Australian T-vasi
 

There are still a few about as it costs to change over. Mildura for example has one of each on each end of the same runway 09/27 as when it was extended to the west a new installation was required. Check ERSA it is all there.

Came out of the murk at 250' into SIN one day with a recently qualified cadet as PF. Four whites (he'd flown a decent ILS approach) whereupon he immediately poled forward "to regain slope". Almost without exception, everywhere else in the network had PAPI where 4 whites was high and it'd been drummed into him to get back on slope. No matter we were at 250' AGL, no matter about inducing a high sink rate, no matter that the runway was some 10,000' long even if we were high.

He'd not mentioned it being a T-Vasis in his briefing so I brought it to his attention, it obviously didn't sink in - almost unlike us!!!!. Lesson learned and it certainly made me lift my game on future trips into SIN and the PF henceforth made me understand that he understood exactly what he was looking for.

There's about a dozen listed in ERSA - some at major airfields.
Witwiw - bit a concern (presumably) your mate hadn't seen a VASIS before - limited training and approach by rote?

The outfit I flew for then went to SIN about 15 times a day so there is every chance the F/O saw it on his line training. Notwithstanding that, PAPI's were the go just about everywhere else. He was also a product of training in Australia (in the '90's) when there were plenty of T-Vasis installations around.

There was a classic at the Maldives, listed as a PAPI but was a T-VASI in fact.
One operator (ME) got REALLY low until a go-around was done.

Took a year or so to get changed as runway was little used, 12 from memory??

Need to read their worldwide AIP! Although I will say that I never knew that in the US, if the PAPIs are flashing, it's a signal from some whizzbang system that you mustn't land (Rumours thread).

Don't worry Leddie, I won't be over there anytime soon! :ok:

Christmas Island, Rwy 18, had one of those. It happens if you get 4 reds and are still getting lower on profile.

Can't find any reference for the YPXM installation - it may have changed.

My reference was 2002/2003 I sincerely hope it has been sorted, been around too long sometimes.

"Yeah - -
that should show the VASI so that's the VASI. Could be it's that foreign kind of VASI - - shows too high, I guess."

The words of the co-pilot of a PANAM 707 that came in too high for runway 25 at Sydney in 1971. The aircraft landed long and slid off the far end of 25 into the mud.
In those days it was termed a Pilot Error accident. That term although apt, is banned now due to political correctness and that sort of nonsense.
See full report: https://www.atsb.gov.au/media/24595/197101852.pdf

Must have been something the local electrician / aerodrome operator thought was a good idea. Being non MoS compliant, I'd say CASA told them to get rid of it pronto. By nature of their design I don't see how you could have a transition from steady 4 red lights to flashing by descending further below the 2 deg 30' angle.

Back onto VASIs though, I flew into Leigh Creek in a lightie one night about an hour and half after last light. From memory I was aware there was a T-VASIS but when you are used to flying only into PAPIs there can be a tendency to drop down a little. The first light below woke me up to the error of my ways :)
What really annoys me though is PALs with no confirmation of activation. :mad:

I've always thought that T-VASIS is better than 4 light PAPI. To me, a simple minded soul, it is much easier to interpret coz it shows me where I'll end up and also for wide bodies it provides a parallel descent path unlike PAPI which is a point source.

Agree! PAPI=cheap and nasty. Only advantage is that some reds and whites are so orange I'm always perfectly on-slope... :ok:

I was in the DCA Essendon Flying Unit when a cyclone hit Townsville way back in the 1970's. The VASIS concrete bases were wrecked so a new VASIS was installed and we the flight tests in the DCA F27. First fly down run was on Townsville 01. We were shocked to find the TVASIS lights had been reversed. When approaching low the lights showed very high FLY DOWN. When approaching obviously high, the lights showed gross undershoot.

Stopped for a cup of tea and a ponder. Turned out that the contractor had laid down the light boxes for Runway 20 on the opposite runway 01. After that was sorted and the TVASIS flight tests were OK, we discovered that during the test runs for runway 20 we were getting spurious red lights. Closer inspection revealed salt water deposits from the nearby coastline were encrusted on the red filters causing refraction and erroneous light signals. Moisture on the lamp lens as in early morning dew or erroneous indications in mist or fog, can cause erroneous light signals meaning spurious combination of fly up or fly down lights.

