I'm a bit confused when it comes to DH, MDA (or MA?), MINS (which you can set BAR or RADIO). All these things have to do with a missed approach (if I'm not mistaken), but... why can you choose (if I'm not mistaken again) between DH and MDA...? What's the difference? And what is the exact function of the MINS...? Is that your MA height? Or the DH height?Maybe someone can explain this or point me to a sitte which explains it all...

Hi there!Ok here we go:First of all, the definitions:DH = decision height (only plays a role during a precision app)MDA = minimum descend altitude (only for non precision apps)MA = missed approach (applicaple to all appraochs)MINS = minimums (the automatic callout you hear during an approach)And now to go into the details:First of all, there are two different types of instrument approaches you can shoot: precision and non precision approaches. An example for a precision approach is the good old ILS approach. A VOR approach would be a non precision approach.Every instrument approach has a legal minimum weather criteria. This describes when, by the latest, you must have visual contact with the runway environment. If by this time you don't see anything, you have to perform a go around.For precision approaches, this minimum altitude is described as a height above ground (therefore decision height). This means, you'll fly the approach, and if you don't see the runway at DH, you'll go missed. Note during an ILS approach (as humans aren't very fast) you'll most probably descend slightly below DH - this is legal.For precision apps, you'll set your minimum marker by reference to ground (therefore radio altiude) and then you should get the aural "minimums" as you pass the DH.Non precision approaches are slightly different. There the minimum altitude is not a height above terrain, but an actual altitude above MSL (sea level). Also, the minimum altitude is not a decision altitude either! Its a minimum descent altitude, meaning you are not allowed to descend even 1 foot below this altitude without visual contact. So how do you fly this approach? You follow your profile, descend to the MDA, around 50 feet above MDA you start your level off (so that you don't descend below MDA) should you not see the runway. Now you maintain this altitude until the MAP (missed approach point). If by this time you still don't see the runway, you go missed. Otherwise, you may continue your landing visually.To summarize:DH is a decision height - you may descend slightly below DH but the decision making process has to be started at DH.MDA is the minimum descend altitude - you must stay at this altitude until you either see the runway or you pass the MAP, whichever happens earlier.Hope this helped!Regards,Mark

Don't forget the DA, which is the barometric minimum for ILS CATI approach. Usually DH never used for CATI ILS.Tero

An excellent explanation Mark, even I get confused at times between when you use Da and when MDA.Interestingly, IIRC the tutorials for the PSS Airbus talk of setting the MDA and not the DA.Dave

Wow! Really great answer, Mark! It's all completely clear now! Thanks! :)

To add to Mark's excellent explanation, there is also the concept of a DA (Decision Altitude) which is essentially the same as a DH except that it's read from the barometric altimeter and not the radar altimeter as Tero so rightly points out. For a normal ILS approach, you use a DA and not a DH to make your decision. There is also a non-precision approach that uses a DA, namely an RNAV approach that is authorized for VNAV when the operator is also authorized for VNAV. I know that sounds like a lot of "if's" but both the type of approach procedure and the authorized operator are becoming more common. The indications to the pilot are similar to a precision approach but the vertical component is generated by the FMS and not in response to ground-based radio signals.cz