Another 'First' for Inter Avionics

 Article courtesy World Airnews
The photograph on the left shows the Angola-based DHC-6-300 Twin Otter which is the first of its type in the world to be fitted with ACAS II. The aircraft made its successful first ACAS II fitted flight from Lanseria Airport, near Johannesburg recently, piloted by Sonair captains Serafin Junior and Serge Corolleur.

The photograph on the right is of the directional ACAS antenna showing the 'dropped' installation using a locally designed mounting bracket (shown still unpainted) to overcome forward radiation shielding problems on the Twin Otter.

Lanseria airport-based lnter Avionics (Pty) Ltd. recently completed the installation of the world's first ACAS II system to be fitted to a de Havilland Canada DHC-6-300 Twin Otter.

The aircraft was equipped with the Collins TCAS-94 system which features a unique dropped aerial installation bracket for the bottom directional ACAS antenna. This bracket was especially designed and installed on the aircraft, which is operated by Angolan carrier, Sonair.

The special bracket was required because of the location of the Twin Otter's forward fuel tank that is situated just ahead of the antenna's original planned position. Had the antenna been mounted flush with the underbelly, engineers fitting the equipment would have encountered forward radiation shielding problems with the directional antenna. For this reason they "dropped" the antenna in the special bracket below the fuselage skin, thus overcoming the problem.

There is an optional TCAS installation available that uses an omni-directional antenna. However, the problem with this system if used on the Twin Otter is that it reduces the bearing-display capabilities of intruder aircraft, hence the need for the directional antenna.

World Airnews, October 2004-12-07