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737-300 1.33 Tutorial 2 Dual-Channel Autoland Issues


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I've looked elsewhere for this topic and have not found anything recent or exactly pertinent to my issue. I'm running X-Plane 11.55 in Experimental Flight Model, Downwind ILS not disabled.   I have 2 years of X-Plane - I'm retired - it's COVID - so I likely have over 1000 hours in on X-Plane.  So not a newbie.  I have not had this AC previously and so had a clean install of the latest version about 3 weeks ago.  I'm running through the IXEG tutorials that are dated 2016, so not sure if there's something wrong with those. (KLAS ILS info has changed but I've taken care of that).  Anyway I've run Tutorial 1 a number of times and am now comfortable with the basics of flying this aircraft.  I've been in Tutorial 2; Autopilot and Flight Director for a week now - probably over 50 hours trying to get the ILS Dual Channel Autoland sequence to work.  I've been successful 6 times with likely over 60 attempts and cannot duplicate those particular runs. 

The issue is that even though I approach the G/S from below, am right on with the heading and inline with the ILS for runway 26L at McCarren Las Vegas the VOR/LOC and G/S armed, they are not captured (with a few exceptions) and I wind up heading for the dirt quite a distance from the runway.  As far as I can tell I have the AC configured and positioned as the Tutorial describes.   

In an effort to cut down on the amount of time required to keep trying this I am now using the X-Plane function to place the AC 10nm out from 26L.  I've attached the pics for the initial configuration and position when I'm spawned 10nm out.  Then I have a pic of the result of that as the approach progresses and attached the log which I'm pretty sure will be useless.  I also pasted the procedure I'm using below.  I suspect it's some very subtle timing and/or positional issue.

Additional info: Coming back to this after a few hours I was able to get it working 4 times in a row, then after that - changing nothing - very weird behaviors primarily with altitude.  Basically not holding the altitude specified, or not acquiring the altitude specified.  Gradual ascents or descents or yo yoing - everything is setup exactly as before when it worked several times.  Also when the plane spawns the aircraft config can be very different; A/T off, FDs off, N1 on instead of SPEED, ALT HDG, APP and ALT HOLD buttons not operational.  Very unpredictable and unreliable.  Anyway if anyone has an explanation for this - I would love to hear it!

737-300 ILS Dual Channel Autoland Procedure

Set plane 10nm out from RNWY 26L McCarren KLAS

 Put flaps and throttle in approximate position needed after spawn.

 Spawn, let equilibrate for 5 seconds or more so to acquire altitude, speed etc. Then hit pause and check configuration and set as necessary.

 Use the EHSI Map setting – 20 nm, EXP VOR/ILS VOR/ADF

 Tune Nav 1 and Nav 2 radio to the ILS frequency for the runway 111.50
 

Set the CRS 1 and 2 and Heading to match the runway heading and make sure it’s in MCP HDG SEL. (259)

 Set MCP SPD at 140 kts flaps 25

 Set MCP ALT to 3800 ft. and MCP ALT HLD 

 AP CMD A on

 APP Mode on

 FD’s on, A/T armed, SPEED mode on

 Unpause

 Press CMD B for the AP. This will set up the dual channel autoland.
The AP should now keep the plane on the ILS heading and will eventually intercept and then fly the glideslope.  Make sure it’s not coming in above the glideslope as that does not work.  When the glideslope is captured the green G/S annunciator will appear.

 When on final speed will be at Vref +5, (127) flaps 40 for low visibility.

 When the glideslope is captured the MCP HDG, APP indicators go dark and only the Speed MCP is active, along with the CMD A and B indicators of course.

Airplane lands. ( I wish) 

X-Plane Screenshot 2021.11.15 - 12.25.32.78-compressed.pdf X-Plane Screenshot 2021.11.15 - 12.28.46.56-compressed.pdf X-Plane Screenshot 2021.11.15 - 09.49.51.85-compressed.pdf

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Hi there!

Glad you are enjoying the aircraft - but sad to hear that you are having trouble with it. From the sound of it, you are doing pretty much everything correctly.

