Big WT G1000 NXi Update

[fppilot 4,371]

7 minutes ago, MarcG said:

I was confused by this last night, quick drop into their Discord server and Matt kindly responded straight away, i was having trouble in the C208b;

"Ah, you'll need to actually intercept the path manually, and then GPS will go from armed (white) to active (green) when you are on an intercept course and you are within 2 dots on the CDI"

I did that and it immediately started working as per normal.

OK.  But when are you in HDG mode and when do you engage NAV mode.  I assume this is if a flight plan is set up in the NXi.  Does the NXi react automatically to the fact it knows a flight plan is loaded?  (ex. separately in the case of an approach the approach at some point must be activated.)  So in the separate case of a flight plan, what in essence is it that activates a flight plan?  What if for instance ATC directs you across the intercept of the flight plan but still wants or keeps you on a vector or heading for the time being.  

I am just trying to get a grip on what is to happen and why, and what triggers or does not trigger it.

Edited September 5, 2021 by fppilot

[MarcG 2,980]

5 minutes ago, fppilot said:

OK.  But when are you in HDG mode and when do you engage NAV mode.  I assume this is if a flight plan is set up in the NXi.  Does the NXi react automatically to the fact it knows a flight plan is loaded?  ex. separately for an approach the approach at some point must be activated.  So separately, what in essence is it that activates a flight plan?  What if for instance ATC directs you across the intercept of the flight plan but still wants or keeps you on a vector or heading for the time being.  

I am just trying to get a grip on what is to happen and why, and what triggers or does not trigger it.

I don't think I had HDG on just NAV (shows as GPS in white on the screen) as i was flying manually, I flew close to the magenta line on the map and as the CDi showed I was within two dots the GPS turned green (Armed) and started to follow the predefined flight path.

I might have a go tonight with HDG and see if NAV automatically takes over. Bearing in mind I'm a complete newbie to all this stuff so it's a little hard to comprehend some times!

Edited September 5, 2021 by MarcG

[cwburnett 1,809]

1 hour ago, fppilot said:

I would like to also see a nice description of the behavior and annunciations that now occur when transitioning from HDG mode to NAV mode in the flight plan. Would someone who has determined it please take a stab at writing a description about it?

Fundamentally, NAV tracking modes, including GPS, LOC or VOR, will only actively track if your aircraft is within a certain deviation from the desired track. In the case of GPS, the desired track is defined by the active leg in the flight plan. So if I'm flying A -> B -> C, and I have my HSI CDI source set to GPS (Magenta Needles in the HSI), then GPS mode is selected (but this does not mean the AP/FD is tracking yet). On the FMA (top of the PFD) it will show the active leg, so perhaps it will show A -> B or B -> C. The HSI will show you your GPS DTK (Desired Track) - that's the magnetic ground track between A and B (if that's the active leg annunciated in the FMA). The needle will show you your deviation from that magenta line - left of the line or right of the course line. The G1000 will ONLY activate and track that leg if two things have occurred: first, you must have pressed the NAV button to ARM GPS mode - you will know if this is the case because GPS will appear in light grey letters to the left of the active (in green) mode; second, you must be less than half-scale deflection on the HSI (the magenta course deviation needle is closer to the middle than the edge) AND you must be on an intercept path to the magenta line. When those criteria are met, and GPS is armed, the GPS will automatically activate - your indication of this will be that the grey GPS annunciation will disappear and the active mode, in green, will become GPS. When GPS is green, it means the flight director (and autopilot, if on) are actively intercepting and tracking the magenta line (the currently active flight plan leg). If, when you press NAV, you're already within activation criteria, GPS will immediately go active (you will see GPS in green, not in grey).

Page 352 of the G1000NXi manual goes into this detail as well: http://static.garmin.com/pumac/190-02177-00_A.pdf

Here's a great video - I've linked it to the timestamp where arming modes is discussed in detail. Worth the 49 seconds to watch this section:
https://www.youtube.com/watch?v=fA2tDXZx1s0&t=60s

 

[fppilot 4,371]

20 minutes ago, cwburnett said:

The G1000 will ONLY activate and track that leg if two things have occurred: first, you must have pressed the NAV button to ARM GPS mode - you will know if this is the case because GPS will appear in light grey letters to the left of the active (in green) mode; second, you must be less than half-scale deflection on the HSI (the magenta course deviation needle is closer to the middle than the edge) AND you must be on an intercept path to the magenta line.

