BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
8.5.2.1.6.1. WARNING: In certain areas, magnetic heading indications may
be unreliable or erratic. If magnetic heading indications are suspect, do not
commence the approach. If already established on the approach and
magnetic heading indications are suspect, execute a missed approach.
8.5.2.1.6.2. WARNING: Flight director commands and CDI deflection may
be grossly inaccurate on aircraft without a true heading source even with
proper set-up of courses, bearings, and headings.
8.5.2.1.6.3. VOR and TACAN approaches. VOR and TACAN final approach
courses do not require correction for magnetic variation. Dial in the true
final approach course as depicted on the IAP. Although the CDI will be
centered when on course, the bearing pointer will point to the true bearing to
the station. When selecting a heading to fly to intercept/maintain the course,
corrections for magnetic variation are required. Use the magnetic variation
at the NAVAID the approach is based upon.
8.5.2.1.6.4. NDB Approaches. NDBs cannot be oriented to true north. ADF
needles always display relative bearing to the station. Corrections for
magnetic variation must be applied to the published bearing(s). When
selecting a heading to fly to intercept/maintain the published bearing,
corrections for magnetic variation are also required. Use the magnetic
variation at the NAVAID the approach is based upon.
8.5.2.1.6.5. ILS and Localizer Approaches (includes LDA, SDF, and LOC
BC). Localizer signals emanate along a fixed path along the final approach
course and cannot be oriented on true north. CDIs always indicate position
relative to the final approach course regardless of what is dialed into the CSW.
However, selection of the correct final approach course is critical to insuring
consistent cockpit indications of position relative to the final approach course.
When selecting a course to dial in, corrections for magnetic variation must
be applied to the published front course to insure consistent cockpit
indications while on final approach. When selecting a heading to fly to
intercept/maintain the published final approach course, corrections for
magnetic variation are also required. Use the magnetic variation at the
airport.