The one thing that raises a flag is the "instability in pitch" that you describe. That sounds like possibly your joystick might be interfering with the autopilot trying to fly the aircraft. On the second picture you posted you can see that the autopilot is in (yellow) CWS P - which means the pitch is controlled by "control wheel steering" - this means that you either never selected a pitch command (like ALT HOLD) or that it disconnected because it detected the pilot giving inputs on the "control wheel" = joystick in the pitch channel.

If you have a "noisy" joystick that is sending erroneous pitch commands, you can increase the "joystick dead zone" in the IXEG preferences menu that comes out if you bump against the left-hand screen edge.

Let me know if this info helped?

Cheers, Jan

 

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Thanks Jan - I've been having fun!  I've spent two years gradually moving up the complexity level starting with single prop, twin props, twin engine very small jets, then larger twin engine jets, and this is my first airliner.  I am engaging all of these at study level and doing a lot of practicing just in case the pilot on one of the many flights I take each year needs help!  Anyway it's been a learning curve, but I'm glad have a firm foundation in the basics.  In addition to the PDF Tutorials I also have the Mike Ray book and have watched a number of tutorials online, including yours!  Ok enough of that....

I understand what you are saying, on the Honeycomb Bravo Throttle quadrant the trim wheel is perilously close to the gear lever, so it does get bumped in tight quarters.  However most of the time I have this issue it's not in CWS P or CWS R mode - it's CMD on the captain's side and on both sides a bit later on in the sequence.   

So now the sim seems to have lost the ability to manage altitude with AP.  With CMD on annunciator, the altitude set at 3800, ALT HLD button lit and ALT HOLD annunciator solid green, it does not control the elevation.  It simply drifts downward at an every increasing angle.  I am getting the main console A/P red flashing warning light, however, and do not understand why.  Just a minute ago with the same scenario it ascended into a stall and then started yo yoing.   What the heck? 

Don't know whether this is related or not, but on occasion some of the buttons like for the EHIS control panel do not work, and ALT HDG and other MCP buttons do nothing no matter what state the AC is in.  

Edited by Mandretti
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Hmm, this sounds like some more serious underlying issue. If the AP light flashes red, the AP is not in control. Check the FMA (flight mode annunciation) - you want green labels in the top row, and also CMD in green on the very right side.

One measure (to rule out simple operator error) I find extremely helpful is uploading a short video of how things go wrong. Even a clip filmed with a smartphone (held fairly steady) can bring a lot of things to light!

After you rule out unwanted joystick interference and things like going too slow (stalling) - the next step would be to (temporarily) uninstall all other addons, especially things like XPUIPC and fly-with-lua.

Another source of trouble could be erroneous joystick button or axis assignments that cause the autopilot to disconnect, especially things like trim (which will disconnect the autopilot) and secondary axis assignments that can double the regular flightcontrol axis assignments.

Last resort would be trying with the joystick disconnected (especially the Honeycomb Throttle, I have read many quirky things about it) and see if that helps.

It has to be something unique to your setup, otherwise this forum would be full of complaints about this with several thousand copies sold... and I am determined to help you find out what it is ;).

Cheers, Jan

 

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Just tried it myself - and I managed to get into a similar state that you describe. What happened in my case is that I was in a rapid climb to 4000 feet when the GS captured - but the plane was not fast enough pitching down to intercept it and it went "out of bounds", so to say.

I would recommend moving the plane manually back a bit further after using the "10 NM final" setup. The plane needs more time to stabilize, and you want to intercept the glideslope at a shallow enough angle that the plane can actually follow it.

To move the plane, just open the map (m key), then drag the plane on the map.

Let me know if that helps?

Cheers, Jan

 

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33 minutes ago, Litjan said:

Hmm, this sounds like some more serious underlying issue. If the AP light flashes red, the AP is not in control. Check the FMA (flight mode annunciation) - you want green labels in the top row, and also CMD in green on the very right side.

One measure (to rule out simple operator error) I find extremely helpful is uploading a short video of how things go wrong. Even a clip filmed with a smartphone (held fairly steady) can bring a lot of things to light!

After you rule out unwanted joystick interference and things like going too slow (stalling) - the next step would be to (temporarily) uninstall all other addons, especially things like XPUIPC and fly-with-lua.

