Anyone have autopilot in their cub?

[frequent_flyer]

What about Notice Number NOTC2741 on the Garmin GFC 500 telling certified users to pull the breaker until Garmin comes up a with a fix.

Only applies if optional auto trim is installed. I don't know how common that option is but it's not used by CubCrafters.

With the basic pitch and roll servos the Garmin system gives a "trim up" or "trim down" alert when the pitch servo is holding torque against an out of trim condition. The proper response is often a change of thrust rather than a change of trim.

[frequent_flyer]

Thanks for the alert notice though. It told me that experimental G3X Touch firmware 9.12 is available. it not only fixes the auto trim problem but includes several other useful system updates.

[sub3]

Stewartb - I am contemplating using a rod here.

[stewartb]

I like it. I’ll be interested to hear if you get full travel with the standard servo arm.

[sub3]

No dice on the full travel. it’s too bad would have been a great location, concealed and easy to access inspect/adjust. Im going to try making a longer arm but im not optimistic, it’s a long swing to cover the elevator travel. maybe someone else smarter than me has a hack to make the arm work vs the pulley?

[Gordon Misch]

it’s a long swing to cover the elevator travel

Might run out of available torque with the long arm, even if adequate travel can be achieved ????

[gahi]

nevermind, thought about it for another 1/2 second

[stewartb]

Good point on required travel. Stop to stop probably isn’t important. My long arm fails to hold the stick in 3-point during setup but as I said earlier, in flight and properly trimmed it works fine.

[gahi]

Good point on required travel. Stop to stop probably isn’t important. My long arm fails to hold the stick in 3-point during setup but as I said earlier, in flight and properly trimmed it works fine.

It would limit travel available overall though right? Hard stops on the servo

[gahi]

possibly a bell crank on the seat tube to match offsets on the tube and servo arm?

[stewartb]

It would limit travel available overall though right? Hard stops on the servo

Yep. Good call.

[skywagon8a]

No dice on the full travel. it’s too bad would have been a great location, concealed and easy to access inspect/adjust. Im going to try making a longer arm but im not optimistic, it’s a long swing to cover the elevator travel. maybe someone else smarter than me has a hack to make the arm work vs the pulley?

You should be using the capstan style of servo for full travel. Mount it aft of the baggage area.

[Olibuilt]

Here is another option, very light weight autopilot at 2.5 lbs complete with servos.

https://www.aircraftautomation.com/products/supereco-autopilot

[Steve Pierce]

Only applies if optional auto trim is installed. I don't know how common that option is but it's not used by CubCrafters.

With the basic pitch and roll servos the Garmin system gives a "trim up" or "trim down" alert when the pitch servo is holding torque against an out of trim condition. The proper response is often a change of thrust rather than a change of trim.

Yea, Have a few friends with the Garmin stuff in a 182 and a Bonanza. I bet there are some Garmin software engineers working overtime. Engaging the autopilot at 2-300 feet in a Bonanza and getting a runaway trim could be disastrous.

[Farmboy]

Steve, they have a software fix which is why it’s released for experimental, but they are waiting on paperwork approval for the certified.


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[stewartb]

Trim tabs are pretty simple to overpower for the duration a guy would need to hit the disconnect button. I don’t know of anyone running a jackscrew trim with their autopilot. I’d suggest a Safety Trim controller for anyone with electric trim on a trimming horizontal.

[frequent_flyer]

I don’t know of anyone running a jackscrew trim with their autopilot.

I have seen reports that some CubCrafers owners have tried it but no reports that anyone who tried it decided to keep it.

Many, if not all, Part 25 aircraft drive the stabilizer jackscrew to compensate for the AP holding elevator against a pitch mistrim. These aircraft typically have fully integrated autopilot and autothrottle.

[Steve Pierce]

Trim tabs are pretty simple to overpower for the duration a guy would need to hit the disconnect button. I don’t know of anyone running a jackscrew trim with their autopilot. I’d suggest a Safety Trim controller for anyone with electric trim on a trimming horizontal.

Main issue I could see would be with the Bonanza where the trim can over power the elevator. I know a guy who did not set the trim on a Bonanza correctly for take off and dam near killed him. My wife and I forgot to set the trim on our 182A once for take off while doing touch and goes, it was very heavy it pitch till I got it trimmed. That was my concern. On a Cub I don't think it would be hard to over power and turn off if the stab trim was rigged up.

[sub3]

By extending my arm .20 I was able to achieve full range of motion at this location and the pushrod is protected by the under seat storage and its clear of all cables and pulleys.

[stewartb]

How acute is the angle of the rod? I wonder how that plays into servo power?

I see you buried the servo below the baggage floor after looking at the other pic, so pretty level rod, I presume. I like that location. Nice work!

[JohnnyR]

​I am making this decision now - whether to include a dedicated controller or just utilize G3X’s onboard functions for our planned 2-axis autopilot (no trim - just altitude hold. We are set to install a trim servo if it’s needed, but the MOAC’s don’t seem to have the same need for trim as the Rev 2 & 3 Backcountry Cubs).

Any updated recommendations for a Cub that will live in AK and frequently goes on long VFR cross countries within the state?

For comparison, I find myself using the Skywagon’s 2-axis STEC30 autopilot much of the time when traveling VFR from area to area. This usage is typically just heading and altitude hold. Very little IFR flying or approaches.


Here’s how Legend Cubs typically sets up a G3X panel with 507 controller to right of primary display. I won’t be putting in an IFR navigator or G5 unit. Pic below that is demo of G3X flight director page displayed along with with primary page.

I sorta wish I had the 305 or 507 controller. The AP would be more functional. No plans to upgrade mine. It does enough as it is.

[Scott A]

FWIW I'm doing the same without the 'full' dedicated controller. The Dynon does have a simplified controller with a physical heading and altitude knob and I have that. For the rest of the stuff I will just use on screen - but not for IFR so mostly use the simple knob panel 90% of time.

[Farmboy]

Another vote for the 507 controller if you’re using a GFC500. While the G3X interface works, if you use it much my opinion is a stand alone controller is really helpful. I like knobs and I’ve spent quite a bit of time “dialing-direction” through heavy traffic areas.


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[frequent_flyer]

Another vote for the 507 controller if you’re using a GFC500. While the G3X interface works, if you use it much my opinion is a stand alone controller is really helpful. I like knobs and I’ve spent quite a bit of time “dialing-direction” through heavy traffic areas.

I have the GMC 305 but only because a GMC 307/507 won't fit in my panel. Having dedicated mode select buttons is more convenient than using the AFCS GUI but I don't really miss the GMC knobs. I find it very easy to set altitude and heading bugs with the left knob pair on the GDU.

Certified (IFR) systems require the GMC 507 since it includes a redundant AHRS that is not provided in any other GMC version. That's not a factor for experimental as attitude redundancy can be provided with a second GSU 25 or a G5.

[thaefeli]

"Here is another option, very light weight autopilot at 2.5 lbs complete with servos.

https://www.aircraftautomation.com/p...reco-autopilot"

Cory Robin posted a youtube a year or so ago about this autopilot in his CC. Nothing since that I have seen. That might tell you something I guess.
Can an RC servo have that kind of duty cycle?

[Skywalker]

Modern RC servos can be bought or ganged together that will fly a 1/2 scale model. Trimming a full scale in no biggie. Don't worry about the servos, it's the cavalier approach to the pushrods, some are scary, I'd be using arrow shafts.