ADAHRS Installation - Yak 50

[cdm1]

Hi,
I have recently had a Dynon Skyview system fitted to my Yak 50 however I suspect the ADAHRS unit has been installed incorrectly. The installer assures me that he followed the directions and that the unit was functioning correctly when tested however I am noticing a swing of approximately 24 degrees in the DG that is in direct correlation to the control stick position. I.e, between full forward and full aft stick the HDG changes by approximately 24 degrees.  I suspect there is some kind of magnetic interference from the elevator control cable which runs approximately 8-10cm away from the ADAHRS unit. Having said that the cable itself is of consistent density and dimensions and its position is not actually moving up or down/side to side relative to the ADAHRS unit. Rather the cable is moving lengthwise from front to back.

The yak is a single seat aircraft and quite limited for space. Could it be the cable causing the interference?  If so, is there any way to counter this without moving (or removing) the ADAHRS unit? Can the unit, or the cable be shielded in some way?

Thanks for your help.

Regards,
Chris

 

[jakej]

You most likely have it figured out already, looks like the install was done that way because it was easy for him to do :-?

8 to 10cm (3+" to 4") is way too close, you need a more benign, magnetically, location for the ADAHRS - finding a better location with a hand held compass is one way

Jake J

 

[cdm1]

Thanks Jake. If there is absolutely no alternative then I will move it however I would like to leave this to the last resort if possible. Do you think that the elevator cable would be the problem?

PS: Sorry for the massive photo.

Cheers

 

[jakej]

Sure do & the nearby nutplates, what else in terms of ferrous metal is close by ? anything behind or under mount ?

Jake J

 

[dlloyd]

Dynon has said in the past that non-moving objects interference can be adjusted out. This is probably true with your cables. But any moving crimped end near the ADAHARS will cause a problem. Passenger seatbelt fastened or unfastened and slack causes a difference in my plane. Right now I keep the unused belts fastened and tight but moving the ADAHARS will be a permanent fix.

 

[cdm1]

Dynon has said in the past that non-moving objects interference can be adjusted out.  This is probably true with your cables.  But any moving crimped end near the ADAHARS will cause a problem.  Passenger seatbelt fastened or unfastened and slack causes a difference in my plane.  Right now I keep the unused belts fastened and tight but moving the ADAHARS will be a permanent fix.

Thanks dlloyd,

The aircraft only has one seat and the unit is mounted approximately 1m behind the cockpit. Given there is a direct correlation between the stick position and the HDG I assume it must be the cable or some part of the cable that is perhaps crimped as you said. Being 1m away from the cockpit I assume that it's not the control stick itself. Is there an effective way to insulate the cable or create some kind of magnetic shield?

Cheers

 

[cdm1]

Sure do & the nearby nutplates, what else in terms of ferrous metal is close by ?  anything behind or under mount ?

Jake J

Thanks Jake J,

There is nothing directly behind or above the unit. The only dynamic item nearby is the elevator cable that's about 8-10cm away and then the opposing elevator cable which is about 30-40cm away (lower). As the tail tapers in moving the unit further back would only place it closer to the cables...moving the unit further forward would put it closer to a large metallic air bottle. If all else fails there is one other possible position that I can think of (slightly forward and higher) however I'm waiting to hear back from the installer as to why he didn't use that in the first place.

Cheers.