Type of Nav System

[KORDATC 80]

This is kind of a geeky post.  I'll admit, I haven't looked through the included manual that much, as I have the real-World AA manual.  Unfortunately, I'll be unable to access the provided manuals for the next day.  Anyways, I've been going insane trying to figure out which NAV system the Flythemaddogx comes with.  Solely GPS, or GPS/AHRS? The only thing I can say for sure that it doesn't have is the IRS system.  

Anyways, in my AAL manuals, it looks like their fleet has a mix of everything.  It seems the original AA MD-80s have (or did have as of 2007), an "GFMS", which was solely provided it's information via GPS.  With the GFMS, the pilot does not even have to enter the present position on the initialization page.  It is already there automatically, as the GPS is the sole provider of information. 

Now, on the MD-80s that American acquired when they acquired TWA (except for the 96xx tailnumbers), they are outfitted with the AHRS system.  This also has a GPS feed into it, and requires the pilots enter the PPOS into the FMS initialization page.  

Finally, the ex-TWA MD-80s with 96xx tail numbers have the full IRS system.  

Now, I am inclined to believe that the flythemaddogx has the AHRS system, but am only wondering, because, according to the AA manuals and also an old Delta manual, the AHRS system has an "AHRS Compass Controller" on the overhead panel that is used to correct for any heading errors.  However, the Flythemaddogx does not have this panel.  I'm confused though, because we still have to enter the PPOS on the initialization page, meaning something needs to be aligned, like an AHRS.

So does the flythemaddogx have the GPS/AHRS, or does it have solely GPS input?  If it has the AHRS, why doesn't it have the AHRS Compass Controller panel?

Best Regards,

Rob

 

 

 

[KORDATC 80]

So, now that I read up on it some more, I think the AHRS Compass Controller is only for AHRS aircraft that do not have the EFIS displays.  Is this correct?

[Meekg 86]

You are correct, there are different variants to this day: GPS + IRS, AHRS + GPS, IRS only.

The Maddog X version reproduces the configuration AHRS + 2 GPS version.

Entering the position in the FMS allows the FMS to determine the FM position, when everything is working this position is basically superseded by the GPS position.

On takeoff initiation the FM position is synchronized with the GPS position (yes, Airbus did not invent that).

During the flight if BOTH GPS are lost, the FMS reverts to MULTI DME mode (using more than two DME to triangulate the position)  DME-DME mode (using 2 DMEs) or VOR-DME mode (using a single VORDME, radial+distance).

If additionally there is no radio coverage the aircraft would revert to DEAD RECKONING mode (which is a bit like when your car GPS/WAZE loses GPS signal in a tunnel).

 

At the moment the degrading of navigation capability (GPS failures) is not yet modeled, but we did start working on it for the next release.  

Edited February 26, 2018 by Meekg

[Meekg 86]

1 hour ago, KORDATC said:

So, now that I read up on it some more, I think the AHRS Compass Controller is only for AHRS aircraft that do not have the EFIS displays.  Is this correct?

Even EFIS equipped aircrafts had the configuration AHRS+GPS.  

[KORDATC 80]

Awesome!  Thanks for the reply Michele!  It was really helpful.  Just to clarify though, the AHRS Compass Controller Panels, those are only found on the non-EFIS AHRS aircraft correct?  That would explain why your addon doesn't have that particular panel on the overhead.  They have the switch to slave or adjust the compass cards.

Edited February 26, 2018 by KORDATC

[SAS443 1,721]

AHRS is more inclined to heading discrepancy between left and right HSI whereas IRS very very rarely caused this. (not to mention it also adds 40secs to the autoland preflight test...)
Maybe in future upgrade we can have IRS+GPS DME DME option.

Edited February 26, 2018 by SAS443

[Meekg 86]

5 hours ago, KORDATC said:

Awesome!  Thanks for the reply Michele!  It was really helpful.  Just to clarify though, the AHRS Compass Controller Panels, those are only found on the non-EFIS AHRS aircraft correct?  That would explain why your addon doesn't have that particular panel on the overhead.  They have the switch to slave or adjust the compass cards.

 

Interesting question.

I think (but somebody more knowledgable might correct me), that it is not really related to the presence of EFIS or not.

That system (which our version does not have), allows you to unslave (disconnect) the compass system from the flux valve, making it somehow like a basic Cessna compass system, where you have to update the heading vs. magnetic compass every so often.

In our variant the flux valve is always slaved to to the Attitude Heading Reference Unit

 

Edited February 26, 2018 by Meekg