How much fog is too much?

[Gerard M]

Had a thought whilst i was driving west on friday morning. When i went past Richmond at 6am i couldn't see past the perimeter fence the fog was so thick. Then when i went past Bathurst airport it was the same story, except 2hours later as well. With Richmond being considered as the second airport for Sydney, and clearly fog is going to be an issue, how much fog is too much before a plane is able/not able to land? Or when planes are diverted from Sydney to Melbourne how much fog has there been? And what measures/procedures do planes use when there is significanly decreased visability when taking off/landing?

Thanks in advance,

Gerard

[Nigel C]

It depends on the available ILS and approach/airfield lighting status. There are 3 categories; Cat I, Cat II and Cat III, and each category allows for a lower minimum.

I can't guarantee the accuracy of it, but Wiki has an entry on it. http://en.wikipedia.org/wiki/Instrument_Landing_System#ILS_categories

[Hugh Jarse]

You can have as much fog (or any other visibility affecting phenomenon) as you like, Gerard, providing it doesn't reduce the visibility to below 800m (in Australia) for landing.

[Jason Mac]

The fog at Richmond during the winter months would reduce vis to well below 800m.

[Gerard M]

Thanks for the help. Was just wondering because if for example Richmond did go ahead then there would be a huge number of diversions..no? And as for regional airports, lets go with bathurst, do carries such a REX factor in the fog during winter into their timetables...or just hope for a good morning and if its foggy then its just a normal delay on the departure/arrival?

[Hugh Jarse]

Gerard, the visibility requirements could be reduced by putting a higher category of ILS in (this applies anywhere).

I can't quote you on REX, but I know Qantaslink does not factor fog into its winter schedules. It just accepts that there may be disruptions, which are addressed on the day of operations.

[NickN]

Is Sydney going to be Cat III anytime soon?

[Nigel C]

No.

1. There's no practical need for it because we don't get enough days/hours of CAT III conditions each year.
2. It's way too expensive to maintain for the very few days we'd need it.

[Mick F]

There are no airports in Australia that are equipped with anything higher than Cat 1 ILS.

Mick

[NickN]

What extra equipment is required to upgrade a Cat I airport to Cat III and what extra maintenance is required?

[Oliver A]

Melbourne was supposed to have Cat III capability by the end of 2008, don't know what happened to that...

http://www.theage.com.au/national/flying-blind-20080604-2ly3.html

[Owen H]

Work has definately been done in preparation for it - new taxiway lights, hold bars, and a new ILS installation.

As to when it will happen - who knows!

[Nigel C]

Nick, the lighting requirements for it are huge, both in initial installation and ongoing maintenance. Upgrades would be required to the taxiways, High Intensity Approach Lighting (HIAL's) and touchdown zones (TDZ). I've not looked into whether the stopbars are a requirement, but I'm sure Google or someone else here would have the answer!

Sydney used to have TDZ lighting and a much bigger HIAL on Rwy 16R but it was removed a few years ago partly because it required upgrading but mainly due to the extreme cost of maintaining it. IIRC Sydney had Cat I ILS and Cat II runway lighting at the time.

[Gerard M]

Thanks for all the help people. Its much appreciated as always!

Gerard

[David Ramsay]

Auckland is the only airport in this part of the world with a CAT III ILS. It was commissioned about a year ago.

[Nigel C]

Does it get used to its full potential often?

[Andrew McLaughlin]

We've got a pea-souper out in the Hills district this morning...how is it at the airport Nigel?

[Nigel C]

It was clear when I left at 0515, but there were small patches around Sylvania. The early TAF suggested vis of 3000 in mist.

[Will T]

David, just had a look at the chart for Auckland's Cat IIIB ILS approach (am still yet to fly one into there), and noticed that for the A330/A380, the Decision Height is 0' RA... ie, the point at which the required visual reference must be achieved (or else a missed approach commenced) is at touchdown! This is the first time I've seen this. The lowest DH on the 744 is always 20' RA for a Cat IIIB ILS.

[David Ramsay]

Nigel, it's probably been somewhere between six and ten times, I haven't really been counting. It certainly proved it's worth on those occasions. Fog season is coming up so it's likely to get a good workout in the next couple of months.

Will, that's interesting but not being a pilot I can't really offer any intelligent comment.

As you'll appreciate, there are some closely defined procedures for CAT III ladnings. These effectively only allow one aircraft to be landing or taxiing at any given time in order to protect the sensitive areas of the localiser.

Aircraft doing practice auto lands in VMC are always advised that the sensitive areas of the localiser are not protected.

