Dynon AP pitch issue

OK folks...... As I had said previously it sounds mechanical!

Well my new servo's arrived and guess what there is movement between the arm and the attachment disc. However the shear screw seemed to be rock solid!

So with the locknut removed and just in my finger tips I played with the fit of the items and to my surprise there was a fair amount (microscopic but large in real terms) of movement of the arm around the head of the shear screw.

I have posted this on the Dynon site and the response I got was .... Do the thread service as per the instructions. Well if you do that the screw is going to be rock solid again but the arm can still move and does move around the shear screw head.

Has anyone else observed this, even after doing the shear screw loctite procedure?

I am not able to fly the plane yet, but some of you guys that are may be able to confirm this. It may not affect every servo, but we are talking about a very small tolerance here and unless you went looking for it you may not find it. If so we should encourage Dynon to look closer at it.

I know how I fixed mine but it should not be broadcast just yet as the Dynon folk do not need 30 different opinions on how to fix a problem in the field.

Cheers
DB

Dave,
I think that the servo's that came back from Dynon after the shear screw update had that "microscopic" play at the screw head. The servo's are working just fine with that "play".
Regards,

Thats good to hear Joe!

As you would know any accumulative backlash in a system will give rise to sloppy control.

Yes the amount of movement around the head is very small, however Dynon said .....

If there is any movement at all between these two
parts, your shear screw is loose and should be repaired per the following instructions.
However, slight movement of the ENTIRE arm/capstan/disc/shaft relative to the
internal gearing is expected.

Click to expand...

So I take that literally!

Glad to hear its all going well for you! I can not wait to take this baby for a lap.

DB

News just to hand..............and makes more sense now!

We may need to revise the wording there. Its really the ability of the shear screw to move in its threaded hole that we want to eliminate. This effect is orders of magnitude worse than the normal manufacturing tolerance between the shear screw head and the hole bored in the arm to capture it.

Click to expand...

All

For what it's worth, I now have an SV42 servo on the way to use as the pitch servo. I have not tried the sheer screw service procedure on my existing servo.

I am still having the pitch issue but after more discussions with Dynon we have a fairly aggressive agenda for figuring this thing out. Will report back with more details when I fly the SV42.

We have those servos in a -7A....

.....that's under construction in my hangar and I just looked at the pitch servo carefully. It appears that the head of the shear screw is too small or the hole is too big...the reason for the slop.

Regards,

Piere

The folks at Dynon say that this is not a problem, compared to the movement you get from the shear screw being loose. If its loose the amount of rocking is quite likely to be considerably more that the clearance in the hole.

I have applied a very small amount of loctite, using the end of a paper clip, and only half of the drop the clip would hold, and run it around the outside of the head. Capilliary action takes it into the gap, and leaving it facing down so it does not go to the back and glue the arm to the disc I left it overnight. All slop gone. Of course I take the risk of it being harder to over power and break the shear screw, but using the very slight amount I used it would be unlikely to get any excess in the wrong place.

If you do this.....be very careful!

Some extra reading here for you.

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1235026530

Jamie,
I'm interested as to why you haven't tried the shear screw fix?
If for instance you get the new -42 servos, and Dynon has made sure those shear screws are tight,and you install them. Then flight test, and everything is wonderful, and then you report that here, what will everyone then know?
If on the other hand, you did the shear screw service, found the AP still oscillates, then replaced the servos and found it rock solid, that would be extremely helpful to everyone. But if you're totally fed up with your Autopilot and just want to get it fixed I certainly would understand.
In any case good luck and best regards,

The reason why I haven't done the sheer screw fix was simply because there was another problem with my servo. The calibration of the 'servo force' reading was incorrect, meaning that even with the airplane trimmed in pitch, engaging the servo would indicate a need a nose down trim. So basically I was going to have to return the servo anyway, so why even try? If I install the SV42 servo and the AP performance is good and time permitting I will perform the service instruction on the old SV32 servo and re-install it to give you guys another datapoint.

The reason I asked for an SV42 servo is because I'm suspicious about the SV32 servos having enough torque. The reason I say this is because with the servos engaged it takes very little force on the elevators (pressing on the elevators, not using the stick) to cause the servo to slip, even with the servo torque at 100%. I'm guessing it takes just a pound or two of force, but I'm going to try to quantify it for the Dynon folks just to give them more data.