A fatal crash to an RFDS King Air happened at Mount Gambier at midnight and misty conditions. The aircraft flew into the ground 4 miles on final in the approach configuration in line with the runway.. The Mt Gambier T VASIS was well known by local operators to give erroneous signals under those meteorological conditions. It could not be proved the pilot followed erroneous light signals in misty conditions but it was the most likely explanation since he had called visual and his landing lights were seen by a witness. After that accident Air Services issued a NOTAM stating RPT jet aircraft not permitted at Mt Gambier.
PAPI is also not immune to erroneous light signals under certain weather conditions.

Years before during operations at Nauru, TVASIS signals were often unreliable because obese kids used to jump on the TVASIS boxes displacing them enough to give an erroneous signal. Or the kids would fire stones from a catapult into the boxes and smash the lens. Often a whole TVASIS box was u/s. That made night approaches a bit tricky since one of the vertical boxes being out of action gave the pilot a different perspective on final. For example if the first two boxes of the three above the on course lights were inop the pilot could mistake that at night for the aircraft flying one dot high. By lowering the nose to get back on slope and the top light went out as expected, in reality you were now coming on final with an indication of being on the 3 degree slope but in fact you were coming in at two dots fly down since two of the vertical fly down lights were inoperative. At Nauru, a Boeing 727 nearly over-ran after landing a bit longer then expected on runway 30 because the pilot was fooled at night and thought he was on slope when he was actually two dots fly down all the way in. One tends to believe the TVASIS on a dark night and a vague feeling of coming in high is easily dismissed as imagination or tiredness.

The answer to that is to use the DME v Height as a back-up if the DME is suitably located. Better still, never completely trust any type of VASIS at some of the more remote destinations since the maintenance could be non-existent and flight tests few and far between - if any at all.

T-VASIS (& AT-VASIS) are quite maintenance heavy, and it also needs to be done by techs who know what they are doing. This generally means ex Departmental guys, who are all retiring about now. The average country airport nowadays probably has to get the local sparky in, or relies on importing specialist expertise to do the job when it's required. AsA kept maintenance of all the navaids, but all aerodrome lighting was given back to the aerodromes, so rarely did they have the quite specialised knowledge to maintain airport lighting, especially precision lighting. PAPI is much cheaper to maintain. Basically once installed, the light units can be unmounted, and a replacement clipped into place without disturbing the alignment. Thus a stock of spare units, (which are all the same I think, just depends on the angle of mounting) may be kept, or the units can be sent away for maintenance, or even just repaired inside at the airport workshop. T-VASIS are very susceptible to ground movement, have to be worked on on-site (2 man job for most tasks), and have many different unit types, thus needing lots of different spares. The lamps are also very expensive (a 100W "Day" lamp was over $100 back in the nineties - there's 4 to each box, 160 in an installation if double end, double side, and for a while, almost unobtainable), short-lived, and require focusing each time one is replaced - EVERY lamp had a different beam characteristic!). They also require specialist tools (ie the long accurate level) which I imagine are getting harder to keep in service, and constant maintenance - spiders love to spin webs inside the dark boxes because lots of insects are attracted to the light - and the webs catch dust and debris which affect the light output. If the airport has a double ended, double sided VASIS system, that's 40 boxes of headaches vs 16 for the same system if PAPI. It's no wonder they are being replaced.
As per flight-testing, I think the Dept used to do annual or bi-annual flight tests of T-VASIS, which consisted of flying in a ground party with a tracking theodolite, and then monitoring the aircraft flight slope with that. Back in the day, I seem to recall that any more than half a turn needed on a levelling screw to bring it back level was required to be reported back up the chain, and would result in an adhoc flight test being scheduled, even if just an approach to check symmetry, which is something ground maintenance can not check. Nowadays they probably only do it randomly, or after a report that the system is out of alignment or needs to be checked after major repair. The airport probably gets charged for that too, which is another reason faults may go unreported.

From my days at the DCA Flying Unit my guess is you won't get too many written reports by pilots observing perceived PAPI light signal problems. Human nature being what it is, if they see what they think may be a problem with PAPI lights, most pilots will think "not my problem" and leave it to the next guy to report it. The process gets repeated and nothing happens.

I was referring more to T-VASIS alignment/symmetry problems, rather than PAPI, but much of a muchness. Things get reported directly at TWR'd airports all the time. It's the unmanned ones that are the problem I guess. Faults are noticed on the approach when things are busy, put on the back burner for comment during the turn, then probably forgotten during the start and takeoff.

In this modern age of high intensity long lived LED. What would it take to make a solid state box as a single fit replacement? Given the choice...VASIS or PAPI?

YLEC has AT-VASI.

DF.

Yeah ok fair enough.

DF.