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TruTrak ADI Pilot II autopilot...problem or not?

Tom @ N269CP

Well Known Member
Hey guys, I have what may be a simple question regarding basic operation of the subject autopilot. I've contact TruTrak who cannot provide any insights.

My plane just came out of annual. While taxiing to the runway for my first post-annual flight my autopilot somehow became engaged....its possible I bumped the right button while setting the altimeter, but I'd never done that before. And because of sunlight on the panel I could not see any of the indicator lights. So I taxiied back to my hangar to troubleshoot. Once there, I saw that the autopilot was in Trak mode. So I simply pressed the right button a couple of times to cycle it to off. But it would not cycle next through Nav mode to off, as has been how I normally turned it off when airborne.

My autopilot disengage button on my grip shuts it off, as does holding the right button for 1-2 secs.

My question is this: Can the autopilot be set in Nav mode while on the ground? Or is it interlocked to prevent this?

The TruTrak manual is silent on this.

I've had instrument issues during and after my last two annuals...had to replace my previously working elevator trim servo and indicator after this latest annual. So am a bit frustrated by this as well as TruTrak's inability to provide any insights into the above simple question.
 
Isn?t there a minimum speed setting in the set up for the autopilot?

There is a setting for this, I honestly don't know what it is. Not sure it applies here. But while stationary it does go into Alt Hold mode and Trak mode and takes control of the stick...it just doesn't go into Nav mode.

This morning I've experimented with seeing if keying the mike turned the a/p on...as reported elsewhere here, but that does not appear to be the case.
 
FWIW If you have an Infinity stick grip or similar you can inadvertently depress the autopilot button on the stick and it will engage the Track mode. I did this once while practicing touch and go's. During a hard landing, my thumb must have depressed the button momentarily but long enough to engage Tracking mode. This can be a real shocker as you are climbing out and feel a "frozen" stick as you start your turn at low altitude.

According to the TruTrak installation manual, only the tracking mode is engaged. I can verify that.

When shutting off my ADI Pilot II, I always simply blip the disengage button on the Infinity grip. I don't cycle through Tracking, Nav, etc. by repeatedly pressing the control button (on right).

The important thing to be aware of is that the "AP disengage" button on the grip is really an "engage" button as well. Only takes about 1.5 seconds to engage. So part of my pre-takeoff checklist is to check that Autopilot is off.

Chris
 
There is a setting for this, I honestly don't know what it is. Not sure it applies here. But while stationary it does go into Alt Hold mode and Trak mode and takes control of the stick...it just doesn't go into Nav mode.

This morning I've experimented with seeing if keying the mike turned the a/p on...as reported elsewhere here, but that does not appear to be the case.


Believe it sets a minimum speed that will allow the autopilot to engage. Maybe not applicable to your issue. Surprised Trutrak didn?t cover that when you called them.
My Trutrak is a different model but it has that in the set up mode.
 
FWIW If you have an Infinity stick grip or similar you can inadvertently depress the autopilot button on the stick and it will engage the Track mode. I did this once while practicing touch and go's. During a hard landing, my thumb must have depressed the button momentarily but long enough to engage Tracking mode. This can be a real shocker as you are climbing out and feel a "frozen" stick as you start your turn at low altitude.

According to the TruTrak installation manual, only the tracking mode is engaged. I can verify that.

When shutting off my ADI Pilot II, I always simply blip the disengage button on the Infinity grip. I don't cycle through Tracking, Nav, etc. by repeatedly pressing the control button (on right).

The important thing to be aware of is that the "AP disengage" button on the grip is really an "engage" button as well. Only takes about 1.5 seconds to engage. So part of my pre-takeoff checklist is to check that Autopilot is off.

Chris

Very interesting, Chris. I didn't know that about the a/p disengage button also engaging the a/p....I can now confirm that is true for mine as well. It's the only a/p button on my grip. Yes, looks like a good checklist item.

I'll bet you were surprised to find the a/p on during climb out.
 
Believe it sets a minimum speed that will allow the autopilot to engage. Maybe not applicable to your issue. Surprised Trutrak didn?t cover that when you called them.
My Trutrak is a different model but it has that in the set up mode.

TruTrak simply referred me to the manual and said they could not answer my question. No attempt to troubleshoot it by them. You'd think they'd have somebody around there, or who they could call, who supported these a/p's. Apparently not.

I was not impressed, nor am I keen on their new "upgraded" version with the single "magic do-everyting" joystick input. This is one of my main concerns with proprietary black box electronics....their typical early obsolescence. It's why I went for steam gauges. The TruTrak ADI Pilot I & II a/p is nice and simple. Don't fix it if it ain't broke.
 
Very interesting, Chris. I didn't know that about the a/p disengage button also engaging the a/p....I can now confirm that is true for mine as well.
ut.

Pushing and holding, for a few seconds, the disengage button, should, on release, bring the autopilot on-line in a specific mode. I think they call it PCS, pilot command steering. The autopilot should attempt to hold the heading you are in when you release the button. If level, it should keep you level. If in a climb, it should keep you climbing, etc.
My opinion: autopilots and electric trim systems should have an obvious, one-action means of disabling them, quickly.
My opinion: I have a Trio autopilot, which, because it uses a slip clutch instead of shear screws, doesn?t suffer from the ?locked stick? problem.
 