Here's my question: The only reason for limiting available servo torque is to allow the user to override the servos in flight, right? Well, with the SV32 servos even at 100% torque it takes almost no force whatsoever on the stick to cause the servos to slip. So why not just use the more powerful servos to give us more range in available torque? In other words, the servo torque setting on my RV-7A with the SV32 servos is absolutely useless.

Jamie,
I noticed the same slipping as you, so I'll be very interested to see how these servos do. Keep us updated.
Thanks,

Would you buy a Dynon AP again?

Wow, would you go with Dynon again on the AP or simply step up to a Trutrak unit? I read all the threads on this and am a little concerned about my current planned decision to go w/Dynon's AP. Given all your troubles and effort I think Dynon needs to send a rep/tech out to inspect your plane, verify install then help you through this effort. I agree Dynon could always use more data collected (ie have you do more flying and possibly record some data) but come on lets verfy that the thing is at least installed correctly first. Given that there are so few of units out there in the first place I think they could user your positive reference. Based on what I read it sounds more like a software/ control algorithum issue. Nothing against Dynon but I think given all that you have been through they owe you a better answer/ support then to try and blame it on installation at this point. True product support and there by product improvement demands good root cause analysis no matter the situation. Dynon, yourself and us potnetial customer's will all benefit from this. As a potenital Dynon customer I would like to read a constructive/ happy resolution to this. Dynon's price point on their AP has me for now but I will continue to do some additional home work before making the final decision.

Hang in there and thanks for sharing,
Steve

Looking for RV7 experience w/Dynon's autopilot

Looking for additional information Good and Bad about other RV pilots experiences w/Dynon's auto pilot units.

Thanks for any feedback

What is the normal size TT servo for an RV6,7,8,9? Is it a "B"?

If so TT rates their "B" at 30in/lbs but do not give at what radius, assuming 1" radius????

Dynon rates their "SV32" at 24in/lbs @ recommended outer hole.

Trio states most install in the outermost hole and that equals around 22.5in/lbs

Should be enough if the rating is real since the rest of the install is the same????

Slagergren

I have not flown the Dynon A/P yet however there are plenty of very happy users so that in itself says something at a very early stage.

There will always be some who have complaints, and usually its from their own errors not the product. In this case there are some problems that Dynon are addressing and pretty smartly I would say. many manufacturers of all sorts of goods bury their heads for months and never admit anything. These guys are different!

This is why we hinged our whole RV10 project on the Dynon system long ago. Time will tell for us in a couple of months, but I do expect a good result.

Having set up a Trio and a new S-TEC........ the Dynon looks like a good thing!

Cheers

DB

Jaime,

IMH(and non-expert)O, your decision to try the SV-42 sounds like a good course of action, based on the slipping you're seeing. Though you can move the servo rod to an inner hole (I know you know that), it sounds like the outer hole provides the best over-center protection, so stepping up to the -42 will give you the chance to up the torque and maintain that outer-hole oc margin...mo betta!

That being said, I was wondering if you saw the same slipping and DN trim annunciations in both the SV-32 servos you tried? (I think you said you were getting another one a while back...not sure if that ever happened.) Also, were you seeing a lot of, or any slipping in flight?

(Same question to Jon...your descriptions along the way have sounded similar to mine...did you see any slipping in flight, before and/or after the shear screw service was done?)

For comparison, in ground testing, done as you have described, I can make the servo slip with somewhat light force on the elevator. However, it sounds like it's not as easy to do as on yours Jaime. Breakout, or slip-inducing force with the stick sounds different as well...it's not hard to make it slip, but it's not "almost no force at all". Seemed to me to be about right...however, I don't have experience with other APs in my -6, so my "sample size" is very small! I'll talk to a 9A bud with a Dynon AP that we are working to dial in, and another 9A bro with a TT, and see if I can do a three way side-by-side comparison on those forces.

In flight, I don't think the servo has shown any slipping at all, even in somewhat bumpy air. Still working and testing it all, and will report the results of the shear screw service when that is done and fully tested. Feels like I'm getting closer to Jon's solid performance...will report back.

