The Localiser Simulator modes 

1. The Control Panel
This is where all input parameters are entered with easy-to-use arrow keys to change the values or introduce system errors directly on the screen. Any phase and amplitude change can be adjusted, as well as any mechanical alignment of each individual antenna element. For dual frequency systems, the power ratio and phase relationship between the course and clearance SBO&CSB signals can be set to any desired value. The CDI (or DDM) for each antenna element at the Antenna Distribution Unit (ADU) is displayed to ease setting-up on ground. For dual frequency systems the course and clearance signals at the ADU can be monitored separately or combined. The airport model is easily made by entering conducting rectangular sheets, described by eight parameters giving the size, location and the orientation of airport buildings front wall, cranes, masts, aircraft tailfins or any other constructions.

2. Play back screen files. 
This mode will display previously computed and saved Black & White curves. By computing and saving several screens with increasing change in a feed or mechanical parameter, or moving a scattering object, one gets a useful animation tool for showing the total impact of gradually increasing errors when they are played back as a movie.

3. Orbit mode.
Simulation of an orbit at a given range to check CDI/DDM and amplitudes in any desired sector. The course sector and course line alignment are computed if the orbit includes the full course sector. The display can show CDI, SBO and CSB amplitudes (together or separately) and the SBO&CSB phase relationship. This mode will show which sectors and how the signal quality will be affected by scattering objects in the model. Airport buildings will reflect SBO and CSB in certain directions and might cause clearance problems. Amplitudes can be displayed either in percent or in dB's relative to peak carrier amplitude on course line. A cursor can be moved along the curves, and a numerical fields display the side lobe level, capture ratio and the beam bend potential at any azimuth angle.

5. Approach mode.
Simulation of an approach path along a straight line. This mode will show how the course line and sectors will change along an approach path for given errors in the antenna system. The graph will also show the bend- or amplitude pattern due to scattering from buildings or aircraft tailfins in the model. A cursor can be moved along the curve, and a numerical field displays the present distance and the CDI value. Bends can be marked and measured on the screen. Marked bend samples can be stored and subsequently analysed in the Bend Analysing Mode to find their origin for training purposes. The receiver or plotter frequency response and the aircraft speed can be adjusted in order to simulate the filtering effect on the curve

6. Fixed Position mode.
Simulation of the signals in one or two positions while a feed parameter is varied between selected limits. This will demonstrate how susceptible the course line and the course sectors will be to errors in the different antennas or signal components. This mode is excellent to compare the far field and near field response to possible errors in the antenna system to examine the correlation of the near field monitor or ground check points relative to the far field.

7. Ground Current.
Visualisation of the ground current induced on the reflection plane, yielding the total reflected signal. Used to compare the available reflection area to the actual system requirements and to get an impression of where the signal reflections basically take place around the antenna system. A 3D graph can be split into the 90 or 150Hz side.

8. Bend Analysing.
This part will analyse the bends and their position along the flight path to find the possible origin of the reflection object(s) as intersections of hyperbolic lines plotted on the ground. For tutorial purposes the process can be reversed by the 'Make Bends' option to start with a known position of a reflecting object. The theoretical bend lengths are then computed at some selected distances and will then be converted to hyperbolic lines in order to give experience in analysing when the answer is known.

9. Sensitive Area.
For computing size of the Sensitive Area, where a taxing aircraft may cause disturbances to an approaching aircraft to a given runway, AXIS will simulate the effect of signal scattering on to the approach path. AXIS will simulate the tailfin of a moving aircraft or any other metallic construction, move it around and optionally rotate it to find the worst case orientation in producing the greatest bend amplitude along the selected receiver flight path or fixed location. Enter the maximum allowed dynamic bend amplitude, the antenna system, aircraft type and the receiver location, and AXIS will compute and draw the sensitive area for the particular airport. The search for Sensitive Area will normally use 1, 2 or 4ľA as a limit for maximum allowed disturbance.


Nordic Air Navigation Consulting, Norway