Very interesting, Chris. I didn't know that about the a/p disengage button also engaging the a/p....I can now confirm that is true for mine as well. It's the only a/p button on my grip. Yes, looks like a good checklist item.

I'll bet you were surprised to find the a/p on during climb out.

Let's say "a little more than surprised". Trying to figure out what was going on at 300 ft altitude is a real lesson in flight discipline and very revealing about what your mental check-list tells you is happening vs. reality. At least I figured out that the elevator still worked ok and the rudder worked ok. So I can fly with that and return to base to figure out what's going on with the ailerons.

BTW, the TruTrack installation guide does mention this, but it is buried in one of those long old-style typewriter paragraph's that you forget about as soon as you read it.

Fly safe!

Chris
 
Pushing and holding, for a few seconds, the disengage button, should, on release, bring the autopilot on-line in a specific mode. I think they call it PCS, pilot command steering. The autopilot should attempt to hold the heading you are in when you release the button. If level, it should keep you level. If in a climb, it should keep you climbing, etc.
My opinion: autopilots and electric trim systems should have an obvious, one-action means of disabling them, quickly.
My opinion: I have a Trio autopilot, which, because it uses a slip clutch instead of shear screws, doesn?t suffer from the ?locked stick? problem.

My TruTrak must use some kind of slip clutch as it didn't require much stick force to override it...which I'm glad to have discovered while still on the ground.

My initial thought was that it was some notchy sticktion somewhere in the aileron control linkages...as mentioned, it had just came out of annual. It didn't dawn on me that the a/p had engaged till I got back to the hangar.
 
The TT does not use a clutch. I suggest you check and see if you sheared the shear screw. At low force levels the autopilot may still function (enough residual resistance depending on how the screw broke).
 
The TT does not use a clutch. I suggest you check and see if you sheared the shear screw. At low force levels the autopilot may still function (enough residual resistance depending on how the screw broke).

That's interesting, Bob. Can you kindly point me to a document somewhere that states this?

Where does this rabbit hole end? :(
 
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That's interesting, Bob. Can you kindly point me to a document somewhere that states this?

Where does this rabbit hole end? :(

Sorry, I cannot. Perhaps my memory is faulty, but when I made my choice (10 years ago, maybe things have changed) the TT used a shear screw for protection against jams; Trio used a slip clutch. That was one of the reasons I chose Trio. Now, I can help with Trio documents -:)
Edit: if you search these forums for TT and shear pin or shear screw you’ll find info. This has happened before.
 
Sorry, I cannot. Perhaps my memory is faulty, but when I made my choice (10 years ago, maybe things have changed) the TT used a shear screw for protection against jams; Trio used a slip clutch. That was one of the reasons I chose Trio. Now, I can help with Trio documents -:)
Edit: if you search these forums for TT and shear pin or shear screw you?ll find info. This has happened before.

Bob,

I've pulled the following excerpt out of the TruTrak manual (Rev B, Dec 2009):

The reason for setting the torque to a setting less than its maximum (12) is to reduce the current draw of the servo and to make it easier to override the autopilot should the need arise. Manual override is not normally required, as using the control-wheel switch or the knob will disengage the autopilot, but it is best to have a setting of torque which can be comfortably overridden if necessary. Starting with the maximum torque setting (12), gradually decrease the value using the knob, until it is observed that the autopilot no longer has the necessary torque to respond to disturbances; then increase the setting somewhat from that level using the knob until no more slippage of the servo is observed. The clearest evidence of servo slippage is that the autopilot is no longer able to roll the aircraft back to a level attitude after a roll disturbance occurs.​

It discusses setting the maximum torque output to a level that allows servo slippage when manually overridden. I'm taking that to mean manually overriding the a/p with the joystick. Perhaps the shear pin design was superceded?
 
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In the TT system the autopilot servos are always ?in the loop?, and under normal use you can overpower them. The shear pin is to guard against an internal gear jam/failure, inside the servo. But apparently some have sheared too easily, and done so when the servo was operating normally.
 
In the TT system the autopilot servos are always ?in the loop?, and under normal use you can overpower them. The shear pin is to guard against an internal gear jam/failure, inside the servo. But apparently some have sheared too easily, and done so when the servo was operating normally.

I'll inspect for a sheared shear pin, but as overriding the pitch and roll servos encounters a similar amount of resistance, there's a good chance the pins are okay. I'll let you know. I sincerely appreciate the heads up as to the shear pins. I'm wondering if TT even sells replacements anymore? I don't see them on Aircraft Spruce.
 
I'm wondering if TT even sells replacements anymore? I don't see them on Aircraft Spruce.

I've been trying to get support for my TT Sorcerer and honestly, I'm having a tough time getting information or my problem resolved. I'll keep trying but yesterday when I called for support no one was even in the office that could help.

