GRT HXr horizon tilt, spoke to everone, tried everything

The Problem : After performing a shallow turn ( half rate turn, one division on display) of approx 30 degrees or more, on leveling out, HXr horizon displays a turn in the opposite direction.

AHARS is installed behind the display

Magnetometer has been tried:

1: Behind the baggage bulkhead
2: On the shelf area under the vertical fin.
3: Two locations in the wing tip.

Greg of GRT was kind enough to replace both the AHARS and the magnetometer, however, the problem remains. He advised me that during a shallow turn the algorithm used to calculate level is biased to the magnetometer data. It would appear the problem is something to do with the magnetometer.

Have sent DEMO files to GRT, they could not find anything wrong.

This issue dose not occur in smooth air. Makes you think either a loose connection or movement of the magnetometer in its mount, cant detect either.

Wiring between the magnetometer and the AHARS has been tested both for correct pin and resistance, all measured 1.5 ohms, so no loose connections ( wiggled wires ).

Magnetometer calibrates perfectly with only minor deviations displayed during calibration.

Only discrepancy I can find is during recommended testing the Mag X value is 800 when faced north, it should be over 1000.

This problem has been going on for two years, I would be reluctant to fly in IFR with this problem, wondering if anyone else is having the same problem ?

I will be at Airventure if anyone has any thoughts.

Peter

Peter,

I'm assuming this is the earlier magnetometer, correct? You might ask Greg about upgrading to the magnetometer they released about the time of SNF.

I'm a little suspect of 1.5 ohms on the wiring. It should be 0, but it may just be your meter. Does your meter show 0 or 1.5 when you short the leads together?

What is Greg's comment about the 800 X reading when facing north?

You say there are "minor deviations" during calibration. The calibration graph has two white lines that are parallel to the x axis (one above it and one below it). Are your deviations less than these? For proper operation they need to be.

For reference, the two RV7's I've worked with mounted the magnetometer in the port wing tip.

In my Europa I also had magnetometer problems. I relocated the magnetometer and did a new calibration but with poor results. I redid the calibration several times and finally it calibrated with good results. When I did the calibration I did it with the engine running and all avionics and electrics that are normally on during flight turned on. I figured that was the environment it was seeing in flight so that is how it should be calibrated. I did my calibration on grass because that's where I'm based. But that avoids any influence from metal in a concrete pad. Carlos (former GRT support guy) helped me with calibration on a paved pad and engine off but that failed. So perhaps you should try away from buildings, and on grass. I just use the magnetic heading in my GNS430 to find north while taxiing and then turn left.

Maybe you can get an idea from all this. I will be at OSH in HBC and would be available to look at the mag cal curve if you like.

Jim Butcher
Europa XS N241BW

h&jeuropa said:

Peter,

I'm assuming this is the earlier magnetometer, correct? You might ask Greg about upgrading to the magnetometer they released about the time of SNF.

I'm a little suspect of 1.5 ohms on the wiring. It should be 0, but it may just be your meter. Does your meter show 0 or 1.5 when you short the leads together?

What is Greg's comment about the 800 X reading when facing north?


Jim Butcher
Europa XS N241BW

Click to expand...

Jim

Thanks for the reply

Magnetometer was replaced the Greg of GRT at last years Airventure.

Ohm meter does read 0 when shorting leads.

Spoke to Todd of GRT about the 800 reading, he didnt seemed worried about it.

The magnetometer readings stay within the two lines, pretty much no deviation during the calibration turn.

Calibration was done on a helipad Tarmac area using GPS for magnetic north and running the engine to make the calibration turn.

Plan on arriving Airventire first weekend, will look for your plane


Peter

petersb said:

The Problem : After performing a shallow turn ( half rate turn, one division on display) of approx 30 degrees or more, on leveling out, HXr horizon displays a turn in the opposite direction.

AHARS is installed behind the display

Magnetometer has been tried:

1: Behind the baggage bulkhead
2: On the shelf area under the vertical fin.
3: Two locations in the wing tip.

