CAT I,II,III...

I know what that means. Here's an explanation for you.

CAT I is a facility that provides operation down to 200 feet decision height and runway visual range not less than 2600 feet.

CAT II is a facility that provides operation down to 100 feet decision height and runway visual range not less than 1200 feet.

CAT III is a facility that provides operation with no decision height limit to and along the surface of the runway with external visual reference during final phase of landing and with a runway visual range not less than 700 feet.

EDIT: I found some information about CAT III.

Category IIIb (CAT IIIb) - An ILS facility providing operation with no decision height limit to and along the surface of the runway without reliance on external visual reference and, subsequently, taxiing with an external RVR of not less than 150 feet.

Category IIIc (CAT IIIc) - An ILS facility providing operation with no decision height limit to and alsont the surface of the runway and taxiways without reliance on external visual reference.

These Categories are not just the facilities. In order to make an appraoch and landing in any of these categories, three conditions must be met.

1. The facility must be equipped with the appropriate electronic aids and they must be functioning correctly.

2. The aircraft must be equipped with equipment that has been approved and allows the full utilization of the category being used and that equipment must be functioning correctly.

3. The pilot must be trained, certified, and current for the category being used.

For instance, I am a rated instrument pilot but even if I was flying an aircraft equipped for category II or III into an appropriately equipped facility, I could not legally fly such an approach because I am certified for only category I approaches and landings.

Are the pilots who decide which of this type of app are going to execute, or is this represented in charts of app and landing?"

The decision about which category approach to make is driven primarily by ceiling and visibility conditions. See a previous post which defines the various minimums for the approach categories. Secondarily, the pilot can choose to make a higher level approach than necessary presuming all of the criteria for that approach are met.

For instance, if an airport is below standard IFR minimums as described in the previous post, I could not legally make the landing because I am certified only for Category I. On the other hand, a pilot certified for Category III in an approporaitely equipped airplane to an appropriately equipped runway could legally approach and land in zero-zero conditions.

I was on a United flight on Saturday into Denver when there was no defined ceiling and where visibility was in excess of ten miles. Nevertheless, the pilot elected to make an autoland approach (Category III). Since I was only listening to the ATC/Pilot radio traffic, I could not tell the reason he did that but it may have been for co-pilot training, for general practice, or to meet some requirment for recency of expereience.