Cat 1/2 Ils???

[Spamcan defender]

Hiya....
I know that this is probably an easy one but....Can anyone clarify exactly what the differences are between CAT 1/2/3 ILS approaches???.
Had a little search through previous threads but couldn't find any...
Go on, impress me with your wisdom.....:D :D :D

[Chris Wannabe]

I'm not an airline pilot.........yet, but I have just sat and passed my first set of ATPL exams.

Cat 1 = standard ILS flown to a decsion height of not less than 200ft barometric

Cat 2 = decision height not less than 100ft on the radio altimeter

Cat 3 = full autoland

This was all I needed to know so someone with operational experience may be able to add further!:)

[mattpilot]

minor additions:

Cat 2: if the pilot is newly certified then he can only fly down to 150 feet for a while

Cat 3: There are 3 of those - a,b, c

a: 700' RVR
b: 150' RVR
c: no minimum

[slim_slag]

......And in certain jurisdictions you can descend to a Cat II DH with a barometric altimeter........

[reynoldsno1]

The category of ILS installation should not be confused with the type of operations permitted. You can have a Cat III ILS installed, but this does not automatically permit Cat III operations. There are a number of other factors to consider, including approach & runway lighting, surface movement surveillance & control, power supplies, etc....

[sharpshot]

And not to forget runway safeguarding, Holding points to meet CAT III specs and also taxiway lighting from runway lead-offs to stand entry guidance.

[Spamcan defender]

Thanks for the replies so far....
Would it be fair to say that CAT 3 ILS is more 'accurate' than say a CAT 1 ILS???.
Just for a bit of background... I'm in the middle of reading CAP 637 Visual Aids Handbook and was reading the section on runway holding points... I am just trying to clarify the differences between the 3 'CATS'. It would seem that CAT 1 holding points are closer to the active than CAT 3 so, by inference CAT 1 would seem to be more accurate as holding aircraft are allowed closer to the runway...:confused: :confused: :confused:
Over to you guys.....

[Duke of Burgundy]

Spamcan - In para 3.1.4 of CAP 637 it tells you that CAT II / III systems need to be provided with greater protection. That is why the holding points are set further back from the runway than those associated with CAT I operations.

Specifically, there is an area contained 137 metres either side of the runway centre-line for the purposes of CAT II/III operations called the Localiser Sensitive Area. This area must be clear of aircraft and vehicles whilst an aircraft is within 2 nautical miles from touchdown during a CAT II/III approach (exceptionally 1nm provided the pilot is warned), otherwise the crew are required to execute a missed approach.

Hope this helps.

DoB

[Rabbit]

Most of what is above is good info, but here is a question to keep the conversation going: Question-

All CAT 11 ILS systems can be CAT 111 but all CAT 111 systems may not be CAT 11 - why?

Each Company has their individually approved RVR minima's for the different class of approach. Our Company has had the RVR gradually reduce over time as experience in gained. And as has been illuded to earlier, some variations do occur, eg. I am rated to CAT 111b, and 75m RVR. However the MABH is just 15ft, and the FLARE process commences at 50 ft and thrust auto selected to IDLE above that, therefore we are operating CAT 111b with no minima, just 75m RVR. We expect CAT 111c soon but theres no fun in that - bit creepy in fact - a lot of confidence in your aircraft is required and at the end of the process you hope you are on the runway centreline and with enough visibility to taxi off the runway and find your gate.

Have a nice day

[Spitoon]

I'm not sure that you're right Rabbit, If I recall correctly, Cat II ground equipment does not require a hot standby glideslope transmitter whereas Cat III does (I think there are a number of other minor differences also).

The operational authorisation to fly a Cat II or Cat III approach is based on many other factors such as runway lighting, aircraft equipment and crew training and currency.

[Rabbit]

Let me clarify the question:

Any CAT 11 ILS can be upgraded to be CAT111 rated, but not all CAT 111 ILS systems can be used as CAT 11

Have a nice day