Mike Howard
I'm New Here
I am looking for a compas rose near Omaha Nebraska to calibrate my newly installed Dynon D-100 EFIS. Does any one know were one is located or how to find one?
Check your airport facility directory. I forget the symbol or wording used, but they should be listed there. good luck.
I just used my trusty Boy Scout compass.
Pulled the plane out, turned the prop vertical (make sure your mags are off), then using the compass, lined the plane up with magnetic North, sighting along the VS and the prop. Turn the plane and repeat as needed.
I think there is a reason for not remembering the symbol. I don't see a listing for a compass rose symbol or contraction in the A/FD legend pages.
So, even though I am resurecting a very old thread, Mr. Howards question still stands...."How does one find airports with a compass rose?"
Using a gps, find an open ramp area, taxi fast enough for the gps to begin recording ground speed, then taxi to align your gps track on north, then stop. Now you have a north/south reference to begin your calibration procedure.
The sad reality is that you won't be able to align the airplane to any compass rose that accurately, in the time it will take before the calibration procedure in the Dynon times out...Thanks Bill, but the Silva is not as accurate as I want. I am looking for something that has been surveyed.
I'd use Google Earth on airports near you. You should be able to find a compass rose right quick. Or you could call the airport and ask.
When referring to runway numbers, remember that runways use only 2 digits rounded off. So the numbers can be off as much as 4 or 5?, and even more if they haven't been recently surveyed.
i.e. The actual heading for runway 17 can be anywhere between 165? and 174?. And that is only if the survey is current.
Also, another bug in the works... Our EAA chapter is thinking of doing a compass rose as a project. We talked to our airport engineer, and he said to be accurate (and really, setting up an EFIS should be accurate) we had to do more than just determine true direction. Compass variations can be caused by metal buildings, fuel tanks, and (according to him) even re-bar in the concrete. He suggested doing it on asphalt some distance from any structures. I really don't know how much of a problem these things can cause, but it is something to consider.
While runway numbers can be off by 4-5 degrees, you can look up the true direction. That may be helpful, at least in seeing how accurate your compass is.
Bob
I also used the GPS trick (GNS430W). Calibrating the D180 required four cardinal headings. I was fortunate to have a ramp large enough to do it.
I'm betting it was at least, if not more, accurate than a compass rose.