INTERSCAN MLS Experimental Installation - 1977 & 2007

The photo above shows two different elevation antennae on the INTERSCAN Microwave Landing System (MLS) experimental installation at Melbourne's Tullamarine Airport in 1977. On the left is a conical elevation antenna and on the right a planar antenna.

The 'planar' antenna produced a narrow, fan-shaped beam which was swept up and down from near zero elevation to an angle of +15°. The alternative 'conical' antenna was 20 feet high and the scanning beam produced was not fan-shaped but formed an inverted conical surface, co-axial with the elevation antenna with apex at ground level.

The photo below shows the same antennae still in place in 2007. They are located north of the Runway 27 threshold, near the VOR. The upper photo looks south whilst the lower photo looks west-south-west. The Fire Station Fire Control Centre watch tower can be seen between the two antennae.

The curved antenna seen lying down in the background is the 'Flare Guidance Antenna', which was an original requirement of MLS but was deleted from the final standard system. Nevertheless, the CSIRO Division of Radio Physics showed it could be done!


The INTERSCAN MLS was developed jointly by the Department of Transport, the Radiophysics Division of the CSIRO, and Amalgamated Wireless Australasia (AWA). This experimental system was originally installed on Melbourne's Runway 27 in 1974. The system was extensively flight-tested during the mid-1970s using wet-leased Douglas DC-3 VH-AGU, which was fitted with comprehensive test equipment.

(Photos: Top-CAHS collection; Bottom-Phil Vabre)

Click here to read an article about the INTERSCAN MLS

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