2 axis vs. 3 axis Autopilots for our Mooneys

[canamex]

I purchased my '67F almost a year ago as a basically VFR aircraft, thinking I could upgrade everything to make it a decent IFR ship. While it does have a nav head with GS, with no DME I'm severely limited on the extent of my IFR operations. I'm slowly upgrading my avionics (a freshly overhauled SL30, GI106A, and a GNC 355a are all going in this annual) and will be doing a panel upgrade to reconfigure my instruments into a traditional six-pack. And after having hand-flown in hard IMC a few times, I now understand the importance of a good autopilot and not just a wing leveler.

My upgrades budget is pretty much tapped out for this year, but with the Aerocruze and Dynon AP options on the horizon (not holding my breath) and the GFC500 available now, I'm planning on installing something next year, or maybe the year after.

So, my understanding is that our vintage Mooneys (and maybe more recent ones) have bungees linking our ailerons and rudder. This being the case, here's my question; do we really need to spend the extra 2-3 AMU's on installing the extra servo for the yaw damper/third axis? Wouldn't the roll servos automatically create yaw input rendering the yaw servo redundant?

[carusoam]

4 minutes ago, canamex said:

I purchased my '67F almost a year ago as a basically VFR aircraft, thinking I could upgrade everything to make it a decent IFR ship. While it does have a nav head with GS, with no DME I'm severely limited on the extent of my IFR operations. I'm slowly upgrading my avionics (a freshly overhauled SL30, GI106A, and a GNC 355a are all going in this annual) and will be doing a panel upgrade to reconfigure my instruments into a traditional six-pack. And after having hand-flown in hard IMC a few times, I now understand the importance of a good autopilot and not just a wing leveler.

My upgrades budget is pretty much tapped out for this year, but with the Aerocruze and Dynon AP options on the horizon (not holding my breath) and the GFC500 available now, I'm planning on installing something next year, or maybe the year after.

So, my understanding is that our vintage Mooneys (and maybe more recent ones) have bungees linking our ailerons and rudder. This being the case, here's my question; do we really need to spend the extra 2-3 AMU's on installing the extra servo for the yaw damper/third axis? Wouldn't the roll servos automatically create yaw input rendering the yaw servo redundant?

Do a search on yaw dampers for the logic of why people find it nice to have…

Forever planes are getting them…

Light IFR planes, on a budget… probably aren’t getting many updates like this…

Best regards,

-a-

[PT20J]

I think it helps to define your needs and also to understand what a yaw damper does.

The main purpose of a yaw damper is to dampen undesirable roll-yaw coupling (Dutch roll) that occurs in some airplanes (notably swept wing jets) and they are often required for these airplanes.

In addition, it will keep the ball centered during climbs, coordinate turns and improve the ride in turbulence. 

A Mooney does not have an objectionable Dutch roll, the rudder aileron interconnect helps coordinate turns, the ride isn't that bad in turbulence, and it's not that hard to keep the ball centered in a climb. So, the yaw damper is a matter of convenience, not a necessity.

Given that, I think it is best to think about what you are trying to accomplish. In my case, I did not install the yaw damper in my J when I had the GFC 500 installed. My primary objective was reliability. The more stuff you cram into the airframe, the greater the possibility that something will fail. So, I didn't add anything I didn't need.

Fortunately, the way Garmin architected the GFC 500 makes it  really easy to add the yaw damper later if you want. So, it might make sense to try it without and if you find the ride uncomfortable, or your right leg getting tired, you can add it later.

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[PeteMc]

11 hours ago, canamex said:

and will be doing a panel upgrade to reconfigure my instruments into a traditional six-pack.

If you're staying with the traditional 6-Pack, can I suggest you consider the G1275.  It is also a great device to drive a multitude of autopilots.  It would also give you multiple views for you instrument flights.