Wish we were closer so we could do a comparison, and it will be interesting to hear your observations with the -42 installed. It will also be interesting to see if, with the SV-42 at 100% Tq, the problem goes away, and then to see if you can step-down the torque setting and re-create the problem. That would be another good data point for all. Not trying to add to your test-card stack though! Hmmm, thinking about it, perhaps that's something I can try as well...see if I can duplicate what you describe by lowering my Tq setting...once I get it dialed in...almost there!

Hope this does it for ya, and good luck!!

Cheers,
Bob

The first set of servos I had indicated trim perfectly. The second set has the invalid trim calibration indicating a need for nose down trim when the airplane is perfectly in trim.

In other words, even when I engage the servo on the ground, the EFIS immediately tells me to add nose down trim. The first servo did not do that. That is simply an instrumentation thing though and doesn't affect the logic (per Dynon) so it shouldn't be problem with flying the airplane, but it's certainly something that needs to be remedied.

Dynon has gone above and beyond to try to make me happy with this thing and I seriously don't have any problems with them. Heck, my day job is writing software that runs in unusual places as well, so I can sympathize with them completely.

If I am still struggling with this issue at Sun-n-fun they have promised to have one of their guys hook up with me and we'll go fly my airplane and I'll let them see first hand the performance of the AP.

My sticks are also very long in my airplane. I shortened them just enough to pass beneath the stock instrument panel. A longer stick certainly yields more leverage against the servo. Bob, how long are your sticks? I know that the -6 aileron bellcranks are different, but I believe the elevator bellcranks are almost identical, right?

Jaime,

Went out to the hangar today, and pulled the floor to check/adjust my aileron trim springs. While in there, I measured the control stick and did some AP breakout/slip force measurements at the stick and at the control surfaces. I used a borrowed spring guage (the kind with a rod that you depress or push with, and the tension is measured on a scale in pounds...not super-exacting, but pretty good ball-park). Did this first on my airplane, and then on Greg Arehart's -9A with a Dynon AP. Here's what I found:

Stick length (to top ot grip) on mine is 14" to the elevator pivot point, and 17" to the aileron push tube connections. Makes it about 10"-11" or so from the spar top (SWAG, forgot to measure this...just mentioned if you don't have the floors pulled up and you compare). The stick-top to panel-bottom gap is about 3.5" at the full fwd stick.

I did the breakout tests where my hand fits the grip, which is about 12" from the elevator pivot point. I first did the tests with the controls neutral, and the servos in ALT/HDG hold. Three tests in each direction (fwd, aft, left, right). Then I did the same tests in servo "test". My SV-32 servo torque is set to 100% (both pitch and roll).

I saw very consistent results at the stick. In all four directions, the servo slipped at about 6 pounds of pressure. Range was 5-7, but on 15 of 18 tries, it was 6.

At the control surfaces, I applied the pressure at the mid-span point of the aileron or elevator, just forward of the trailing edge. Breakout force on the elevators was 6 pounds, and it was 9 pounds on the ailerons. Probably more on the ailerons due to the shorter chord length versus the elevator.

On Greg's airplane, though his sticks are longer (story of my life...had to beat you guys to that punchline! ), I measured them close to where I did the tests on mine. His breakout force at the stick was also consistently 6, with a 5-7 range. At the elevators it was 4 (maybe due to a bigger elevator on a 9?) and at the ailerons it was 9-10.

Pretty consistent results, albeit somewhat unscientifc. Possibly completely useless info, but it may give you something quantitative to compare to as you eliminate bogeys in this quest!

As far as the elevator bellcrank goes, I think they are similar/the same in the 6 and 7, though can't say for sure. The Dynon install guide has only one diagram for install of the 6,7,9 pitch servo, so it is likely that it is. I'll post the diagram, and then some early pix of mine, so you can compare. Also have a couple thoughts about the mechanical installation that might be trouble-shooting ideas. I'm sure you already have that aspect well in hand, but just have some thoughts...plz take them as a wingman covering your six!

Here's the diagram for the 6,7,9 pitch servo:



Straight-on view of my pitch servo:


Side view:


Please forgive the sloppy "poor-man's torque-seal" (fingie-polish)...since been cleaned up!

