4 hours ago, Stearmandriver said:

@aniiran I wonder if the IAN thing is getting you too.  It still gets me in the PMDG, and it's not really their fault (except it would be nice if you could turn it off!) but made troublesome by the fact that in the sim the ILS range is only like 8 miles or something.

As far as the autopilots swapping - that's what happens whenever you select the other autopilot, except if you're in approach mode on an ILS.  In every other case, only one autopilot can be selected, so pressing the other button will just swap to that autopilot.  In approach mode on an ILS, it understands you want to autoland and both autopilots will show selected. 

So in the sim, what can happen is, you get yourself on an intercept and select approach, but if you're too far out for the sim ILS signal, you'll end up in IAN, which looks real similar to an ILS, it's easy to not notice.  But then the second autopilot won't take.  I've been there in the PMDG and didn't realize I was in IAN until I had that exact problem.  It's an insidious combination. 

Anyway, not saying that's for sure what happened; I wasn't there to see it.  But it's just an idea, it can get anyone.  It's cool that PMDG modeled IAN, but I REALLY wish they'd allow an option to turn it off!

 

Hmm, most of my ILS captures are beyond 8NM in MSFS 2020, and I am pretty sure that I am always in ILS approach mode (VOR/LOC and G/S on the FMA).

Edited February 11, 20251 yr by Christopher Low

PMDG very recently changed the APP logic of the 737 to ARM LNAV+V after selecting APP for the missed approach. I'm wondering if this has affected the ILS /IAN portion in any way as IAN to LNAV /VNAV is the same AP mode whereas ILS to VNAV /LNAV is mode switching and (in theory?) would therefore require pilot intervention? 

Probably scraping the barrel here but missed approach training is important too! 

5 hours ago, Christopher Low said:

Hmm, most of my ILS captures are beyond 8NM in MSFS 2020, and I am pretty sure that I am always in ILS approach mode (VOR/LOC and G/S on the FMA).

Yeah I was just guessing on distance, I don't know the exact value but I know the in-sim ILS signals are much lower range than in reality.  I've seen it get me when vectored out pretty far at a busy Vatsim airport for instance.  Someone should test this; just put yourself in slew and slide backwards from the runway at around 3,000ft until losing the signals.

4 hours ago, sloppysmusic said:

PMDG very recently changed the APP logic of the 737 to ARM LNAV+V after selecting APP for the missed approach. I'm wondering if this has affected the ILS /IAN portion in any way as IAN to LNAV /VNAV is the same AP mode whereas ILS to VNAV /LNAV is mode switching and (in theory?) would therefore require pilot intervention? 

Probably scraping the barrel here but missed approach training is important too! 

Yep, that's an option that most 73s have these days and it's handy.  It works just fine on an ILS; your active lateral mode is VOR/loc and your armed lateral mode is LNAV.  The mode switch will occur with a toga press or if you're still airborne a predefined distance beyond the runway waypoint, so no real intervention required other than ensuring you're in the mode you think you're in / want to be in.  

On an LNAV/VNAV approach, you can have an active lateral mode of LNAV with an armed lateral mode of LNAV which looks weird, but it's just the plane telling you what it will do on a missed.

At KSJC 30L.  I do a full circuit at 15 miles with the plane in CMD A, HDG and ALT 3000, I turn to heading 040 then 330 20 seconds later.

I am below the glideslope.  As soon as I start to see the lateral diamond move I hit APP  then CMD B 5 seconds later.   Normally, what happens is CMD B kicks off CMD A.  But sometimes it kicks off APP as well.  Even though APP and CMD A are not illuminated i get the SINGLE CH in YELLOW.  I watched it really carefully on the approach.  Several times it just stayed SINGLE CH in yellow and there was never an idication it was going to autoland but it did anyway, I did not touch it and it flared and retarded the throttle by itself (I'll have to show this on video).  However,  sometimes it does work and around 1500 AGL I see a blinking on the PFD and it goes from SINGLE CH in Yellow to CMD in Green with FLARE in white under G/S in Green.  Then I know the autoland is going to work.

After testing 10 times.  The only way to ensure a Autoland is to make sure CMD A and CMD B and APP are all illuminated.  Ususally having to press CMD A then CMD B twice and if APP kicked off APP.  

I was going to make a video last night but NVidia Experience is crashing the game.  I'll get OBS and try again.

3 minutes ago, aniiran said:

At KSJC 30L.  I do a full circuit at 15 miles with the plane in CMD A, HDG and ALT 3000, I turn to heading 040 then 330 20 seconds later.

I am below the glideslope.  As soon as I start to see the lateral diamond move I hit APP  then CMD B 5 seconds later.   Normally, what happens is CMD B kicks off CMD A.  But sometimes it kicks off APP as well.  Even though APP and CMD A are not illuminated i get the SINGLE CH in YELLOW.  I watched it really carefully on the approach.  Several times it just stayed SINGLE CH in yellow and there was never an idication it was going to autoland but it did anyway, I did not touch it and it flared and retarded the throttle by itself (I'll have to show this on video).  However,  sometimes it does work and around 1500 AGL I see a blinking on the PFD and it goes from SINGLE CH in Yellow to CMD in Green with FLARE in white under G/S in Green.  Then I know the autoland is going to work.

After testing 10 times.  The only way to ensure a Autoland is to make sure CMD A and CMD B and APP are all illuminated.  Ususally having to press CMD A then CMD B twice and if APP kicked off APP.  

I was going to make a video last night but NVidia Experience is crashing the game.  I'll get OBS and try again.

I may be incorrect in this, but I thought that Cmd B was only supposed to be engaged, when you were already stabilized  on the G/S and LOC. 

