Wellington Fog

[Massey058]

Given the number of times Wellington has been fogged in already this year would it not be a good idea to consider a CAT II or greater ILS? The present CAT I ILS is rather limiting with its 500 ft DA (510 ft for CAT D on RWY 34) and 3000 m vis. Has it not got to the point where the delays and disruptions justify the expense of having an approach that could reduce said disruptions?

Any thoughts?

[MOR]

You can't do it because of the lack of suitable terrain for the radalt to read at the end of the approach. You have to have a smooth, even surface at both ends and in the case of Wellington, you have a ramp at one end and a ditch at the other.

Cat II's are flown as coupled approaches to DH, which is normally around 100 feet. At the point at which you get the Cat II green light from your FCS, your autopilot is using the radalt for vertical guidance down to your disconnect height. You couldn't do that at Wellington for obvious reasons.

I doubt you could anyway with the close-in terrain... which is why the existing ILS has such high minima.

[Massey058]

Can EGPWS not be programmed for the intricices of the immediate terrain re the ditch and the ramp?

[Big Kahuna]

Massey058,

You are missing the point that MOR is making.

Decision Height(DH) for a Cat II approach is base on radar height not barometric altitude. Therefore terrain on the approach ends of the runways is important.

Furthermore the hills on each side of the airport must be infringing the clear fan that is required if you have a lower minima.

Best thing for Wellington would be to get a big bulldozer and get rid of those hills. ie land reclamation what a lovely thing.
Oh, but then all the bleeding heart greenies in NZ wouldn't like that.

[MOR]

Massey058

You probably could - I am sure the new generation of EGPWS/TAWS gear could do it, especially with the new radalt agreement sytems and so on. However, Cat II approaches are certified using radio altimeter, so unless you developed a procedure incorporating the EGPWS gear, and had it certified, you are out of luck.

The next two developments in Cat II approaches are GNSS and LAAS. maybe one of them will incorporate EGPWS. Bring it on, I say!

By the way, we used the new HUD systems on our Canadair RJ's, and found them to be super-accurate. You drop out of the murk and the runway is exactly where the runway outline in the HUD is. I'd rather have one of those than traditional Cat II gear.

[WITCH]

Why not just cut out the "middleman" and stop using Wellington as a hub?

[MOR]

Hey... careful... that's fighting talk... :p

[1279shp]

... we'd plop into WN in all sortsa low-vis. Is today's vis worse than then? Or are the eyes?! :)

What about OH as the new hub? It aint doing much!