[LANCECASPER]

30 minutes ago, PeteMc said:

If you're staying with the traditional 6-Pack, can I suggest you consider the G1275.  It is also a great device to drive a multitude of autopilots.  It would also give you multiple views for you instrument flights.

Yeah not sure what currently produced new-install auto-pilot you could put in an F model with a 6 pack and have the option of a yaw damper. Maybe an STEC. A Garmin GFC500 is going to need at least a G5. A GI-275 makes sense.

[PeteMc]

12 minutes ago, LANCECASPER said:

A GI-275 makes sense.

Depending upon the other glass displays are installed, there are a few things to consider between the G5 and the GI275.  But if you're looking to put one or the other in, the GI275 is the newer more robust device.  In multiple Webinars I've heard Garmin say it is the preferred choice if you don't have a specific need for the G5.

[PT20J]

The only two reasons I can think of to install a G5 instead of a GI 275 is if your budget is very tight, or if you are installing a backup instrument for a G3X as the G5 will integrate with the G3X but the GI 275 will not.

[Niko182]

Why not get a g5 hsi instead of the 106? If you have no autopilot, you can hook up the sl30 and the 355 to it.

[canamex]

4 hours ago, LANCECASPER said:

Yeah not sure what currently produced new-install auto-pilot you could put in an F model with a 6 pack and have the option of a yaw damper.

When I install the AP, I'll be deleting the vacuum system in favor of twin GI275's, regardless of if I go for the GFC or the Aerocruze or Dynon (should the angels bless us with their approval).

@PT20J appreciate the description, exactly what I was looking for. My thinking as well is along the lines of installing only that which is absolutely necessary while still performing its role. K.I.S.S. principle...

@Niko182 I got the GI106a for a song and the way I see it, it's a great backup instrument should anything happen to the eventual GI275's I'll be installing...

Thanks for the feedback, everyone! The install will be a year or two out, first things first...

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On an unrelated note, how do I get those nifty colored maps everyone has in their signatures?

Edited February 28, 2022 by canamex
Additional question about colored maps

[LANCECASPER]

13 minutes ago, canamex said:

When I install the AP, I'll be deleting the vacuum system in favor of twin GI275's, regardless of if I go for the GFC or the Aerocruze or Dynon (should the angels bless us with their approval).

@PT20J appreciate the description, exactly what I was looking for. My thinking as well is along the lines of installing only that which is absolutely necessary while still performing its role. K.I.S.S. principle...

@Niko182 I got the GI106a for a song and the way I see it, it's a great backup instrument should anything happen to the eventual GI275's I'll be installing...

Thanks for the feedback, everyone! The install will be a year or two out, first things first...

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On an unrelated note, how do I get those nifty colored maps everyone has in their signatures?

The Dynon autopilot will need the Dynon HDX and at this point won't work with a GI-275

[canamex]

30 minutes ago, LANCECASPER said:

The Dynon autopilot will need the Dynon HDX and at this point won't work with a GI-275

Gotcha. I was under the impression that it needed only a GPS but it makes sense it also needs something to reference attitude. So GFC or Aerocruze then...

[LANCECASPER]

I believe the Aerocruze is self contained. It will follow a heading or a GPS nav signal, has GPS Steering, altitude hold and pre-select, but I don't believe it's approved for approaches.

https://aerospace.honeywell.com/content/dam/bendixking/en/documents/downloads/n61-2105-000-000_aerocruze100-brochure.pdf

[PeteMc]

1 hour ago, canamex said:

On an unrelated note, how do I get those nifty colored maps everyone has in their signatures?

OH, not only do you want to ask questions but NOW you want into the Secret Club too!!!!!    (I had to ask also to figure it out...)

Got to: http://visitednorthamericamap.com/

Create the map and download the image.  Then add it to your Profile.

 

And I really need to do some flying this year to fill in the blanks.

