Trio Altitude Hold - looking for your trim experience

Hi - I'm installing a Trio Altitude Hold Autopilot in my plane, either an EZ-2 or EZ-3.... I'm looking for information about the use of pitch trim with the autopilot.

Trio's website has the follwing blurb (my emphasis added):
The altitude hold system microprocessor uses algorithms that detect when the system is demanding excessive servo pressure to maintain altitude ? which would be the case when the elevator control system is out of trim. This might happen on a long flight as fuel is burned off and the aircraft exhibits a tendency to climb. The A/H system will prevent if from climbing, but as fuel is burned the pressure that it must exert on the elevator control will grow. At some point, the system will ask the pilot to re-trim the aircraft by using the manual elevator trim system. Once trim is reestablished the message will be removed. (Note: If the aircraft has the Trio automatic elevator trim option, the trim motor will automatically keep the aircraft in trim as the flight progresses)

I have 2 questions:
#1 - For anyone with a Trio altitude hold and manual trim: How often does the system ask for a re-trim? Is it really "touchy"?

#2 - Is there anyone out there who has the automatic trim option and can share their experiences? For "only" a few hundred it seems pretty cool. I would like to know how it works in real life. It would be great to hear how you did your trim controls (still have a manual trim switch?, etc.) I see that you can adjust the trim using the Trio knob when the autopilot is off. Does that eliminate the need for a trim speed controller (because it makes smaller steps)?

Thanks for any info,

IowaRV9Dreamer said:

Hi - I'm installing a Trio Altitude Hold Autopilot in my plane, either an EZ-2 or EZ-3.... I'm looking for information about the use of pitch trim with the autopilot.
#1 - For anyone with a Trio altitude hold and manual trim: How often does the system ask for a re-trim? Is it really "touchy"?
Thanks for any info,

Click to expand...

I have the EZ-3 in my RV-6 with manual elevator trim. I have never seen the retrim message and find the manual trim works great with the EZ-Hold. I am, however, picky about having the plane in trim before engaging the EZ-Hold.

If someone has already committed to the electric trim then the EZ trim feature might be worthwhile, but certainly not necessary. I would not make a change to electric trim just for the auto-trim feature.

I can only address Question #1 as I don't have the auto trim.

Touchy is a relative term. At cruise, the trim in general is a bit touchy. You will adjust to that and learn how long to hold the switch (electric trim) or how much to turn the knob (manual.) I have electric and just flick the switch very briefly to get trim set. Since there is an apparent range of acceptable trim settings for the AH, I would say that it is probably less sensitive while in alt hold.

My experience is that, when I have the trim set well before engaging the AH, it will not give me an out-of-trim notice for a long time. If I get an out-of-trim notice, I usually disengage the AH, retrim, and re-engage. Not hard at all and to me easier than making a change while engaged and waiting for the unit to recognize it. It asks by way of a yellow notice on the trim set button. Normally the only time I get a notice is during a turn. For those times, I add a little back pressure and complete the turn. The notice goes away on its own (usually.) Also you will get notices on significant throttle changes.

BTW, I have EZ-2 and really like the controlled descent feature, although I rarely use controlled climb. Well worth the money. Don't think the pre-set alt is all that important, at least not to me. If I had extra money to spend, I would have gotten the auto trim before going to the -3. YMMV.

Bob Kelly

Sam Buchanan said:

If someone has already committed to the electric trim then the EZ trim feature might be worthwhile, but certainly not necessary. I would not make a change to electric trim just for the auto-trim feature.

Click to expand...

Sam, thanks, this is what I'm considering doing. I haven't yet committed to either type of trim, but I need to at some point. I'm hoping someone out there has the Trio auto-trim feature and can share their opinion.

Basically I'd like to know if the auto-trim feature is really worth it. If so, then I'll go for electric trim.

Someone out there with auto-trim like to comment ? Anyone ? Buehler ?