Thank you for that entire explanation. Exactly what I was looking for.  I will also peruse the Garmin NXi manual.  Have not done so yet as this is only a partial implementation at this time.  Thank you again.

[RobJC 2,069]

1 hour ago, MarcG said:

I was confused by this last night, quick drop into their Discord server and Matt kindly responded straight away, i was having trouble in the C208b;

"Ah, you'll need to actually intercept the path manually, and then GPS will go from armed (white) to active (green) when you are on an intercept course and you are within 2 dots on the CDI"

I did that and it immediately started working as per normal.

So if I takeoff and engage AP it will not actually turn to the correct path until I steer the plane manually intercept the path? Then AP will actually engage? 

[fppilot 4,371]

20 minutes ago, RobJC said:

So if I takeoff and engage AP it will not actually turn to the correct path until I steer the plane manually intercept the path? Then AP will actually engage? 

It will activate the NAV function of the AP.  Prior to that the NAV function must be armed.  So you can preset a heading, take off, engage the AP, engage HDG mode.  Then use changes in your heading under that active AP HDG mode to set up an intercept angle to the flight plan path.  Once you have established that angle to intercept you  can then arm the NAV mode (white GPS annunciation).  When you are within 2 dots the AP NAV mode will then capture the path (green GPS annunciation) and begin to follow it.  That is what I understand at this point.

Edited September 5, 2021 by fppilot

[Bert Pieke 7,585]

2 hours ago, RobJC said:

So if I takeoff and engage AP it will not actually turn to the correct path until I steer the plane manually intercept the path? Then AP will actually engage? 

When you engage the AP, with the CDI set to GPS, the AP will be in ROLL mode (default), or HDG mode, or NAV mode, if you push the HDG or NAV buttons, your choice to make..

What is being recommended is that you start your flight in HDG mode, where you have full control of where the AP is taking you..

Edited September 5, 2021 by Bert Pieke

[RobJC 2,069]

50 minutes ago, fppilot said:

It will activate the NAV function of the AP.  Prior to that the NAV function must be armed.  So you can preset a heading, take off, engage the AP, engage HDG mode.  Then use changes in your heading under that active AP HDG mode to set up an intercept angle to the flight plan path.  Once you have established that angle to intercept you  can then arm the NAV mode (white GPS annunciation).  When you are within 2 dots the AP NAV mode will then capture the path (green GPS annunciation) and begin to follow it.  That is what I understand at this point.

That worked. Thanks! 

[cwburnett 1,809]

It might be worth talking a bit at a more foundational level about what the AP/FD do and what the guidance modes are. The first thing to remember, is that autopilots are dumb. They don't know what you want to do, so it will always just do what you tell it to. I'd suggest taking a few minutes and just see what the modes do. Sit on the runway and make sure your FMA is clear - nothing in green. When you press the FD button, this will activate the flight director.

The first thing to know is - what is a flight director versus an autopilot? An autopilot (AP) is just a small little brain hooked up to some servos on the control surfaces of the plane - if the AP says turn right, the servos move the control surfaces to achieve a turn. Now, imagine you turned off the servos - the AP's little brain is saying turn right, but because the servos are off, the plane doesn't actually turn: this is a flight director (FD). The FD shows on the PFD what the AP would command the plane to do, if it were on. So you can always see what the AP will do by watching the FD, and we can test out our modes with the FD on and the AP off.

So, back to the runway, click the FD button and that will turn on the FD. You'll know it because the FMA will come to life and the magenta 'v bars' will appear on the PFD. The default modes for the FD/AP are ROLL for lateral and PTCH for vertical. In this mode the AP will fly the ROLL and PTCH that existed when that mode was activated - PTCH can then be adjusted with the UP/DN buttons on the AP panel, and when you click the UP button, you should see the magenta FD v bars go up, showing that's what the AP's little brain says it needs to do to achieve the target PTCH.

