The one and only purpose of T-VASIS is to provide the pilot with on-slope, fly-up and fly-down indications, especially in poor visual conditions. The concept that T-VASIS seem to provide exactly the opposite signals to those required under some poor visual conditions, thus creating a more unsafe situation than if they were switched off seems a bit stupid.
Why do they still exist when there are safer visual approach indication systems such as PAPIS available? Is it simply cost? Is it because the users (us pilots) don’t complain enough about the limitations of such systems? And why is it that Australia seems to be one of the few (only?) countries in the world that still use T-VASIS?
Has anyone had any personal experience that might validate the possibility of erroneous T-VASIS glide slope indications at Mount Gambia?