Unable to conclude satisfactory AP test JABIRU 430

[knowlesbg]

Problem with pitch calibration and performance in Jabiru 430
cruise is ok
Pitch activation will work more efficiently in decent than climb
There appears to be some form of resistance
This is apparent when testing AP after calibrating
No problem with roll left and pitch forward
But pitch back movement after satisfactory roll to right does not exist
It appears to have excessive resistance at this stage
By removing significant trim resistance by taking tension of forward trim spring allows the calibration test to complete but of course with that trimming performance when not using autopilot is impeded
I dont think Im alone with this problem. It has been suggested there could be to much resistance in the pitch control cable
Any ideas out there :-/ :-/ :-/ :-/ :-/ :-/
:exclamation :-/

 

[dynonsupport]

Re: Unable to conclude satisfactory AP test JABIRU

If there is too much resistance for the servo to overcome with its available torque, you'll see the slip indication in the form of a yellow backgrounded mode on the screen. Of course, pay attention to the trim indications as well. If the servo is fighting significant trim, it will slip and won't be able to fly the airplane. If that's happening, and you're using the SV32, you can try the SV42 on the offending axis. As a first step, though, make sure you have the torque set to 100%. There's no real down side to cranking it up, and it lets the servo try its hardest to get the movement it desires.

 

[knowlesbg]

Re: Unable to conclude satisfactory AP test JABIRU

Thanks Dynon for reply
have TWO SV42 installed
returned PITCH servo back to Dynon thinking there was a problem with servo
Dynon replaced servo didn't make any difference
In flight there is significant response with pitch setting although I feel it should be smoother
Torque setting 90 so will up it to 100
As already stated ground test after calibration there is no pitch up movement
overall the AP performance is up to expectations
It does lose GPS Tracking on occasions
Perhaps there is someone out there with a Jabiru Installation that has a satisfactory pitch response who could put light on the problem  

 

[jakej]

Re: Unable to conclude satisfactory AP test JABIRU

FWIW - IMO it's not worth the effort doing Alt Hold in the Jabby, the results are so variable and never consistent.  This applies to all autopilot systems I've installed in Jabirus so far.  

IMO the elevator/trim system is a crude/basic system that was never designed to be used with an autopilot however the ailerons work reasonably but better with some 'tweaking' .

The backlash of the cheap control cables (the manufacturer makes a better teflon lined version) has a major impact on a/p ops causing the system to hunt either side of optimum track or altitude as the case may be.

The SV32 is all you need for the ailerons but the SV42 is not strong enough for the climb/descent to overcome the trim system unless you retrim.

I also have noted that many Jabby owners are cutting off the elevator trim tab to improve the handling.  The ideal situation would be for Jabiru to change it to an electric trim and use the higher quality cables but I would think that's unlikely at this stage or during my lifetime :

Jabiru has done a lot for aviation to get people flying in an aircraft that is reasonably priced but ,to be fair, I don't think they ever envisaged using autopilots when they were first designed.

HTH
Jake J

 

[knowlesbg]

Re: Unable to conclude satisfactory AP test JABIRU

Thanks Jake for the info
Perhaps : using the SV 52 would address the problem for pitch response
:-/

 

[jaba-who]

Re: Unable to conclude satisfactory AP test JABIRU

While Jake is possibly right - as a generalization - don't get too despondent.

I have installed an AP in my Jab 430 (and while I am having some problems of a different sort ) the same problem you described happened to me but seems to be solved fairly easily. I have to say that I have only flown about 6 hours with the pitch servo installed.

I simulated descent and climb by altering the QNH while on the ground and very early found the same problem you describe - ie: pitch servo (SV42) would override the trim system on "descent" but stuck (not strong enough) when tried to "climb."

I moved the retaining washer and cotter pin forward a hole on the front half of the trim bar at the elevator. This then allowed the servo to move the elevator - but left me with a slightly "looser" trim which didn't seem to be very solid when on the ground. I was worried and doubted it would be usable in the air.

But when I tried it it actually holds in the air so I have left it at that and it seems to be OK. My pitch servo holds the altitude fairly well - I get a drift of +/- 50 ft but very slow oscillation to correct it. So it's quite comfortable to fly.

I know that Rod Stiff (designer of the Jabiru) goes apoplectic if anyone mentions to him the idea of doing ANYTHING to the trim tabs. Don't know what the specific problem is but he vehemently doesn't like the idea.

John Martin

 

[knowlesbg]

Re: Unable to conclude satisfactory AP test JABIRU

Thanks for the info it seems your experience gets close to mirroring mine
I agree there has to be fix
You are right the trim adjustment does get a little sloppy when decreasing the spring tension in fact as I stated I could only get positive pitch up during AP ground test when Tension on the forward trim spring was completely released.
I'm in the process of installing a SV52 to see if this will overcome the resistance generated with current setup if not where to next
Apart from this minor issue I am very happy with the rest of AP
performance

Bruce

 

[jakej]

Re: Unable to conclude satisfactory AP test JABIRU

BGK

AS John said 'it's a generalization' however you can improve the system by backing off the trim spring tension (not too much as you may lose trim effect) and lubricate (I use silicone grease) the aft end of the elevator cable under the dust seal.
Also slide/back off that seal at the stick end. You can do this to the ailerons as well - reduces the inherent friction and makes the controls lighter and easier for the autopilot.

HTH

Jake J

 

[JR]

Re: Unable to conclude satisfactory AP test JABIRU

Its possibly not recommended and not so relevant to new aircraft but I pulled back rubber sealing boots on each end of cables x 4, wiped clean and sprayed small amount "Ezy Glide"
Difference was dramatic. My SV32 is running 50% torque on roll now
In the rear trim compartment under tail it can get dirty and dry, clean mechanisim and lubricate. Makes big improvement

 

[knowlesbg]

Re: Unable to conclude satisfactory AP test JABIRU

Why didn't I think of that
After I put my Jabiru former hydraulic lifter engine back in the plane (300 hrs) after having to strip it down change the cam shaft replace valves and pistons rings and convert it back to an adjustable lifters configuration
I will be able to squirt a bit of lube and get back into the sky :-[ :-/

 

[dynonsupport]

Re: Unable to conclude satisfactory AP test JABIRU

Hi all,

We're for folks that have autopilots installed and flying, particularly D10/D100 series customers, who are running the latest firmware (5.3 currently), and have tried everything they can to dial in the autopilot - particularly in pitch - but aren't quite seeing the performance they would like. If this is you and:
-you're fairly technical - you understand how to use the Dynon Support Program to load firmware into your unit and you're comfortable with that process
-you're available to fly and iterate firmware and report back at least a few times over the coming weeks and months
-you're patient and fault-tolerant, and understand that testing "beta" firmware is an experimental thing

...then we want to hear from you. Please email betatest at dynonavionics dot com with the following information:
-airplane type
-dynon equipment, particularly, which servos you have
-roll axis setup:
servo type
short description of mounting method
all settings from the roll axis page in the ap setup menu
your performance notes/issues (in turbulence and smooth air if they're different)
what you've done so far (settings tweaked, results,etc) to try to dial it in
-pitch axis setup:
servo type
short description of mounting method
all settings from the roll axis page in the ap setup menu
your performance notes/issues (in turbulence and smooth air if they're different)
what you've done so far (settings tweaked, results,etc) to try to dial it in

Thanks!