Bjorn From Netherlands, joined Oct 2010, 0 posts, RR: 0 Posted (15 years 3 months 3 weeks 2 days 2 hours ago) and read 2024 times:
Every autumn, because of fog, I end up 200km from my hometown, looking forward to a 3 hour bus ride. We have a 6-7 per day SAS B737NG frequency but the airport only has Cat 1 landing. I've made some investigations and found out that just a few airports in the country (Sweden) has something better than Cat 1. But I guess the B737NG can land by itself if the ILS equipment is up to date? How come that ILS standard in my industrial western country is at the same level as 40-50 years ago (with a few exceptions)?
OPNLguy From , joined Dec 1969, posts, RR:
Reply 1, posted (15 years 3 months 3 weeks 2 days ago) and read 1978 times:
>>>But I guess the B737NG can land by itself if the ILS equipment is up to date? How come that ILS standard in my industrial western country is at the same level as 40-50 years ago (with a few exceptions)?
While CAT-I ILSs have been around the longest, CATs II and III are more recent developments, and not quite the same 40-50 years old. Not trying to split hairs here, but only to point out that II and III were later refinements.
Those improvements had a cost. The ground installations for CATS II and III are more expense, due to requirements for back-up power and more extensive approach light systems. A country's main airports with high airline traffic would be more likely to see the expenditure made versus a smaller domestic airport with fewer airline operations.
That's just the economic side. Operationally, there are some places where a CAT II or III approach isn't feasible due to terrain or other obstructions.
DC-9CAPT From , joined Dec 1969, posts, RR:
Reply 2, posted (15 years 3 months 3 weeks 1 day 12 hours ago) and read 1952 times:
What you have both brought up here is more "fuel for the fire" for the case of GPS.
As a background, here are the GENERAL categories:
CAT I---MINIMUM OF 200 FT DECISION HEIGHT
CAT II--MINIMUM OF 100 FT DECISION HEIGHT
CAT III--NOW, WE ARE INTO RVR (RUNWAY VISIUAL RANGE)
CAT IIIA---RVR 700FT
CAT IIIB--RVR 100FT
As OPNL correctly pointed out, terrain and obstacle factors impinge on the precision of ILS, and in many cases, can eliminate it outright. I am not sure what airport Bjorn is referring to, but I would guess that the terrain of Sweden may play a role on the accuracy of ILS there.
In europe, there is also a great deal of frequency congestion. Correct me if I am wrong Bjorn, but that probably isn't a factor in Sweden.
Then there is the economic factor. A standard CAT I ILS costs $1.2 million per runway end. I guess if Bjorn's hometown has only 6--7 flights per day, the politicians don't want to make the investment to upgrade the ILS capability--PROBABLY DUE TO COST v BENEFIT!
The Local Area Augmentation System (LAAS) is a GPS based system corrected for all precision and induced errors. It has been discussed on here before. The use of LAAS is said to be cheaper. More importantly it can make all runway ends usuable down to CATIIIC standards, anywhere in the world to great accuracy.
Until the day comes when GPS is accessible to precision approach standards, many airports will have to live with RNAV CAT I.