ILS Issues

[Mandretti]

I'm having difficulty getting the ILS to acquire the G/S or Loc  with APP mode.  I've tried many times and cannot get this to operate as I would expect.  I have attached a video.  I must be doing something wrong, but I cannot identify what that could be.  This happens at multiple airports.  I have the correct ILS frequency, I'm established under the glide slope altitude and approach heading at the point I should join and thereafter. I have the correct course set, A/T, CMD A, FMC is set up for the flight situation, I'm close to Vref.  So don't know what else to do.   The video is pretty short given the file size, so this show a brief segment but you can get the general idea.  I was established much sooner than this of course.  

[Litjan]

Hi Mandretti,

judging from your video, everything looks to be set up correctly and I can not understand why the G/S mode is not capturing. It should do so within 0.4 dots deviation.

The usual troubleshooting advice would be to (temporarily) remove all add-ons and plugins - or maybe just post a log.txt here first, sometimes we can learn something from it and give you a more precise hint at what could interfere. The biggest red flag is "fly with lua" as that opens up the door to all possible weird scripts that can basically mess with everything.

Cheers, Jan

 

[Mandretti]

I did a new install of XP and the 737.  I still had similar problems.  I discovered that if I engaged the APP mode too early sometimes the G/S would never lock on, and less frequently the VOR LOC wouldn't lock on.  That only took 100 tries to figure out over the last two weeks. 

It works the same way on the old install.  So the AP is very particular about the circumstances in which it will engage,  and when the APP mode works.  

[Litjan]

3 minutes ago, Mandretti said:

That only took 100 tries to figure out over the last two weeks.

Wow, thanks for doing this detective work!

I will try to verify your findings and see what is going on with that.

 Cheers, Jan

 

[Mandretti]

BTW I was using the XP Map function you told me about to do some of the testing so that I could do it repeatedly.   I believe that when xp pause goes off after setting up the map flight parameters if the actual aircraft flight status/configuration doesn't match up in some ways, this problem is likely to occur.    

[Litjan]

Yes, I can imagine that maybe some values for deflections get confused when resetting the aircraft in that way and create a brief "captured" logic but then deflect out of bounds... so that the autopilot rejects following them from now on.

So it is especially important to NOT set the APP mode until the reception of the ILS is steady after unpausing.

Edited April 6, 2022 by Litjan

[Mandretti]

8 minutes ago, Litjan said:

Yes, I can imagine that maybe some values for deflections get confused when resetting the aircraft in that way and create a brief "captured" logic but then deflect out of bounds... so that the autopilot rejects following them from now on.

So it is especially important to NOT set the APP mode until the reception of the ILS is steady after unpausing.

Yes.  I was having this issue on regular flights when AP was engaged the whole time, and engaging APP as I intercepted the ILS at what I believe was a valid altitude.  I'm going to go back and do the arrival segments to intercept the ILS and see how those do.  I was having a lot of issues with those, which is why I switched to using the map function and shorter approach - just to save time.  Now that I can pretty regularly get APP going I'm going back to the arrival phase and see what gives.  

Edited April 6, 2022 by Mandretti

[Mandretti]

Based on my latest testing I think for my regular flights the problem has been engaging APP too soon, or under the wrong conditions.  But I wasn't ever doing anything drastically wrong - like coming in from 90 degrees, or 1000 ft high or 30 kts over speed.  Seems very touchy and dissimilar to other aircraft.  Is this how the real aircraft is?  

[Litjan]

5 minutes ago, Mandretti said:

Is this how the real aircraft is?  

No, the real aircraft is pretty reliable when capturing the ILS - but then again you are the first one to report problems with this in 7 years of selling this aircraft and thousands of users flying ILS approaches with it.

So this makes me believe that you are doing something unique - not wrong, but different from everyone else that makes you have these problems.

It must be something weird that is confusing the capture logic - you could try to "reboot gizmo" before trying a new approach, this should clear out any data variables that the AP logic might have engaged from previous flights.

 

Edited April 6, 2022 by Litjan

[Mandretti]

Yep that's what I thought too...very frustrating. 

I am getting Gizmo errors periodically - the things it's referencing don't seem that important.  I doubt that's related.  

[Litjan]

25 minutes ago, Mandretti said:

I am getting Gizmo errors periodically

hmm - any Gizmo error can have unpredictable results on all systems. So as soon as you have a Gizmo error, consider the flight flawed!

If you do, please post those with a screenshot and the log.txt in the relevant forum so we can see what the problem is.

There should be no Gizmo errors on your flight at all - note that you can not change any altitude or speed restrictions in the FMS (yet).

