I'm curious as to why some major US airports, such as MIA, only have ILS Cat I runways? Is it not worth the cost based on the low percentage of weather occurrences that would warrant an ILS IIIb approach?

Obviously not. Lots of overhead, infrastructure, and upkeep.

Why bother when the weather is benign all the time. I live in Canada and the sheer number of airports in the US with CAT II/III ILS is enough to make us drool. There was a point not too long ago you could count the number of CAT III approaches in the COUNTRY on one hand. And you could be missing a couple fingers.

Now you can look at say Halifax, Canada and wonder why in the hell a place with such horrendous weather would not have at least a CAT 1 ILS strung to every runway there. Which they don’t.

If a major US airport is lacking CAT II/III, then I would seriously think there just is t any need for it. That any weather situation would be very rare and short lived.

anthonycII wrote:

I'm curious as to why some major US airports, such as MIA, only have ILS Cat I runways? Is it not worth the cost based on the low percentage of weather occurrences that would warrant an ILS IIIb approach?

I'm going to go ahead and guess probably not. I would think the certification requirements are more stringent for CAT IIIB than it would be for CAT I.

CAT III ILS was pushed in Great Britain and in mainland Europe, because of the frequent fog.

When British Airways replaced their Tridents with Boeing 757, they went for a plane with a worse ILS capability. For a long time, CAT III ILS wasn't a usual feature of US-built airliners.

David

This web-site has a good list
https://sites.google.com/site/ilsapproaches/Home/cat3

Even some particularly seasonally foul weather airports have a CAT III approach. FAT is one due to our winter Tule fog.

This web-site has a good list
https://sites.google.com/site/ilsapproaches/Home/cat3

Even some particularly seasonally foul weather airports have a CAT III approach. FAT is one due to our winter Tule fog.

A large number of aircraft in the US aren’t CAT III capable. Heck, some of the regionals aren’t even CAT II certified

With the recent snow in Seattle this has me wondering...is there a standard for distance from CAT III to non CAT III? Or do you just enjoy a ground stop till the weather is better?

bhill wrote:

With the recent snow in Seattle this has me wondering...is there a standard for distance from CAT III to non CAT III? Or do you just enjoy a ground stop till the weather is better?

Not sure what the question is...technically you're not allowed to depart if your destination is below minimums.

Seattle is messed up because there's not enough infrastructure to handle snow because it doesn't snow here often. The poor visibility was one factor, but the shortage of deiciers, snowplows, and other such equipment played a bigger role.

About half my flying is and has been to the US and Canada and has been for decades. The rest is mostly Europe. Been flying Cat.II and III since late eighties, early nineties. I have never done a Cat.II/III in the US/CAN but whole weeks of nothing but those in continental Europe.
Different climates.

[*]

arcticcruiser wrote:

About half my flying is and has been to the US and Canada and has been for decades. The rest is mostly Europe. Been flying Cat.II and III since late eighties, early nineties. I have never done a Cat.II/III in the US/CAN but whole weeks of nothing but those in continental Europe.
Different climates.

You've had better luck in the US than I ever had. I recall one period where I flew 5 CATIIIs in the US in the span of 6 weeks (CLE and IAH). I've also flown actual CATIIIs at DEN, EWR, LAX and SEA (there may be another one or two).

Fun fact about CAT II/III ILS's: due to the lower minimums and the safety involved CAT II/III systems have more stringent flight inspection tolerances meaning the CDI has to be centered about the centerline (or glidepath for GS) tighter than CAT I systems. When the A380 came onto the scene, because of the huge vertical stabilizer the LOC radiation would interact with the tail and cause oscillations of the LOC CDI (i've heard it referred to as the CDI windshield wipers) of aircraft landing behind it, usually this was most prevalent when the A380 is vacating the runway or when they are holding short of the runway as the angles of the radiation are just right to produce this interference effects. Due to the A380 traffic in Frankfurt they actually developed specific hold short lines when operating under CAT II/III (search up FRA in google earth), which is interesting because other airports that have high A380 traffic dont have these hold short lines (or not that i know of anyway).

N47 wrote:

Fun fact about CAT II/III ILS's: due to the lower minimums and the safety involved CAT II/III systems have more stringent flight inspection tolerances meaning the CDI has to be centered about the centerline (or glidepath for GS) tighter than CAT I systems. When the A380 came onto the scene, because of the huge vertical stabilizer the LOC radiation would interact with the tail and cause oscillations of the LOC CDI (i've heard it referred to as the CDI windshield wipers) of aircraft landing behind it, usually this was most prevalent when the A380 is vacating the runway or when they are holding short of the runway as the angles of the radiation are just right to produce this interference effects. Due to the A380 traffic in Frankfurt they actually developed specific hold short lines when operating under CAT II/III (search up FRA in google earth), which is interesting because other airports that have high A380 traffic dont have these hold short lines (or not that i know of anyway).

ILS holdlines aren’t new, nor specific to the A380.

N47 wrote:

Fun fact about CAT II/III ILS's: due to the lower minimums and the safety involved CAT II/III systems have more stringent flight inspection tolerances meaning the CDI has to be centered about the centerline (or glidepath for GS) tighter than CAT I systems. When the A380 came onto the scene, because of the huge vertical stabilizer the LOC radiation would interact with the tail and cause oscillations of the LOC CDI (i've heard it referred to as the CDI windshield wipers) of aircraft landing behind it, usually this was most prevalent when the A380 is vacating the runway or when they are holding short of the runway as the angles of the radiation are just right to produce this interference effects. Due to the A380 traffic in Frankfurt they actually developed specific hold short lines when operating under CAT II/III (search up FRA in google earth), which is interesting because other airports that have high A380 traffic dont have these hold short lines (or not that i know of anyway).

