A new generation of electronic warfare decoy, succeeding the AN/ALE-50, the AN/ALE-55 Fiber Optic Towed Decoy consists of an aerodynamic decoy body, with variable drag fins and air brakes, a fiber optic connection to the towing aircraft, and the aircraft side of the cable, which connects to the onboard electronics warfare systems. It is part of a three-part architecture for electronic warfare, in which the towed decoy is the final line of defense, using a technique whose power has been known for millennia: seduction.
Traditional electronic warfare systems first try to suppress enemy search sensors. Against a radar sensor, suppressive jamming can come from antennas on the towed decoy, on the towed aircraft, or from antennas on escort or standoff electronic warfare aircraft. Passive radar-reflecting chaff, ejected in cartridges from the AN/ALE-47 countermeasures, can confuse the search radar, or later, tracking radar.
If suppression fails and the enemy locks tracking radar onto one's own aircraft, the next step is to deceive that radar. Since tracking and search radar signals are often different, the deception phase will involve changing the defensive transmissions to match the new radar type(s). A deceptive decoy does not attempt to suppress the enemy sensors, but to confuse them, often presenting multiple images of which only one is real.
Seduction is the final line of defense. A maneuvering towed decoy potentially can move in a way that the missile cannot follow. If necessary, the towed decoy can sacrifice itself by appearing to be the target aircraft. This differs from deception, in that one particular image will try to attract the sensor rather than present it with multiple choices.
In addition to the towed decoy, the aircraft can also eject more chaff, as well as expendable radar jammers. The latter, such as the RT-1489/ALE (GEN-X), are especially effective against semi-active radar homing, where the missile is looking for the reflections from a separate radar illuminator. The GEN-X, falling away from the aircraft it protects, receives that illuminator signal, and regenerates it to be "brighter" than the true reflection.
Decoy handling and users
As opposed to the cable on the earlier ALE-50, the tow cable can that can withstand the afterburner of a F-18 Super Hornet or B-1 Lancer, while the aircraft maneuvers at supersonic speed. While the decoy can be jettisoned, an aircraft-side cable manager, implemented on the C-130 Hercules, can reel the decoy back aboard, for reuse.
If the EW system decides the jamming would best come from the decoy, it uses the onboard computers to generate an optimum jamming pulse, converts it to light, sends it down the fiber optic cable, where the ALE-55 converts light to the appropriate frequency and radiates it. In contrast, the earlier ALE-50 had to make all its decisions with its limited onboard logic.