Greg of GRT was kind enough to replace both the AHARS and the magnetometer, however, the problem remains. He advised me that during a shallow turn the algorithm used to calculate level is biased to the magnetometer data. It would appear the problem is something to do with the magnetometer.

Have sent DEMO files to GRT, they could not find anything wrong.

This issue dose not occur in smooth air. Makes you think either a loose connection or movement of the magnetometer in its mount, cant detect either.

Wiring between the magnetometer and the AHARS has been tested both for correct pin and resistance, all measured 1.5 ohms, so no loose connections ( wiggled wires ).

Magnetometer calibrates perfectly with only minor deviations displayed during calibration.

Only discrepancy I can find is during recommended testing the Mag X value is 800 when faced north, it should be over 1000.

This problem has been going on for two years, I would be reluctant to fly in IFR with this problem, wondering if anyone else is having the same problem ?

I will be at Airventure if anyone has any thoughts.

Peter

Click to expand...

Wondering if Stein has seen this problem ?

Peter,

The resistance in the wires is suspicious to me. Is it possible to make up a temporary cable from the mag to the AHRS for a test?

Also the mag and AHRS are mounted so each axis is parallel to each other, correct? And non magnetic mounting hardware (nylon or brass - some stainless is magnetic) is being used.

I'd try a calibration on grass with engine and all normal electrics turned on to be sure no interference from metal in the tarmac.

Do you have corrections loaded for TAS? If so, try without them. I've seen funny situations with those corrections.

Running out of ideas. Keep us posted of your progress.

Jim Butcher

h&jeuropa said:

Peter,

The resistance in the wires is suspicious to me. Is it possible to make up a temporary cable from the mag to the AHRS for a test?

Also the mag and AHRS are mounted so each axis is parallel to each other, correct? And non magnetic mounting hardware (nylon or brass - some stainless is magnetic) is being used.

I'd try a calibration on grass with engine and all normal electrics turned on to be sure no interference from metal in the tarmac.

Do you have corrections loaded for TAS? If so, try without them. I've seen funny situations with those corrections.

Running out of ideas. Keep us posted of your progress.

Jim Butcher

Click to expand...

Jim

Appreciate your suggestions.

For the wire resistance I ran a wire from the magnetometer "D" plug to the AHARS "D" plug

Mag is mounted in the wing tip parallel to the rib, AHARS attached to rails attached to firewall and bulkhead behind instrument panel, both parallel to line of flight. All hardware for Mag attachment is brass.

Yes I do have TAS corrections, never thought that would cause a problem, will try without

In regards to TAS, the tilt shows up at low altitudes, around 3000 feet, and not at 6500 feet, I put this down to light turbulence at the lower altitude as it was smooth at 6500. Will
Test tomorrow

Regards Peter

D-sub

I'd suggest you check that the D-sub pins are fully seated in the connectors and won't push back when installed. If not seated the pins can be just touching on the ends but not coupled properly. I've seen that several times create an intermittent problem.
Good luck
Tim

Peter,

You state that both are parallel to line of flight. Are you certain the mag and the AHRS are parallel to each other in all three axis? It's easy to have some tilt or yaw which will cause errors.

For wire resistance, you ran a temporary wire from a pin on the AHRS dsub and measured the resistance between the temporary wire and the appropriate pin on the mag dsub, is that correct? I still don't buy 1.5 ohms. If you take temporary wire twice the length of the wire between the AHRS and mag and measure the resistance of it with your meter do you get 0 ohms or 1.5?

I'm betting on the TAS corrections, but not a lot of cash

Jim Butcher

For those who are following this thread and thinking that aligning the magnetometer and the AHARS so they are the same in 3 axes, I tend to agree. That's why GRT has come out with their new "Adaptive AHARS" which supports their (also new) adaptive magnetometer. No more heavy duty labor boresighting the alignment of the boxes.

I just sent my GRT gear in for upgrade as I had no desire to go through the boresighting process in our dual EFIS configuration. Needless to say, I'm really, really looking forward to getting the new hardware back so I can move forward with the rest of the installation.

