[petersb]

Having trouble with my EFIS not showing exact level after completing a turn, ( previous thread " GRT HXr horizon tilted" )

I understand that the EFIS does not have a normal gyro but rather rate gyros that calculate level from various sensors including the magnetometer.

Therefore, I assume errors build up that causes the horizon to show a tilt after leveling out, question, how long does it take for the system to recalculate and display the correct horizon ?

This usually shows up after a shallow turn of 90 degrees or more and is enough to cause concern in IFR. The backup Dynon D10A doesn't seem to show this problem even though it is less sophisticated.

I did a sharp steep turn approx 180 degrees today and the tilt was considerable and took quite some time to resolve itself, and yet a steep turn the other way immediately afterwards did not show as much of a tilt.

I have spent a week moving the magnetometer to three different locations, the last in the wing tip, it is aligned to 0.1 degrees in pitch and roll and has passed the calibration.

Numerous calls to the manufacturer, many suggestions but problem still there.

Run out of ideas

 

[ColoRv]

Perhaps it's time to involve an avionics shop like Stein? Let a pro go through your install, do a bunch of pin tracing and see if you've hooked it all up correctly. How did you determine all of the pin connections? A Stein like pro diagram or hunt and peck through the owners manuals?

For reference, I paid Stein's gurus to whip me up a wiring diagram. In a previous life I was in R&D electronics for the big three and consider myself a "has been expert"....and I still had a couple pins in the wrong holes. It happens.

 

[skylor]

EFIS ACCURACY

As I stated in your previous thread, I'm flying a GRT HS/HX (single AHRS) in my RV-8. I have 320 hours on my set up with at least 60 hours of solid "under the hood" IFR training. The EFIS attitude indications have been absolutely rock solid. Yes, I can make the horizon indication lean a bit when doing serious acro, but under any normal flight regime the indications are perfect. The normal flight regime includes steep turns (60+ degree bank 360's included), slow flight, stalls, many approaches, vectors to final, etc.

If you are experiencing problems, there are several areas you need to look at:

1. Be sure your wiring is good, especially power and ground circuits to the AHRS and magnetometer. Poor quality connector contact crimps are a pretty common source of electrical issues for amateur builders).

2. As previously mentioned, be sure your magnetometer is in a good, magnetic influence free location. It sounds like you may have that covered by mounting it in the wing tip.

3. AHRS and magnetometer mounting: Both of these items need to be aligned well with both the airframe level flight attitude and with each other. I have mine within 0.1 degrees on both accounts. Also, be sure you don't have magnetic interference from your mag mounting hardware. I used stainless screws, aluminum nuts, and an all aluminum mounting platform. I've also found that some DB9 connector shells have some magnetism which can be another source of magnetic interference.Make sure your AHRS and magnetometer mounting platforms are rigid enough that they don't exhibit resonant vibration modes or significant flex from flight G loads.

4. Be sure you have solid GPS data feeding the EFIS (although my experience indicates that this is not really that important for solid attitude data).

5. Be sure that your magnetometer wiring is run clear of potential electrical interference sources. I made sure to keep my wiring well separated from strobe wires and COM antennae cables.

6. Make sure that the ground wire for the magnetometer shares a solid ground with your AHRS and EFIS display, such as dedicated grounds run to a dedicated ground block (i.e. Forrest of tabs).

As I've said, I've found the GRT Horizon to be a very solid system, but there are some potential installation pitfalls that can cause performance issues (true with any EFIS system)

Skylor RV-8

 

[TomVal]

Peter,

Based on your previous thread on this problem, at this point, I would suggest you send both the EFIS and magnetometer to GRT for diagnosis.

 

[blueflyer]

me too

I look forward to reading the various opinions on this matter because my Dynon D100 does the exact same thing.

 

[BillL]

< snip >

I used stainless screws, aluminum nuts, and an all aluminum mounting platform. <snip>

Skylor RV-8

Caution - 400 series stainless is a permeable material, 300 is not. I checked the so called stainless screws purchased at the hardware store and a magnet picked them up. I used brass for this reason. Just check your hardware with a magnet and don't assume.

The experts can say what effect this may or may not have.

Why don't you just fly to the factory and get them to check it with hands on? Just a thought.

disclosure: not flying yet

 

[petersb]

Gentlemen, thank you for your replies, some answers...

As I stated in your previous thread, I'm flying a GRT HS/HX (single AHRS) in my RV-8. I have 320 hours on my set up with at least 60 hours of solid "under the hood" IFR training. The EFIS attitude indications have been absolutely rock solid. Yes, I can make the horizon indication lean a bit when doing serious acro, but under any normal flight regime the indications are perfect. The normal flight regime includes steep turns (60+ degree bank 360's included), slow flight, stalls, many approaches, vectors to final, etc.