[Owen H]

Hi Will,

Its odd isn't it! Same applies for London. That said, I believe BA have 0' minima for their 744's, so I guess we're a bit primative in this part of the world! haha.

The sooner Melbourne gets its cat II or III the better really!

[Michael Mak]

The sooner Melbourne gets its cat II or III the better really!
I remember from reading last year that Melbourne is getting ILS cat IIIa/b installed and should be ready for opereation sometime this year.

[Mick F]

Will or Owen, might be able to help.

While reading through the Head Office NOTAM's the other day (and the week before and the week before, etc.), I noticed this NOTAM:

AD FROM: 12 010615 TO: PERM YMMM C7899/08 REVIEW C7078/08
A380 OPERATIONS
EXCEPT AT YSSY, YBBN AND YMML, WHERE SPECIFIC CALCULATIONS HAVE BEEN
CONFIRMED, A380 PILOTS MUST USE LOC MDA IN LIEU OF PUBLISHED ILS DA
REF AIP DAP EAST AND WEST

Why can't the A380 use the ILS DA? I would have thought the minima is the same for everyone (of the same category of course)?

Mick

[Will T]

Mike, I believe that's because the ILS Decisions Alts have only been surveyed for Category D aircraft, except at those specific airports mentioned. I'm sure that Cat E surveys will be carried out in due course for the remaining airports/runways that are A380-capable.

I'm sure someone else out there will be able to add further information?

[NickN]

Will would the 0ft RA at Auckland be due to the Autoland capabilities of the Airbus aircraft? From memory Airbus aircraft can still perform an Autoland from an altitude of 100ft and under with no G/S (the aircraft uses inertial reference to set the aircraft on the tarmac) and from 20ft and under (maybe 10ft? cant quite recall) with no LOC signal so perhaps that has something to do with it?

[Mick F]

Will, even Sydney doesn't have Cat E on the ILS though.

Unless they've needed to resurvey it for Cat D?

And Nick, Boeing aircraft are also capable of Autoland.

Cheers

Mick

[Chris Roope]

Nick the 0ft RA is an Airbus thing not an Auckland thing.

[Will T]

Mike, if you mean the charts don't show a dedicated Cat E minima, then you're right. But I believe the 'specific calculations' referred to in that NOTAM are the results of a survey conducted at those specific airports, which allows them to use the full Category D minima, even though they're technically Category E.

[Owen H]

I know less about it than Will (as usual!), but I can remember the initial notams restricted the A380 to LOC minimas except for at Sydney, but they have clearly now done the surveys for Brissie and Melbourne too.

I guess whenever you have such a large new aircraft, with different geometry etc, you will need to confirm that the installations are suitable for that aircraft.

NickN, it would also be an operator thing. As I said before, BA use 0ft as the minima on their 744's... just depends what you can convince the regulator and manufacturer to give you I suppose!

For all intents and purposes, however, 20ft and 0ft are the same thing... if you can't see the runway at 20ft you are unlikely to have the required 100m (75 for the 'bus) visibility anyway.

[NickN]

Mick, I understand Boeing have autoland, just not familiar with the limitations of the system.

NickN, it would also be an operator thing. As I said before, BA use 0ft as the minima on their 744's... just depends what you can convince the regulator and manufacturer to give you I suppose!

For all intents and purposes, however, 20ft and 0ft are the same thing... if you can't see the runway at 20ft you are unlikely to have the required 100m (75 for the 'bus) visibility anyway.


Your right Owen, was just putting the suggestion forward to see if it was related thats all.

[Gerard M]

We've got a pea-souper out in the Hills district this morning...how is it at the airport Nigel?

Too true. Don't remember getting this much fog out here this early in the year? But i cant remember.

Saw the fog from Sydney this morning on the news, nothing diverted from Sydney did it ..looked pretty thick over the harbour?

[Chris W]

Didn't lift at Bathurst Airport until about 1000-1030. Apparently very very bad out there this morning.

[Gerard M]

Well i didn't quite get up in time, hence the missed lecture this morning but thats what people were saying here (bathurst) that the fog was pretty dense. Its great for collisions at round abouts!!

See that would presumably delay the REX flights in and out that and the other flights? Im presuming bathurst airport doesnt have anywhere near the same kinds of lighting at sydney?

[Nigel C]

Re the lighting standard at Bathurst compared to Sydney.....errr....no. I don't think Bathurst Council could either afford it or justify its need to the rate payers.

[Gerard M]

Thanks Nigel. Was just asking because i didnt know, its a slow learning process you see.

[Nigel C]

That's why the forum is here! You won't learn if you don't ask.