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a flight plan consisting of dozens of waypoints, avoiding
the tedious typing of data and the error potential of latitude/
longitude coordinates. Rather than simply navigating pointto-
point, the master system would be able to maneuver the
aircraft, permitting use of the system for terminal procedures
including departures, arrivals, and approaches. The system
would be able to automate any aspect of manual pilot
navigation of the aircraft. When the first system, called the
UNS-1, was released by Universal in 1982, it was called a
flight management system (FMS). [Figure 3-44]
3-27
An FMS uses an electronic database of worldwide
navigational data including navigation aids, airways and
intersections, Standard Instrument Departures (SIDs),
Standard Terminal Arrival Routes (STARs), and Instrument
Approach Procedures (IAPs) together with pilot input through
a CDU to create a flight plan. The FMS provides outputs to
several aircraft systems including desired track, bearing and
distance to the active waypoint, lateral course deviation and
related data to the flight guidance system for the HSI displays,
and roll steering command for the autopilot/flight director
system. This allows outputs from the FMS to command
the airplane where to go and when and how to turn. To
support adaptation to numerous aircraft types, an FMS is
usually capable of receiving and outputting both analog and
digital data and discrete information. Currently, electronic
navigation databases are updated every 28 days.
The introduction of the Global Positioning System (GPS) has
provided extremely precise position at low cost, making GPS
the dominant FMS navigation sensor today. Currently, typical
FMS installations require that air data and heading information
be available electronically from the aircraft. This limits FMS
usage in smaller aircraft, but emerging technologies allow this
data from increasingly smaller and less costly systems.
Some systems interface with a dedicated Distance Measuring
Equipment (DME) receiver channel under the control of the
FMS to provide an additional sensor. In these systems, the
FMS determines which DME sites should be interrogated
for distance information using aircraft position and the
navigation database to locate appropriate DME sites. The
FMS then compensates aircraft altitude and station altitude
with the aid of the database to determine the precise distance
to the station. With the distances from a number of sites the
FMS can compute a position nearly as accurately as GPS.
Aimer visualized three-dimensional aircraft control with
an FMS. Modern systems provide Vertical Navigation
(VNAV) as well as Lateral Navigation (LNAV) allowing
the pilot to create a vertical flight profile synchronous with
the lateral flight plan. Unlike early systems, such as Inertial
Reference Systems (IRS) that were only suitable for en route
navigation, the modern FMS can guide an aircraft during
instrument approaches.
Today, an FMS provides not only real-time navigation
capability but typically interfaces with other aircraft systems
providing fuel management, control of cabin briefing and
display systems, display of uplinked text and graphic weather
data and air/ground data link communications.
Electronic Flight Instrument Systems
Modern technology has introduced into aviation a new
method of displaying flight instruments, such as electronic
flight instrument systems, integrated flight deck displays, and
others. For the purpose of the practical test standards, any
flight instrument display that utilizes LCD or picture tube like
displays is referred to as “electronic flight instrument display”
and/or a glass flight deck. In general aviation there is typically
a primary flight display (PFD) and a multi-function display
(MFD). Although both displays are in many cases identical,
the PFD provides the pilot instrumentation necessary for
flight to include altitude, airspeed, vertical velocity, attitude,
heading and trim and trend information.
Glass flight decks (a term coined to describe electronic flight
instrument systems) are becoming more widespread as cost
falls and dependability continually increases. These systems
provide many advantages such as being lighter, more reliable,
no moving parts to wear out, consuming less power, and
replacing numerous mechanical indicators with a single glass
display. Because the versatility offered by glass displays is
much greater than that offered by analog displays, the use
of such systems will only increase with time until analog
systems are eclipsed.
Primary Flight Display (PFD)
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