Autopilot Servo and trim

[Owl-Eagle]

Hello Dynon support,

A simple way to know if the aircraft is in trim or not is to add on the EFIS screen the value of the torque force developped by the servo.
In trim, should read Zero force.
a + or - sign will indicate to trim manually up or down until the value is 0.
Seems to be simple but is it feasible ? :question

 

[PilotKris]

This goes right along with a discussion in another thread. The concensus was that a Trim-Prompt (what you are asking for) is wanted.

To summarize:

1. Manual Non-electric Trim + altitude hold only AP = Trim-Prompt is just nice to have

2. Manual Electric Trim + altitude hold only AP + Trim-Prompt is important

3. Manual Non-electric Trim + multimode AP = Trim-Prompt is VERY important

4. Manual Electric Trim + multimode AP = Trim-Prompt is a MUST HAVE!

5. Automatic Trim + multimode AP = Trim-in-motion/annunciate is a MUST HAVE!

PilotKris

 

[PhantomPholly]

The consensus was imagined by PilotKris!



A separate annunciator can fail, and if you decide to install one you should NOT allow that to persuade you to set torque limits extremely high on your autopilot. It is certainly nice to have, but is irrelevant if you don't have an autopilot (you will feel an out-of-trim situation developing immediately). If you DO have a torque limited autopilot (one where you can configure how much maximum force is applied before it starts "stepping/slipping") then you already have the best possible annunciator - you will know an unsafe out-of-trim condition is imminent before it gets so bad you cannot control the airplane in a critical phase of flight. If THAT fails, you are back to hand-flying - where you don't need the annunciator!

 

[PilotKris]

The consensus was imagined by PilotKris!

I forgot to mention that Bill (PhantomPholly) was the only one who dissagreed

PilotKris

 

[PhantomPholly]

The consensus was imagined by PilotKris!

I forgot to mention that Bill (PhantomPholly) was the only one who dissagreed

PilotKris

lol - what you "forgot" was that someone else didn't think it was necessary, either - so does that mean that you forgot that you forgot?



Really - in a heavier aircraft it can be a problem - but for our (experimental world) using stepping-motor servos sized appropriately it is actually impossible to create out-of-trim stick forces too high to safely correct for.

 

[Ken_Kopp]

I certainly do not agree with PilotKris...

 

[Ken_Kopp]

I should have added that I'm not opposed to adding a trim indicator at all.

I am however, opposed to having to pay for a feature I consider a luxery - if it is as simple as adding code to a future release then I'm a 100% supporter and you'll be one person nearer to your concensus. If it requires additioinal hardware, an interface module - with power, ground, signal wires, switches (with all the associated failure modes), etc... that cost money and time to install I'm 100% against.

 

[PhantomPholly]

I should have added that I'm not opposed to adding a trim indicator at all.

I am however, opposed to having to pay for a feature I consider a luxery - if it is as simple as adding code to a future release then I'm a 100% supporter and you'll be one person nearer to your concensus. If it requires additioinal hardware, an interface module - with power, ground, signal wires, switches (with all the associated failure modes), etc... that cost money and time to install I'm 100% against.

Yep - it really would be nice to have a visual indication of how hard the servos are working.

I think Dynon already said that the servos contain the force-feedback sensors which can communicate that information back to the EFIS - if that is so, then it would certainly be possible to add a pair of indicators with software, and even set alarm limits. With the latter, I would be concerned with a lot of beeping in turbulent weather, but some people might like it. But, like vertical tracking, it may only be available as a "premium feature." Now, if they would offer those two features as non-premium, then I'd sell my TruTrack and switch.

 

[PilotKris]

I should have added that I'm not opposed to adding a trim indicator at all.

I am however, opposed to having to pay for a feature I consider a luxery - if it is as simple as adding code to a future release then I'm a 100% supporter and you'll be one person nearer to your concensus.  If it requires additioinal hardware, an interface module - with power, ground, signal wires, switches (with all the associated failure modes), etc... that cost money and time to install I'm 100% against.  

So you're saying that you actually do agree (depending on price, effort)...

Isn't owning a plane a "luxery"(sic.)?

Certainly owning a plane with an autopilot is...

 

[PilotKris]

...I would be concerned with a lot of beeping in turbulent weather, but some people might like it.

Hey Bill, you aren't you the one who thinks that a low torque setting on the autopilot servo is the best out-of-trim indicator ever invented?

How is a flashing indicator and/or beeping more annoying than the clunking/clicking of the autopilot servo along with nose of the plane bobbing up and down?

 

[PhantomPholly]

...I would be concerned with a lot of beeping in turbulent weather, but some people might like it.

Hey Bill, you aren't you the one who thinks that a low torque setting on the autopilot servo is the best out-of-trim indicator ever invented?