Now, if you click the HDG button, you'll see ROLL change to HDG on the FMA, now we're telling the AP we want to fly a specific heading - and that's the heading we've set with the HDG knob and appears in the HSI. These are the only two non-arming lateral modes - ROLL and HDG - these modes will always immediately activate and steer. For vertical modes, the non-arming modes are PTCH, VS and FLC - these modes will activate immediately and the plane will attempt to meet the target. You can always see what the AP wants to do by watching the FD v bars in the PFD. (it is maybe worth mentioning that FLC cares deeply about your selected altitude. It will never go away from the selected altitude - so if you're at 2000' and your selected altitude is 1000', it will never climb, so it can seem like it ignores your command to go to a slower speed because it isn't allowed to pitch up when you should be descending and vice versa...but I digress...)

Arming lateral modes are GPS, VOR and LOC. They will only ever become active if they've been armed by the pilot, otherwise they will not. The AP/FD will ONLY do what you tell it to, nothing more, nothing less, except for the case of HSI auto-switching on an approach from GPS to LOC (but that's a separate topic).

So, standard procedure for a takeoff is to set the runway heading in heading mode and plan to start out in heading mode, and then use the heading knob to get yourself to a place where you can intercept the flight planned track. This is because in most departures, you will receive an initial heading from the tower, if you're at a controlled airport, whether you're VFR or IFR. "N123AB Fly Heading 220, Runway 27 Right cleared for take off" - this means that once you're a couple hundred feet off the ground (400' is a good general rule), you're expected to turn from runway heading to 220 - for all of this you need heading mode.

An exception to this is if you're flying an RNAV departure procedure. An RNAV departure will be indicated in the chart - it will be called an RNAV SID (at least in the US) and in these cases, it's okay to engage GPS on the runway. Say we're taking off from 8R at KATL and clearance delivery gave us the GAIRY2 departure. Tower would call, "N123AB RNAV RONII, Runway 8 left cleared for take off." Here they nicely reminded us that our job is to take off and fly to the first fix on the RNAV departure - this reminds us that we are not flying a heading, but following the SID with our GPS. Of course you ONLY want to do this with the FD on and the AP off. So when you line up with the runway for an RNAV SID departure, click the FD button, but DO NOT click the AP button. Make sure you're HSI is in magenta needles (GPS HSI Source), then press the NAV button and GPS should come alive right away - meaning it will be shown in green. Set your altitude correctly (at the first constraint if there's a below constraint, otherwise set it to the TOP ALTITUDE for the RNAV departure, or other altitude as cleared by ATC - if you received a 'climb via the SID' with no other instruction, then you're cleared to climb via the SID to the top altitude listed on the chart - but I digress...).

Start your takeoff and follow the FD commands to track the departure course. After you get above activation height (I recommend 500' AGL), you can press the AP button and the AP will take over flying the departure procedure.

Whenever you have a MANSEQ or manual sequence leg in your flight plan, that's because the procedure dictates that part of the procedure is dependent on ATC vectors - these also require using HDG mode. Normally ATC would give you some vectors to some other place on the flight plan - if you're flying without ATC, you can manually vector yourself, or you can use the DIRECT TO function to fly directly to the next waypoint on your plan.

GPS mode's job is not to get you to the magenta line; it's to keep you on the magenta line. It doesn't know how to get you there, that's your job as the pilot, and this is because 99% of the time ATC is going to clear you to get to the magenta line in a way that works for them - and if the AP just did it on its own, ATC would lose that control and/or you'd get a phone number to call.

The usual situation when not on an RNAV departure is, at least in my neck of the woods:

I call up clearance and get "N123AB is cleared to the Seattle Boeing Field via radar vectors, Boise VOR, Victor 4, Pendelton VOR, CHINS4 arrival, climb and maintain seven thousand, expect one-two thousand ten minutes after departure, departure frequency 123.9 squawk four zero two two."

When I call tower ready for takeoff, they give me: "N123AB, fly runway heading, runway 10 right cleared for takeoff" - I set my heading to 100 (runway heading), set my selected altitude to 7,000', turn on the FD and maybe set a VS target of 800 fpm.

After takeoff I'm flying a heading of 100 and climbing out - at about 500' AGL, I press the AP button and the AP takes over flying 100 and climbing to 7000'. At this point, ATC's job is to get me to my route because the first item in my clearance was 'radar vectors'. I might get something as simple as:

"N123AB, turn left direct EMETT" - this means they want me, via a left turn, to go direct to EMETT. Now if they give you a turn direction, you either need to make sure that's the shorter turn, or use heading mode to get started in that direction, before activating the direct to - because their instruction might not ALWAYS be the shortest turn, which is what the AP will give you if you do a DTO and then activate GPS mode. So, I'd turn my heading to the left and get that turn started, then activate the direct to via the FPL menu, arm GPS mode and then continue setting the correct heading until GPS activates. You can always look at where the plane is relative to the magenta line to decide what you should do to intercept the course.

