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be certified for GPS non-precision approaches and meets the
requirements of and is certified to TSO C-129, class B1/C1.
Inertial Reference Sensor (IRS)
Inertial Reference Sensors are designed around either conventional
gyroscopes or the ring-laser gyroscopes. Those sensors utilizing
conventional gyros depend upon accelerometers mounted on a gyro
stabilized platform to sense velocity in all three axes. With laserreference
gyros, the difference in resonant frequency between light
beams traveling in opposite directions is used to sense the rotation
about each aircraft axis. These angular rate changes are combined
with accelerometer measurements on each of those axes to
determine the aircraft's orientation in space and to track its position.
Whichever method is used, conventional or laser, the acceleration
forces are the basis for computing directional velocities and for
keeping track of the aircraft's present latitude/longitude position in
the earth's coordinate system.
Section I
System Description
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The FMS can accept inputs from up to three IRSs. Units from
several manufacturers can be accommodated.
GPIRS
Combination GPS/IRS sensors are able to provide position and
velocity data that take advantage of the best attributes of individual
GPS and IRS sensors. GPS data has good long term accuracy (i.e.,
it does not degrade with elapsed time). However, the data can have
short term perturbations due to aircraft maneuvering or poor satellite
geometry. IRSs on the other hand have excellent short term position
resolution, however, they will tend to drift with time. A GPS/IRS will
output three different sets of data: pure GPS, pure IRS, and hybrid
GPS/IRS. It is the latter data that is used by the FMS. Hybrid
GPS/IRS data will exhibit the long term accuracy of GPS, and will
also exhibit the short term accuracy of an IRS during those periods
of poor GPS performance.
Air Data
The FMS accepts digital or analog air data from a remote air data
computer. True Airspeed, barometrically corrected or non-corrected
altitude, and Static Air Temperature are utilized. Baro-corrected
altitude is required for vertical guidance display during approaches
and for VNAV below 18,000 feet. Air Data Computers from various
manufacturers can be interfaced with the FMS.
Section I
System Description
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Data Transfer Unit (DTU)
The Data Transfer Unit (DTU) is a floppy disk drive unit, which is
designed to be mounted in the aircraft and used to update the FMS
navigation data base within minutes. A portable unit is also available
for multi-aircraft operations. The DTU is connected directly to the
FMS such that the data is transmitted directly to the FMS during the
update process. The update data is contained on 3 1/2 inch
diskettes, which refresh the entire navigation data base with each
update.
A separate subscription service is available through Universal, which
provides navigation data base updates on a 28 day cycle.
The DTU is also used to load aircraft specific performance data into
the FMS for computation and display of aircraft performance data.
The DTU may also load pilot-defined data created with off-line flight
planning software loaded into an IBM compatible computer. FMS
inflight data parameters can be written to a disk utilizing the DTU.
Maintenance log diagnostic history is also downloaded to a disk
using the DTU. FMS software updates can also be loaded via the
DTU.
Radio Tuning Unit (RTU)
The optional Radio Tuning Unit (RTU) allows the operator to use the
FMS control display unit to tune a selected radio and store up to four
preset frequencies for later use by each selected radio. COMMs,
NAVs, ATC, ADFs and TACAN are selectable through the RTU
depending upon the specific aircraft configuration.
CONFIGURATIONS
The configurations shown on the following pages represent the basic
single and dual installations for the UNS-1C, UNS-1Csp, UNS-
1B/UNS-1D and UNS-1K FMSs. The configurations shown depict
installations using all available long range navigation sensors ports.
The configuration for each aircraft will depend on the types and
quantities of sensors selected. The maximum number of each input
type has been indicated.
Triple configurations are also possible but are not shown here, as
they are extensions of the dual installation shown.
Section I
System Description
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Single Systems
In a single FMS installation the FMS simultaneously accepts inputs
from either digital DME and VOR receivers or DME/VOR/TACAN
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