. MaxFledglingFacts & Sunday Quiz: Aero Navigation & the "Declination Diagram"!

MaxSez: First & Last Quiz of a Sunday Series;

Intro: Aeronautical Maps/Charts (synonymous term) come in many forms. They are almost all UTM graphics representations of the earths surface draw to scale on a plane (flat surface) with “Grid North” at the top… The Poler Projection Chart is an exception it’s spherical. The IF Chart is a good example of a typical UTM aerial Chart although it does not include Marginal Information nor Horizontal or Vertical Grid Delimitation among other things. Unlike most Aero Charts the IF Chart has been “KISS’ed”, it’s oriented to “Magnetic North” at its top so it’s not necessary to extrapolate. If you now or in the future intend to become an aviator or outdoorsman you’ll need to understand magnetic deviation when chart reading while route planning.

Background: In the real world when Flight Planning one routinely Plan’s the route on an aerial chart like a Sectional. As mentioned above, directions on aerial charts are measured & formatted utilizing “Grid North” for orientation (top of the map). Most aircraft have navigation devices/avionics which provide direction/headings utilizing “Magnetic North” orientation to include most GPS devises which are factory set or user set to “Magnetic North”. Below find a “Declination Diagram” found on most aero charts, it graphically represents the declination utilizes in its development. The Declination Diagram below depicts the variance between True North, Grid North and Magnetic North as calibrated for its region. The problem below will require you to understand the foregoing and apply the appropriate heading during the pre-flight planning and in flight directional guidance:

QUESTION; You’ve planned a route utilizing a Sectional Chart, the first leg is 25 miles long to fix Peanut, the “Grid North” Heading is 182 degrees, measured by protractor off your Chart. Utilizing the Charts Declination Diagram above, what heading would you fly to Fix Peanut with accuracy utilizing a stand by compass or in an aircraft with modern avionics/ NavAids. Pls answer by comment, First correct answer gets a Golden Peanut!

(Note: Student Pilots, Licensed Pilots & Boy Scouts need not reply).
(Tip; Remember the “LARS” Rule.)


I’m giving this a few more hours, and then I’m giving you the answer regardless!



@MJames… By default, knew you had the answer! Congratulations, Max


not sure if I’m reading the chart correctly or not, is the chart depicting that at 70 miles, the difference between the magnetic north and grid north is 4 degrees?

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Grid convergence for center of sheet: does that mean starting at the center of the sheet, every 20.5 miles adds 1 degree of difference?

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And if what I’ve asked above is correct, is the goal to then figure out the difference at 25miles out? (I have to break it down into easier terms lol)

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MaxSez: @CaptainPlanet… The Declination Diagram show variations only not distance.
Your correct the variation is 4 degrees from Grid North to Magnetic North,
The 4 degree variance from grid to Mag should be added to the 182 Grid heading measured on the map by protractor to get your mag heading. Thus your Mag heading flown is 186 deg (Answr). Reread the annotations ; From Grid add or subtract based on the orientations depicted. Mag Left of Grid, Add… Mag Right of Grid, subtract. Nemonic: LARS. The 25 miles was a distractor it has no effect on the out come which is “correct Magnetic heading” only. No geometry today, maybe next time, KISS to start.

Problem with the explanation PM me. Thanks for trying !


Interesting information thank you.

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Thanks max, learnt something new today.

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