Some airlines dictate using RA on CAT I approaches. I have an article describing an approach into a Spanish airport where an RA warning was suggested to be ignored for that specific approach.

You probably misunderstand article and the word "using".Ignoring RA warning does not mean "using RA" it.RA is only used for establishing DH (cat II/III). By using RA everyone in this thread means "using for establishing approach minimums". This is the only proper use of RA if it is called for. RA typically kicks in at certain altitude in and starts to provide radar altitude to pilots regardless what approach they fly. This does not mean that pilots are "using" it, it simply means the RA data is there but pilots are not making decisions based on that, they are not "using" it.I can bet my pilot's certificate there is no airline that require its pilots to use RA for determining DA during ILS cat I.By the way if you get confused what "using" RA means in relation to IFR procedure you end up like this infamous crew of the Polish Tu-154 that killed all VIPs on board.

Some airlines dictate using RA on CAT I approaches. I have an article describing an approach into a Spanish airport where an RA warning was suggested to be ignored for that specific approach.

What article is that? When you say RA warning, are you meaning GPWS?

I believe it was a couple of years ago in Airways magazine. It might have been an Air Berlin flight between LEPA and Ovieda, not sure.It was a first officer familiarization flight if I recall. There was something about the approach that required familiarization before allowing it to be flown by the PF.

Here's two articles on the technical aspects of RA;http://en.wikipedia.org/wiki/Radio_altimeterhttp://en.wikipedia.org/wiki/FMCWThe second type, continuous wave or FMCW, is claimed to be the industry standard. Traditional radar uses a pulsed transmitted wave and measures the return time of the reflection. The CW transmits continuously and and that is mixed with the returning signal creating a phase difference measurement. It is claimed that is more reliable.The first article states accuracy is good to 2,500 AGL. Nothing is mentioned about heavy precipitation interference and limitations.

Some airlines dictate using RA on CAT I approaches. I have an article describing an approach into a Spanish airport where an RA warning was suggested to be ignored for that specific approach.

The lowest DH for a CAT I approach is 200'. At 200' you're nowhere near being over the runway. You could be approaching a mesa/tabletop airport and have a RA of 750' at your DH. Alternately, you could be approaching over sloping or rough terrain and have an RA approaching 200' multiple times on final.You don't get RA warnings, you get GWPS warnings. I've been to some airports where GPWS nuisance warnings happen, but again it's GPWS, not RA. Check out GPWS and EGWPS.

Hey GuysSo I am looking at the approach charts for 7R at Anchorage, they have seperate charts CAT II & III (top) and an ILS Approach chart (bottom)For the CAT II & III approach, I understand that I would set Radio & DH of 100. So this would give me radio altimeter call out "MINIUMUMS" at 100 feet above the runway... if no runway in sight, go around!For the CAT I approach, I would set BARO & DA of 740. This would give me the call out 588 feet above the runway (740 above sea level)

NG-Av,The CAT II mins is correct, you'd set 100RA, but you've got the circling approach mins on the bottom chart. I think your example is missing the 330'DH that you'd set in the Baro. Good idea to post a pic of the chart, though.

The second circle highlights the DH and MDA of the approach. It says 700'(548')-1 1/2. Other minimus have -3/4, -1 3/4... What they mean?

I don't know what you mean, I don't see any 700'(548') on the above approach plate. But all these numbers like 1 1/2, 3/4, etc. mean required visibility in miles.

The fractional entries are visibility in miles but you also have the RVR numbers (Runway Visual Range) in hundreds of feet. On METAR REM sections you may find specific runway RVR listings in hundreds of feet in low visibility conditions.

I don't know what you mean, I don't see any 700'(548') on the above approach plate. But all these numbers like 1 1/2, 3/4, etc. mean required visibility in miles.

Sorry. I was posting from my cell phone and couldn't see the numbers very clearly :(.

The fractional entries are visibility in miles but you also have the RVR numbers (Runway Visual Range) in hundreds of feet. On METAR REM sections you may find specific runway RVR listings in hundreds of feet in low visibility conditions.

So let me see if I got this right. In that case, the minimums for a Cat "Charlie" aircraft flying the ILS DME approach would be 740' MSL (or 588' AGL) or 1 1/2 mile DME, whichever is lower. Is that it?

would be 740' MSL (or 588' AGL) or 1 1/2 mile DME, whichever is lower. Is that it?

NO.There are two separate minimums - one for altitude and one for visibility (every approach has vertical/horizontal mins.). 740 MSL is the minimum descent altitude for this approach, 1 1/2 miles is the required minimum visibility (based on weather observations). By the way there is no "DME" here, visibility has nothing to do with DME.

NO.There are two separate minimums - one for altitude and one for visibility (every approach has vertical/horizontal mins.). 740 MSL is the minimum descent altitude for this approach, 1 1/2 miles is the required minimum visibility (based on weather observations). By the way there is no "DME" here, visibility has nothing to do with DME.

I was thinking that the distance was refering to the distance of the aircraft to the localizer antenna. So, they're all about visibility. Thanks, Michael. I spent a long time trying to figure out what those fractions could be. Perhaps my researches were not thorough enough.

When would you use both radio and baro minimums?Thanks

When would you use both radio and baro minimums?

never..because you can't fly two different approaches at the same time