Aviation Electronics Technician 1 - Historic Naval Ships Association

Maximum range for tracking is 40,000 yards. Atranges beyond 40,000 yards, the return echo will betoo weak to maintain lock on. If unlock occurs, thesystem is automatically returned to automatic search,and the cycle of manual track and acquisition must berepeated to regain target tracking.Fire Control (Breakaway)The final submode of fire control is known asbreakaway. This mode occurs automatically if thetarget is tracked to a range that would endanger theattacking aircraft. During automatic track of a targetthat has a decreasing range (attacking aircraft isclosing on the target), the range circle is removed atthe time the range to the target gets to 3,500 yards. Inits place, a large X is displayed, which indicates timeto breakaway from the attack (fig. 3-14). Also at thistime, the steering dot will move to a position on thescope to indicate the safe direction for the attackingaircraft to turn to execute a safe breakaway. In theillustration, minimum range has been reached and thebreakaway X has appeared. The steering dot ispresently positioned to the right and above center.Bomb Director ModeWhen the bomb director mode of operation isselected, information is displayed on the PPIindicator. In this mode, the antenna automaticallygoes to sector scan, scanning a 60-degree arc, 30degrees to each side of dead ahead. Antennaelevation is manually controlled. The PPI scope has aFigure 3-15.-PPI presentation in bomb director mode.depressed center, which appears as a wedge-shapedscan on the indicator face, as shown in figure 3-15.The antenna is positioned in elevation so it will scanthe surface of the earth during a bomb attack. TheB-scope will only display the artificial horizon in thebomb director mode.The target tracking range and azimuth strobesappear on the indicator; they are moved manually sothe marks form a cross hair effect, and are centeredover the target to be tracked. Tracking is maintainedmanually in the bomb director mode. The azimuthand range strobes are controllable from 0 to 80,000yards, and, in azimuth, 25 degrees to either side ofcenter.IFF SYSTEMSLearning Objective: Recognize componentsand operating principles of an IFFtransponder set and an IFF interrogator set.There are two systems that make up the IFFsystem on an S-3 aircraft. These systems are theAN/APX-76A and the AN/APX-72. Both systemswork in conjunction with the radar set for total andsecure identification.TRANSPONDER SET AN/APX-72Figure 3-14.-B-scan presentation breakaway indication.The transponder set provides IdentificationFriend or Foe (IFF) radar replies when challenged bya valid IFF interrogator. The IFF transponder3-15