ILS Status Indications in Tower

[Oilhead]

Can any of our ATC brethren tell me what "BYPASS" means with regard to an ILS status indicator in the tower? If it is indicating BYPASS (other modes are NORMAL, and ALARM) should it be used for a CAT II ILS with CAT II RVR prevailing?

Thanks.

[U R NumberOne]

Oilhead,

Our system is slightly different, using a red, amber and green light for each ILS. Red and green are straight forward - unservicable and servicable respectively. The amber indicates 'maintenance required'. Have to admit at this point we phone the engineers and leave it to them, but the bottom line is that on an amber light the ILS is still usable, and whatever the failure is, it is non-critical.

Our kit is CAT 1 only, so a higher catagory of ILS may become unusable with an 'amber' indication or equivilent in bad weather.

[Spoonbill]

Hi Oilhead,
Have to agree - if it's amber it's OK for cat 1 use, but it has to have the agreement of the DTO. Amber usually means the system has gone onto standby, (which I suspect is your equivilant of BYPASS), and can still be used.
At our unit, there is no DTO on duty at night, and if it goes beyond amber, we have to assume the system is U/S.

[Oilhead]

Thanks a lot - after I posted this I got a call from an ATC type here in USA. Apparently BYPASS means maintenance has control of the facility - approach aid. I am interested because we had a problem tracking LOC and GS at an airport last week. After landing I called about the drifting I was experiencing. Autopilot just didn't perform - dumped twice. Tower siad teh ILS was in BYPASS, but couldn't tell me what that meant. Interseting to say teh least - RVR 1400feet etc.

Oilhead