Dual Skyview First Flight

[thibault]

Flew my Lancair 360 this AM for the first time with the all new panel.

Skyview configuration is 10" display with single ADAHRS and backup battery, 7" display with single EMS and backup battery, SV-GPS-250, Dynon heated AOA pitot probe, plus pitch and roll servos.

These are backed up with steam airspeed (separate pitot), altitude (common static), and vacuum attitude indicator.

Everything works out of the box execpt the Dynon compass swings 10 degrees to the left whenever the Dynon pitot heat cycles on. When the pitot heat cycles off, the compass swings back to normal. If I pull the pitot heat breaker, the compass is steady all the time.

I do have the pitot heater power lines bundled parallel to the ADAHRS-to-display SV net wires for about 3 feet. I guess the 10 amps of pitot heat DC are upsetting the DC supply to the ADAHRS, so I will re-route the pitot heat supply wires.

Has this problem already been seen to date? If so, does anyone have a recommendation about how far to separate these wires from SV net wires? One alternative path would be right next to the SV net wires leading to the servos. Will that be just as bad? If so, I guess there can't be any significant current flowing in wires near the SV net power and ground wires.

Would twisting the pitot heat power and ground wires together likely help?

Welcome any suggestions.

 

[dynonsupport]

Tom,

How close do the high current pitot heat wires get to the ADAHRS itself?

 

[thibault]

No closer than about 4.5 feet

 

[dynonsupport]

That is odd indeed. Only the magnetic sensors themselves are affected by magnetic fields, not the wires that go to the ADAHRS. 4.5 feet is pretty far away. Our generic advice would be to reposition some the heated pitot wires if you can, even though they're not really all that close to the ADAHRS in the first place.

 

[tl9039]

While installing the sub connector on the network cable I checked the screws(finger fastners) to ADHARS and found they where magnetic. Did I receive the wrong fastners or is this OK ?
Thanks

 

[dynonsupport]

There are ferrous metal in the connectors, but we've tested them and they do not measurably affect the ADAHARS. However, if you tested with a magnet, you may have magnetized them, and in that case you might have turned it into a magnet itself, which could conceivably have an effect. In that case you'd need to demagnetize the connector with a degausser.

 

[meljordan]

Tom,

How far away from the ADHARS do you have your battery mounted? Also, what else is back there, master relay, starter relay, strobe supply? Anything else back in the tail cone with the ADHARS, like antennas?

Mel

 

[thibault]

Mel,

The battery is in the engine compartment. The only thing back there that you mentioned is one of the comm antennas. It is on the other side of the fuselage, probably two feet away. The other comm antenna is in the vertical stab. I have not noticed that transmitting causes any changes in ADAHRS output.

The ADAHRS correlation I do see is that when the Pitot Heat C/B is pushed in and the ammeter shows a ten amp rise (the heater turning on), the compass swings. When the draw goes back down (after about 10-15 seconds) the compass swings back where it belongs. Pull the C/B and the compass does not swing at all.

Doesn't it sound like the current flow in the pitot heat wires is upsetting the regulated DC going to the ADAHRS?

Thanks,

Tom