Hi everyone,

Because the F1 GTN does not support the new Garmin GTN trainer, I purchased the RXP GTN and have it running on the Flysimware Lear 35.  Earlier, I posted a question about the F1 GTN not displaying the en route VNAV path on the HSI.  I now have the same issue with the RXP version.  Al had a fix for the F1 version.  Is there a similar fix for the RXP, or do I have something set wrong in my RXP configuration? 

Approach mode appears to be working fine. 

Thanks!

Rich Boll

1 hour ago, richjb2 said:

Hi everyone,

Because the F1 GTN does not support the new Garmin GTN trainer, I purchased the RXP GTN and have it running on the Flysimware Lear 35.  Earlier, I posted a question about the F1 GTN not displaying the en route VNAV path on the HSI.  I now have the same issue with the RXP version.  Al had a fix for the F1 version.  Is there a similar fix for the RXP, or do I have something set wrong in my RXP configuration? 

Approach mode appears to be working fine. 

Thanks!

Rich Boll

Hi Rich,

The RXP GTN750 does not have the option to drive the yellow 'glide slope' needles to indicate it you are on the correct en route VNAV path as the Flight1 does. However, you can set up one of the four 'User Fields' in a corner of the map display to display VSR -- Vertical Speed Required to meet the next waypoint altitude constraint as entered in your flight plan.  By monitoring this you can adjust your descent rate as/if needed to meet a waypoint altitude requirement. In addition, once you enter a target waypoint altitude in your flight plan, there is VNAV info available on the GTN750 under Utilities\VNAV , e.g., VSR, time to TOD, FPA, etc. The system seems pretty flexible, i.e., you can set a waypoint target altitude offset, e.g, the altitude you want X miles before or after a waypoint. 

Al

Edited January 27, 20215 yr by ark

Rich,

Here are some shots of the RXP GTN750 in the Lear35 on the way to KDFW where I set up a target altitude of 3000ft 10 NM out.

Al

 

VNAV display under Utilities.

 

 

VSR displayed in lower left corner.

 

 

 

 

 

Edited January 27, 20215 yr by ark

5 hours ago, ark said:

Hi Rich,

The RXP GTN750 does not have the option to drive the yellow 'glide slope' needles to indicate it you are on the correct en route VNAV path as the Flight1 does. However, you can set up one of the four 'User Fields' in a corner of the map display to display VSR -- Vertical Speed Required to meet the next waypoint altitude constraint as entered in your flight plan.  By monitoring this you can adjust your descent rate as/if needed to meet a waypoint altitude requirement. In addition, once you enter a target waypoint altitude in your flight plan, there is VNAV info available on the GTN750 under Utilities\VNAV , e.g., VSR, time to TOD, FPA, etc. The system seems pretty flexible, i.e., you can set a waypoint target altitude offset, e.g, the altitude you want X miles before or after a waypoint. 

Al

Thanks Al!  

I was afraid you were going to say that.  I guess that's one advantage of the F1 GTN.  

I have used those user defined fields and did set up one for the VSR as it's helpful even when using the VNAV needle.  However, there's nothing in the G750 to let you know that you're getting above or below path on a descent as the winds & TAS change. I'm surprised that Garmin didn't actually put a vertical path display on the map, something similar to what Boeing did.  

Thanks again, sir!  I still owe you the test flight of the Lear 35 cab file.  Contemplating a move to P3D v5 next week.  

Rich 

3 hours ago, richjb2 said:

However, there's nothing in the G750 to let you know that you're getting above or below path on a descent as the winds & TAS change.

Rich,

In the third picture above it shows the VS Target as -1118, and below that the VS Required as -1590, all based on current groundspeed.  I have very limited experience with this, but I assume the VS Target is what is needed for the selected 3 deg FPA descent (you can change the FPA). Since the indicated VS Required is greater, I assume that indicates the a/c is above the target 3 deg descent slope, and probably above by the indicated 990ft vertical deviation. Yes; No; Maybe?  🤔

As I've previously mentioned, I'm not a fan of the Flight1 en route VNAV implementation as implemented -- in my opinion they should at least change the color or shape/design of the 'yellow' indicator needles to clearly distinguish between en route and approach glide slope/glide path use.

Al

Edited January 28, 20215 yr by ark

On 1/27/2021 at 5:28 PM, ark said:

Rich,

In the third picture above it shows the VS Target as -1118, and below that the VS Required as -1590, all based on current groundspeed.  I have very limited experience with this, but I assume the VS Target is what is needed for the selected 3 deg FPA descent (you can change the FPA). Since the indicated VS Required is greater, I assume that indicates the a/c is above the target 3 deg descent slope, and probably above by the indicated 990ft vertical deviation. Yes; No; Maybe?  🤔

As I've previously mentioned, I'm not a fan of the Flight1 en route VNAV implementation as implemented -- in my opinion they should at least change the color or shape/design of the 'yellow' indicator needles to clearly distinguish between en route and approach glide slope/glide path use.

