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station and deviation from a preselected course. When turned to an ILS frequency,
the system provides a display of the lateral and vertical deviation from the optimum
landing path .
DME (Distance Measuring Equipment ) DME system measures the slant
range distance to the selected DME facility.
ATC (Air Traffic Control )------ ATC system transmits airplane identification
and altitude data to a ground facility.
ADS (Air Data system ) --------ADS system measures pitot and static
pressure and total air temperature and computes various air data parameters.
IRS ( Inertial Reference System ) -------this system provides outputs of key
navigation parameters such as heading, attitude, and airplane present position.
EFIS ( Electronic Flight Instrument system ) -------This system provides
displays of information from various airplane systems.
WXR (Weather Radar ) ------This system provides a display of the weather
conditions forward of the airplane, and can also provide a map display.
LRRA (Low Range Radio Altimeter ) ------This system measures the
absolute height of the airplane above the earths surface.
GPWS ( Ground Proximity Warning System ) -----This system provides the
pilot with aural and visual warning of an unsafe flight path relative to the earth's
surface.
FMCS (Flight Management Computer System ) -----This system uses inputs
from other systems to navigate the airplane and provide optimization of the flight
plan.
MKR BCN (Marker Beacon ) ------This system provides an indication when
the airplane is passing over a specific position .
TCAS (Traffic alert and Collision Avoidance System )------This system
provides the pilots with warnings and advisories of unsafe flight conditions with
regard to other airplanes operating in the area.
[2] Previously, airplanes were navigated by flying from station to station along the
route from the airplanes origin to destination. The pilot used distance measuring
equipment (DME), VHF omni range (VOR ) and automatic direction finder (ADF )
to fly to each station. With the advent of inertial navigation system (INS), it became
possible to fly a more direct route from origin to destination.A direct, great circle
route is highly desirable because of potential fuel and time savings. Because of
possible position errors in inertial systems the pilot is required to verify the inertial
position with the DME, VOR and ADF systems. The computations required to
verify the inertial position are lengthy and time consuming and are much more
suited to an onboard computer. Also, since the airplane is not on a course to a
nearby station but on a direct course to a distant destination, the computations are
more complex.
[3] The flight management computer system (FMCS) continuously calculates the
optimum flight path and engine thrust to save time and fuel. During takeoff, the
FMCS provides optimized thrust setting for takeoff based on gross weight of the
airplane and outside temperature. During climb, the FMCS provides optimized
climb profiles by predicting both opimum altitude and cruise speeds. Further, the
FMCS provides projections of top of climb and step climbs. During cruise, the
FMCS optimizes descents by predicting top of descent based on the navigation data.
Throughout the descent phase, descent speeds are targeted to make maximum
utilization of the potential energy of the airplane.
[4] There are two important equipment used in navigation system, one is the
integrated flight systems accessory unit (IFSAU),the other is the digital to analog
adapter (DAA). The IFSAU is a line replaceable unit (LRU ) located in the
electronic equipment compartment. It contains two printed circuit card (A1,
A2) .Each of the cards is connected to a different rear connector on the LRU. The
A1 card is the IFSAU autopilot card, it has circuits that operate independently to
monitor, engage, and set autopilot and navigation modes. The A2 card is the IFSAU
flight instrument card, it has circuits that operate independently to monitor, set, and
test flight instrument system. It also contains suppression diodes and load resistors
for externally connected circuits.
[5] Two digital to analog adapters (DAA)are installed in the 737 airplane. The DAA
is part of inertial reference system (IRS). It stores inflight failures of the IRS in
memory and monitors the IRS for its current status. The DAA converts the ARINC
429 data bus output from the IRS into an analog format and sends that data to the
radio distance magnetic indicator (RDMI). The DAA converts an IRS BITE request
discrete from the flight management computer system into an analog signal and
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