Hi all, I have been struggling for a while to understand what do I need to use/configure my NGX before landing based on the charts.
I know the concept of DA(H): BARO/RADIO, but what I don't know is what do I need to use.

I need to know what I need to use/configure on a precision approach (with a glide path instrument) and with non-procision approach (without a glide path instrument

here is the Example:

precision approach (ILS):
on the chart I am seeing the following, DA(H):2610' (250')
on the NGX I have the option to configure the BARO or RADIO.

what number (2610 or 250) I need to use and on what settings (BARO/RADIO)

non-precision approach (LOC):
on the chart I am seeing the following, DA(H): 2940' (580')
on the NGX I have the option to configure the BARO or RADIO.

what number (2940 or 580) I need to use and on what settings (BARO/RADIO)

I know what those value / settings mean, so no need to explain what they are, what I didn't really manage
to comprehend yet is what number (AGL/MSL) I need to use and on what settings (BARO/RADIO) for both kinds of approach (if there is a different procedure as for those settings).

From what I understand of the 737, you select one (either it doesn't matter) and key it into the knob. If you use baro, be sure to have the correct QNH set (you should have that anyway)

 

The lower altitude on the chart should always be the radio height minimums.

 

For your ILS example, 250' is the radio height (AGL) and 2610' is the barometric minimum (MSL). Things will complicate if you are landing anywhere that has a negative MSL. Landing at EHAM, say the radio minimum is 200', the baro minimum wil be 189' because EHAM is -11ft MSL.

 

Hope this helps

so which one of the combinations is the "best practice" for both the approaches (assuming I have the QNH configured correctly for the Airport in question)?

 

the the 250 on the RADIO or the 2610 on the BARO?

 

the same for the None precision Approach:

the the 580 on the RADIO or the 2940 on the BARO?

Firstly, for the benefit of others that may read this thread: DA(H) stands for Decision Altitude (Height); "Altitude" is how high you are above sea level (known as AMSL), "Height" is how high you are above the airfield (know as AAL or AGL). "Decision" means that if PF cannot see the runway lights by this point, they must go around.

 

You put the Decision Altitude in BARO, or the Height (the bracketed numbers on your chart) in RADIO (since the Radio Altimeter always reports how high you are above the terrain directly underneath you). Generally the preference is for a RADIO Decision Height since it is not dependent on you setting the correct QNH or pressure errors. However, if the DA(H) is above 300 ft using BARO can be preferable since it is not subject to errors caused by unevenness of the terrain passing underneath the aircraft.

 

You may also read about MDA, Minimum Decision Altitude; this is basically the same thing as DA(H) but used on Non-precision approaches (LOC, VOR etc) and guarantees obstacle clearance between the Final Approach Fix (FAF) and the Missed Approach Point (MAP).

 

That's basically it, although for the pedants out there I should point out you can place the Height in to BARO if you set the altimeter pressure setting to QFE. Altimeters set to QFE pressure will read zero when you've landed (just like a radio altimeter), altimeters set to QNH (which is normal) read the airport's altitude above sea level (AMSL) when on the ground.

To keep it simple, on Non precision approaches or Category I ILS approaches you should use BARO and the Minimum Descent Altitude or Decision Altitude as appropriate for the approach. Use RA when on Category II or III ILS approaches & the Decision Height.

 

Well, that's what I use (based on both of the VA's I fly in's SOP's) and it works pretty well.

 

 

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Is use of RA mandatory for ILS Cat II and above ?

Or boeing recommandation ?

 

Just wondering.

Is use of RA mandatory for ILS Cat II and above ?

 

Mandatory, it's always a Radio DH. And if the RA is unserviceable the aircraft is degraded to CAT I.

Copy that.

 

Tnx.

If you use Jepps or LIDO, the decision height will always have RA next to it, when you are supposed to use RADIO mins. If that is not present, use DA. (not DH).

 

 

The key is that on non precision approaches and CAT I ILS you use BARO because the decision altitude is based on height above the runway but at 200 feet (standard DA for ILS) the terrain is not necessarily at the same altitude as the runway so RA would not be accurate . On CAT II ILS approaches they actually measure how high the plane will be above the ground when it is 100 feet above the runway which is why it is not always 100 feet exactly. For CAT III its easier because on a 3 degree ILS you will pass over the end of the runway at 50 feet so you can just set 50 RAIDO for those. I hope my explanation is not too confusing. So as has been mentioned before the proper use of BARO vs RADIO is BARO for non precison and CAT I ILS and RADIO for CAT II/III.

Wow, thank you guys a lot, it was a great help.

fabo, you really gave it a sweet punch ere with that jepp screenshot and the RA condition.

Now I really know what to be looking for in the charts as well.

 

Lucky me I just got off a 738 of Jet2 an hour ago, and it happened to be that the 1st officer was in the cabin chatting with someone, I grabbed him aside just before he was about to go back into the cockpit and I asked him the same question I posted here.

Well he explained to me in details and he pretty much said the same as you guys did.

ILS CATIII is the only time they use RADIO and DH.

For CAT I or below, they Always use BARO.

I then asked him what about CAT II, and he replied back, "A very good question, I don't remember as most of my flights are either CAT III or CAT I."

So I am assuming that you answer about CAT II is correct as well.

guys, thank you very much.

Really appreciate it.

The FCTM that came with the product (thanks Mr Boeing) contains a very clear explanation of things on pages 183 (Landing Minima) & 184 (Radio Altimeter).

 

Always worth a 'scan read' (PMDG NGX FCTM) ...especially during the cruise.  It answers probably 90% of the questions posted here.

Or just this:

 

Wow, thank you guys a lot, it was a great help.

fabo, you really gave it a sweet punch ere with that jepp screenshot and the RA condition.

Now I really know what to be looking for in the charts as well.

 

Lucky me I just got off a 738 of Jet2 an hour ago, and it happened to be that the 1st officer was in the cabin chatting with someone, I grabbed him aside just before he was about to go back into the cockpit and I asked him the same question I posted here.

Well he explained to me in details and he pretty much said the same as you guys did.

ILS CATIII is the only time they use RADIO and DH.

For CAT I or below, they Always use BARO.

I then asked him what about CAT II, and he replied back, "A very good question, I don't remember as most of my flights are either CAT III or CAT I."

So I am assuming that you answer about CAT II is correct as well.

guys, thank you very much.

Really appreciate it.

Most of the runways we use that are CAT II are also CAT III so we will always just set up for CAT III since it has lower minimums. There are still a few that are only CAT II and some airplanes that can do CAT II and not CAT III so that's mainly when that would be used.

 

Or just this:

 

I think I recognize the symbols. The manual is connected to your avatar, is it not?