Al

Hi Al,

The Vertical Deviation (990' ft) does show that you're above path.  Yes, the higher vertical rate is indicative of being above path, as well.   But all this is analogous to the FMS saying that your Desired Track is 132, but actual Track is 140, and that you are 1.5 NM right of course, which these four fields can to be set to show.  It's much easier and more intuitive to look at the HSI and see that you're 1 and 1/2 dots right of course and you better turn left.  This is why we insist on having a CDI show lateral deviation with RNAV as opposed to relying on pilots to divine their position from TRK, DTK, and TKE.

The Lear 35 and similarly equipped steam gauge instruments do not have flexibility in how they display information.  For example, in the G5000 that I fly in the Lear 75, I see magenta needles when FMS/RNAV guidance is provided and green needles when ground based NAVAID guidance (VOR, ILS, etc.) is displayed.  When FMS/RNAV guidance is displayed, in the vertical deviation window I see a magenta "doghouse" when baro-VNAV vertical guidance is generated or a magenta diamond when SBAS vertical guidance is generated.  I see a green vertical deviation needle when ILS glideslope is generated.  But this is only because I have an electronic display with a signal generator that can places these different color needles on the tube. 

In the Lear 35, I have an FIS 84 Attitude Director Indictor (ADI) and a HSI that was designed long before any type of RNAV system with lateral or vertical guidance was available and the norm.  This is circa 1980 technology.  Adding the Garmin FMS or any other FMS doesn't change the limitations on these electrotechnical instruments.  Those needles are actual mechanical needles that can't change color.  They can be driven by different inputs based switch selection, NAV or GPS, but that's it.  

I only had a brief period where I actually flew the Lear 35 with an FMS that drove electromechanical mechanical needles.  The FMS was the old GLSx system from 2000-2003, and that system did drive ILS glideslope indicator to show vertical deviation when the FMS was providing input to  the system.  The same things was true in the Lear 35 simulator that I posted the YouTube video when they upgraded that simulator from the UNS 1m to the UNS 1ew.  I had chance to fly it a few times before it moved to FSI ATL.  

Can these "federated" systems get you into trouble?  Yes, been there, done that, have the t-shirt.  The old Westwind I used to fly in the '80s didn't have an FMS.  It has a Global 500 VLF/Omega navigation system.  Think of a CVIA  INS 10 waypoint navigation system, but without the "inertial" part.  It used the 10 station Omega navigation system and piggybacked on the US Navy's VLF communication systems for submarines to generate position information. You loaded 10 LAT/LON waypoints, typically the VOR/VORTACs that formed the airways, or the SID or STARs.  I had switch that would set the CDI on the HSI to either NAV or "VLF".  However, the VLF lacked capability to slave the the HSI needle, so you had to keep watch of the current Track Angle and periodically reset the HSI CDI to the correct track angle or you would get off of track quite easily.  The FD-109 FD was horrible when tracking the CDI in NAV mode (ILS, VOR, or VLF....didn't matter), so we used heading (HDG) mode to fly keep the CDI centered.  It didn't take long to get screwed up and get off course.    Also, it didn't take much to push the wrong button, or neglect to make switch when it came time and track NAV mode when should have been tracking VLF, or vice versa.  

There is an expectation that professional pilots know and understand their displays, especially when we cobble together modern FMS technology with Jurassic jet instrumentation and flight guidance systems.  Opinions may differ, however, I think you'll find that it is not an undesirable feature, and in fact, it would a requirement if I were spec'ing out an installation & STC for the Lear or any similar type steam gauge airplane.

Thanks again for your help and making this airplane fun to fly.  Like I've said, it's one of best simulations of business jet aircraft available. 

Rich 

 

 

Hi Rich,

24 minutes ago, richjb2 said:

It's much easier and more intuitive to look at the HSI and see that you're 1 and 1/2 dots right of course and you better turn left.  This is why we insist on having a CDI show lateral deviation with RNAV as opposed to relying on pilots to divine their position from TRK, DTK, and TKE.

I certainly agree 'VNAV needles' are generally more convenient. I was just pointing out the GTN750 does provide the info on whether or not you are on your VNAV track even without the needles.

