STEC 3100 and G1000 Integration - Current Situation

[Jeff_S]

I wanted to start a new thread focused on the issues interfacing the S-TEC 3100 with the G1000, for those 100+ Mooneys that are still flying around with the 55x.  There's no doubt that the 3100 would add significant new features over the 55x and it would be a nice replacement.  And Genesys's offer of the $9995 upgrade is quite reasonable.  However, there are challenges with getting it to interface with the G1000 that are not adequately described in recent posts on this topic, so I'm trying to get a more complete story out there. I apologize if this is somewhat lengthy...I'll try to summarize as best I can.

Contrary to what has been written recently, Genesys has NOT gotten the 3100 to work with the G1000 in any airplane model. I know this because I spoke directly with one of the lead engineers on the project.  I won't mention his name, but I will say that he is very forthright and not afraid to "tell it like it is". He also really wants to get this working as best they can, so perhaps as a group we can help.

The problem presented by the G1000 is the tight level of integration between it and the A/P at several layers of the software stack.  Unlike other avionics components, which are generally designed with a singular set of common interfaces, the G1000 evolved to support different hardware elements before Garmin finally standardized around their own components. So when you are setting up the G1000, config settings tell it whether it is interfaced with a Garmin A/P (the GFC700), the 55x, or w/o any autopilot. This config setting drives other behavior throughout the user interface.  So the overall behavior of the G1000 is heavily influenced by these settings and not something that is easily modified.

One conflict is the types of information that can pass between the G1000 and the 3100.  Aside from the main flight control data, which is used for navigation purposes, the G1000 also manages altitude preselect.  The 55x does not know its altitude...it merely takes instruction from the G1000 to either climb or descend to the altitude selected in the G1000. But the vertical speed is selected at the 55x, and it passes this info to the G1000.  So the G1000 knows the current VS as set on the 55x, but as you climb or descend to reach the desired altitude, the G1000 sends instructions to the 55x to gradually decrease the VS vector and level off at the new altitude.

In contrast, the 3100 does know its actual altitude, and it has a built-in capture mode and algorithm for modifying the VS vector as the desired altitude is reached to smooth the arrival. This is where one conflict arises.  Which method should be used? The G1000 isn't designed to capture this mode output from the 3100, so if the 3100 is driving the behavior it won’t (can’t) send the target altitude to display on the G1000. But the G1000 method for altitude preselect uses a different algorithm and may create conflict when deployed on the 3100.

This also points out the issue of what data the G1000 could even display. With the 55x, the G1000 displays the mode annunciations and the VS as displayed on the 55x.  But the 3100 has several new modes that are not in the 55x interface (IAS climb, straight & level, altitude capture, VNAV).  And while certain versions of the G1000 do have these annunciations as part of the GFC700 interface, it is highly unlikely that Genesys would be able to use them for the 3100--at least not without some programming help from Garmin. One option is to force the pilot to use the annunciators on the 3100 itself and not show them at all on the G1000.  But this would be a significant human-factors change from current operations and could cause confusion among pilots…not a good thing when relying on such a significant tool as the A/P.

As one example, suppose the decision is for all mode programming to be made and shown only on the A/P and not on the G1000. Now take a busy pilot in the soup who is used to the old method of operations—me, for example! If I’m in the clag and given the instruction to descend and maintain 4000’, I would have to enter this into two different boxes for everything to work. If I only enter the altitude into the G1000 and then the VS in the A/P (the current procedure), then the A/P will not stop at that target altitude and I'll bust my instruction.  Or if I enter it only on the A/P, then the plane will descend and stop correctly but my SVT highway in the sky boxes will start getting smaller and higher in the screen, and the G1000 may even start beeping at me as I pass the 200’ mark because I’m not holding its programmed altitude. (Unless that feature is deactivated in the G1000 and the aural alert is provided by the 3100…another possibility, but further increasing the complexity.)

This is just one example of the potential for confusion that can develop if the two devices are not allowed to communicate, at least to the same level that the G1000 and 55x can talk today. But it points out why the integration effort for the G1000 is significantly more complex than with other devices.  Even what seems to be the simplest solution, i.e. replicating the existing functionality with the 55x on both units, and forcing the 3100 to handle and annunciate the rest, means that now pilots have different places to see and manage the functions of the A/P.  This would require documentation and a learning curve. (And since the 3100 outputs only in digital format, it would require a digital-analog converter to output the same signals to the G1000 that the 55x currently does.  This alone may be doable, but does it provide the best user experience?)

Let’s get to the crux of the matter, which is that the Genesys sales representative has recently stated that they need 8-10 more “non-reversible” purchase orders to satisfy the business case internally for the STC to continue. While I understand the business rationale of balancing the costs of development with the potential revenue, as I stated to the Genesys engineer, there is no way I (or any reasonable G1000 owner) can commit to paying for this upgrade without a firm understanding of what the bare minimum integration will be and deciding whether or not that is satisfactory.  The engineer understands and agrees with this point.

So he has said that Genesys will study this issue in more detail and provide a better description of what the integration effort can provide. There should be a set of baseline integration features they can commit to, and then a list of others that might be possible as they pursue development.  Then we can make an informed decision about an actual purchase order.

Here is where we can all help.  Any “customer input” that we can use to prod Garmin into working with Genesys on this project may help promote deeper integration. At the moment, Garmin has provided limited support, even though they don’t seem to be pursuing a competitive retro-fit option.  Myself and @Deb would like to compile a list of similar G1000-55x owners and use this to lobby with Garmin for the project. We will do the best we can with the FAA registry, but if you would like to be on this list please drop me a PM and we’ll add you.

