Autopilot settings guide
- Thread starter JTD
- Start date
mmarien
Murray M.
For my Glasair II with spring loaded pitch trim and SV32 servos I used the default settings but turned the roll sensitivity down to 10. The SV32 servos display trim constantly so I need a larger servo for pitch.
jakej
Well-Known Member
FWIW - I know of another brand of autopilot, with their standard servo, in a Glasair without any trim issues. The trim indication just maybe a sensitive indication and not really a problem, I'm guessing that if the indication wasn't shown you wouldn't know/feel any difference in it's operation
Jake J
mmarien
Murray M.
True. If I ignore the TRIM warning it still seems to maintain the altitude. I've only done limited testing. I try and adjust the sensitivity and see if that helps.
dabear
New Member
I believe the Trim (and arrow) indication is the system telling you that it is using excessive force to keep the airplane in the indicated heading/pitch and that it recommends you trim to reduce the force.
I've seen the trim indication when I engage the AP right after leveling off and before I've hand flown the altitude and trimed the aircraft. Once I've trimed the airctaft, the indication doesn't come back. I don't know that you need a larger servo as much as to trim the plane.
Then again, if you have already done the triming as above and get the indication, I could be wrong. It has happend (frequently).
I've seen the trim indication when I engage the AP right after leveling off and before I've hand flown the altitude and trimed the aircraft. Once I've trimed the airctaft, the indication doesn't come back. I don't know that you need a larger servo as much as to trim the plane.
Then again, if you have already done the triming as above and get the indication, I could be wrong. It has happend (frequently).
mmarien
Murray M.
Bear - I have it trimmed and fiddle with it constantly but pitch is extremely sensitive on the early short coupled Glasairs. A little pressure on the stick is all that is required to change altitude and the pitch trim springs are fairly tight so I'm amazed at how well the AP altitude hold works even while it complains. If my passenger leans forward I take a dive. When I make a turn and the nose drops a bit the TRIM warning comes on. Not that I'm complaining. I like the sports car feel of the Glasair.
I'm going to experiment with the settings in the next week to see if I can make it work with the SV32. I'll let you know if I come up with a solution other then an upgrade to the SV42.
I'm going to experiment with the settings in the next week to see if I can make it work with the SV32. I'll let you know if I come up with a solution other then an upgrade to the SV42.
dabear
New Member
mmarien, ok. I don't know the Glasair. Would like to know what you find out.
jakej
Well-Known Member
The 'sensitivity' ( a salesman once told me it was responsive) isn't unique to any one aircraft, but mostly to the closer coupled, or light effort elevator force, airframes - the RV9, 6, early Glasair and many others have this pitch issue, I know some Glasairs here have an aerodynamic mod to dampen it. Airframe aerodynamics affect Roll as well - another day ...
There are many things that influence the ability of an Alt Hold system to do it's job properly, some builder induced and others as a result of airframe issues, it just takes time & effort to sort out.
Jake J
mmarien
Murray M.
Just an update. I turned the sensitivity of the pitch servo from 12 to 15. The servo now keeps it closer to the target altitude so the magnitude of the pitch adjusted is smaller and the TRIM warning doesn't come on as much.
Changing altitude does require trim adjustments but that I believe is normal behavior. The good news is that it doesn't SLIP unless you forget to re trim after leveling out on an altitude change. I can still get the TRIM warning to come on by just leaning forward but I believe that's also is normal behavior for pitch sensitive Glasair I and II's.
So to answer the original question, for a Glasair I or II dial back the sensitivity a bit on the roll axis and dial up the sensitivity a touch on the pitch axis. Otherwise the default setting seem to work well.
Changing altitude does require trim adjustments but that I believe is normal behavior. The good news is that it doesn't SLIP unless you forget to re trim after leveling out on an altitude change. I can still get the TRIM warning to come on by just leaning forward but I believe that's also is normal behavior for pitch sensitive Glasair I and II's.
So to answer the original question, for a Glasair I or II dial back the sensitivity a bit on the roll axis and dial up the sensitivity a touch on the pitch axis. Otherwise the default setting seem to work well.
jakej
Well-Known Member
Great to hear you've got it sorted, default settings are just that - changes will/may be required on different aircraft types, it's called fine tuning ;D
Jake J