Lecture 8 Distance Measuring Equipment DME by W8Eo5Nf

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									   Lecture 8:
    Distance
   Measuring
Equipment (DME)
                                    Outlines

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           • Introduction
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           • The uses of a DME
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           • DME Equipment
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           • How DME work?
           • Advantages of DME
           • Disadvantages of DME
                                              Definition

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           • DME is stand for Distance Measuring
Previous     Equipment.
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           • DME is a type of en-route navigation system
             for aircraft.
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           • DME often installed near VOR stations so as to
             provide combined bearing and distance.
           • When DME is installed with the VOR, it is
             referred to as a VOR/DME.
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                                    The uses of DME

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           • DME provides the physical distance from the
Previous     aircraft to the ground DME transponder
             expressed in Nautical Miles (NM).
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           • DME also calculates ground speed and the time
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             needed to reach the station if the aircraft is
             fitted with appropriate computer.
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                        DME System Components:

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           The DME system consists of three basic
Previous     components which are:
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           • DME antenna on the aircraft body
           • DME navigation display unit in aircraft cockpit
           • DME transmitter/receiver in the ground
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           DME INDICATOR IN THE
           COCKPIT
                                             DME Indicator

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           • DME enables aircraft to establish its range to the
Previous
             ground station: Distance in nautical miles, Ground
             speed in knots, Flying time to the station in minutes
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           DME PRINCIPLE
                                How DME works?
    Home
           • DME provides distance (slant range) from the
Previous
             aircraft to the ground DME.
           • DME operates on Ultra High Frequency (UHF)
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             which is between 962 to 1213 MHz.
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           • DME works based on pulse techniques, where
             pulse means a single vibration of electric current.
           • The aircraft’s antenna sends out paired pulses at
             specific spacing.
           • The ground DME station receives the pulses and
             then responds with paired pulses at the same
             spacing but a different frequency.
                                 How DME works?
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           • The aircraft receiver measures the time taken to
             transmit and receive the signal which is transmitted
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             into distance.
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           • Beside that, the distance formula is also used by the
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             DME receiver to calculate the distance from DME
             station in Nautical Miles.
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                                Advantages of DME

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           • DME is extremely accurate: Provide continuous
Previous     and accurate indication of the slant range
             distance.
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           • Aircraft Handling Capability: The transponder
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             equipment should be capable of handling 100
             to 200 aircrafts.
           • Large coverage: DME facility provides coverage
             up to 200 NM.
                             Disadvantages of DME

    Home
           • As VOR the DME is also restricted to line-of-
Previous     sight transmission. For example, the aircraft at
             altitude below 10’000 ft is unable to detect the
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             DME signal.
 Help
                               Disadvantages of DME

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           • Errors and abnormal indications:
Previous      – Slant range
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              – Speed and time calculation
              – Ground system saturation – 100 aircraft
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              – System error
                                                  Exercise

    Home
           • What is DME? Give two 2 uses of DME? (3 M)
Previous
           • How DME works? (10 M)
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           • What the advantages of DME ( 2 M)
 Help
           • What are the disadvantages of DME (1 M)
           • What are 2 differences between VOR and DME?
             (2 M)
           • An aircraft flying at altitude about 3 N.M
             (18’000ft). The ground distance is about 4 N.M.
             What is the distance (slant range) of the aircraft
             in N.M calculate by DME? (2 M)

								
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