[Mandretti]

Ok - thanks for the info.  I've reinstalled the AC.  Still not working as expected - so after weeks of struggling I'm giving up ILS.  I am following the tutorials, manuals, YouTubes exactly as far as I can tell, and you as well can not find anything wrong with my technique.  So whatever it is is not solvable as far as I can tell.  Too bad - but I've spent enough time   I like the AC otherwise.  Thanks for your help!

[Litjan]

Hmm, that is too bad - but of course, there is still the option to remove your other plugins to test if they interfere.

Cheers, Jan

 

 

[Mandretti]

I did that.  I installed a clean version of X-Plane 11, downloaded a fresh copy of the 737.  No plugins.  Same result.  Very weird. 

[Mandretti]

 Hi Jan, Ok - one more time.  I've figured out how to capture the ILS most of the time, and how to recover quickly when it doesn't.  Whew....now the second step - which isn't actually much related to the ILS itself, instead its landing.s  I've been practicing landings for several months on and off, and have several hundred attempts with 2 successes.  I've watched videos on 737 landings, read the Boeing 737 NG Training Manual on approach, flare and touchdown and it doesn't work for me.  At Vref - 10-20 ft above the runway, I pull gently back on my Honeycomb Alpha Yoke to achieve a 5-7 degree attitude as instructed, I'm also retarding the throttle gradually.  As I do that I usually  start a gentle ascent, then float several thousand feet down the runway before touching down.  I am at Vref when I start pulling back to get the proper attitude.  If I don't get that attitude, I just slam into the runway.  If I slow the ascent as I approach the runway I wind up floating down the runway several thousand feet.  I'm nothing if not persistent, but so far nothing I try is really working.  I suspect that part of it at least is how my yoke is set up.  Maybe too sensitive, not sensitive enough or whatever.  Because very slight differences in timing, speed of pull back etc. have large affects on results.  Anyway I'm sure it's a combination of things, but so far it's alluding me after probably several hundred (not exaggerating) attempts.  So - looking for some resources to assist me in figuring this out.  I've provided a link to a YouTube video of one landing.  

https://youtu.be/Qq1FJEHC6uY

 

[Litjan]

Can´t watch the video as it is set to private. I also can´t provide private tutoring on flying the 737 due to time constraints - but if you float for "several thousand feet" with thrust at idle....either your thrust is not idle (bad hardware throttle setup) or you are not at Vref (wrong weight input in FMS).

[Litjan]

I can see the movie now - as I suspected, you are not at idle thrust - idle thrust should be about 35% N1, it is a bit hard to read on your video, but you are at ca. 55% N1, so there is obviously something wrong with the way your controller axis for thrust is set up.

You are also coming in with a solid tailwind, which will naturally extend your flare distance some more.

I assume you are the same guy (Fiddle Sticks) that asked for help on the .org forum? As you are also not arming the speedbrake on touchdown... the third reason why this isn´t working for you.

Here are some screenshots and a video how it is supposed to look. Approach speed should be Vref+5, bleeding off to Vref upon touchdown, you do this correctly.

 

 

[Mandretti]

1 hour ago, Litjan said:

I can see the movie now - as I suspected, you are not at idle thrust - idle thrust should be about 35% N1, it is a bit hard to read on your video, but you are at ca. 55% N1, so there is obviously something wrong with the way your controller axis for thrust is set up.

You are also coming in with a solid tailwind, which will naturally extend your flare distance some more.

I assume you are the same guy (Fiddle Sticks) that asked for help on the .org forum? As you are also not arming the speedbrake on touchdown... the third reason why this isn´t working for you.

Here are some screenshots and a video how it is supposed to look. Approach speed should be Vref+5, bleeding off to Vref upon touchdown, you do this correctly.

 

Yes - Fiddlesticks/Mandreti.  Thanks for taking an interest in this with me.  So much time and energy whew..  And Yes - I can actually land now.    Definitely several things I was not doing correctly, including off and on, having the wrong GW and therefore about 10-20 kts to hot at touchdown.  When you run the same landing 30 times in a row, you use some fuel.  So the Vref calc is no longer valid after a while.  It really felt like my approach was way too fast....and it was.  Speedbrakes - that was wrong.  Never knew if they were that important or not.  And I think my throttle is Ok - just wasn't dropping fast enough given how fast I was coming in and descending.  Thanks again.  

 

[Litjan]

Glad you have some success with this!

When I flew the 737 we were taught to listen to the radio altimeter count down from 50... at 30 we would do a short "break" (yank back the yoke to break the sinkrate, hold new pitch attitude about 3 degrees MORE than what you had during the final approach), then at 20 slam the throttles all the way to idle quickly. As soon as you feel the wheels touch, rip open the speedbrake all the way - just in case the automatic deploy fails.