If the area were busy, they might give me a bunch more heading vectors before getting me onto my airway - maybe "N123AB, for traffic, turn right 180, climb and maintain 9000" - and so forth until eventually I'd get a direct to some waypoint on my cleared flight plan and that's when I'd let GPS take over as described above.

All of the above is why arming modes will only activate when you're very close to being 'on track' - because otherwise we'd always be guessing "what is this thing gonna do?" - and that's something we never want to be asking ourselves in an airplane, and certainly not in congested airspace. You can try to arm a mode by just pressing the button - if it can arm, it will - then once armed it will 100% activate when you meet the activation criteria - be less than half scale deflection on the CDI and be on an intercept (converging) track to the magenta line. Otherwise it will never activate. If you want to disarm a mode, just press the button again - if GPS is armed and you don't want it armed because you just got a new vector, just press the NAV button again and GPS will disarm (will disappear from the FMA). If you're in GPS active (GPS is green) and you press NAV, then GPS will disappear and ROLL will appear, meaning you've turned off NAV and the AP/FD has reverted to it's default mode, which is ROLL.

You can always arm GPS - there's no harm in arming it right away - if you want to intercept the magenta line as quickly as possible - no matter the phase of flight you can always arm it, but it won't activate until it can. There's no harm in arming UNLESS you don't actually want it to activate.

Edited September 5, 2021 by cwburnett

[ctalpas 113]

22 minutes ago, cwburnett said:

It might be worth talking a bit at a more foundational level about what the AP/FD do and what the guidance modes are. The first thing to remember, is that autopilots are dumb. They don't know what you want to do, so it will always just do what you tell it to. I'd suggest taking a few minutes and just see what the modes do. Sit on the runway and make sure your FMA is clear - nothing in green. When you press the FD button, this will activate the flight director.

 

Hi Chris,

Just wanted to express my appreciation for you taking the time to go through this detailed explanation.  It really helps those of us who are new to the G1000 NXi.  Matt's video on the CJ4 opened my eyes to that plane and your wonderful mod -my favourite jet!

Really appreciate your presence on this forum.

Chris

[Bert Pieke 7,585]

12 minutes ago, ctalpas said:

Just wanted to express my appreciation for you taking the time to go through this detailed explanation.

I also would like to thank you... Some folks here have been led to believe that an autopilot only exists to follow a flightplan, which leaves a pilot with little to do, except to watch it fly the airplane.

Your explanation puts the pilot back in charge... which ultimately is a much more interesting role to play 🙂

[fppilot 4,371]

4 hours ago, ctalpas said:

Just wanted to express my appreciation for you taking the time to go through this detailed explanation.  I

He is in receipt of my gratitude as well.  Took a great deal of time to put that together an IMHO it should be pinned into the MSFS 2020 Tips and Tricks topic here,  I would ask a moderator to accomplish that if not already done.

[JHaas 27]

I was under the impression that the hotfix was made to allow the hardware addon units to function correctly since the latest NXi update. My Honeycomb Bravo autopilot functionality is inoperable even with this hotfix  after the latest release. I confirmed that my hardware in working ok by deleting the NXi mod and then using the old G1000 panels. My Bravo  autopilot works fine with the G1000. Does that mean that I need to wait to able to use the NXi until the big update if I want my hardware to drive the autopilot? At first I thought it was an issue with the Turbo Bonanza mod but I tried the 172 glass plane and got the same results. Just trying to confirm here that the fix only works with the logitech panel.

Thank you.

[cwburnett 1,809]

4 hours ago, JHaas said:

Honeycomb Bravo autopilot functionality is inoperable even with this hotfix

Can you share how you have your bravo configured? That would help us track it down and fix it. Thanks!

[petejohno1 63]

That's strange. The hotfix fixed the autopilot problems i had previously with the nxi. All my autopilot functions and lights operate on my bravo as normal now. So there must be a problem at your end. Sorry can't be of more help.