1. Advanced Radio and Radar Part 7 Types of Radar

2. Introduction We have already looked at the general principle of operation of both radio communication and radar. We will now look more closely at a variety of different types of equipment used in the RAF, to see how and where they are used.

3. Precision Approach Radar (PAR) The purpose of PAR is to plot the approach of an aircraft and allow ATC to give accurate guidance to achieve a safe landing. The system can be used in poor weather conditions (i.e. low cloud, limited visibility), thus reducing interruptions to a station’s flying programme.

4. PAR consists of a Radar Head cabin connected to the ATCC. The Radar Head can rotate around a central point, so it can serve whichever runway is in use. The Radar Head itself has three distinct assemblies; The Radar Cabin, The Azimuth Antenna, The Elevation Antenna. Precision Approach Radar (PAR)

5. Narrow beams are transmitted from each antenna. One horizontal (2° wide by 0.5° high) for height, the other vertical (0.5° wide by 2° high) for bearing. Precision Approach Radar (PAR) Height Bearing Controlled by the ATC the beams are interlocked, and allows the aircraft to be "captured" in the beam pattern.

6. Precision Approach Radar (PAR) The cross beam information is shown on a screen with two displays. One display is of the elevation scan, the other shows the azimuth scan. Using both displays the controller is able to guide the aircraft down a safe "glide path" to approach the runway on the correct course. Elevation Azimuth

7. Instrument Landing System (ILS) ILS is a runway guidance system for a safe landing without a ground controller and provides the pilot with: a.A visual indication of the aircraft’s azimuth. (on a cockpit instrument) b. A visual indication of the aircraft’s elevation. (on the same cockpit instrument) c. Both an audio and visual indication of the aircraft’s distance from touch down. d. An audio indication of the identity of the airfield (in Morse code), to confirm landing at the right airfield.

8. Instrument Landing System (ILS) This system has 3 separate elements: a.Localiser Transmitter. b.Glide Path Transmitter. c.Outer, Middle & Inner Marker Beacons. RUNWAY LT OM MM GT IM Provides Azimuth to keep the aircraft on a central approach line. To give the pilot elevation information.

9. Aircraft Passes Outer Marker (5 miles out) Glide Path Beams Emitted Passes Middle Marker (¾ mile out) RUNWAY LT OM MM GT RUNWAY LT OM MM GT Instrument Landing System (ILS) To use the ILS a pilot must position the aircraft in line with the instrument runway at a range of some 20 to 25 miles.

10. Instrument Landing System (ILS) The pilot has a 2-point meter. One gives the lateral direction to fly (left or right), the other gives the vertical direction (up or down). When the two pointers cross in the centre the pilot is on the correct glide-path and heading. The instrument also has warning flags which remain "set" until there is sufficient signal strength for the system to operate. Flags Set Signed strength Low

11. Instrument Landing System (ILS) Flags Set Signed strength Low RUNWAY LT 90 Hz 150 Hz The airfield Localiser Transmitter (LT) radiates two beams, one at 90 Hz, the other at 150 Hz. If the aircraft is ‘off’ course to the left, 90 Hz is dominant and the azimuth pointer moves to the right. If the aircraft is ‘off’ course to the right, 150 Hz is dominant and the pointer moves left.

12. Instrument Landing System (ILS) Above Glide-path Below Glide-path On Glide-path Flags Retracted Signed strength OK GTOM MM 90 Hz 150 Hz RUNWAY The glide path transmitter sends out 2 beams modulated at 90 Hz and 150 Hz If the aircraft is ‘too high’ on approach, 90 Hz is dominant and the lateral pointer moves downwards. If the aircraft is ‘too low’ on approach, 150 Hz dominates and the pointer moves upwards.

13. Digital Resolution Direction Finding Ground-based DRDF equipment provides a direction fix for aircraft, or as an auto-triangulation system. DRDF provides the controller with information on aircraft bearings in the following forms: a. Digital pulses to give a digital read-out and a vector display. b. Direct Current (DC) voltage proportional to the angle of the bearing. c. Combined pulses from other installations to triangulate the aircraft’s position.

14. Digital Resolution Direction Finding DRDF is used primarily for aircraft in distress, by accurately pinpointing an aircraft. The ‘distressed’ aircraft transmits a code used to determine a directional bearing of the aircraft. Using similar information from other installations, the aircraft’s position is triangulated. There are two control centres in the UK, one at West Drayton and the other at Prestwick.

15. Check of Understanding What are the distinct elements of a PAR assembly? Radar cabin, Elevation antenna and Range finder Radar cabin, Range scanner and Azimuth antenna Radar cabin, Elevation antenna and Range finder Radar cabin, Elevation antenna and Azimuth antenna

16. Check of Understanding What does PAR stand for? Primary aircraft radar Pin-point approach radar Portable aircraft radar Precision approach radar

17. Distance Elevation Azimuth Range Check of Understanding What does this screen portray on PAR?

18. Check of Understanding What does ILS stand for? Interim Landing System Interim Landing System Immediate Landing System Indicator Lights System Instrument Landing System

19. Far, Middle and Runway First, Middle and Final Outer, Middle and Inner Distant, Middle and Inner Check of Understanding What are the marker beacons in an ILS?

20. At 1 nautical mile only Within 25 nautical miles Under 5 nautical miles only Over 50 nautical miles Check of Understanding At what distance could a pilot use ILS?

21. In this diagram, what state is displayed? Check of Understanding Flags set – Flags set – signal strength high Flags retracted – signal strength high Flags set – signal strength high Flags retracted – signal strength low

22. Runway bearing number Azimuth approach angle Azimuth descent angle Height to touchdown Check of Understanding Which of the following is information supplied to a pilot from ILS?

23. In this diagram what action should the pilot take? Gain height Gain height Move left Lose height Move right Check of Understanding

24. Which three elements make up ILS? Marker Beacons, Glide-path Transmitter and Localiser Transmitter Marker Buoys, Azimuth Antenna and Localiser Transmitter Marker Beacons, Azimuth Antenna and Localiser Transmitter Marker Buoys, Glide-path Transmitter and Localiser Transmitter Check of Understanding

25. In an aircraft using ILS the meter’s flags are set because... The aircraft is not on beam The meter needs re-calibration Signal strength is adequate Check of Understanding Signal strength is inadequate

26. Direct Radar Direction Finding. Digital Resolution Direction Finding. Digital Radar Direction Finding. Direct Resolution Direction Finding. Check of Understanding What does DRDF stand for?

27. Check of Understanding DRDF provides the controller with data in three forms, digital pulses, a DC voltage and which other? A sinusoidal output An AC voltage A sawtooth waveform Combined digital pulses

28. Advanced Radio and Radar End of Presentation