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Lecture 8 : D istance M easuring E quipment ( DME )

Lecture 8 : D istance M easuring E quipment ( DME ). Outlines. Introduction The uses of a DME DME Equipment How DME work? Advantages of DME Disadvantages of DME. Definition. DME is stand for D istance M easuring E quipment.

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Lecture 8 : D istance M easuring E quipment ( DME )

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  1. Lecture 8: DistanceMeasuring Equipment (DME)

  2. Outlines • Introduction • The uses of a DME • DME Equipment • How DME work? • Advantages of DME • Disadvantages of DME

  3. Definition • DME is stand for Distance Measuring Equipment. • DME is a type of en-route navigation system for aircraft. • 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.

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

  5. DME System Components: The DME system consists of three basic components which are: • DME antenna on the aircraft body • DME navigation display unit in aircraft cockpit • DME transmitter/receiver in the ground

  6. DME INDICATOR IN THE COCKPIT

  7. DME Indicator • DME enables aircraft to establish its range to the ground station: Distance in nautical miles, Ground speed in knots, Flying time to the station in minutes

  8. DME PRINCIPLE

  9. How DME works? • DME provides distance (slant range) from the aircraft to the ground DME. • DME operates on Ultra High Frequency (UHF) which is between 962 to 1213 MHz. • 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.

  10. How DME works? • The aircraft receiver measures the time taken to transmit and receive the signal which is transmitted into distance. • Beside that, the distance formula is also used by the DME receiver to calculate the distance from DME station in Nautical Miles.

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

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

  13. Disadvantages of DME • Errors and abnormal indications: • Slant range • Speed and time calculation • Ground system saturation – 100 aircraft • System error

  14. Exercise • What is DME? Give two 2 uses of DME? (3 M) • How DME works? (10 M) • What the advantages of DME ( 2 M) • 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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