D10A and remote compass "error"

[edwardsjo]

anyone help or seen this...  repositioned the compass sensor to the wingtip. aircraft is rv-4 taildrager.  recalibrated usng the procedure in the install manual.  flew it for first time time today.  although compass is seems bob on when on the ground, in the air it is by varing amounts way out...

Today heading south it was indicating 300 instead of about 230 for instance...
Did the calibration at the airports compass swing area - and as i mentioned all good on the ground.

When doing the calibraton - do we need to do it with the aircraft oin a level attitude or should it be ok when sitting on the ground ?

When i installed the remote compass i followed the instructions to the letter and it is mounted very very close to the required tolerances..

With this error... we were getting huge winds aloft reported by the D10A.

cheers

Any ideas ?

 

[dynonsupport]

Where are you in the world, and what values did you program in for your inclination and intensity values?

The aircraft's can be calibrated with the tail down, but, it's important that the compass orientation match in the instrument orientation.

Also, are the tabs down and the connector forward?

 

[edwardsjo]

In the UK, about 30 miles south of Birmingham.  I used the values for Birmingham from the recommended site.  Not near the aircraft now - but was going to recheck the figures as soon as I can get to it.

Yes the connector is certainly to the front.  I used a digital measure to ensure I got the angle (between sensor and D10A) within tol, but again have not rechecked since calibration.

Don't understand the tabs bit - what am I looking for please ?

Thanks for the quick reply.

 

[edwardsjo]

Ok, did go to the aircraft yesterday evening.  Checked the settings and discovered that the MAGINC was incorrect by a long way (about 70 degs)... I know why - and so had been wrong for more than a year, and before we had moved the sensor.

So looks like I'll need to do the calibration again.  

Is MAGINC only used during the calibration process ?  Once I'd changed the setting to the correct value, the shown heading did not change.

Had a look at the install manual and the tabs are down...

Cheers

 

[edwardsjo]

Not tested in the air yet, but revisited the whole installation and found the sensor was not mounted exactly on same plane as the D10A. Repositioned to within 0.2 deg and recalibrated..

 

[dynonsupport]

Maginc and magint are only used during calibration - but if they're significantly wrong at that time, the heading will never work right until the calibration is redone with accurate values.

 

[SammyQ2]

Support, can you elaborate on your statement "The aircraft can be calibrated with the tail down, but, it's important that the compass orientation match in the instrument orientation"? Does this mean you are supposed to tilt the compass?

My winds aloft numbers have always been way off. I got some good help from the guys in the booth at Oshkosh and they pointed out I was using the wrong numbers from the NOAA page.

I have a taildragger and I am going to go through the entire procedure again and need to understand more about the planes attitude during calibration.

 

[jakej]

What DS is saying is that the mounting angle or tilt for eg, say 2 degree of the EFIS, is the same for the Magnetometer ie 2 degree off horizontal so that it is in effect 90 degree to the face of the EFIS - hope I've made this is clear enough ?

Jake J