Another source of trouble could be erroneous joystick button or axis assignments that cause the autopilot to disconnect, especially things like trim (which will disconnect the autopilot) and secondary axis assignments that can double the regular flightcontrol axis assignments.

Last resort would be trying with the joystick disconnected (especially the Honeycomb Throttle, I have read many quirky things about it) and see if that helps.

It has to be something unique to your setup, otherwise this forum would be full of complaints about this with several thousand copies sold... and I am determined to help you find out what it is ;).

Cheers, Jan

 

That's great Jan - I'll start working on these ideas.  I figured that since I wasn't seeing it plastered all over the Internet it was something quirky about my config.  And I'm determined to figure it out.  Thanks - I'll get a video uploaded tomorrow.  

Edited by Mandretti
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24 minutes ago, Litjan said:

Just tried it myself - and I managed to get into a similar state that you describe. What happened in my case is that I was in a rapid climb to 4000 feet when the GS captured - but the plane was not fast enough pitching down to intercept it and it went "out of bounds", so to say.

I would recommend moving the plane manually back a bit further after using the "10 NM final" setup. The plane needs more time to stabilize, and you want to intercept the glideslope at a shallow enough angle that the plane can actually follow it.

To move the plane, just open the map (m key), then drag the plane on the map.

Let me know if that helps?

Cheers, Jan

 

Ok - thanks I'll try that.  I didn't know you could do that - cool!   I'm been having the sense that it's something about the initial state when it's spawned.  And slight variations cause major issues.  Also the sim persists many but not all status, sometimes changes some of the status when spawning etc etc.  So how it arrives in the air is unpredictable.  Probably something about differences in the final state persisting in some weird way into the next spawn -  unpredictably!

Edited by Mandretti
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36 minutes ago, Litjan said:

Just tried it myself - and I managed to get into a similar state that you describe. What happened in my case is that I was in a rapid climb to 4000 feet when the GS captured - but the plane was not fast enough pitching down to intercept it and it went "out of bounds", so to say.

I would recommend moving the plane manually back a bit further after using the "10 NM final" setup. The plane needs more time to stabilize, and you want to intercept the glideslope at a shallow enough angle that the plane can actually follow it.

To move the plane, just open the map (m key), then drag the plane on the map.

Let me know if that helps?

Cheers, Jan

 

I will try this - and many times I've come into the glideslope at level flight 4000 ft and just pass through to the other side without capturing the glideslope.  But perhaps there was something else going on....

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50 minutes ago, Mandretti said:

Also the sim persists many but not all status, sometimes changes some of the status when spawning etc etc.  So how it arrives in the air is unpredictable.

Yes, this is very much the case - especially when using the "10NM final approach" - X-Plane will try to set up the plane correctly for the approach, but this will not work reliably with a custom aircraft that is using many variables that our outside X-Plane´s control.

A surefire way to start up in the air is this:

Spawn on the ground, startup state "ready to fly". Then PAUSE, use the map to first set altitude to 3000 or 4000 or so...then set up speed to 220 kts, and pitch to 5 degrees (also heading if needed). Then drag the plane to about 20 NM out.

Now unpause - then immediately click on AP A CMD and select a pitch mode (like ALT HOLD), then turn on the Autothrottle (this will engage speed mode). Now you are safe ;-)

Now you can raise the gear (and release the parking brake), and then use the autopilot to set up for an approach at leisure.

Cheers, Jan

 

Edited by Litjan
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22 hours ago, Litjan said:

Yes, this is very much the case - especially when using the "10NM final approach" - X-Plane will try to set up the plane correctly for the approach, but this will not work reliably with a custom aircraft that is using many variables that our outside X-Plane´s control.

A surefire way to start up in the air is this:

Spawn on the ground, startup state "ready to fly". Then PAUSE, use the map to first set altitude to 3000 or 4000 or so...then set up speed to 220 kts, and pitch to 5 degrees (also heading if needed). Then drag the plane to about 20 NM out.

Now unpause - then immediately click on AP A CMD and select a pitch mode (like ALT HOLD), then turn on the Autothrottle (this will engage speed mode). Now you are safe ;-)

Now you can raise the gear (and release the parking brake), and then use the autopilot to set up for an approach at leisure.

