Trio's Customer Service gets an A+
Alt Hold Update:
While working out the clutch slippage issue mentioned above I went and tightened the clutch to much and broke a gear inside the servo. This is a built in safety feature to guarentee that the pilot can manually take control of the plane if the clutch is locked up. Well, it works as designed.
With a call to Trio and a confession that I ham fisted an adjustment and broke the gear I was told "No problem."
Trio gave me a choice of receiving a new gear and installing it myself, or shipping the servo to them. We talked a little about the slip message and it was decided to return the servo to them so that they could verify that everything was good inside the clutch. At my request they set the clutch as tight as it could be and not risk gear failure so that if there is more slippage I would know the problem was in my plane, not in the servo. With a quick turn time and return of the servo the flight testing was going on again.
On the next flight there was more clutch slippage, but when the message would appear I would immediately dis-engage the alt hold and found the plane WAY out of trim with dramatic forces needed to hold the stick . So in response the trim was turned all the way down and trimming manually was done to try out the system again. The result was more porpoising. Dang, this was frustrating. The folks at Trio had suggested disconnecting the static port from the alt hold and venting it to the cabin and trying to see if the porpoise went away. So it was disconnected for this flight and when flying along basically level I adjusted the eyeball vent for a little more fresh air and what a ride! The transducer in the Trio really felt it and the ride could be much like a roller coaster with a kid at the controls of the vent so this thing had to be hooked back up. The idea did help however as the manufacturer thought it would so it looked like the fix was running a new static line dedicated to the Trio. Apparently the placement of the ports on my plane is causing some kind of fluctuation that the ultra sensative transducer feels, but the VSI can't even see. Not wanting another hole in the side of my plane the search for another idea was on.
Bring my father in law into the mix now. He is very, very sharp and told me to try the following. So the household "T" fitting that I used to split off of the 1/4" OD static line tubing that Van's provided was disconnected where it went to the autopilot. The brass ferril that slides into the end of the tube was removed and one was installed that I had filled with epoxy and once cured drilled at .040". This idea was to dampen the pressure changes that were occuring at my static ports and off I went for another flight. Bingo, level flight! I'm posting this because I've had people contact me with suggestions of the mount for the servo flexing causing the porpoise which was not the case. If anybody else has this problem it is an easy way to rule out the servo. I was a little concerned that if this idea fixed the porpoise that the dampening would be so great that the autopilot couldn't keep up with the pressure at the static ports on climb or decent effectively making the vertical speed feature useless. This wasn't the case at all so things are looking promising.
With a call to Trio to report the findings they were still concerned about something going on at my static ports. There was optimism however an a suggestion that I do a system restore to get the factory settings back in the autopilot and going up again. With specific directions on setup in flight now that the porpoise was basically gone the flight was made. After setup the plane flys very good level, and in vertical modes, but the altitude intercepts are not right.
So with a vertical speed setting of say 800 fpm and an intercept altitude the following is happening. As designed, before the cruise alt is intercepted the climb reduces to 200 fpm for a smooth intercept. Then after leveling off the plane works its way into a decent at the 800fpm rate that is set up from the climb. Disengaging the autopilot again the plane is way out of trim. It is a little alarming so another call to Trio. Again, the static port is looking like the problem. The theory is that there is a pressure change at the port after leveling off and the autopilot is trying to seek the cruise altitudes pressure as felt by the erratic static ports. Well out of clever ideas the plane was put away while life continues.
Today I'm thinking of taping off one of the static ports and trying the intercepts again, and then reversing. I'm wondering if the air spiraling off the prop could be causing the probem as it hits the side of the plane. The idea of putting another static port in is bothering me. Where would I put it to make it better? Then there is the lack of places to run the line thru the spar and another hole isn't a good idea.
So, any ideas out there? The one constant in this is Trio's customer service. There is no sign in their voices that I'm being a pain in their side when they receive another call from me. They are sure that running a new static line will fix my problem but they are being very reasonable with my experimenting. What a great bunch of folks to work with me as I don't follow the tradional path on this. It has been volunteered to ship me another electronic module so it can be ruled out even though they are sure the problem isn't that. A company that allows us to be homebuilders without arguing with our ideas is special indeed. I'm determined to put a bandaid on the problem. There has to be a way.
I can see that when my airplane issue is fixed this thing is going to be fantastic. Well, off to the airport for another round of flying. Somebody's got to do it.
(If I knew exactly where to put a dedicated port for success I would do it, but ???)
Those of you flying alt holds, did you use the standard placement for your static ports?
