What is the difference between ILS CAT's

[heroturkey 0]

Hello,

Nowadays I'm trying to make ILS landings with my darling B737ngx pmdg I land it smoothly without problems but my problem is a bit technical. Anyway, let me ask questions
1 - In approach charts, there are ils without category such as ILS/DME Rwy 17L.Why they don't indicate CAT? As I know, all ILS systems must have a CAT.

2 - I want my flight is closer to real life so in reality, All runways doesn't have CATIII in reality so when an ils system become disabled that is CAT I or II? Is It already written in the charts? or where can I learn it? According to this, I will turn off A/P and try to land manually as if the ils is disabled.

3 - What is the difference between Radio or Barometer Altitude Settings? And what does Aproaching Minimums....Minimums...Minimums ! callouts mean?
 

Note: This is my first topic on the avsim forum. So there might be some violations of rules and I know my english is suck and i wish you will understand it. Sorry

[cianpars 1,165]

The CAT of ILS depends on 2 things: RVR and Decision height.

RVR is the Runaway visual range, and it's how far you can see on horizontal plane (assuming that you are on the runaway it says how many feet you can see). The DH is the altitude when the pilot must see the runaway lights, else he must abort the landing. The categories are:

 

CAT I: DH>200 ft, RVR>2400 ft

CAT II: 100 ft< DH <200 ft, RVR>1200 ft

CAT III: in general DH<100 ft and RVR<700 ft, but there are different sub-classes ABC. CAT III C dosn't require and DH or RVR, an aircraft with CAT IIIc can landing with no visual, only using instruments.

 

A barometric altimeter translates the air pressure into height.  Assuming that the altimeter is set to real pressure an mean sea level (typically QNH), then your altimeter will read height above mean sea level.  However, a radio altimeter sends a radio signal to the ground and will measure your actual height above the ground at that point.

 

Note that if your altimeter is set to QFE then it will read the height above the airfield that the QFE is provided for.

 

IAN

[heroturkey 0]

The CAT of ILS depends on 2 things: RVR and Decision height.

RVR is the Runaway visual range, and it's how far you can see on horizontal plane (assuming that you are on the runaway it says how many feet you can see). The DH is the altitude when the pilot must see the runaway lights, else he must abort the landing. The categories are:

 

CAT I: DH>200 ft, RVR>2400 ft

CAT II: 100 ft< DH <200 ft, RVR>1200 ft

CAT III: in general DH<100 ft and RVR<700 ft, but there are different sub-classes ABC. CAT III C dosn't require and DH or RVR, an aircraft with CAT IIIc can landing with no visual, only using instruments.

 

A barometric altimeter translates the air pressure into height.  Assuming that the altimeter is set to real pressure an mean sea level (typically QNH), then your altimeter will read height above mean sea level.  However, a radio altimeter sends a radio signal to the ground and will measure your actual height above the ground at that point.

 

Note that if your altimeter is set to QFE then it will read the height above the airfield that the QFE is provided for.

 

IAN

Thanks for quick responce. Well, I don't need to turn off A/P when my aircraft passes the DH and I can see runway till the flare. Or vice versa? 

[FLEX1978 373]

Hello,

Nowadays I'm trying to make ILS landings with my darling B737ngx pmdg I land it smoothly without problems but my problem is a bit technical. Anyway, let me ask questions

1 - In approach charts, there are ils without category such as ILS/DME Rwy 17L.Why they don't indicate CAT? As I know, all ILS systems must have a CAT.

2 - I want my flight is closer to real life so in reality, All runways doesn't have CATIII in reality so when an ils system become disabled that is CAT I or II? Is It already written in the charts? or where can I learn it? According to this, I will turn off A/P and try to land manually as if the ils is disabled.

3 - What is the difference between Radio or Barometer Altitude Settings? And what does Aproaching Minimums....Minimums...Minimums ! callouts mean?

 

Note: This is my first topic on the avsim forum. So there might be some violations of rules and I know my english is suck and i wish you will understand it. Sorry

 

 

Very nice explanation from Ian.

 

Regarding point 2 - The ILS signal has nothing to do with the category.

 

Even if the runway is CATI you are still able to follow the glide slope and also perform an autoland as long as you are visual with the runway by 200ft. 

 

The higher the category the more safety measures are in place.  CATII for example will have additional runway lighting, low visibility procedures, hold short zones to avoid aircraft or vehicles on the ground affecting the ILS signal.

 

CATIII will have even more safety measures put in place, and of course the crew and aircraft must be certified.

 

As long as you can see the runway at or before the DH you may continue.

 

Regards

[heroturkey 0]

Very nice explanation from Ian.

 

Regarding point 2 - The ILS signal has nothing to do with the category.

 

Even if the runway is CATI you are still able to follow the glide slope and also perform an autoland as long as you are visual with the runway by 200ft. 

 

The higher the category the more safety measures are in place.  CATII for example will have additional runway lighting, low visibility procedures, hold short zones to avoid aircraft or vehicles on the ground affecting the ILS signal.

 

CATIII will have even more safety measures put in place, and of course the crew and aircraft must be certified.

 

As long as you can see the runway at or before the DH you may continue.

 

Regards

Lol, finally i understood xD Anyway, I'm keeping swearing to fsx because of these problems.

[mgh 89]

The European requirements (and others) are more complex.

 

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:254:0001:0238:EN:PDF

CAT I the RVR can be as low as 1850 ft (550 m) with a 200 ft DH, depending with the runway Facilties.

CAT II the RVR can be as low as 1000 ft (300 m) with a 100 ft-120 ft DH, depending with the runway Facilties.

CAT IIIB the RVR can be as low as 250 ft (75 m) with a DH less 50 ft or no DH. There must be a Fail-operational Roll-control/guidance system.

The type of ILS system is important. For example a CAT III approach requires ILS stand-by transmitter.