(Now if only I could get GRT to provide some sort of compensation for so shamelessly plugging their equipment...)

tim2542 said:

I'd suggest you check that the D-sub pins are fully seated in the connectors and won't push back when installed. If not seated the pins can be just touching on the ends but not coupled properly. I've seen that several times create an intermittent problem.
Good luck
Tim

Click to expand...

Tim

Yes, checked security of pins when doing the resistance check

Resistance reading of 1.5 ohms was an error in the meter, so actual corrected reading is 0 ohms.

If the outboard wing rib is parallel to aircraft centre line then Mag and AHARS are parallel. Mag is .1 degree from level with fuselage cross beam behind seat and when in AHARS maintenace page AHARS is level with cross beam.

I have been very diligent in checking ever possibility regarding installation error, in fact I would welcome finding one, I'm sure it has to be my fault somehow, however, can't find anything


Peter

This is a weird one...and when they typically are this weird...it's typically some sort of install problem (like a loose pin, a tiny shorted hair of a shield, bad crimp, etc..). Gremlins that only appear in rough air typically are not unit related (these new solid state systems don't have many if any moving parts to get jostled around).

I'd start by powering it up on the ground, then walk around grabbing every lead / harness/ wire and yank them around a bit to see if you can induce any strangeness in the display.

While it may be possible to have a hardware problem, at this point it's less probable (especially since they've replace several units already)...that points to something else as most likely. Also, while we joke about the "boresight" of Mag's to AHRS, the reality is none of them out there are quite that sensitive to minor install alignments. That said, it pays to double check that everything is facing the same direction (both upwards, downwards, sidwards, backwards, whatever) because more than once we've seen people think they had everything correct, yet still manage to have the compass upside down. Not saying that is the issue at all, just something to double check.

Sorry I can't be a bigger help at the moment, but too many variables to try and troubleshoot without seeing the install.

Just my 2 cents as usual.

Cheers,
Stein

SteinAir said:

This is a weird one...and when they typically are this weird...it's typically some sort of install problem (like a loose pin, a tiny shorted hair of a shield, bad crimp, etc..). Gremlins that only appear in rough air typically are not unit related (these new solid state systems don't have many if any moving parts to get jostled around).

I'd start by powering it up on the ground, then walk around grabbing every lead / harness/ wire and yank them around a bit to see if you can induce any strangeness in the display.

While it may be possible to have a hardware problem, at this point it's less probable (especially since they've replace several units already)...that points to something else as most likely. Also, while we joke about the "boresight" of Mag's to AHRS, the reality is none of them out there are quite that sensitive to minor install alignments. That said, it pays to double check that everything is facing the same direction (both upwards, downwards, sidwards, backwards, whatever) because more than once we've seen people think they had everything correct, yet still manage to have the compass upside down. Not saying that is the issue at all, just something to double check.

Sorry I can't be a bigger help at the moment, but too many variables to try and troubleshoot without seeing the install.

Just my 2 , cents as usual.

Cheers,
Stein

Click to expand...

Stein, thanks for responding, will be at Airventure if you would like to look.

I install and trouble shoot alarm systems etc for a living, so I have applied some of those techniques you suggested, no luck unfortunately.

The reason I checked the dsub connectors is I thought the same as you, bad connection, unfortunately could not identify any.

Thanks for your response

Peter

petersb said:

Stein, thanks for responding, will be at Airventure if you would like to look.

I install and trouble shoot alarm systems etc for a living, so I have applied some of those techniques you suggested, no luck unfortunately.

The reason I checked the dsub connectors is I thought the same as you, bad connection, unfortunately could not identify any.

Thanks for your response

Peter

Click to expand...

You know, there's really not much to this,

Two boxes need mounting, aligned with each other and away from magnetic influence, simple.

Then approx five wires need to connect them together, that's it.

What could possibly be going wrong ! Is there some software setting that I have wrong ?

This is getting frustrating.

