DA and MDA are near interchangable for all intents and purposes and it's considered to be good airmanship to put the DA value into the FMGS as the MDA, [At least in my operation it is]

Hm, I was taught the difference between MDA/DA as stated above (important in the G/A case). Otherwise, of course you can do it that way, in fact it might be the only way that makes sense for that particular system. Still it's technically not precise IMHO.

Euh.... don't know exactly which discussion you want to launch here but I'm looking forward to it. You refer to ILS/MLS?You can fly a visual approach while using the ILS signal as a reference for accuracy...?Or is a PAR approach a precision approach? Bert Van Bulck

Nope, not there yet, but thanks for guessing. The MLS is a precision approach and even though the last one was decommissioned here in 2008, may be coming back in Europe. This is a full blown instrument approach that can be flown down an electronic glide slope without talking to someone on the ground.

Radio Minimums for CAT II/IIIBaro minimums and MDA for CAT I and NPAs.Simple as.[unless of course specified on the specific aerodrome chart, which takes precedence over afore mentioned standards] Rónán O Cadhain Snr. CAT I is not an NPA.

Thank you! Bert

Radio Minimums for CAT II/IIIBaro minimums and MDA for CAT I and NPAs.Simple as.[unless of course specified on the specific aerodrome chart, which takes precedence over afore mentioned standards] Rónán O Cadhain Snr. CAT I is not an NPA.

Not in the U.S. MDA is for non-precision approaches only. DA applies to CAT I. And there is a big difference. This FAA publication is helpful (and authoritative). http://www.faa.gov/l...media/CH-05.pdf Further, the definition of MDA should be useful: The Aeronautical Information Manual) (AIM) defines minimum descent altitude, or MDA, as "the lowest altitude, expressed in feet above mean sea level (MSL), to which descent is authorized on final approach, or during circle-to-land maneuvering, in execution of a standard instrument approach procedure (SIAP) where no electronic glideslope is provided." http://www.faasafety...l.aspx?id=17273

Not in the U.S. MDA is for non-precision approaches only. DA applies to CAT I. And there is a big difference.

Hence why I said "Baro Minimums" Referring to the Decision Altitude (DA). I fly state side, I'd know.

Actually, once an *cough* Airbus check captain wanted to convince me a CAT I ILS used MDA and not DA. Obviously it turned out this was a direct result of them placing their CAT I DA in the MDA field in their FMS. Apparently for 'bus pilots the following rules apply: MDA = their baro referenced field, and DH = their radio referenced field in the FMS. Quite an interesting design flaw IMHO (correct me if I'm wrong). So for their CAT I DA, just because it's baro referenced, they placed that into the MDA field. After years of using this system, it obviously makes people think that CAT I has an MDA and no DA. Was quite an interesting discussion though. Thanks for the IM/AM insight BTW! EDIT No, of course I'm not. I dearly hope it didn't come across that way. EDIT2 Oh yes, just re-read my phrasing. CAT I "just like all other NPAs" yeah right *facepalm*. Correct, thanks for the heads-up. Bad wording on my part. Was meant to say CAT I and all NPAs are baro referenced, if you will.

Etienne, you are right in stating this. However with the release of the R1A update software for both Thales Topflight and Honeywell Pegasus FMGCs, the 'MDA' and 'DH' has been changed to read 'BARO' and 'RADIO'. This to avoid the confusion you talk about. It's not really an airbus design flaw. Cheerz

And to add to this discussion, more and more european airports are adopting a DA for non precision approaches. Back in the day non precision approaches used to be 'step down' approaches, where you would pas a boundary there after descend to the next lower altitude until finally reaching the 'MDA' where you would stay, look out for the runway and at the MAPt go around. Nowadays with modern technology (FMS, GPS...) we are able to fly these non precisions the same way in lateral field but thanks to technology we have better means of constructing a self assessed glide path to the runway (usually 3°) . This implies that if this guidance can be accepted as accurate, you can consider flying a continuous descent final approach (CDFA). However the definition of the MDA is not coherent with this technique, therefore decisions were made by the airlines themselves to either add 50' to the MDA and fly the approach CDFA instead of the older less stabilized step-down approach. Now, more and more authorities are updating their procedures to have a DA instead of a MDA, because the redesign usually implies the procedure to be flown CDFA. (of course this is not alway possible) Also, regarding the 'authority'. The only thing an authority will define for an approach, is an OCA (obstacle clearance altitude)/OCH(obstacle clearance height). The regulations say the MDA/DA >= OCA and MDH/DH>=OCH . that's it. there is nothing saying you have to fly an NPA with a MDA/H.

with the release of the R1A update software for both Thales Topflight and Honeywell Pegasus FMGCs, the 'MDA' and 'DH' has been changed to read 'BARO' and 'RADIO'. This to avoid the confusion you talk about. It's not really an airbus design flaw.

Thanks a ton! Very interesting insight. Yeah indeed it's been a few years, so things might have changed. Good to see they addressed this, should be much clearer and more consistent now.

Hence why I said "Baro Minimums" Referring to the Decision Altitude (DA). I fly state side, I'd know.

Ah, it sounded like you were saying that "baro minimums and MDA" apply to BOTH CAT I and NPA. After all, MDAs an DAs are both "baro minimums". Well, hopefully we've convinced folks that CAT I ILS approaches don't have an MDA, because a few people were adamant that they do.

Hm, I was taught the difference between MDA/DA as stated above (important in the G/A case). Otherwise, of course you can do it that way, in fact it might be the only way that makes sense for that particular system. Still it's technically not precise IMHO.

Sorry yes, but what I was referring to was in regard to Airbus operations. There is a very real difference in MDA and DA as discussed previously.

There is no ability to set MDA in the 737NG. The normal procedure is to set a "derived decision altitude", MDA + 50FT. This 50FT buffer is used to allow crews to initiate the go around at the MINIMUMS callout without going below the hard floor of the MDA. MDH are seldom used. Source: FCTM 5 Non-ILS Instrument Approches - Decision Altitudes (DA(H)) or Minimum Descent Altitude (MDA(H)).

Note: If using an MDA(H), initiating a missed approach approximately 50 feet above MDA(H) may be neccessary to avoid descending below the MDA(H) during the missed approach, if requred for the procedure or by the regulatory authority.

There is no ability to set MDA in the 737NG.

Why not? Set it to BARO...? Of course, as previously explained, actually DDA will be used nowadays, but if you wanted, why do you think you couldn't set an MDA.

You could, but the problem is, once you hear the work "MINIMUMS" without being visual, you've already busted the MDA!

I hadn't thought of that. Well you could always use the visual indication on the altimeter, but nevertheless, good point!

There is no ability to set MDA in the 737NG. The normal procedure is to set a "derived decision altitude", MDA + 50FT. This 50FT buffer is used to allow crews to initiate the go around at the MINIMUMS callout without going below the hard floor of the MDA. MDH are seldom used. Source: FCTM 5 Non-ILS Instrument Approches - Decision Altitudes (DA(H)) or Minimum Descent Altitude (MDA(H)).

No ability? I use MDA for circling approaches.