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ILS capture query


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As far as I am aware CAT I , and CAT II , and CAT III have the same ground equipment comprising ,

** Glideslope transmitter and antenna .


** Localiser transmitter and antenna .


Both equipment elements have the same level of both precision and calibration .


That is not true. CAT II and III ground equipment are more highly tuned and maintained, adding to the cost. Which is one reason why you do not see them at airports that would rarely require those levels of minima.


For example, ILS equipment must automatically shut itself down if it detects an internal fault.


A CAT I localizer must shut down within 10 seconds of fault detection. A CAT III LOC must shut down in less than 2 seconds.


If all ILS ground equipment was the same you would see CAT III approaches everywhere.


It costs a lot more to maintain the ground equipment for a CAT III than it does a CAT I. That is why you only see CAT II and III at airports that regularly see weather that would require those approaches.


Oh, and you forgot one category of ground equipment. Approach lighting. Which is another subject in itself and comes into play when determining available ILS categories.


So yes, for the third time (at least), the category of ILS available at any given airport is dependent on the ground equipment. Period. End of story.


Bean out.



the Bean

WWOD---What Would Opa Do? Farewell, my freind (sp)


Never argue with idiots.

They drag you down to their level and beat you with experience

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As has been pointed out, it's a simulator. Am I cheating, doing it "realistically", doing it all wrong, whatever? No, I'm doing it the way I enjoy doing it most. It's my copy, on my PC, with my joystick, so I'm going to fly and land the planes I want the way I want.

If another person want's to ONLY ever push tubes around by pushing buttons, then I say good for him! Someone else only wants to drive a J3 Cub up in Alaska, delivering mail to remote camps, more power to him. How someone uses their sim is their business, none of mine.


But hey, all that's just me.

Have fun all!



Thanks Pat, very well put! And, I will guess there are many more out there that would agree with what you have said!


Rick :cool:

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So yes, for the third time (at least), the category of ILS available at any given airport is dependent on the ground equipment. Period. End of story.


Well said, Bean. Of course whether a particular pilot/aircraft combination can take advantage of that is subject to other factors, but for what's available at that airport, that short, succint statement says it all.


But to expand a bit: Airfield requirements are very specific for CAT II/III operations, including things that might surprise many folks, such as:


* For CAT II or CAT III operations, the runway centerline marks, as shown in

Figure 5.2, must have a width not less than 0.90m


*The taxi-holding positions must be as shown in pattern A for the closest marks to

the runway and pattern B for the other markings (see Figure 5.3). [There are figures showing this]


* Runway lights on runways intended for use by CAT II or CAT III operations consist

of high intensity threshold lights, runway end lights, runway touchdown zone lights,

runway edge lights, and runway centerline lights. The basic pattern of runway lights

is shown in Figure 5.4.


*The lights forming the centerline are placed at longitudinal intervals of 30m, with the

first one located 30m from the threshold. These lights consist of barrettes showing

variable white. Each barrette is at least 4m in length. When a barrette is composed

of point sources, the lights are uniformly spaced at intervals of no more than 1.5m.


I've included these excerpts from a document entitled:

getting to grips with CAT II / CAT III operations


Just a very slight indication of a very few of the airfield requirements, not even getting into the electronics yet, just to show how important airport equippage is to making CAT II/III available. Of course aircraft equippage and pilot training and currency have their own long sets of requirements.


Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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The 27NM is the FS default range of an ILS signal, it's not when you're supposed to capture the LOC or GS. Approach plates or ATC will give you that.


About CatIII, I read somewhere that both runway and aircraft need to have CatIII equipment, and pilots have to be certified to do CatIII landings. Isn't Autoland used with CatIII conditions?


About AP use. I handfly the SID if available, or until at 10000ft. At cruise I'm usually AFK. On approaches, I should try to handfly STARs more often but I have already enough going on (and I can't always use my copilot Mr. Pause...), so I only cut AP some 5NM out. It's a sim, we do whatever we want...

In RW however, I think airline pilots are not getting enough flying hours. As I read in an article, most airlines (over here in Europe) no longer train their pilots themselves, they come from private pilot schools. And those schools make their money by getting as much people thru as possible. So you get lots of "button pushers". They take off and they land... And then something happens at cruise at night. They have to handfly, they get disoriented, they don't see what their instruments are telling them and they crash. An example of this is the AF447 crash.




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