Avidyne IFDs Found To Have Displayed Incorrect Course Deviation Indication Information During GPS Approaches

The latest Emergency AD to be issued by the FAA has involved the new generation avionics systems introduced by Avidyne.

According to the Emergency AD, the action was prompted by "...reports of Avidyne IFDs displaying incorrect course deviation indication information during GPS approaches (incorrect display of lateral deviations). This condition occurs when the airplane is flying in certain approaches, the leg to the Final Approach Fix (FAF) is active, and the leg to the FAF is not aligned with the final approach course (i.e., an angled entry to the FAF). The software of the Avidyne IFDs as referenced above will produce lateral deviations to the final approach course as soon as the leg to the FAF becomes active. Therefore when the leg does not align with the final approach course, the CDI will show a deviation when, in fact, the aircraft is on the proper course for the active leg. This could result in the pilot making flight decisions that put the aircraft in unsafe flight conditions, flying into airspace that was, by the GPS approach design, to be avoided (terrain, obstacle, traffic, restricted)."

Affected are "...owners and operators of all aircraft that incorporate Avidyne Corporation (Avidyne) Integrated Flight Displays (IFDs) part number (P/N) 700-00083-( ) loaded with software release 9.3.1.0 or earlier release (referred to as Model R9 – 10 inch), P/N 700-00171-( ) loaded with software release 9.2.5.0 or earlier release (referred to as Model R9 - 12 inch), and P/N 700-00182-( ) loaded with software release 10.0.3.0 or earlier release (referred to as Model IFD540)."

The AD requires incorporating an operational limitation into the Limitations Section of the airplane flight manual (AFM) or airplane flight manual supplement (AFMS). The operational limitation will contain the following:

• “Flying a full procedure (non Vector-to-Final) GPS approach, with a course change at the Final Approach Fix (FAF), is prohibited.”
• “Flying a GPS approach, with a Direct-To or with an Omni-Bearing Selector (OBS) leg to the FAF, is prohibited.”

FMI: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/24d8d8ba6cb57e4f86257d1d0055dec4/$FILE/SA00282BO_AML.pdf