platform's electrical system.
Human-machine interface (HMI) requirements Integrated display and control functions are desirable to avoid duplication on instrument panels where space is limited. If a platform is equipped with both radar and missile warning systems, the HMI should display both threats clearly and unambiguously. The integrated HMI must also indicate the system's operating status, serviceability status, mode of operation, remaining decoy quantities etc. Separate control panels are justified only for safety of flight purposes such as ECM on/off and decoy jettison functions.
Cost considerations Procuring electronic warfare (EW) self-protection systems has direct and indirect cost implications. Direct costs involve the initial price of the system, spare parts as well as test equipment to ensure that the performance and availability of the systems is maintained throughout their entire life cycle. Installing and integrating EW systems on aircraft is another direct cost Indirect cost on the other hand involves degradation of the aircraft's performance as a result of having the system on-board which in turn impacts negatively on the operating cost of the aircraft. The lowest initial price of a system does therefore not necessarily offer the best solution as all the factors needs to be considered. The overall cost effectiveness of systems i.e. price versus performance is more important in deciding which system to select. ==Types of MAW systems==