Cheers, Jan

 

OMG - such erratic behavior with moving the AC with the map.  I was able to position it as you suggested, but as soon as I unpaused the aircraft started shaking and pitched straight up and rolled.  The video I'm sending you is what is happening now.  I've rebooted, restarted XP multiple times, reloaded the aircraft, did repair failures - anything I could think of.  Probably tried this 15 times, with differing results.  The AC looks normal when circling around and inspecting.  Also sometimes the generators are not on when it spawns, sometimes they are.  Sometimes the IAS changes.  Most things stay the same, which means the aircraft is partially remembering the state from previous flights.  Is there a way I can make it 'forget'?  It seems like something is really messed up.  

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Hehe, you need to read exactly what I wrote.

It is vitally important for this to work. I will quote myself again:

22 hours ago, Litjan said:

Then PAUSE, use the map to first set altitude to 3000 or 4000 or so...then set up speed to 220 kts, and pitch to 5 degrees (also heading if needed). Then drag the plane to about 20 NM out.

The behaviour you describe is exactly what I would expect if you drag an aircraft across uneven ground at lightning speed - then put it into the air at 0 airspeed ;-)

 

Edited by Litjan
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2 minutes ago, Litjan said:

Hehe, you need to read exactly what I wrote.

It is vitally important for this to work. I will quote myself again:

The behaviour you describe is exactly what I would expect if you drag an aircraft across uneven ground at lightning speed - then put it into the air at 0 airspeed ;-)

 

Isn't that what you told me to do?  I thought I was following your instructions.  And I've tested this with other aircraft and they don't do that.  

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7 minutes ago, Litjan said:

Hehe, you need to read exactly what I wrote.

It is vitally important for this to work. I will quote myself again:

The behaviour you describe is exactly what I would expect if you drag an aircraft across uneven ground at lightning speed - then put it into the air at 0 airspeed ;-)

 

Ok - got it.  I'm  pretty sure it's done that no matter what the order, and it didn't matter with other AC.  But I'm trying it again.  It does the same thing no matter what the order.  

Edited by Mandretti
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Just got back - hmm, so it does sound like there is a deeper problem in your system.

Reinstalling the aircraft is probably not going to help, although it can´t hurt, either.

To really troubleshoot the problem you will have to revert your X-Plane setup to a "vanilla" situation (as if you just downloaded it from Laminar Research) and then install the 737. That would be the basis to really find out what is going on, without possible interference from other plugins and add-ons.

Cheers, Jan

 

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6 hours ago, Litjan said:

Just got back - hmm, so it does sound like there is a deeper problem in your system.

Reinstalling the aircraft is probably not going to help, although it can´t hurt, either.

To really troubleshoot the problem you will have to revert your X-Plane setup to a "vanilla" situation (as if you just downloaded it from Laminar Research) and then install the 737. That would be the basis to really find out what is going on, without possible interference from other plugins and add-ons.

Cheers, Jan

 

Yep - sounds about right....thanks.  It's a little puzzling that the sim works fine with other aircraft. 

Edited by Mandretti
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Just now, Litjan said:

You can simply copy an existing installation wherever you want. You can simply make a new folder called "X-Plane Vanilla Testbed" and then a subfolder X-Plane 11 in there...

Thanks - and I see that the installer lets you pick a different location so that can work too. 

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Have you tried (before you do a fresh clean XP installation) to remove the contents of the 'preferences' folder:

....: \ X-Plane 11 \ Output \ preferences \

???

(i.e. move it a safe place or copy and rename - so as not to lose the joystick settings etc)

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Actually I think I'll start by copying over the existing AC folder to see what happens.  If there's no problem, I'll leave it like it is.  If there still is the issue the next step would be to download a clean copy of that.  If all that doesn't work I'm going to need a parachute to bail out....

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1 hour ago, Mandretti said:

then I'll copy my preference file to the new install.  

If your preference file is the cause of your problem, you are just copying over the problem. Dont do that.

And I would recommend installing the 737 totally fresh, that way also the plugin will be the correct version and such...

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