What does CAT II mean?
(I saw it at the edge of a taxiway on a holding point)
in terms of autolanding a catagory 2 is the avionics ability to track both the localiser and the glidescope i think....
Every runway has a 'category' which tells pilots the sort of approach s/he can carry out on it. Category II approaches permit landing with a 100 foot decision height and visibility as low as 1200 ft (366m).
Just as an aside, regarding airport signage. I'm told that the FARs (Federal Aviation Regulations, in the US but similar across the world) regarding this subject run to some 27 pages in the manual
The posts above define the various levels of ILS instrument approaches but they do not address the meaning of the sign the OP saw along the runway.
Every taxiway intersection with a runway at a controlled airport has a "hold short" line on the taxiway. That is the line beyone which an aircraft on the ground is not allowed to pass without a specific clearance from ATC to do so.
On runways equipped with ILS, you may also see signs along the taxiway as you approach the runway. The signs may say "ILS", "CAT II", or "CAT III". On such taxiways, there will be a second "hold short" line painted that is further from the runway than normal. During periods when the runway is in use for instrument approaches, every aircraft approaching a runway having such signs is required to hold short at the further line rather than the closer.
That provides a larger margin of safety for aircraft who are making instrument approaches so if they are slightly off the center line, the risk of a wing strike on the aircraft holding is eliminated.
ILS Categories (US)
CAT I DH no lower than 200 ft. or visibility below 1/2 mile or 2400 RVR (1800 RVR on
some) Normal ILS approach.
CAT II DH no lower than 100 ft. or visibility below RVR of 1200 ft.
CAT IIIa No or DH lower than 100 ft. or visibility below RVR of 700 ft.
CAT IIIb No DH or DH less than 50 ft. RVR 700-150 ft.
CAT IIIc No DH no RVR
CAT II thru IIIc require special aircraft and crew qualification.
Only some runways are certified for CAT II or CAT III operations.
Most airline large jet aircraft are CAT II qualified.
Some airline aircraft are CAT III qualified
RVR- Runway Visual Range: The distance in ft or meters that a pilot should see high intensity runway lights. Given for a specific runway via sensors along certain runways. Normally given for 2 or 3 areas. Touchdown, Mid, Roll out. Some runways report only two.
DH - Decision Height: The altitude on ILS approach that the pilot must have some portion of the landing environment in sight in order to continue and land visually.
Love you guys
Thanks for all, i needed that.