For those trouble-shooting thoughts:

On the side view, you can see where on first install, the nut on the rod-end bearing was very lightly rubbing on the bellcrank. Didn't damage metal, just rubbed primer (lightly re-coated since the pic was taken). I had to use some spacer washers to move the rod further from the bellcrank, and those can be seen in the front pic. Thought is to make sure that the rod, bolt head, or nut is not contacting or dragging on your bellcrank or the vertical fuselage/baggage wall support. If it is, would likely cause fits with the servo and the elevator. (Dan H and Mike S...this is the bolt I couldn't turn around per your recommendation, due to clearance...did the others, and thanks!)

On the front view, the space between the bellcrank halves gets a washer installed as you pass the bolt through the bellcrank. Was a pain to install, but a little fuel-lube "sticky" on the washer made it more workable, and I got lucky on the first try. If that is not there, I think it could cause crushing/closing of the gap, and perhaps some drag on the elevator system...maybe, maybe not.

You've probably already checked this too, but the securuty of the mounting bracket to the airplane is pretty key, and I used 6 rivets in the side and 3 through the bottom, and it turned out pretty stiff and taut. Movement there would mess up the servo's performance, for sure.

Just some thoughts. I hope the new servo drops in and alleviates all the issues! Best of luck, and looking forward to success for you!!

Cheers,
Bob

Hi Bob:

Those are some good numbers. I appreciate it.

I'm going to simply put a fish scale on my stick to see how many pounds of force are required to cause the servo to slip. I will hopefully get out tonight or tomorrow to do this. It's supposed to be crummy around here all weekend so I'm not sure if I'll get to fly it.

I did the same as you can spaced the pushrod bearing off the elevator bellcrank with washers. My washer is in place inside the bellcrank and the mount is very, very rigid.

Jamie

Here's the e-mail I sent to Dynon this morning:

I have some *very* interesting follow-up from my day yesterday at the hangar. Here's what happened.

As mentioned, the new servo was allowing 4 degrees of movement (+- 2 degrees) in the elevators. I got in the airplane with the servo in test mode started pushing and pulling on the elevator pushrod to see what I could see. Looking very closely I could see the servo arm slightly twisting. In other words, looking closely I could see the arm lifting off of the attachment disk.

I decided to go ahead and pull the arm to check the sheer screw. The first thing I noticed was that when I pulled the cotter pin, the castle nut was quite loose. Yes, I understand the need for this to be loose to allow the sheer screw to break more easily. However, the castle nut was not even finger tight. The sheer screw was definitely locked in place and was not loose at all.

So, I put the arm back on, this time following the service instructions of making the castle nut finger tight, then turning until the shaft hold lined up with the next slot. I inserted a new pin temporarily, and reconnected the servo->bellcrank pushrod and checked the elevator travel. Voila. Now the travel is down to just about 1.2 degrees. This is very good and is the best I have seen. So in short there was one and only one change, and that was tightening the nut on the shaft. Now when I engage the alt hold on the ground I can very clearly see every little move on the stick that is made. I have not been able to do this yet.

As a temporary test I replaced with nylon washer with some steel ones. Elevator travel was subsequently reduced to 0.8 degrees.

I am of course a software guy and not a mechanical engineer, but I believe what is happening is the nylon washer is compressing and allowing the arm to twist. The rod-end bearings will place a twisting load on the arm and this twisting load is increased when a longer bolt and spacer washers are used on the arm, which many folks are doing with the pitch servos. The path from the servo arm to the elevator bellcrank is angled, increasing the twisting load even more.

I believe my findings are consistent with other people performing the sheer screw service instruction and then seeing a marked improvmenent in performance. I believe the performance improvement can in large part be attributed to the tightness of the cast nut.

I will also perform this procedure on my aileron servo. Now when I engage the AP in test mode on the ground, I can *barely* move the stick forward and backward without slipping the servo, maybe 0.5 inches or so. The side-to-side movement of the stick is about 4 inches!

So my plan is to fly the airplane as-is for now (with the nylon washer and nut finger tight + one slot). I'm very hopeful with the alt hold. I will then perform the same procedure (tightening the caste nut finger tight + one slot) on the aileron servo to see how it performs.

Now if wx would just cooperate we could get somewhere.

