View Full Version : CAT I, II or III?

8th Apr 2003, 06:01
I fly helos uncertified for anything below CAT I ILS's, so I have no exposure to CAT II or lower.

I was wondering why, if given the option, most airlines do not opt for the CAT II Approach if the weather is at CAT I limits? Are the procedures that much more complicated? Why would you not take the approach that would give you the lowest possible limits everytime? We often hear the controller giving the option to the pilots but it isn't often that its taken.

Any input appreciated!

8th Apr 2003, 07:52
I don't have a magic answer to that one but here are some suggestions:

1) To fly a CAT II or III approach, low vis procedures must be in force at the aerodrome in question. ( I assume this would be the case if ATC is offering it). This has certain requirements regarding shielding of the ground equipment as well as ground movement limitations.

2) Flying an autocoupled approach requires a different set of procedures than a standard manual CAT I approach. Perhaps the crew elected to continue with their current approach rather than change procedures half-way down (if the offer of CAT II was not made early enough)

3) Low Vis approaches normally require crew recency, aircraft recency, and certain system redundancy. Perhaps one or more of these requirements were not met?

Hope this helps,


11th Apr 2003, 13:28
There are also additional maintenance, training & licencing costs associated with keeping up a Category II capability within an airline plus the currency requirements.

I beleive that the majority of US regionals do not qualify their crews to better than CAT I. This contrasts with the majority of European airlines that have a CAT III capability even on their regionals (with manually-flown HGS) and also have an operational CAT II Autopilot capability as well.

These different approaches (pardon the unintended pun) are mainly due to weather - Horizon in the Pacific NW, that gets more than its fair share of fog, also installs HGS (Head-up Guidance System) for a CAT III capability on its Dash-8s as did Xerox on their company CRJs owing to operating into fog-prone Rochester, NY.

12th Apr 2003, 02:27
Thanks for the replies!

Maybe someday we'll get into some newer equipment thats capable of the lower limits. (Flying S61's, certified in 1961, no autopilot/Flight Director/etc.....)