Tactical Air Navigation (TACAN) System
TACAN is a radio navigational set that provides
slant range and relative bearing to a transmitting ground
(surface) station. It has Distance Measuring Equipment
information. The Bearing Distance Heading Indicator
(BDHI) provides a visual indication of the navigational
situation for that aircraft.
Global Positioning System (GPS)
The Global Positioning System (GPS) is a
space-based radio position and navigation system
designed to provide highly accurate three-dimensional
position, velocity, and time data to suitably equipped
aircraft anywhere on or near the earth. The Satellite
Vehicle (SV) consists of 24 operational satellites in six
circular orbits (10,900 nmi) above the earth at an
inclination angle of 55E with a 12-hour period. The
satellites are spaced in orbit so that at any given time a
minimum of four satellites will be in view to users
anywhere in the world.
The GPS Navigation Set receives and processes SV
signals, combines them with air data information, and
then calculates and displays the aircraft position for
navigation. The information includes present aircraft
position, course information, distance and time to
waypoint and desired track, along with other navigation
information. GPS consists of three independent
segmentsthe satellite segment, ground segment, and
the user segment.
navigational equipment is now in use in naval aviation.
This equipment does not use a radio receiver as the
equipment, and inertial navigation equipment.
NAVIGATIONAL COMPUTERS.One of the
navigational aids now in use is a latitude and longitude
type of airborne computer system. This system can
make the following computations during flight:
The latitude and longitude of the present
position of the aircraft. This information is
continually displayed on the pilot's console.
! The aircraft ground track angle, relative to true
! The distance from the present position of the
aircraft to a preset target or base, as selected on
the control panel.
! The bearing of the preset target or base, as
selected, relative to true heading.
The computer is an analog-type computer. It
includes a group of servomechanisms that receive
navigational information and, by solving trigonometric
equations, produces output information. Data input
consists of the following:
! Compass heading
! True airspeed
! Magnetic variation
! Base position latitude and longitude (usually
the starting position)
! Target position latitude and longitude
! Aircraft's latitude and longitude (if not
identical to base)
The magnetic compass and the true airspeed
transmitter automatically furnish compass heading and
true airspeed. The remaining inputs are set manually by
control knobs on the counter-control panel. The com-
puter sections continuously reposition the POSITION-
LATITUDE and LONGITUDE counters to show the
aircraft's present position and/or the intended target's
Doppler navigation is based on a radar wave trans-
mission beamed toward the earth behind the aircraft.
This radar does not sense range and bearing (direc-
tion) as ordinary search radar does. Instead it uses a
continuous wave (CW) transmission to measure the
ground-speed and drift angle of the aircraft. The Dop-
pler navigation system operates anywhere. It is rela-
tively unaffected by weather conditions, and is inde-
pendent of ground-based navigation aids. This permits
an aircraft crew to compute an aircraft's track. The track
is projected on the ground from any known position
(usually the position of takeoff) to any position desired.
Therefore, long-distance navigation is possible.
INERTIAL NAVIGATION EQUIPMENT.
An inertial navigation system (INS) is an automatic aid
to navigation that is independent of outside references.
An INS is a portion of the overall tactical system that
provides accurate velocity, attitude, and heading data to
a digital data processing system. This overall system
permits accurate weapons delivery. To function
properly, the system must be aligned with reference to
initial conditions of altitude, latitude, and longitude.