Hope that helps,
Jamie

Click to expand...

Jaime,

I just found the same thing on my pitch servo (we must have the same maintenance schedule!). I just pulled my pitch servo arm to look at and service the shear screw, and I found a very similar situation. When I pulled the cotter pin from the castle-nut, the nut turned pretty freely in my fingers. No resistance at all to start it turning. I wasn't sure if the act of wiggling out the cotter pin loosened the castle-nut, but it just seemed a bit too loose to me.

When I discussed the torque requirements (max 4.5 in-lb) for the castle-nut with an A&P buddy, he remarked "heck, finger tight is about 5 in-lb" (caveat: that's an unscientific analysis, not gospel or a recommendation).

When I put it back together, I used the original parts (new cotter pin), and like you, went to finger tight, then to where the next slot lined up (took almost no torque), and it felt more secure than when I took it off.

Really windy here, so haven't tested it yet. Didn't see a marked difference in movement at the stick after doing the service, but I wasn't seeing quite the movement in the control surfaces or at the stick that you were...certainly not 4 inches in the side to side movement. More like the .5" (all directions) before slipping that you describe seeing now with your fore-aft movement. But it does feel better at the servo arm.

So like you, I'm very hopeful that the last of the small pitch oscillations I've seen will go away, and we'll have performance like Bill, Jon and others are seeing!

One thing (lesson learned) I'll pass along about roll servo performance. During initial tests, my heading hold would wander quite a bit. Looked to me like heading itself was wandering as well. So I did a compass cal, and it worked better, but not quite as well as NAV hold. Later, after one round of tweaking the mechanical set-up, I did another servo cal and compass cal, and noted that I had different MAG INT (Intensity) settings on the D100 and D10A, though MAG INC (Inclination) matched. I matched them up, but used the wrong value (50-50 chance, as I didn't bring my notes to the compass rose that day, and I chose poorly!), and HDG hold went back to wandering. Rechecked (via the link on Dynon's site) for the proper value, set both EFISs to the correct value, and HDG hold now works like a champ, as does NAV hold. So, a difference in compass settings between the units may have been responsible for minor HDG wandering, but it looks like an incorrect setting (my MAG INT was pretty far off) will really cause issues with HDG hold! Just thought I'd mention it as you dial in both of your servos.

Good luck with the flight testing!!

Cheers,
Bob

Since it was asked earlier, I'll mention that 1 inch pound equals a force of 1 lb acting on a lever 1" long.

If you're only seeing 8 lbs or so (at the servo 1" out from the center) before slippage, then the servo isn't providing the advertised torque. If the distance from the center is 2", then 8 lbs = 16 inch-pounds, which is closer.

And, just to steer off any bad jokes, yes, length matters...

breister said:

Since it was asked earlier, I'll mention that 1 inch pound equals a force of 1 lb acting on a lever 1" long.

If you're only seeing 8 lbs or so (at the servo 1" out from the center) before slippage, then the servo isn't providing the advertised torque. If the distance from the center is 2", then 8 lbs = 16 inch-pounds, which is closer.

And, just to steer off any bad jokes, yes, length matters...

Click to expand...

Bill,

Not sure if you're referring to the breakout/force-to-slip measurements I took, but if so, just to clarify, those measurements were taken at the stick grip and at the center of the trailing edges of the control surfaces. So they weren't really designed to measure the actual servo torque at the slip point, but rather to give Jaime (or others) a point for comparison in how easily his servos slipped with pressure on the stick (or surfaces).

Your calculations on torque values are of course correct. I applied pressure at 12" up the stick, so the torque applied to the elevator pivot point to slip the servos was in the 'hood of 6 foot-pounds. With all the mechanical advantage of the control system, I'm sure that's far more than was being exerted at the servo arm. Might be a way to sleuth that all out, but it's been a long time since I took physics!

I didn't have the tail open when I did the tests, but it would have been interesting to see what the force required at the outer hole would have been (though my servos don't slip at all in flight, so the outer hole at 100% torque works well!)

Hopefully our next test flights will show it's not a torque issue at all!

Cheers,
Bob

Good test flight today!

With Greg Arehart in the right seat, we launched to wring out the Dynon AP in my 6 today. We were both impressed by the performance after servicing the pitch servo per Dynon's instructions (aided by the posts here...thanks much!).

