EFIS Heading Tolerance

[pilot28906]

Hey all,
Have a GRT Sport EX with the remote magnometer.(sp) Just wondering how close the heading indication should be when aligned with the centerline on the runway.

Thanks,
John

 

[DMFenster]

Mine is right on. Have you calibrated the magnetometer?

 

[Ironflight]

Don’t forget to check the tower of the runway number! They can be a long ways off if they haven’t been changed for a long time - our runway 5 (at our airpark) will become runway 7 next time it’s repainted for instance. A little digging can get you the actual runway orientation.

 

[jclark]

"Approximately"

Hey all,
Have a GRT Sport EX with the remote magnometer.(sp) Just wondering how close the heading indication should be when aligned with the centerline on the runway.

Thanks,
John

It is "roughly right".

Variation/Declination can cause a change in what the number painted on the runway SHOULD be. Even when correct, 09 is not exactly 90 degrees but for maybe a year or two (as I recall). Eventually, it is greater than 95 degrees and continually getting closer to 100 degrees. If changed, you could be off by lets say 5 degrees either way. If not changed, you could be off 10 degrees or more.

A good example of how real this is, the runways at Lakeland are no longer 09/27, but instead, as of this year, 10/28. (I saw some tee-shirts that will need re-printing.)

I wonder how often the SMALL airports have "surveys" (or calculations or table lookups) done and as a result update the runway paint.

 

[DMFenster]

Do a slow taxi somewhere and use a gps source (foreflight, or whatever you got) and compare with the heading on the EFIS. You have to be moving for a gps source to output a reliable heading. Keep in mind that if the magnetometer hasn't been calibrated, it will show wildly inaccurate heading info. Contact me offline and I can walk you through the calibration. Takes 5 minutes of taxing around in circles...

 

[pilot28906]

Thanks all for the info. Yes I did perform the calibration per the instruction and it seems to be off around 7-10 degrees from runway marking. The info from the facility directory for runway 26 says for alignment 255* (251* True). However, I think it has been at least 25 years sense the last number change on the runway; maybe 30 years. I will do the slow taxi with GPS to see how close that is. Thanks for the info.

 

[maxmirot]

My AFS EFIS says use a compass rose to calibrate the magnetometer. I think the nearest one is 250 miles away. I used a a good hand held compass so I have 10 degree error.

 

[gasman]

Don’t forget to check the tower of the runway number! They can be a long ways off if they haven’t been changed for a long time - our runway 5 (at our airpark) will become runway 7 next time it’s repainted for instance. A little digging can get you the actual runway orientation.

The magnetic north is moving towards Siberia at over 25 miles per year.
And it can actually flip with the south pole.... Not Good!

Let's hope this does not fall under "Climate change."