If you are experiencing problems, there are several areas you need to look at:

1. Be sure your wiring is good, especially power and ground circuits to the AHRS and magnetometer. Poor quality connector contact crimps are a pretty common source of electrical issues for amateur builders).


2. As previously mentioned, be sure your magnetometer is in a good, magnetic influence free location. It sounds like you may have that covered by mounting it in the wing tip.


3. AHRS and magnetometer mounting: Both of these items need to be aligned well with both the airframe level flight attitude and with each other. I have mine within 0.1 degrees on both accounts. Also, be sure you don't have magnetic interference from your mag mounting hardware. I used stainless screws, aluminum nuts, and an all aluminum mounting platform. I've also found that some DB9 connector shells have some magnetism which can be another source of magnetic interference.Make sure your AHRS and magnetometer mounting platforms are rigid enough that they don't exhibit resonant vibration modes or significant flex from flight G loads.

4. Be sure you have solid GPS data feeding the EFIS (although my experience indicates that this is not really that important for solid attitude data).

5. Be sure that your magnetometer wiring is run clear of potential electrical interference sources. I made sure to keep my wiring well separated from strobe wires and COM antennae cables.

6. Make sure that the ground wire for the magnetometer shares a solid ground with your AHRS and EFIS display, such as dedicated grounds run to a dedicated ground block (i.e. Forrest of tabs).

As I've said, I've found the GRT Horizon to be a very solid system, but there are some potential installation pitfalls that can cause performance issues (true with any EFIS system)

Skylor RV-8

That is my main question answered .. is there any tilt left for a brief period, after normal manouvers, no.

Answers to other items discussed :

1. Connector pins came with unit and are crimp type, look OK. Wires between AHARS and magnetometer have been traced and are connected to correct pins

3. Alignment to 0.1 degrees. Used brass hardware on aluminum bracket designed by GRT. DB shell is plastic. Mounting bracket is per GRT design and is mounted on tip rib across spar, you can move bracket slightly as rib flexes, dont think it will move in normal flight. There are three nut plates holding the tip on ( with stainless screws ) close to the magnetometer, GRT says any interference will be cancelled out with calibration.

5. Magnetometer wires go through a common conduit in the wing carrying Nav, landing lights , Heated Pitot......Tech support says no problem.....flight testing was done with these items turned off.

6. All grounds go back to "forest of tabs "

When in "AHARS Maintenance " menu the "x, y, z " readings are mostly within specs, tech help says discrepancies not a problem.

When observing "Magnetic Heading" tech says it should not move more than 2 degrees when manipulating controls etc, mine flickers around more than that when sitting still and doing nothing.

 

[ColoRv]

Have you sent the mag and Adahars back in or better yet swapped with known good units from a buddy?

 

[skylor]

Gentlemen, thank you for your replies, some answers...

When observing "Magnetic Heading" tech says it should not move more than 2 degrees when manipulating controls etc, mine flickers around more than that when sitting still and doing nothing.

If your magnetic heading is moving around when the plane is still, you definitely have a problem. Is the heading moving around that much on the heading tape when the EFIS is in the normal flight modes or are you just talking about the heading data in one of the mag cal menus?? If the former is the case then my guess is the problem is actually with the AHRS, either the unit itself or some installation factor causing the problem. Keep in mind that the magnetic heading display on the EFIS operates more like an HSI in that it is really driven by the AHRS in the short term, but slowly "corrected" by the magnetometer over a longer period of time. Thus short term fluctuations would seem to indicate some sort of instability in the AHRS platform itself.

If you're seeing the heading fluctuation on one of the raw data displays in the settings menu, then I would focus more on the mag itself and/an installation issue with it as the problem.

Skylor

 

[skylor]

Gentlemen, thank you for your replies, some answers...

...DB shell is plastic...

I was actually referring to the steel connector body itself, not the back shell. I have found that these are sometimes magnetized (they are all magnetic).

 

[petersb]

If your magnetic heading is moving around when the plane is still, you definitely have a problem. Is the heading moving around that much on the heading tape when the EFIS is in the normal flight modes or are you just talking about the heading data in one of the mag cal menus?? If the former is the case then my guess is the problem is actually with the AHRS, either the unit itself or some installation factor causing the problem. Keep in mind that the magnetic heading display on the EFIS operates more like an HSI in that it is really driven by the AHRS in the short term, but slowly "corrected" by the magnetometer over a longer period of time. Thus short term fluctuations would seem to indicate some sort of instability in the AHRS platform itself.

