I don`t know if airfield operators must notify the state of the signal radiated by an ILS... below CAT I minimums, for example.
After a new installation, a big modification/repairment, or periodically, an in-flight inspection of the ILS system shoud be performed.
The company who carry out the flight test ( Flight Precision Ltd. for example ) should issue a certificate of availability of the navaid, and the subsequent report, including those "famous" graphics showing the behaviour of the beam along all of its nominal coverage, between others.
This documents should be preserved by the National Air Navigation Service Provider, wich is the company who is responsible of providing navigation services ( between others ) under several requirements ( In Europe, under "Single European Sky" certification requirements ).
Another copy of the report must be sent also to the Regulator Authority ( CAA in UK, for example ), for the archive files, as far as I know.
That's all I know about it.
As I told you before, I've seen CAT III ILS graphics that appeared very "critical", with a lot of "noise" in the beam received ... and CAT I ones, that could be used until touchdown. Even I've seen lot of problems concerning terrain profile in CAT III ones.
But I've never heard nothing about any official report or warning about beam quality, comung from Airport authorities. Apart from operations airlines manual, of course.
Why ?.
Pay attention to this, please.
If the enviromental conditions change ( buildings, trees, system ageing ) the signal quality can be affected, and we ( ATSEP's ) will not aware of it, because our monitors are reading "near field" signals. Far fierld monitors are used only in CAT III ( And they aren't not so far.
So, the signal structure may be affected but our ILS can be Ok for CAT I, according our monitors. Monitors are adjusted, of course in each flight test.
This is, of course apart from any violation of the protection area. We only will know something about this changes in the next periodical flight test, not before.
The first one to see the "real one" beam, can be anyone of you at the arrival. If you are performing an Autoland landing in this CAT I ILS, please take care !
This is why I think that real information about beam quality below CAT I minimums... In my humble opinion it's a risk suppose that!.
Anyway, if during your trips are witness of any problem in the air navigation signal provided, please make a sort of complaint in your OPS office, or best of all, simply tell the problem encountered to the ATCo. They will know what to do. And local ATSEP's will correct it, for sure !.
Last edited by Ferrobus; 7th Nov 2007 at 21:48.