IFD course presentations on VOR 27 to 1G5

The depicted course depends on type of navigation the IFD leg uses. The IFD appears to generally a form of two types of navigation (Fly Direct and Fly Course).

Fly Direct navigation calculates a great circle between waypoints or to a waypoint during a Direct to operation. Fly Direct legs appear to always depict the IFD calculated magnetic course. The leg between ACO and COLEN is a Fly Direct leg and 282 is the IFD calculated magnetic course out of ACO to COLEN (which overlays the ACO 278 radial out of ACO). Fly Direct is indicated on the expanded FPL tab for the COLEN waypoint.

Fly Course calculates rhumb line courses to/from a waypoint. Fly Course is used in OBS mode, parts of some procedures, as well as holding courses (Hold). The depicted courses for Fly Course are normally magnetic; except when using OBS mode to/from a VOR waypoint or generally when the waypoint is based on a VOR or VOR radial while part of an active procedure; then the VOR declination appears to normally be factored in so that the depicted IFD course matches charted VOR radials.

In this approach, the legs from COLEN to NVRTL and NVRTL to RW27 are Fly Course legs (as indicated on the expanded FPL tab) and their respective IFD displayed courses take into account the ACO declination so they match the ACO 278 radial depicted on the approach chart.

Unless they overlay a true north or south course or overlay the equator, Fly Course legs are not great circle and may not precisely connect two waypoints in the same manner a VOR radial or Fly Direct routing (both great circle) do. If you zoom in on the map view of COLEN or NVRTL you will notice that the start of the leg from COLEN to NVRTL as well as the start of the leg from NVRTL to RW27 do not exactly line up with COLEN or NVRTL respectively; this will lead to a slight left correction to stay centered on the GPS course after crossing each of these waypoints if this approach were flown as an overlay using GPS steering instead of in VLOC.

Navigating this approach with a GFC 500 in VLOC from ACO would most likely require adjusting the auto-slewed VOR course to 278 to match the charted VOR radial.