In IFR-GPS-equipped (/G) aircraft, a pilot flies most of the segments with GPS as primary navigational resource* even the route is along victor airways or VOR radials. However, when we start the approach, we have to switch the nav source from GPS to the nav source specified for the approach. In this context of using GPS for non-GPS approaches,
- When should a pilot switch away from GPS? Is it from an IAF, FAF or upon ATC vectors to intercept the final approach course?
- If the a pilot executes a missed approach, when can the pilot switch back to GPS? Is it when established on course direct to the holding fix?
*By primary navigational resource, I mean it provides the signal/data source for the CDI needle on a HSI, that a pilot, autopilot or flight director refers to make actions or action suggestions.