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View Full Version : Is automatic pitch trim worthwhile?


kcameron
10-27-2007, 06:24 PM
I'm going to purchase a Trutrak Digiflight II autopilot for my RV-4. I've never used an autopilot so I'm not sure what to expect. I can think of two reasons why the auto pitch trim might be a good idea:

Convenience: It's one less thing to have to do myself.

Safety: One thing I've been wondering about is "what happens when the autopilot is switched off or loses power at a time when there's a big trim imbalance?" It seems like it could be pretty uncomfortable or even dangerous at high speed.

Perhaps I'm overblowing the importance of one or both of these. Can someone with experience please enlighten me?

Thanks.

scard
10-27-2007, 07:33 PM
It really isn't needed unless you just can't resist the toys (which I'm often guilty of). The TruTrak DFII will annunciate when it is really unhappy with the current pitch trim. It is no big deal to make a little adjustment and all is well. The usual operation is to trim for whatever flight condition you want to be in, then engage the A/P. If something changes and it doesn't like the new condition, it will tell you with a little scrolling graphic on the head unit. Auto trim can be nice, I've flown plenty with it in other airplanes, but isn't needed too much in our application.

Jerry Cochran
10-27-2007, 08:00 PM
It really isn't needed unless you just can't resist the toys (which I'm often guilty of). The TruTrak DFII will annunciate when it is really unhappy with the current pitch trim. It is no big deal to make a little adjustment and all is well. The usual operation is to trim for whatever flight condition you want to be in, then engage the A/P. If something changes and it doesn't like the new condition, it will tell you with a little scrolling graphic on the head unit. Auto trim can be nice, I've flown plenty with it in other airplanes, but isn't needed too much in our application.

Just depends on how much you want to spend a few seconds adjusting pitch trim... One can do this with el trim or small power adjustments..

If you are sold on just sitting and managing resources, like big iron pilots do, then by all means, install the pitch autopilot. I, for one, worry about falling asleep whilst the roll A/P flies my course...

Amazing how far we've come since the last decade... I am starting to worry about making fying too easy other than takeoff and landing... Does that make me old? I wonder, if it matters, if we could actually navigate if our modern crutches, aka GPS and Autopilots, were taken away from us...One of my next cross country 3 hour flights will be done sans GPS, A/P, just sectionals and see how it goes...

Just hope I can remember how wind triangles work...

Love my RV-6a Time Machine,
Jerry

Jerry Cochran
10-28-2007, 12:39 AM
It really isn't needed unless you just can't resist the toys (which I'm often guilty of). The TruTrak DFII will annunciate when it is really unhappy with the current pitch trim. It is no big deal to make a little adjustment and all is well. The usual operation is to trim for whatever flight condition you want to be in, then engage the A/P. If something changes and it doesn't like the new condition, it will tell you with a little scrolling graphic on the head unit. Auto trim can be nice, I've flown plenty with it in other airplanes, but isn't needed too much in our application.

Just depends on how much you want to spend a few seconds adjusting pitch trim... One can do this with el trim or small power adjustments..

If you are sold on just sitting and managing resources, like big iron pilots do, then by all means, install the pitch autopilot. I, for one, worry about falling asleep whilst the roll A/P flies my course...

Amazing how far we've come since the last decade... I am starting to worry about making fying too easy other than takeoff and landing... Does that make me old? I wonder, if it matters, if we could actually navigate if our modern crutches, aka GPS and Autopilots, were taken away from us...One of my next cross country 3 hour flights will be done sans GPS, A/P, just sectionals and see how it goes...

Just hope I can remember how wind triangles work...

Love my RV-6a Time Machine,
Jerry

Ironflight
10-28-2007, 07:01 AM
I have the simple Altrak, which means I do have to get the trim in the ballpark before engaging, but I don't find that to be a problem. If you are planning on going with a vertical rate guidance A/P in the future, then you probably want the trim sensing servo, because I think it is required, but for altitude hold, I have not missed it - just my experience.

Paul