SEARCH RADAR SYSTEM

CHAPTER 3 RADAR As an avionics supervisor, you must be knowledgeable of the operation principles of various complex search radars, fire control radars, IFF sets, and the associated peripheral equipment. Chapter 2 of Aviation Electronics Technician 2 (Organi- zational), NAVEDTRA 12330, explains the basics of radar. This chapter discusses the search radar found on the P-3C aircraft, the fire control training device 11D13A, and the IFF system found on the S-3 aircraft. The peripheral equipment, such as the tactical displays, computers, and navigational systems, are discussed in other chapters of this TRAMAN. (See table of contents.) SEARCH RADAR SYSTEM Learning Objective: Recognize components, operating principles, and characteristics of a typical search radar system. The AN/APS-115B radar set used in the P-3C aircraft is an airborne, X-band search radar system. It provides detection and surveillance of submarines operating under snorkel conditions, surface vessels, and aircraft. It is made up of two radar receiver- transmitters, two antennas, two radar controls, an antenna control, an antenna position programmer, an antenna parking control, an antenna scan control, and a radar interface unit. The receiver-transmitters are selective, long and short pulse-type radar receiver- transmitters. The antennas are located in the nose and the aft of the aircraft, providing 360-degree azimuth coverage. Radar search scan and data pickup are performed independently by each radar set. The antenna position programmer (APP) combines video information from both radar sets. The APP then sends this information to the radar interface unit (RIU), which sends it to the sensor data display (SDD) for display. The two antennas are tilt-stabilized by servomechanisms, receiving pitch and roll data from the central repeater system (CRS). The tilt of the antenna can move from 20 degrees down to 10 degrees up, referenced to the horizontal. Antenna scan is selectable to either full (360 degrees) or sector (45-degree scan about a selected heading). With only one antenna system, the scan can be no more than 240 degrees in azimuth. Either antenna may be stopped to searchlight a specific area. With both antennas in full scan, the crossover points are at 90 and 270 degrees relative to aircraft heading. In sector scan, crossover points are at 120 and 300 degrees when the antennas are rotating in a clockwise direction. The crossover points are 60 and 240 degrees when they are rotating in a counterclockwise direction (fig. 3-1). The nonacoustic sensor operator station displays the search radar information. The display presentation is true north or aircraft heading stabilized, with a computer-generated symbol depicting aircraft true course. The nonacoustic operator station contains the radar systems operating controls. AN/APS-115B MAJOR COMPONENTS The APS-115B search radar system includes the following equipment: l C-7511A/APS-115 radar antenna control panel l MX-7930/APS-115 antenna position pro- grammer . RT-889/APS-115 receiver-transmitter . AS-2146/APS-115 antenna l A361 antenna elevation parking control l C-7512/APS-115 radar control panel l C-7557/ASA-69 radar scan converter control . MX-7974/ASA-69 radar interface unit 3-1