CFI-to-CFI Newsletter - Volume 13 Issue 4 - 27
CHART CHALLENGE
VARYING MAGNETIC VARIATION
WHY IS THERE A DIFFERENCE BETWEEN THE MAGNETIC VARIATION FOR
AN AIRPORT AND THE VOR LOCATED AT THE SAME AIRPORT?
When a navigational aid (navaid) is first constructed, the antenna is
physically oriented to true north. Then a potentiometer or position sensor
adjustment is made to slave the navaid with magnetic north. This action
matches the isogonic line making it agree with a magnetic compass.
Initially these two values are the same, but the magnetic variation of the
earth changes at differing rates depending upon location and time.
Once a navaid goes into service, it is available 24 hours a day, 365 days a
year. And, although the FAA performs periodic maintenance on navaids,
an adjustment to match the isogonic value requires a total shutdown
of the equipment, plus recertification and flight check verification. So,
readjustments are made when a navaid is out of tolerance by at least +/-6
degrees. GPS databases use a magvar model to calculate the most up-todate
magnetic variation.
Note, on VFR charts, a small open circle indicates the navaid location when
collocated with an airport icon. Airports are plotted in their true geographic
position unless the airport symbol conflicts with a navaid at the same location.
In such cases, the airport symbol will be displaced, but the relationship
between the airport and the navaid will be retained.
If you notice a charting error, please bring it to the FAA's Aeronautical
Information Services attention. Call: 800-638-8972 or use the web portal for
aeronautical inquiries.
Be safe!
Machteld Smith is a senior editor for the AOPA Air Safety Institute.
She holds a commercial pilot certificate with multiengine, instrument, and
seaplane ratings. She loves flying seaplanes and the adventure of landing on
rivers and lakes!
Email: machteld.smith@aopa.org
BY MACHTELD SMITH
https://nxt-staging-books.s3.amazonaws.com/nxtbooks/aopa/cfi_vol13issue4/src/Chart_Challenge_VOR_Rose.jpg
https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/Aeronautical_Inquiries/
CFI-to-CFI Newsletter - Volume 13 Issue 4
Table of Contents for the Digital Edition of CFI-to-CFI Newsletter - Volume 13 Issue 4
CFItoCFI Newsletter—Volume 13 Issue 4
CFI Notes
From the Editor: Collision Avoidance Resource Center
Crew Resource Management for CFIs
ASI Message: Inspiring Pilots
CFI News
CFI Tips: We're Only Human—The Human Factors of Aircraft Cockpits
New CFI: Things I Wish I Had Known as a New CFI
Checkride Checklist: DPE Answers for Students and CFIs
Accident Case Study: Hazardous Attitudes
Chart Challenge: Varying Magnetic Variation
Pilot Short Story: The French Disconnection
You Can Fly: Flight Training's Hidden Gold—Find It In AOPA's Flight Training Advantage
Safety Quiz: Night Ops
CFI Tools: Be Winter Weather Wise—Prepare for the Cold Weather Season
Chief's Corner: Eating Humble Pie
ASI Safety Tip: Aiming Point
CFI-to-CFI Newsletter - Volume 13 Issue 4 - CFItoCFI Newsletter—Volume 13 Issue 4
CFI-to-CFI Newsletter - Volume 13 Issue 4 - CFI Notes
CFI-to-CFI Newsletter - Volume 13 Issue 4 - From the Editor: Collision Avoidance Resource Center
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 4
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Crew Resource Management for CFIs
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 6
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 7
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 8
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 9
CFI-to-CFI Newsletter - Volume 13 Issue 4 - ASI Message: Inspiring Pilots
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 11
CFI-to-CFI Newsletter - Volume 13 Issue 4 - CFI News
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 13
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 14
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 15
CFI-to-CFI Newsletter - Volume 13 Issue 4 - CFI Tips: We're Only Human—The Human Factors of Aircraft Cockpits
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 17
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 18
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 19
CFI-to-CFI Newsletter - Volume 13 Issue 4 - New CFI: Things I Wish I Had Known as a New CFI
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 21
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Checkride Checklist: DPE Answers for Students and CFIs
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 23
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 24
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Accident Case Study: Hazardous Attitudes
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 26
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Chart Challenge: Varying Magnetic Variation
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 28
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Pilot Short Story: The French Disconnection
CFI-to-CFI Newsletter - Volume 13 Issue 4 - You Can Fly: Flight Training's Hidden Gold—Find It In AOPA's Flight Training Advantage
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 31
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Safety Quiz: Night Ops
CFI-to-CFI Newsletter - Volume 13 Issue 4 - CFI Tools: Be Winter Weather Wise—Prepare for the Cold Weather Season
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 34
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 35
CFI-to-CFI Newsletter - Volume 13 Issue 4 - Chief's Corner: Eating Humble Pie
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 37
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 38
CFI-to-CFI Newsletter - Volume 13 Issue 4 - 39
CFI-to-CFI Newsletter - Volume 13 Issue 4 - ASI Safety Tip: Aiming Point
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