Wx was good (and cold...38F at the airport and 15F at 12.5K). Air was mostly smooth, with very intermittant light chop up high, and some very light turbulence down low. Tests run at WOT, 2300 RPM, 165 KIAS/197 KTAS (eased the throttle a bit to maintain the same speed in descents for testing).

At 12.5K altitude hold was very solid...+/- 10', an occasional excursion to +/- 20', with small 50-100 fpm corrections shown on the VSI (almost insignificant, and we had to be watching it to see the excursions). Turns, both during heading bug commanded turns and NAV tracking turns, also showed very solid altitude hold, same parameters. Pitch corrections were for the most part unfelt, with occasional slight "bumps" felt in the seat of the pants (and we attributed most of those to times when the air wasn't quite smooth).

Descents, both straight ahead and in turns, showed the same, mostly smooth corrections. With the Dynon internal climb/descent preset at 500 fpm, each 500 feet of descent took 1 minute +/- 1-2 seconds. VSI showed 500 fpm, +/- 150 fpm (most of the time), with greater VSI excursions being attributable to bumpier air as we descended. Both level-offs were smooth and right on the selected altitude.

Started out with pitch sensitivity at 15, and adjusted down to 14 for the lite chop, and it handled quite well throughout (except for that one big bump that caught us by surprise and had us laughing!)

Roll performance was equally good, with heading hold solid (+/- 1-2 deg), turns being smooth (with the occasional aileron bump...moved the roll sensitivity from 8-7, and it did well), and roll-outs being on target with no hunting noted. 180 deg turn feature and NAV tracking also checked out quite well.

It was a really pleasing test flight, and thanks Greg for riding shotgun! Your 9A Dynon AP test hop is next!

Good stuff!

Cheers,
Bob

One other thought for pitch-sensitive problems.

Be aware that the autopilot doesn't care what your actual altitude is, so if you were to disconnect it from the static system and simply use cabin air it would still work.

That may actually be advantageous in our airplanes, as some static systems are "accurate" but have small lag or other changes they sense with pitch which can be "magnified" at the autopilot. In my prior plane with a competitor's autopilot, switching from the static ports as static source to cabin air resulted in markedly smoother pitch changes and leveler altitude hold.

breister said:

One other thought for pitch-sensitive problems.

Be aware that the autopilot doesn't care what your actual altitude is, so if you were to disconnect it from the static system and simply use cabin air it would still work.

That may actually be advantageous in our airplanes, as some static systems are "accurate" but have small lag or other changes they sense with pitch which can be "magnified" at the autopilot. In my prior plane with a competitor's autopilot, switching from the static ports as static source to cabin air resulted in markedly smoother pitch changes and leveler altitude hold.

Click to expand...

Just be ready for some altitude excursions when you open an air vent!

(Found this out when I unknowingly had a loose static connection on a test flight)

My thoughts too

Better to fix your static problems!

Sam Buchanan said:

Just be ready for some altitude excursions when you open an air vent!

Click to expand...

lol - yeah, I forgot about that!

It's been a few years since that airplane. Just disengage autopilot when changing the vents!

(Found this out when I unknowingly had a loose static connection on a test flight)

Click to expand...

Exactly - I had a problem when my static line developed a leak and ingested a bunch of water, which is why I switched to cabin static. That was when I noticed how much smoother the AP was on cabin air. It was months later (and warmer) when I first opened a vent in flight.

YEE-hah!!!!

User beware!

Jamie said:

Here's the e-mail I sent to Dynon this morning:

Click to expand...

Jamie, what was Dynon's response to you email? I'm about to permanently attach my wings and it's a lot easier tweaking the servo before the wings go on. Did they agree with your nut tightening method?

Hey Jamie, Any updates?

Hey Jamie,

Any updates on your pitch servo issues? Did you try the larger servo????

Brantel said:

Hey Jamie,

Any updates on your pitch servo issues? Did you try the larger servo????

Click to expand...

Hi Brian:

Yes, I tried the larger servo. No luck. It was about the same as before...it would (sort of) hold altitude but it wasn't smooth at all. I have some more verbose updates and I will post as soon as I have a few minutes (hopefully later today).