 

[Ragsf15e]

Regardless of 2 or 3 axis, you probably want to budget for the trim servo.  Technically you can do a 2 servo gfc500 but you lose a good bit of automation because it will just alert you that you need to trim every time it trys to level off or you change airspeed.  I don’t see a good reason to leave out the trim function on such a capable AP.

[canamex]

3 minutes ago, PeteMc said:

OH, not only do you want to ask questions but NOW you want into the Secret Club too!!!!!    (I had to ask also to figure it out...)

I thought I would get a few posts in before asking  - thanks!

[ArtVandelay]

I think it helps to define your needs and also to understand what a yaw damper does.
The main purpose of a yaw damper is to dampen undesirable roll-yaw coupling (Dutch roll) that occurs in some airplanes (notably swept wing jets) and they are often required for these airplanes.
In addition, it will keep the ball centered during climbs, coordinate turns and improve the ride in turbulence. 
A Mooney does not have an objectionable Dutch roll, the rudder aileron interconnect helps coordinate turns, the ride isn't that bad in turbulence, and it's not that hard to keep the ball centered in a climb. So, the yaw damper is a matter of convenience, not a necessity.

V-tail Bonanzas apparently have serious roll-yaw as well.
I try to avoid prolonged flights in turbulence and moderate chop there is very little dutch roll in my mid body J.
Plus I rarely have rear seat passengers, if I did I’d probably get the YD for their comfort.

[jamesm]

With GFC500 you could  install the  yaw dampener later it's bracketed allows for it and since it use CAN all would have to do run power set of wires to Yaw dampener  servo to have it installed at later date.

[ArtVandelay]

With GFC500 you could  install the  yaw dampener later it's bracketed allows for it and since it use CAN all would have to do run power set of wires to Yaw dampener  servo to have it installed at later date.

Does each servo have it’s own circuit breaker? If not you can just daisy chain off the pitch servo.

[StevenL757]

6 minutes ago, ArtVandelay said:

Does each servo have it’s own circuit breaker? If not you can just daisy chain off the pitch servo.

The GFC500 installation in a 2, 3, or 4-servo configuration is supported by your "A/P" circuit breaker (at least, in the Ovation).  Not sure about the "J".

 

23 hours ago, jamesm said:

With GFC500 you could  install the  yaw dampener later it's bracketed allows for it and since it use CAN all would have to do run power set of wires to Yaw dampener  servo to have it installed at later date.

True.  The yaw damper servo - like others - is really only 3 wires...Power, Ground, and CanBus.

[0TreeLemur]

Go Brittain!   You just gotta be in a real secret club.   We put a 3-axis vacuum actuated, Apollo-era, full autopilot in our C for less than about 5 amus.  Went in owner assisted like a dream.  Great way to go if you can find the parts and don't mind going analog (and old school), and have friend who can help.

[jamesm]

6 hours ago, ArtVandelay said:

Does each servo have it’s own circuit breaker? If not you can just daisy chain off the pitch servo

on my 'C' model with no yaw dampener, it  has two circuit breakers "trim switch" and "autopilot". I am not sure if the yaw dampener has it own or not.

[PT20J]

The GFC 500 with pitch trim, and with or without a yaw servo, uses two circuit breakers labelled AUTOPILOT and TRIM. The AUTOPILOT breaker turns off power to the GMC and the servos -- in other words, it kills everything. The TRIM breaker only protects the manual electric trim switch and wiring -- the autopilot can still run the trim with the TRIM breaker pulled! Also, on a G3X Touch (maybe other installations as well) pulling the AUTOPILOT circuit breaker will cause the autopilot disconnect aural alert to sound continuously and pressing the yoke disconnect will not silence it (because this switch goes to the autopilot which is powered down and the sound is coming from the G3X). The only way to silence the alert is to touch the 'AP' annunciation in ACFS Status Box at the top of the PFD, or push the G3X BACK button. This latter method is undocumented but I was told about it by Garmin support and I verified that it works. 

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