Signal Protection

[EI-MICK]

hi all,
can anyone please tell me what is meant when ATC announce theyre giving signal protection when carrying out a ILS CAT 2/3 approach??

[Pole Hill]

EI-MICK,
One aspect of this that I am aware of is that maneouvering aircraft are not allowed as close to the runway, so for example aircraft waiting to line-up/cross the runway in use must wait at a holding point more distant than the usual holding point.
(You usually see these holding points specifically marked, for example F3 CAT II/III if F3 was the holding point.)
The reason: aircraft on CAT II & CAT III approaches are using the ILS to a lower height, and a big lump of metal near a transmitter will interfere with radio signals - so keep the aircraft further from the runway so it can't interfere with the ILS.
Just out of interest, aircraft on CAT II appraoches have a minimum decision height of 100ft, CAT IIIA approaches 50ft, and CATIIIB approaches 0ft.
Hope this helps, :ok:
POL

[EI-MICK]

excellent,exactly what i wanted.I was aware of the interference etc with the signal,but was unaware of the procedures on the ground and keeping aircraft at the relevent CAT holds,thanks for the quick reply PH.

thanks im aware of the CAT 1,2,,3 approach minimums.Thanks

[Pole Hill]

EI-MICK,
I've just added a bit to the end of the post.
No problem.
POL