Jamie said:

Hi Brian:

Yes, I tried the larger servo. No luck. It was about the same as before...it would (sort of) hold altitude but it wasn't smooth at all. I have some more verbose updates and I will post as soon as I have a few minutes (hopefully later today).

Click to expand...

Sorry to hear that Jaime. Was hoping that "no news was good news", and you were just busy doing cool stuff like flying special kids around (that was a great story)! Interested to hear your results, scratching my head for a vicarious solution, and sure hoping for the best!

Cheers,
Bob

See here for my update.

Jamie,

When on the ground with the AP engaged do you see any of the slop in the control surfaces that you saw with the Dynon AP Servos?

647jc said:

Jamie,

When on the ground with the AP engaged do you see any of the slop in the control surfaces that you saw with the Dynon AP Servos?

Click to expand...

I see less movement with the Trutrak than the Dynon -- less than 1/2", although it's a little more difficult to quantify with the Trutrak because there's no way to engage the pitch servo without it moving.

Jamie said:

I see less movement with the Trutrak than the Dynon -- less than 1/2", although it's a little more difficult to quantify with the Trutrak because there's no way to engage the pitch servo without it moving.

Click to expand...

Try this: Engage the AP on the ground and observe whether the steering is commanding nose up (climb) or nose down. If nose up, set a descent rate of 100fpm. Play with it a few times between alt hold and +/- 100fpm, and it usually settles down.

The one I can never get to be solid is heading mode - it's always "click-click-clicking" one way or the other.

breister said:

Try this: Engage the AP on the ground and observe whether the steering is commanding nose up (climb) or nose down. If nose up, set a descent rate of 100fpm. Play with it a few times between alt hold and +/- 100fpm, and it usually settles down.

The one I can never get to be solid is heading mode - it's always "click-click-clicking" one way or the other.

Click to expand...

I have the "straight" Digiflight II, which only does altitude hold, so I can't command a decent or climb.

Jamie said:

I have the "straight" Digiflight II, which only does altitude hold, so I can't command a decent or climb.

Click to expand...

Ah - well, in that case save your pennies! Last I heard they will upgrade for only the cost difference, and as I posted elsewhere you can simulate a REALLY smooth precision approach by "dialing in" the right descent rate. The swap-out is painless as it does not require any re-wiring.

Note: In your case you would only upgrade to the VS because your GPS does not provide ARINC GPS steering.

It would be nicer if they had a comparison grid on their website for product/feature. They used to, but I can't find it anymore.

Cheers,

Bill

breister said:

Ah - well, in that case save your pennies! Last I heard they will upgrade for only the cost difference, and as I posted elsewhere you can simulate a REALLY smooth precision approach by "dialing in" the right descent rate. The swap-out is painless as it does not require any re-wiring.

Note: In your case you would only upgrade to the VS because your GPS does not provide ARINC GPS steering.

It would be nicer if they had a comparison grid on their website for product/feature. They used to, but I can't find it anymore.

Cheers,

Bill

Click to expand...

http://www.trutrakap.com/autopilot2_2.htm

Not completely up to date, but I think it's what you were looking for.

TrutrakTech said:

http://www.trutrakap.com/autopilot2_2.htm

Not completely up to date, but I think it's what you were looking for.

Click to expand...

Yep, that was it! Navigation is a bit less obvious than it used to be (probably several years back, I'm dating myself).

I had a difficult time locating it at the bottom of the home page. You may wish to consider adding "feature cross-reference" as an entry in the FAQ's page and / or add a line entry on your "Products" page similar to the line entry for "EFIS Pricing/Features" near the top.

Cheers,

Bill

breister said:

Yep, that was it! Navigation is a bit less obvious than it used to be (probably several years back, I'm dating myself).

I had a difficult time locating it at the bottom of the home page. You may wish to consider adding "feature cross-reference" as an entry in the FAQ's page and / or add a line entry on your "Products" page similar to the line entry for "EFIS Pricing/Features" near the top.

Cheers,

Bill

Click to expand...

We are working on getting client editor software here so we can make changes to our own website. As it is right now, it's pretty difficult because we don't host our own site we have to send all changes to the webmaster. It will get better, I promise!