How is a flashing indicator and/or beeping more annoying than the clunking/clicking of the autopilot servo along with nose of the plane bobbing up and down?

Glad you asked Kris!

One must presume based on YOUR assessment that such an indicator is a MUST HAVE rather than a NICE TO HAVE, that the flasher / beeper would do their thing at lower out-of-trim forces than servo slippage (otherwise, it wouldn't be annunciating anything other than the self-apparent fact that the servo is slipping!).

Since the goal of setting proper torque for the servos is to leave it possible to override them "comfortably", that means that they supply just enough force to stay in control in moderate to rough turbulence. To annunciate BEFORE torque slippage, therefore, means that these bells and whistles would be frequently excited in turbulent weather.

Thus the annoyance factor...

Now, a nice graduated force scale would another story, but would require more programming and take up more screen real-estate than a simple threshold limit annunciator. Where we agree is that that would be a great feature for a future release.

And I DO think such an indicator would be NICE TO HAVE....

 

[PilotKris]

And I DO think such an indicator would be NICE TO HAVE....

Excellent! We do have a consensus.

If you recall, the consensus ranged (depending on the situation) from:

"Nice to Have"
"Important to Have"
"Very Important to Have"
"Must Have"

As I said, It would only be nice to have a trim-prompt for altitude hold only autopilots (like your TruTrack).  But everyone seams to agree that trim-prompt is a "Must Have" for mulit-mode autopilots.

It seams that even TruTrack agrees with the consensus as ALL of their mulit-mode autopilots include a trim-prompt indicator.

 

[Bill_Denton]

After multiple threads and much argument...

Dynon has not participated in this discussion as far as I know.

Dynon has not released any documentation indentifying all of the features that will be in their autopilots.

Dynon is not a stupid company.

Have any of you guys considered asking Dynon about their plans for trim annunciation?

If I were at the point where it was an issue for me that's what I would do...

 

[Brantel]

Sure did, a few days ago in another thread:

"Hey Dynon,

How about those promissed pics of the AP interface in action?  Or better yet a short video showing it in action up on the main site????

How close are we to seeing some install details in the manuals etc?

Any word yet on the cost of the installation kits?

With all the talk about trim sensing, are your units capable of feeding back torque?  And if so, do you envision a future release that will annunciate trim required? (simple software compare if you have the torque feedback)
"

So far no response  :'(

But wait:

I did find this response to someone else a while back:

"Trim sensing and control won't be a launch feature, but we've designed the system to be able to grow to possibly do both over time.

The initial autopilot features - HDG, TRK, horizontal NAV, and ALT hold/change (either with or without an AP74) haven't required either to be able to fly the core airplanes we've been testing with (RVs).

As we add the more advanced vertical modes such as vertical speed and approach modes with the AP76 later on, we'll be doing some deeper R&D in this area.

And obviously, annunciating out-of-trim conditions is a nice feature for the customer too. "

After multiple threads and much argument...

Dynon has not participated in this discussion as far as I know.

Dynon has not released any documentation indentifying all of the features that will be in their autopilots.

Dynon is not a stupid company.

Have any of you guys considered asking Dynon about their plans for trim annunciation?

If I were at the point where it was an issue for me that's what I would do...

 

[PilotKris]

Since question was already asked in another thread (with much discussion), I (stupidly) thought I'd nip-it-in-the-bud and summarize the consensus in the 1st response to this thread to present to Dynon. Boy was I wrong.

Some people (you know who you are) will find something to argue about in anything (even when they actually agree).

All I was trying to do was to let Dynon (since they seamed wishy-washy on the subject) know that there is strong demand for a trim-prompt and that it is also a very good idea to have one as a safety enhancement.

 

[PhantomPholly]

Since question was already asked in another thread (with much discussion), I (stupidly) thought I'd nip-it-in-the-bud and summarize the consensus in the 1st response to this thread to present to Dynon. Boy was I wrong.

Some people (you know who you are) will find something to argue about in anything (even when they actually agree).

All I was trying to do was to let Dynon (since they seamed wishy-washy on the subject) know that there is strong demand for a trim-prompt and that it is also a very good idea to have one as a safety enhancement.

Hehe - how long have you been a pilot, and when did you ever see any of us agree on anything? That would be worth a trip to wherever you are just to see more than two such pilots ...



Having disagreed with you on the necessity of the feature (still unnecessary!), I will now switch to my software development hat and point out that displaying relative force indications in a similar manner to CDI deflection needles could be entirely similar to the code they use for, well, the CDI deflection needles. Thus, if the "smart servos" send the information on torque up the DSAB, it should be a relatively simple matter to generate a display widget showing how hard the servos are working and in which direction (crosshairs, like an ILS). If they are REALLY clever, they could re-use the ILS display code, just pasting the crosshairs somewhere on the engine instruments screen ...