-Marc
 
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TruTrak is, I believe, understaffed to deal with the onslaught of "certified" installations. Not getting a warm body on the phone who can help troubleshoot is not typical of TT operations in the past. Something has changed and it can only be the new certified market that is straining their internal resources.

With all that having been said, my reading of the posts so far in this thread have left me shaking my head. I won't even ask for forgiveness for being harsh in my comments.

So we've got an autopilot in our airplane. Is there some reason why we would launch into the air with a complex piece of hardware capable of taking over control of our aircraft, without knowing how it works?

Would we jump into a helicopter and try to fly it without any idea what the collective stick does?

It's time to crank our game up a notch or two. READ the manual. Take it with us along with a safety pilot and "ground fly" the system so we get familiar with all the button functions. Then go fly the airplane - while we punch buttons, the "safety pilot" is responsible for manually flying the airplane, keeping it shiny side up.

It is profoundly disappointing to learn that a pilot would go flying an autopilot-equipped airplane without a clue as to the function of CWS (Control Wheel Steering) or an understanding of the different means by which to engage the autopilot.

The momentary-action button on the stick has three functions. The one most of us know about is "A/P Disengage". Punch the button and George goes to sleep. Want to wake up George? Punch and hold the button for 1.5 or more seconds. When in track mode, punch and hold the button and George will "snooze" until you have manually steered the airplane to the new track you want it to fly - releasing the button reawakens George so he can keep on flying the track that was active when you released the button.

Come on guys - the autopilot has the capacity to be a great boon to safe operation of our aircraft, but only if we know how to use it. Not knowing how to use it has the potential to turn it from a safety enhancement into something that can kill us. READ the manual and KNOW how the autopilot works, before it has a chance to kill!

OK, rant mode off. Fly safe out there.
 
I took it up for the first flight of the season this morning. A nice flight up past Taos to the CO border, west across the vast valley to the Jemez Range then back south to Santa Fe. A glorious start to the new season. Found some beautiful potential camping and fishing sites in some high meadows.

I'm pleased to report the the a/p worked fine in every respect. I can conclude that the TT ADI Pilot II a/p simply cannot be placed into Nav mode on the ground. It's a feature, not a bug.

Thank you all for your very helpful and educational comments. 😁
 
With all that having been said, my reading of the posts so far in this thread have left me shaking my head. I won't even ask for forgiveness for being harsh in my comments.
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Come on guys - the autopilot has the capacity to be a great boon to safe operation of our aircraft, but only if we know how to use it. Not knowing how to use it has the potential to turn it from a safety enhancement into something that can kill us. READ the manual and KNOW how the autopilot works, before it has a chance to kill!

Lemme see...

1. I read the TT manual multiple times (I'm an engineer). It's not a very well written or comprehensive manual. It deals mostly with installation and tuning, but not so much with operation or troubleshooting.

2. I discussed the issue with my A&P's avionics specialist who also read the TT manual from cover to cover to no avail.

3. I contacted TT twice about the issue and they provided ZERO support.

4. I posted a question here on VAF which elicited several very helpful suggestions.

Is there some source of knowledge I overlooked? :D

The only stupid question is the question that isn't asked. I'll risk coming across as a bonehead if I don't know the answer to something. :)
 
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Lemme see...

1. I read the TT manual multiple times (I'm an engineer). It's not a very well written or comprehensive manual. It deals mostly with installation and tuning, but not so much with operation or troubleshooting.

2. I discussed the issue with my A&P's avionics specialist who also read the TT manual from cover to cover to no avail.

3. I contacted TT twice about the issue and they provided ZERO support.

4. I posted a question here on VAF which elicited several very helpful suggestions.

Is there some source of knowledge I overlooked? :D

The only stupid question is the question that isn't asked. I'll risk coming across as a bonehead if I don't know the answer to something. :)

Tom - your point is well made, however it was this statement in one of your earlier posts that prompted my post above:
"I didn't know that about the a/p disengage button also engaging the a/p."

I'm a very firm believer that one should not fly an autopilot until one understands thoroughly how to engage and disengage it. Not knowing this most basic level of functionality is at about the same level of safety threat as not knowing how a magneto switch works, hence the sharper-than-usual tone of my posting above.

With regard to your original question, if you think about it for a minute the answer almost becomes self-evident. In order for NAV mode to work the a/p has to know a few pieces of information... Where you're going and the relative bearing/track to that destination, as well as your current track, airspeed and attitude. From these data points it figures out how much control input is required to drive the airplane around toward the destination.

On the ground we're going to be missing some of that critical information such as reliable track and airspeed. The number crunching to come up with a steering solution can't work reliably without this data, thus the a/p will not engage in NAV mode while we doodle around on the ground.

Interestingly, one can get NAV mode to work while on the takeoff roll because we're now producing valid track and airspeed numbers. This could lead to a surprise if one doesn't know how the a/p is engaged. Hmm I think I've just come back to my original point about the importance of knowing all the ways the a/p can be engaged and especially disengaged!

I do hope you are able to get your questions to TruTrak addressed in a satisfactory manner. From my experience the TruTrak products work quite well, and I can only wish for a similar experience for you.
 
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