TruTrak Turn Rate

[hevansrv7a]

While being vectored in terminal airspace while using my TT DigiFlight II I noticed the same thing reported by Paul Dye - that I wasn't getting standard rate turns when I commanded a new heading/track with the twist knob. My IAS was about 130-140 kts as I recall.

Zack at TruTrak answered many questions for me today and he was very patient. Those are very good people with whom to do business.

He explained that the "bank angle" setting - low, medium or high, controls this to some degree. I don't know what mine was set to because it's in for repair, but setting it higher might help. Zack said he thinks the factory default is medium but he didn't sound certain. Unfortunately, it isn't capable of being set to turn rate, but then, the bank angle setting isn't a fixed number of degrees. Rather, it's affected by speed and how big a turn is commanded.

I note in passing that "lateral activity" and "lateral torque" are different settings than "bank angle".

Perhaps some of you have more detailed information on this?

[Geico266]

There is a Yahoo TruTrac forum you might want to try if no one has good answeres here.

http://groups.yahoo.com/group/trutrak/

A factory rep answers questions so you are getting the straight scoop.

[zkvii]

Originally Posted by hevansrv7a

He explained that the "bank angle" setting - low, medium or high, controls this to some degree. I don't know what mine was set to because it's in for repair, but setting it higher might help. Zack said he thinks the factory default is medium but he didn't sound certain. Unfortunately, it isn't capable of being set to turn rate, but then, the bank angle setting isn't a fixed number of degrees. Rather, it's affected by speed and how big a turn is commanded.

Hi,

We have upped the rate to 'HIGH' but still not enough. I think you are GRT EFIS based, there are a couple of controlling variables for roll and bank gain which I've started playing with to get closer to rate 1 turn. So far roll gain is up to 1.8 from memory and it is more reasonable for cruise but I haven't got to the bottom of it all yet.

Carl

[breister]

"Lateral Torque" is the maximum amount of force the system will use to correct roll (up to the maximum available from the servo). It should be set high enough to handle turbulence, but not so high that you cannot override the autopilot in case of a malfunction. Setting it too low will result in frequent "slipping" in turbulence (which you can feel) or in a severe out-of-trim situation.

"Lateral Activity" is best described as "how aggressively will I attempt to correct for what I, the autopilot, perceive as incorrect roll positioning." Another way of saying it is this determines how frequent and how large each individual correction is. In a no-turbulence situation you would prefer this low to give a smooth ride; in high turbulence a low setting will not correct quickly enough and may result in repeated overcorrections. It is best to play with this setting in flight to determine what works best for your airplane and what you feel comfortable with (too high, and it feels like the AP is "stirring the stick" even in calm weather).

Hope that helps.

[frankh]

Yes my Pictorial pilot only turns at about half standard rate...which means I constantly turning the thing off....

Wow that would be cool to get it to turn at close to standard rate!!...I could take a nap when being vectored to final..

Frank

[hevansrv7a]

Originally Posted by zkvii

Hi,

We have upped the rate to 'HIGH' but still not enough. I think you are GRT EFIS based, there are a couple of controlling variables for roll and bank gain which I've started playing with to get closer to rate 1 turn. So far roll gain is up to 1.8 from memory and it is more reasonable for cruise but I haven't got to the bottom of it all yet.

Carl

Yes, I do use the GRT, but the '496 is driving the TT directly and the EFIS is not. I am doing that because this way I can both follow a GPS flight plan and see the VOR needle on the PFD while flying XC.

It's the ANGLE you want to adjust on the TT, not the GRT, I think. I'll know more next week; my AP will arrive on Monday from repair.

[zkvii]

Originally Posted by hevansrv7a

Yes, I do use the GRT, but the '496 is driving the TT directly and the EFIS is not. I am doing that because this way I can both follow a GPS flight plan and see the VOR needle on the PFD while flying XC.

Interesting - with the VSVG and GRT the select alt / vspeed or ias plus heading stuff is all very smooth. I have a switch on the ARINC lines (as per GRT documnetation) to be able to select between GPS and GRT for the AP.

Originally Posted by hevansrv7a

It's the ANGLE you want to adjust on the TT, not the GRT, I think. I'll know more next week; my AP will arrive on Monday from repair.

I know there is the ANGLE option on the TT - but I've found even 'HIGH' isn't enough. There are two other options on the GRT which I think help here:

From GRT manual:

• Roll Gain - Put the airplane on course; with ero cross-track error (use the GPS on a 500' range scale to see when very close to being on track.) Note how much activity there is in the ailerons in smooth air while on course. Set the roll gain as high as possible, but not so high that it results in any noticeable roll activity in smooth air. Note that Roll Gain affects all modes except Heading.
• Heading Gain - Slow the airplane to the minimum speed at which you will use the heading select function. Adjust the Heading gain as high as possible without excessive roll or heading oscillations.

I'm still just starting with this stuff so maybe I'm going in a wrong direction, but worth having a look at anyway.

Carl

[Ironflight]

The problem here is that there are different flavors of "Tru Traks" guys, and I think that you're talking apples and oranges to a certain extent. My Pictorial pilot, for instance, can't get anywhere near a standard rate turn (and I have confirmed that with the TT tech support), whereas the more sophisticated units can. The PP takes an error signal from the GRT's - it doesn't get turn rate commands. I don't know about the fancy units that talk on the ARINC line, but I suspect they might.

Just thought I'd point that out - saying "I have a Tru trak" is like saying "I have a Chevy"....are you talking Impala or Corvette?