I do understand the limitations of physical analog gauges when it comes to colors, etc. In one of the Lear35s that Joe flies these days with a UNS-1 FMS and electronic HSI, I believe the enroute VNAV needles are white vs yellow when on approach. I guess with the analog HSI you would just have to see if the GTN750 is showing that you are in TERMinal or ENRoute mode. Interestingly, one of the other Lear35s that Joe flies has a GTN750 and GTN650 instead of a UNS-1. I'll have to ask him what type of HSI it has and if enroute VNAV info is displayed.

Al

Edited January 29, 20215 yr by ark

13 hours ago, ark said:

Hi Rich,

I certainly agree 'VNAV needles' are generally more convenient. I was just pointing out the GTN750 does provide the info on whether or not you are on your VNAV track even without the needles.

I do understand the limitations of physical analog gauges when it comes to colors, etc. In one of the Lear35s that Joe flies these days with a UNS-1 FMS and electronic HSI, I believe the enroute VNAV needles are white vs yellow when on approach. I guess with the analog HSI you would just have to see if the GTN750 is showing that you are in TERMinal or ENRoute mode. Interestingly, one of the other Lear35s that Joe flies has a GTN750 and GTN650 instead of a UNS-1. I'll have to ask him what type of HSI it has and if enroute VNAV info is displayed.

Al

The EHSI needles might show different different.  IIRC, the RNAV needles are white and VHF NAVAID needles are green.  There are problem more options for colors on later model EHSIs as well.  

I have friend flying a Lear 55 with the GTN 750. I believe their instrument panel is the same as the Lear 35 FC530.  I'll check with him as well.

I assume the limitation on display of the VNAV path lies with RXP and not Flysimware, correct?  If so, I'll begin bugging folks on the RXP forum. 

Thanks again, Al!

Rich 

13 minutes ago, richjb2 said:

I assume the limitation on display of the VNAV path lies with RXP and not Flysimware, correct?  If so, I'll begin bugging folks on the RXP forum. 

Hi Rich,

Yes, the absence of enroute VNAV path needles is an RXP issue.

The Lear35 with the GTN750/650 that Joe flies also has the older FC200 AP. The plane was built in 1982, but only has 3800 hrs total on it. He says it's the best flying Lear35 he has ever flown.

Al

Edited January 29, 20215 yr by ark

On 1/29/2021 at 11:15 AM, ark said:

Hi Rich,

Yes, the absence of enroute VNAV path needles is an RXP issue.

The Lear35 with the GTN750/650 that Joe flies also has the older FC200 AP. The plane was built in 1982, but only has 3800 hrs total on it. He says it's the best flying Lear35 he has ever flown.

Al

We had three Lear 35s, and the oldest N182K, was the best flying of the bunch as well.  Part of it was because I could get the seat further back.  Unfortunately, after we sold it, it met an unfortunate and untimely demise at Bridgeport CT in the mid-2000s.

3800 hours on a Lear 35 with an FC200 AP is very well kept airplane! 🙂   

Would you guys say that this makes one better than the other?  RXP vs F1?  In all my years of flightsimming, I've never had one of these add-on GPSs, but I'm starting to get weary of the limitations of using the default GPS/Flight Planner system.

1 hour ago, HowAreYourRides said:

Would you guys say that this makes one better than the other?  RXP vs F1?  In all my years of flightsimming, I've never had one of these add-on GPSs, but I'm starting to get weary of the limitations of using the default GPS/Flight Planner system.

In my opinion the RXP is the much better way to go, and I started out with the Flight1 GTN750 before switching over to the RXP GTNs.  For one thing, RXP provides GREAT support and quickly updates the GTNs whenever needed. Flight1 support is poor in my experience. For example, the RXP units work with the fairly recent update of the Garmin Trainer (upon which both the RXP and Flight1 depend), while Flight1 has said they have no intention of updating to use the new version of the Garmin Trainer. And, RXP is running a 30% off sale on the GTNs until the end of April 2021.

Other opinions welcome.

Al

Edited April 18, 20215 yr by ark

As Al said if you want / need support and / or updates then go RXP. F1 is truly hopeless in the support department!

 

G

I ended up getting the RXP GTN750.  Wow, it adds so much to the experience!  I feel so much less handicapped.  I've only flown the Falcon 50 with it, but it makes the plane intercept LNAV courses better than ILS's!  (I'll admit to still being a little turned off by the database tradeoff though.  I think the FMS add-on in development will be the game changer.)

4 hours ago, HowAreYourRides said:

I ended up getting the RXP GTN750.  Wow, it adds so much to the experience! 

Good to hear you are happy with the RXP GTN750.  😀

Al