B. DME Arc (Only the Leg Mode is Used)

First, understand that the DME Arc approach utilizing GPS is becoming extinct since it is an overlay approach. They are being replaced with stand-alone GPS approaches. We use the Topeka, KS VOR or GPS Rwy 22 approach, dated 10 Nov 00 for the following example.

After the approach and IAF (LEBVY) has been loaded into the Active Flight Plan you can expect the following situation. If you are approaching from the northwest and the aircraft's present track intercepts the arc between the waypoints that define the beginning of the arc and the turn-on-to-final waypoint, the GPS will define a new waypoint at the intersection of the DME arc. This new waypoint is designated as the IAF. The segment of the arc that will not be flown will be a dashed line. Remember D312Gi means 312 degree radial at 7 miles whereas the letter G is the seventh letter of the alphabet.

If ATC is providing vectors to intercept the arc, the GPS can designate a waypoint based on the aircraft's current ground track. From either the FPL 0 or Nav 4 page:

1. Highlight the waypoint of arc intercept (IAF)

2. PRESS  or .  will appear in the bottom right corner of the Nav 4 screen (If a new waypoint is NOT desired, PRESS  or  again.)

3. PRESS . The GPS will move the original arc intercept waypoint to a new one based on present ground track. NOTE: If the present ground track does not intercept the arc the GPS will display .

As the aircraft approaches the arc the GPS will provide waypoint alerting and turn anticipation to intercept the arc. Guidance to follow the curved arc is then provided by the GPS.