The Glide Path Simulator modes
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The main module where all input
parameters are loaded from the default setup file, which can be changed by each
user according to the most used values. New values or simulated system errors
can be entered with the arrow keys or a mouse directly on the screen. This works
like a Spreadsheet where all feeds and physical distances (toggle between meters
and feet) are instantly computed and displayed on the lower part of the panel
when changing the basic input data in the upper part.
Simulation of an orbit crossover in the
azimuth plane to see the deviation, SBO&CSB amplitudes or RF-phase at a given
distance and elevation angle. This is a quick and efficient way of checking if
the system feeds have drifted.
Simulation of the resulting Glide path
deviation and amplitudes along a vertical line above given coordinates in the
terrain. This mode is designed to check angle and sectors as well as clearance
below and above the full sectors. The display can be a table, 2-Dimensional or
3-Dimensional graphic diagram. The graphics show the Deviation, SBO& CSB
amplitudes and SBO&CSB phase. After a 2D vertical trace, the theoretical Glide
path angle and sectors are computed.
The 3D graphs are identical to the 2D
graphs while showing 13 curves side by side in different azimuth angles from
-l2° to +12°, making a curtain-like grid diagram. This will give an instant view
of the sideways coverage of CDI and carrier field strength in the required ±8°
azimuth coverage sector. CDI, SBO, CSB and Clearance amplitudes can be shown
either separately or all together in 4 smaller diagrams.
This will display the ISO-Deviation lines from
300µA fly up to 225µA fly down in the coverage sectors of the GP system. This
set of lines can be taken as a footprint of the system condition where even the
smallest change in phase or amplitude in the feeds as well as small mechanical
misalignments can be detected. Any change in this window indicates that
something is going wrong. The main usage is diagnosis of erratic symptoms based
on Flight Inspection measurements or as a tutorial tool to learn the impact of
certain changes in the feeds and the environments.
The computed elevation angles and half
sector widths at ±8° and 0° azimuth are displayed with the window diagram. After
a completed computation the values are stored in memory. A menu enables a quick
look at the SBO, CSB amplitudes or the RF phases. The Window relates directly to
the curtain (3D) diagram, and one can easily switch between these display modes
while a computed window resides in the memory.
Simulation of an approach path at either
constant level, ideal hyperbolic line of constant zero deviation or tracked by a
theodolite located at user-determined coordinates. After a Level Run the Glide
path angle and sectors are computed, while after the Hyperbolic or Theodolite
approaches, the average actual & achieved GP angles and Datum heights are found
using a linear regression, the Least Mean Squares method. If reflection objects
are entered into the terrain model, reflections may show bends and scalloping
along the approach. Distance scale is either in kilometres, feet or Nautical
Simulation of the resulting deviation and
amplitudes in one or two positions while a selected feed parameter is varied
between chosen limits. Also the impact of increasing snow depth is simulated.
The main purpose of this mode is to compare the far field and near field
(monitor or test mast position) response to possible errors in the antenna
Visualisation (2D or 3D) of the ground current
induced on the reflection plane from the different glide path systems. As the
total reflected signal from the ground plane corresponds to the total ground
current, this mode is used to compare the available reflection plane area to the
actual system requirements. When this reflection plane is limited, changes in
system feeds will be seen to have significant impact on the signal quality along
the approach path. M-ARRAY glide path can be optimised to operate satisfactory
under such environment.
This part will analyse the bend wave lengths
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.
It can also reverse the process in computing the bend wavelength at selected
distances by entering the coordinates of a suspected reflection object. This
feature serves as tutorial tool for flight inspectors to gain experience in bend
analysing. The approach mode will give a graphic presentation of the theoretical
bend pattern of suspected reflection objects.
Some useful utilities are included:
This is to simulate adjustments directly on a
'graphical' Antenna Distributing Unit (ADU), which can be brought up on the
screen. The phase and amplitude ratios between the antennas can be adjusted by
moving the controls with the arrow keys. One may also disconnect some signal
components inside the Unit or one or two antennas (simulates terminating in 50
Three green numeric display fields on
the Control Panel show the CDI/DDM from the Monitor Combining Unit (MCU)
outputs. These fields show monitor response to any setting of the Glide Path
System parameters, such as antenna phase error settings, clearance transmitter
power or deviation etc. The fields are preset to emulate THETA, 0.88 THETA and
0.45 THETA on the runway extended centreline, but can be set to any desired
elevation angle for monitoring by means of changing the attenuation from the
pickup loops in each antenna element. The proper attenuation and phasing of each
pickup signal are automatically computed, but can be changed to any practical
value in order to simulate errors or actual measured values in the MCU. The
elevation angle of the DS channel (0.88 THTEA) can be adjustments directly on a
'graphical' MCU which can be brought up on the screen.
The Reflection Plane (RPL) module will determine the
average weighted slope of the reflection plane by entering measured terrain
heights along a line in front of the antenna system. In addition to the slope,
the correct zero height for the antennas will be found. The computation uses the
least squares method as well as optical reflection geometry combined with
estimated ground current for the actual GP antenna system. This method is based
on many years of experience to find correct antenna heights during setup and
will save a lot of flying time to verify antenna heights based on each elements
lobing diagram, which might be very unreliable in adverse terrain. The resulting
Forward Slope can be entered into the Control Panel by a key stroke.