On a CATIII to IAH and behind a Fedex MD-11 (IIRC) that was exiting the runway, we received such distortion of the localizer that we had to fly a missed approach. In other words, aircraft other than an A380 can cause such interference.

I'm surprised they had you that close to the MD.

CosmicCruiser wrote:

I'm surprised they had you that close to the MD.

That's a good point, but we were initially greater than 5 miles behind the FDX MD-11. However, I suspect they slowed on the runway and rolled to the end or nearly so and that's why or how it fell apart.

FlyHossD wrote:

CosmicCruiser wrote:

I'm surprised they had you that close to the MD.

That's a good point, but we were initially greater than 5 miles behind the FDX MD-11. However, I suspect they slowed on the runway and rolled to the end or nearly so and that's why or how it fell apart.

Being further down the runway would mean they were closer to the LOC and more potential to interfere. Plus the engine of MD-11 is long and perfectly aligned with the horizontal polarization of the LOC. The amount of antenna elements also determines the quality of the LOC signal. 8 and 14 element LOCs are the most common in the US (all LOCs at IAH are so) with some airports having/getting 20 elements LOC. The fewer the elements the wider the beam more prone to interference, opposite is true for more elements. From what I've seen 8-element arrays are only used for CAT I. Challenging sites (lot of hangars terminal buildings etc) tend to have 20, in Europe they have even more than 20 (i counted 32 elements at LHR RWYs). There was a recent case in Chicago where it is suspected that LOC deviations might have played a role: (https://aviation-safety.net/wikibase/wiki.php?id=212473, and https://www.youtube.com/watch?v=yYiSrTUyXbo&feature=youtu.be).

If it was CATIII I'm sure they were not going to expedite any turn offs. So they did take it easy on the exit.

flyingturtle wrote:

CAT III ILS was pushed in Great Britain and in mainland Europe, because of the frequent fog.

When British Airways replaced their Tridents with Boeing 757, they went for a plane with a worse ILS capability. For a long time, CAT III ILS wasn't a usual feature of US-built airliners.

David

Where do you get this impression? MD80s can autoland to CATIIIA minimums (and CATIIIB if they have a HUD). Of course the 757 and 767 can. In fact, they had a highly advanced autoland system installed from the start - which was developed specifically for those aircraft.

N47 wrote:

Fun fact about CAT II/III ILS's: due to the lower minimums and the safety involved CAT II/III systems have more stringent flight inspection tolerances meaning the CDI has to be centered about the centerline (or glidepath for GS) tighter than CAT I systems. When the A380 came onto the scene, because of the huge vertical stabilizer the LOC radiation would interact with the tail and cause oscillations of the LOC CDI (i've heard it referred to as the CDI windshield wipers) of aircraft landing behind it, usually this was most prevalent when the A380 is vacating the runway or when they are holding short of the runway as the angles of the radiation are just right to produce this interference effects. Due to the A380 traffic in Frankfurt they actually developed specific hold short lines when operating under CAT II/III (search up FRA in google earth), which is interesting because other airports that have high A380 traffic dont have these hold short lines (or not that i know of anyway).

Something similar happens in LGW, if you happen to be vectored behind the EK A380 you have to fly the RNAV approach instead of the ILS.

DiamondFlyer wrote:

A large number of aircraft in the US aren’t CAT III capable. Heck, some of the regionals aren’t even CAT II certified

Every current Boeing airplane is Cat 3B autoland capable as a baseline feature, including the 757. The exception is the 737 in which Cat 3B capability is available, but optional.

BoeingGuy wrote:

DiamondFlyer wrote:

A large number of aircraft in the US aren’t CAT III capable. Heck, some of the regionals aren’t even CAT II certified

Every current Boeing airplane is Cat 3B autoland capable as a baseline feature, including the 757. The exception is the 737 in which Cat 3B capability is available, but optional.

The airpanes are capable but the crews are not, mostly due to the operators unwillingness to spend the $$ for initial Low Viz training and subsequent recurrent. If the airports they frequent don't generate those Lo Viz days enough on an annual basis, they take a pass. It wasn't that long ago that SWA didn't do CAT lll landings.

sixtyseven wrote:

Obviously not. Lots of overhead, infrastructure, and upkeep.

Why bother when the weather is benign all the time. I live in Canada and the sheer number of airports in the US with CAT II/III ILS is enough to make us drool. There was a point not too long ago you could count the number of CAT III approaches in the COUNTRY on one hand. And you could be missing a couple fingers.

Now you can look at say Halifax, Canada and wonder why in the hell a place with such horrendous weather would not have at least a CAT 1 ILS strung to every runway there. Which they don’t.

If a major US airport is lacking CAT II/III, then I would seriously think there just is t any need for it. That any weather situation would be very rare and short lived.

FIVE STAR ANSWER! A few years ago, Saint John (CYSJ) was planning a multi-million dollar upgrade to its terminal building. I wrote a letter to the local newspaper which resulted in the upgrade being cancelled due to lack of runway infrastructure. If any single airport in Canada needs a Cat II/III runway, it's CYSJ. That letter was written over 10 years ago. Still no Cat II let alone III ILS.

Welcome to Canada...