OK, now all you salty pilots out there, take it easy with us newbie non-pilots, but...I'm getting ready for weekend two of my Observer training at Mission Aircrew School, trying to do some route planning ahead of time, and am now confused.
I know the "East is least and West is best" saying...so I know you subtract the magnetic variation from headings between zero and 180, and add the variation to headings between 180 and 360. BUT...I'm flying darn near directly due south...my departure airport is equidistant from the two mag variation lines on the sectional...the 10-degree variation dotted line is 35 nm to the east of my departure airport, while the 9-degree variation dotted line is 33 nm to the west of my departure airport.
Do I add 10 degrees or 9 degrees. And, on a 21-nm flight to the NW corner of a grid square, will that degree make a gigantic difference? I guess because the mag variation lines are running at angles, as I fly south I'm getting closer to the 9-degree line and further from the 10-degree line...so do I do 9?
Help! ???
Your 1 degree difference will make a difference of 0.37nm...not all that much in the grand scheme of things.
The variation from winds aloft will be greater, and I've not met many pilots who can hold a DG heading to 1 degree...and if it's a G1000 (because it has an actual numeric readout of heading), well, then it's all moot because the GPS will guide you in anyway.
Quote from: JeffDG on July 22, 2011, 02:35:34 AM
and if it's a G1000 (because it has an actual numeric readout of heading), well, then it's all moot because the GPS will guide you in anyway.
It is...it's a C-182 Glass. But I'm also pretty certain the instructor is going to make sure I can plan and navigate without relying on the G1000. Last week, I had an objective about 16 miles north of the field, so I got us pointed to the VOR, flew over it so that it "zeroed," then came back around and did 4 DME...calculated we would be over the objective in 2:30...and darned if it didn't show up off the left side of the aircraft at 2:31...wow!
So I think I'll do the 9-degree given that I'm flying toward that variation line, since as you say it kinda doesn't matter much anyway.
THANKS for the quick reply!
You could always just do 9.5 degrees... ;)
Your pencil and paper nav talk pretty much boggled my mind. I'm an ole avionics tech and am wondering what DME is in the 182 you are driving?
I recently found this and was wondering if anyone else thought it would be useful. Thoughts?
http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp
^^^I mention that site when I teach navigation so that students know where to look for current magnetic declination. USGS topo maps show the mag declination but many maps are old and the declination has changed significantly since the map was published. Of course, even more maps don't even show the declination.
Here is a site mentioned in a recent CAP Talk thread that has a number of kml files that are Google Earth interfaces for many functions on the NGDC website and other useful functions. "MagDec" allows the user to click on a point in Google Earth and get the current magnetic declination and rate of change at the point. http://www.metzgerwillard.us/EarthSurvey.html
Mike
Quote from: ccrop on July 24, 2011, 05:59:28 AM
Your pencil and paper nav talk pretty much boggled my mind. I'm an ole avionics tech and am wondering what DME is in the 182 you are driving?
OK, so I should have been more clear. The 182 was what I expected to fly this weekend (and, it was!). The previous weekend we were all working in the GA-8, and I was sitting in the right seat...that's when I did it with a scribble sheet and an E6B.
Got in two more flights this weekend, and got signed off. Woo-hoo!
And thanks everyone for replying...it was useful and helpful stuff.