Popped in there last night. Can anyone shed some light what are the reasons / benefits for the replacement of the T-VASIS to a PAPI system?
I thought the different aim point options provided by the 'T' (assuming if one wished to use it for such a purpose) would be of greater assistance than a point source aid - single aim point (aside from acknowledging the varying approach paths to the same point) being provided with the 'P'.
Gee Muffinman I thought a man of your great knowledge and life experience would already know this stuff! Only reason I know all this is that I was asked it in a interview and had no idea at the time!
The answer is Three fold.
One being international standardisation. Everywhere else in the world use PAPI and so therefore we have to as well.
Two being they are expensive to maintain due to the fact that T-Vasis run up to 20 lights at a time which makes for a hefty power/maintenance bill. Also installation is tricky as it requires alot of surveying and ground work.
Thirdly after the RFDS accident in Mt Gambier there were some issues raised in regard getting false indication when in areas of visible moisture and fog.
So the real answer is that it's a cost saving issue however Darwin airport will be claiming that it will be improving safety and bringing themselves into line with world's best practice. Even though T-Vasis was considered a superior system when it came out, so much so that there was a push to make it the world standard at the time.
Rumour has it that T-VASIS was well in the running to become a World standard with ICAO, but the Poms were spitting the dummy that Decca wasn't taken up over the USA's LORAN, so T-VASIS didn't get up over the 4-bar [and later 6-bar] VASIS and the Poms were happy [sorta?]
That is a red herring. ATSB report gives that as a minor factor.
Try again. The ATSB never investigated previous pilot reports of erroneous light signals from the Mt Gambier T-VASIS. In fact they also never interviewed the one and only witness to the final flight path of the RFDS aircraft. They did say the T-VASIS was test flown the next day and nothing found wrong. In other words all the light bulbs worked OK. The test flight was not flown by a qualified airways surveyor. There was no low cloud, fog or mist the next day when the so called "flight test" was conducted so the test was a waste of time.
There was no doubt that the Mt Gambier T-VASIS was well known by local pilots to give erroneous light signals under certain atmospheric conditions of light rain, mist and low cloud. Erroneous light signals under similar conditions were also present at some other locations around Australia and AIP warned of this limitation of T-VASIS. It also occurs with PAPI when the conditions are right.
Several months after the Mt Gambier accident, and after conversations with local pilots confirmed the specific problem, Air Services published a caution in ERSA Mt Gambier page and on the Mt Gambier aerodrome chart that the T-VASIS should be treated with caution under certain weather conditions. Mount Gambier was the only aerodrome in Australia where a specific caution was published with regard to use of the T-VASIS. Eventually the VASIS was replaced by PAPI. Cost was the main factor - not erroneous light signals.
Rose? yeh but no but Shiraz? yeh but no but Cabsav? yeh no but.....
I'm with you Clarrie - same location, same out of body experience and the above title is what I mutter all the way down final when I watch the circus sideshow that's supposed to be an approach lightshow
I did a google (t-vasis) and found NOTHING that pushed P over the finish line ahead of the T except $$$$ plus the ol' world standardisation dribble.
One Oz installation site I visited claiming the quote "the BENEFITS of the Papi were "ENORMOUS". T'was curious. Again all $$$$. Not one repeat one safety or ergonomic benefit mentioned. Yep I know who's getting those enormous benefits and it aint the pilot.
GA trojan (is that pronounced gee eh or g-aye) How's it goin - is my name still on your CV
oh yeh '...
HH - Will the Turnball globe policy mean we are all back to diesel soaked toilet rolls?
Last edited by Muffinman; 21st May 2007 at 00:10.
Reason: just remembered....
Anyone remember 'X-Vasis'? Used to be one at YBMA. Lights were arranged in an X pattern - low on approach gave a red arrow point up, high gave a white arrow pointing down, and on slope was a whaite X. Last saw it there in '85, never seen or heard of it since.