Peter

Suggest you check the magnetic field around the magnetometers. There are a few apps for both Apple and Android that are free. I had a problem with my magnetometer mounted in the wingtip of my RV4. Similar issues of calibrations errors plus a few others. This happened after everything was fine for a year. Greg walked with me out to the N40 and we troubleshot together. Once we checked the magnetic field around the magnetometer it was high. I unmounted the magnetometer and had a buddy hold it a couple feet from the wingtip in the correct orientation and then everything was fine. Using the phone app I was able to find a better position in the wingtip and after remounting it in the new location everything worked perfectly. For the trip home I actually taped it down inside the wingtip at a different position from the original mounting point and all was good until the perminent remount done at the hangar.

Capflyer said:

Suggest you check the magnetic field around the magnetometers. There are a few apps for both Apple and Android that are free. I had a problem with my magnetometer mounted in the wingtip of my RV4. Similar issues of calibrations errors plus a few others. This happened after everything was fine for a year. Greg walked with me out to the N40 and we troubleshot together. Once we checked the magnetic field around the magnetometer it was high. I unmounted the magnetometer and had a buddy hold it a couple feet from the wingtip in the correct orientation and then everything was fine. Using the phone app I was able to find a better position in the wingtip and after remounting it in the new location everything worked perfectly. For the trip home I actually taped it down inside the wingtip at a different position from the original mounting point and all was good until the perminent remount done at the hangar.

Click to expand...

Mike, thanks for your response. I have tried two locations at the wing tip, the first at the main spar and the second halfway back from the spar to the trailing edge. Both calibrated successfully, however, the spar area was better, it showed very minor deviations during the calibration. I did try the iPhone mag app.

You can see I have done due diligence in finding installation errors, but without luck.
The only other thought I have is the wiring is bundled with other wiring from the fuel selector to firewall and under the panel, possible interference. GRT says this should not be a problem, I did shut off all but avionics to check , without success

Peter

Peter - since you have been 'going the extra mile' in troubleshooting, I'll suggest another means of troubleshooting... Pull your magnetometer and pull its pins from the AHARS. Tie the magnetometer on top of the AHARS with double-sided velcro so you know they are exactly aligned. Fabricate a foot long harness from AHARS to magnetometer. Calibrate and fly. If this isn't feasible, mount the magnetometer somewhere easy, like on the glareshield. Anywhere to remove the magnetometer wiring from the equation and to ensure both mag and AHARS are in alignment.

BTW, the first magnetometer I installed was aligned with the AHARS, or so I thought. I made the mistake of believing a structural member in the aircraft was actually mounted parallel to the lateral axis of the airplane. Big mistake. I suspect somewhere along the line something as simple as a similar assumption has been made. It's so achingly easy to do... When in doubt, bring in another set of eyes to review; often we miss the easy stuff because we're looking for the trees instead of the forest.

Canadian_JOY said:

Peter - since you have been 'going the extra mile' in troubleshooting, I'll suggest another means of troubleshooting... Pull your magnetometer and pull its pins from the AHARS. Tie the magnetometer on top of the AHARS with double-sided velcro so you know they are exactly aligned. Fabricate a foot long harness from AHARS to magnetometer. Calibrate and fly. If this isn't feasible, mount the magnetometer somewhere easy, like on the glareshield. Anywhere to remove the magnetometer wiring from the equation and to ensure both mag and AHARS are in alignment.

BTW, the first magnetometer I installed was aligned with the AHARS, or so I thought. I made the mistake of believing a structural member in the aircraft was actually mounted parallel to the lateral axis of the airplane. Big mistake. I suspect somewhere along the line something as simple as a similar assumption has been made. It's so achingly easy to do... When in doubt, bring in another set of eyes to review; often we miss the easy stuff because we're looking for the trees instead of the forest.

Click to expand...

Good thought, will relocate to glare shield as you suggest, will also eliminate possible electrical interference.

Just came back from another air test and confirmed it is related to turbulence.

Was at 4500 in smooth air and it worked perfectly, however at 3000 in light turbulence the problem was back.

Now this should suggest loose mag mount or bad connection somewhere both of which I have strenuously eliminated. Unless it is in the mag circuit board, however, I have tried two mags courtesy of GRT.

Unfortunately GRT is busy preparing for Airventure and Greg is laid up. I don't like to bother them at Airventure as they are there to sell and promote their business, so it may be a while before this is hopefully resolved

Peter