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