49 minutes ago, Bobsk8 said:

I may be incorrect in this, but I thought that Cmd B was only supposed to be engaged, when you were already stabilized  on the G/S and LOC. 

yeah Possibly, that's what I'm trying to get to the bottom of.  I have been "flying"  the PMDG 737 since the early days and have always gotten a VOR/LOC and G/S indication and the plane has always gotten me to the runway. So I never really got into the weeds. 

As a matter of fact for years I have always pushed CMD B first and then APP. That results in a yellow single CH indication. (I assume this is because during testing I was not putting in approach config info into the FMC or decision height and with no flight plan and no landing alt either.) but it still captures the LOC and G/S so I never really thought about what the airplane is telling me in every single anunciation as long as i see VOR/LOC and G/S in green. I also never do autolands.  I do like to "play" the "game" at some point instead of watching it play autonomusly.

I spent 2 hours just flying circuits around KSJC and was not getting consistent results. Tried to capture the approach and ended up with a CTD,  thanks Nvidia Experience. I'll try pushing CMD B only when im on LOC and G/S.

1 hour ago, Bobsk8 said:

I may be incorrect in this, but I thought that Cmd B was only supposed to be engaged, when you were already stabilized  on the G/S and LOC. 

I find this very logic as well. However the FCTM seems to just say that they both should be armed and shown on the FMA

https://ibb.co/WvTxGdnS

Michael Moe 

Second autopilot can be selected immediately after you select approach mode.  IF you're receiving ILS signals and therefore don't enter IAN mode, both autopilots will show selected at that point. 

However, the Single Channel announiation will remain until approx 1400ft, when the relay opens and the nav system does its self test.  You'll see the loc and GS diamonds blink while this occurs.  If the test passes and both autopilots are selected, you'll see "single channel" switch to CMD (fail passive) or Land 3 (fail operational).  This won't happen until roughly 1400ft on the GS.

When @aniiran says sometimes it "kicks off approach" as well, I'm guessing you mean that the green light in the Approach button extinguishes?  This will happen on every ILS approach you fly, even single channel or manual.  If it doesn't, you're actually in IAN.  It happens because the only thing that green light actually indicates is that the mode can be deselected by pushing that button again.  Once loc and GS are captured, you cannot deselect approach by pushing the button.  The light extinguishing is a good thing, as long as the FMA indicates VOR/loc and GS. You can't trust the lights in those buttons to know what mode you're in... Those are just requests.  They're fantasies.  Reality is what's displayed on the FMA.

As far as it looking like autoland worked in single channel, I'd be interested to see a video but I can take a guess.  There's no flare logic in single channel, but the autothrottles will always enter retard mode at around 30ft if they're engaged.  This will even happen on a manually flown approach with the A/T engaged (which Boeing does not recommend and we don't do, but I've seen it in the level D sims, and there are a few airlines that opt to use autothrottles for a manual landing for whatever reason).  

So, the autopilot is sliding down the glideslope (with no intent to flare) and all of a sudden the power slides back to idle.  All the autopilot wants to do is continue to track that (now very sensitive) glideslope beam, and since the power reduction causes an increased descent rate, it pitches up to compensate.  It can look like a flare but it's not; there's no speed protection logic, there's no tail strike prevention logic, and the touchdown is usually still very hard.  

What am I doing wrong? Why are there no 'RETARD' and 'LAND' alerts in the PFD when autolanding in KSJC?
 

 

It's starting to become clear, congratulations!!!

Uh, are you doing an ILS with autoland or ILS? In an "autoland" you have to disable the PA when rolling in RWY. "RETARD" is not announced but it is displayed on the PFD (watch your video at 01:11)

NB: You haven't defined the Vref and you're going too fast

Selecting Vref

1/ Selecting the approach speed
It is determined with the weight of the aircraft at touchdown. To do this, go to the PROGRESS page and calculate the difference between the fuel on board and the estimated fuel at arrival. Let's assume: 3.8 and 3.4 and subtract the difference from the GROSS WT by removing the 0.4.

2/ In FMC/PERF enter the Vref

Correct: GROSS WT
enter: FLAP/SPEED.

Edited February 13, 20251 yr by Area

1 hour ago, anavsun said:

What am I doing wrong? Why are there no 'RETARD' and 'LAND' alerts in the PFD when autolanding in KSJC?
 

 

You're too fast. The speed selector on the MCP is set to 190, while a typical approach speed for flaps 30 is around 140 knots. Note also that the autothrust is limiting the speed to 175 knots, as that's the limit speed for flaps 30. (This is also why the "B" is flashing in the MCP speed window.)

Because the approach speed is too high, you have a distinct nose-down attitude, and that is likely confusing the flare logic, causing the autopilot to disconnect in the flare.

I would recommend watching some tutorial videos to understand more of the background of how to work out the correct speeds for the approach and the like.

@martinboehme is right, you should watch tutorials but there is some sorting to do. A reference is the youtuber A330; examples: 

 

 

 

See tutorials from PMDG 737-700 for MSFS - Tutorial 1 to PMDG 737-700 for MSFS - Tutorial 15

Edited February 13, 20251 yr by Area

Alternatively, if you prefer written tutorials, the PMDG tutorial that I believe you've been following should also cover how to determine the correct approach speed.

But you do need to make sure you're following the procedures correctly and completely. That takes some effort, but if you try to "fudge it", it's likely that things won't work, and you'll end up frustrated.

2 hours ago, anavsun said:

What am I doing wrong? Why are there no 'RETARD' and 'LAND' alerts in the PFD when autolanding in KSJC?
 

 

One thing i noticed  is  that you havn't  armed the app mode

here is one utube plenty more on auto land

https://www.youtube.com/watch?v=Zl0EYkI0jZY&list=PLtFw-RsDhI85SH4R18hrswGV39hebQIyy&index=9