In the meantime, any non-G1000 users who are considering the 3100, please keep your interest known to Genesys and heck, go ahead and make that deposit!  You won’t face the same integration issues, and this may give Genesys enough of a demand forecast that they will proceed regardless.  That is good for the entire Mooney fleet.

I haven’t relayed all the details that I’ve learned about this, so if you want to ask me other questions I’m happy to tell you what I know.  Thanks!
 

[mike_elliott]

The stumbling block is money. Jeff, your well thought out detailed post elaborates the technical issues that can be solved with money. No one wants to pocket the development costs  on the come. Genesys feels the market isnt worth the developement cost unless the owners foot the bill. Garmin isnt in business to do it for free. Mooney doesnt have a profit stream here unless they become the STC holder and charge a significant mark up on it, and Mooney doesnt owe owners and upgrade path of AP's., just as Honda doesnt owe me an upgrade path to make my 2005 odyssey an EV.

chicken/egg.

If Genesys wants in this market, they will have to make a decision to get into it with both feet. Pay Garmin the vig needed and get on with it, or announce it is not plug and play with the 55x and disclaim any interfacing with G1000. A shame, I just wound up another new G1000/stec owner on this upgrade path.

[PaulM]

The 55X G1000 integration for vertical preselect, mode annunciation and FD cue display was done through emulating the STEC remote annunciator protocol and remote altitude pre-select systems. 

The lines are listed as ALT/select RS485 and Remote SYNC/CLOCK/DATA.  So Garmin emulated the protocol for the STEC remote annunciator, and sends RS485 commands for VS control and altitude capture. 

If Stec has not made the 3100 backwards comaptible with the 55X digital protocols, then integration at the current level is not possible, of course they could design a converter. 

The 55X already receives a ARINC 429 feed from the G1000 so that IAS data should be in that stream for capture.   I cannot say what other 429labels are in that stream that could be used (baro selection, ALT preselect etc)  but the annunciation only uses the 55X custom protocol. 

As you indicated Genesys has not been forthright in their public statements about G1000 compatibly, I am not willing to risk 10K+install on a system that may be less integrated than today's 55x.   I had really hoped for a slide in replacement for the 55X.   

Garmin won't do any work, and even if they did, Mooney won't certify and release it.  (They haven't release a V15 based software... ref -34 is v14.02)  Garmin has developed the GFC700.. they only did S55X and KAP140 integration because they want to get to market in 2005 and didn't have the GFC700 ready but Cessna/Piper and Mooney had to sell planes with autopilots.  Beech and Piper waited until it was ready. 

We would be better off asking Mooney to make a GFC700 retrofit available to us.  it might cost more but it would have IAS climb, Vertical modes. FLCH etc.   I don't want to manage two altitude bugs, two altimeter settings etc. The G1000 KAP140 integration showed the problems with that.   

 

[Barry LeBlanc]

Hi,

       First of all, I was under the impression that the 3100 and the G1000 was tested with a Cessna A/C, I was wrong and do apologize for the misinformation. Below is from the design team. I am under a deadline and been granted till next Monday , July 8th, 2019 to come up with 7 to 8 more purchase orders, or my management will place the Mooney’s off the STC schedule. If you have any influence with the G1000 crowd, please ask them to act now. It is a short week. 

Please share and forward this information via email with your fellow G1000 owners.  

I have scuttled my vacation plans and working to contact every registered Mooney owner I can find. From now till Sunday you can reach me via email or cell: 940.327.0707 

Have a great 4^th.  

Thank You,

Barry LeBlanc

Genesys Aerosystems

Regional Sales Manager

M: 940.327.0707

Below is a description of the proposed interface between the Garmin G1000 system and the S.pdf

[PaulM]

Barry,

  There does not seem to be any discussion about the FD modes or the single/dual cue FD display (it is not on your list)   This is done via the sync/clock/data interface that was specific to the 55 & 55X for the ST-645 remote annunciator. 

[Doug Tellef]

16 hours ago, PaulM said:

Barry,

  There does not seem to be any discussion about the FD modes or the single/dual cue FD display (it is not on your list)   This is done via the sync/clock/data interface that was specific to the 55 & 55X for the ST-645 remote annunciator. 

Paul,

Our tech guru has now updated the table to address the FD interface, please see the newest version which i have attached to this post.  If you have any more questions please let myself or Barry know.  Thank you! 

Mooney G1000 Interface.pdf

Edited July 3, 2019 by Doug Tellef

[Barry LeBlanc]

15 hours ago, PaulM said:

Barry,

  There does not seem to be any discussion about the FD modes or the single/dual cue FD display (it is not on your list)   This is done via the sync/clock/data interface that was specific to the 55 & 55X for the ST-645 remote annunciator. 

Hi Paul, Glad you asked, the attached table has been updated to include your question. Thank You Barry

Description of the proposed interface between the Garmin G1000 system and the 3100.pdf

[PaulM]

Barry,

  When I look at the wiring diagrams that I have , there are no Analog FD connections from the 55x and the g1000 it seems to only use the ST645 digital bus for both annunciation and FD output.   Does the 3100 speak the ST-645 digital interface, that is not clear in the response as it refers to ARINC and Analog interfaces.