ALDAS ALDASIn order to examine the input and output data from ALDAS, extensive graphics have been provided. Here is an example using a F-111 aircraft. The structure geometry in ALDAS must be a combination of cylinders and flat plates with a complex fuselage. The F-111 model has been constructed of a cylindrical fuselage having an elliptical cross-section wuith a truncated cone as nose. There are also 4 cylinders, 30 flat plates whose corners number between 3 and 15 and 15 flat plates which have 4 corners each. The wings and tail planes are formed of several plates. Figure 1 shows the position and direction of polarisation of a blade antenna for IFF on a rendered visualisation of this geometry.
IFF coverage for an aircraft is required in the upper and lower hemisphere so there is also a second IFF blade on the lower fuselage. The radiation patterns of each blade have been calculated over the full hemisphere and then the ALDAS plotting facility has been used to taked the maximum gain of two radiation patterns at any point in the sphere. The final radiation pattern which gives the complete IFF coverage on an F-111 can be processed in various ways. Figure 2 shows a polar plot of the data at 5.0 degrees Elevation. Rectangular format plots may also be output. The results can also be presented as a Mercator contour plot (Figure 4) or a spherical contour plot (Figure 5). These types of plots are useful to an antenna enegineer installing an antenna system on a structure because such a presentation enables him to pick out angular zones where coverage is less good and improve these areas.
