The FAA has issued a special airworthiness information bulletin (SAIB) alerting owners and operators of aircraft equipped with Garmin G1000, Perspective, and Prodigy Integrated Flight Decks installed with GFC 700 autopilots of an issue with the navigational radio auto-tune feature while performing a VOR or ILS approach.
“Changes to navigation frequencies that occur between navigation database cycle distributions may cause a mismatch between the automatically tuned LOC/ILS frequency and the frequency shown on the approach chart or applicable notam. In these cases, the mismatched (incorrect) automatically tuned frequency may cause the HSI to automatically slew to the wrong course,” the bulletin states. The issue is not an unsafe condition that would warrant an airworthiness directive.
If the auto-tuned LOC/ILS frequency does not correspond to the frequency shown on the approach chart or applicable notam, the FAA recommends manually tuning the navigation receiver to the correct LOC/ILS frequency, assuring that the correct inbound course is selected, manually flying the approach, or choosing a different terminal procedure. The GFC 700 will not capture, track, or give flight director commands for a manually selected course.
Garmin is planning to resolve this issue with GDU software version 10.00, and later versions will provide the capability to couple the autopilot to the VOR or LOC/ILS approach when the pilot manually tunes the correct frequency and manually selects the proper course for the approach.