If you're seeing the heading fluctuation on one of the raw data displays in the settings menu, then I would focus more on the mag itself and/an installation issue with it as the problem.

Skylor

The jumping around is in the "mag cal menu" not the EFIS display when flying.

Just come back from flying and I officially give up. Shallow turns of one division mark on display (approx half rate one turn ) result in half division mark off level when turn of 45 degrees is stopped. It takes 20 seconds for the display to return to level horizon once wings are leveled.

 

[jclark]

What Skylor said ... Plus ...

The jumping around is in the "mag cal menu" not the EFIS display when flying.

Just come back from flying and the mag heading raw data display has settled down .

IF, your connection to the Magnetometer for some reason is not a good one, as in loose or something on them (I had mine get wet one time), then you will get UNRELIABLE readings from a RELIABLE Magnetometer. When this happen, the EFIS attitude indicator will NOT be correct.

Now, IF your magnetometer and all the connections are correct, then when you do calibration there should be reasonable swing as you make the 380 degree turn. If that data is "out of spec" then all bets are off.

Assuming all of the above, you MAY just have a Magnetometer with a bad part in it and it may need to be sent back for replacement.

Have you discussed this with GRT?

Feel free to contact me offline and I will go through my experience with you.

James

 

[petersb]

IF, your connection to the Magnetometer for some reason is not a good one, as in loose or something on them (I had mine get wet one time), then you will get UNRELIABLE readings from a RELIABLE Magnetometer. When this happen, the EFIS attitude indicator will NOT be correct.

Now, IF your magnetometer and all the connections are correct, then when you do calibration there should be reasonable swing as you make the 380 degree turn. If that data is "out of spec" then all bets are off.

Assuming all of the above, you MAY just have a Magnetometer with a bad part in it and it may need to be sent back for replacement.

Have you discussed this with GRT?

Feel free to contact me offline and I will go through my experience with you.

James

Thanks for the response James.

I did remove DB connectors at both ends and verified continuity but not resistance.

The mag calibration read "valid"

Lots of phone calls to GRT, have done everything they suggested

Only thing I can think of that is out of wack is the bracket the magnetometer is attached to has a slight bow in it. Could this somehow be screwing up the sensors in the magnetometer, not sure how the electronics are mounted inside.

When mounted in the tail the bracket was flat and I still had problems

 

[skylor]

Thanks for the response James.

I did remove DB connectors at both ends and verified continuity but not resistance.

The mag calibration read "valid"

Lots of phone calls to GRT, have done everything they suggested

Only thing I can think of that is out of wack is the bracket the magnetometer is attached to has a slight bow in it. Could this somehow be screwing up the sensors in the magnetometer, not sure how the electronics are mounted inside.

When mounted in the tail the bracket was flat and I still had problems

I suggest 2 things:

1. Get GRT to swap your magnetometer with a new unit. They are really good about things like this.

2. Disassemble the DB9 mag connectors at both end (including removing the pins from the connector) and perform an end to end resistance check on each wire while wiggling the wires and doing gentle pull checks). Or, cut and replace the connector contacts. I know this isn't that easy with a wingtip mounted magnetometer, but it can be done. My experience with my GRT has been so solid that I have to believe you either have a bad mag or a weak crimp somewhere in the system. You might also do the same with the power and ground wires to the AHRS just to be thorough. Low voltage to the AHRS can cause this type of problem as we'll. I have had a few issues with poor AMP PIDG connector crimps causing intermittent low voltage to some of my avionics (and I even used a genuine AMP crimp tool for all my crimps).

Keep at it. You will get it right with a little patient persistence!

Skylor

 

[petersb]

I suggest 2 things:

1. Get GRT to swap your magnetometer with a new unit. They are really good about things like this.

2. Disassemble the DB9 mag connectors at both end (including removing the pins from the connector) and perform an end to end resistance check on each wire while wiggling the wires and doing gentle pull checks). Or, cut and replace the connector contacts. I know this isn't that easy with a wingtip mounted magnetometer, but it can be done. My experience with my GRT has been so solid that I have to believe you either have a bad mag or a weak crimp somewhere in the system. You might also do the same with the power and ground wires to the AHRS just to be thorough. Low voltage to the AHRS can cause this type of problem as we'll. I have had a few issues with poor AMP PIDG connector crimps causing intermittent low voltage to some of my avionics (and I even used a genuine AMP crimp tool for all my crimps).

Keep at it. You will get it right with a little patient persistence!

Skylor

Skylor, thanks for the response .

I believe the AHARS and magnetometer are a match set, but you are probably right, they may have to be sent back. Trying to eliminate any self induced errors before laying it on the manufacturer.

Peter