The Precision Visual Glidepath
by Roger Meyer

The first installation of a new night landing aid, the Precision Visual Glidepath (PVG) came into operation at Mangalore Airport (Victoria) in December 1947.

Pilots on approach to landing had reported difficulty in judging their visual approach to the runway on moonless nights when the foreground was unlit and the horizon was obscured by darkness or terrain. So it was that a joint research, design and development project team was formed and led by Mr R.W. Cumming of the Aeronautical Research Laboratories and Dr J.C. Lane, Director of Aviation Medicine of the Department of Civil Aviation.

This exercise in the new field of ‘human engineering’ made particular use of the well-known fact that the human eye can judge the alignment of adjacent lines with great accuracy. The PVG system comprised three sets of differently coloured lights. The first was a bar of white lights at ground level and set transversely astride the runway. Further out and elevated on poles were amber lights, while two flashing red lights warned of ‘undershoot’ if the aircraft was dangerously low.

The pilot of the incoming aircraft, flying to the amber lights, had his correct approach defined when he brought the white lights into line with the amber lights. If the white lights appeared lower than the amber lights he was too low; if higher then he was too high. Thus, for a perfect approach the amber and white lights were kept accurately in alignment until the aircraft crossed the threshold. Click here to read the Pilots Notes on the Precision Visual Glidepath.

Six PVG systems were installed in Australia, at Nandi (Fiji) and at Canton Island. The PVG system was replaced by today’s T-VASIS in the mid 1960s.

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