The FAA is notifying owners and operators of aircraft equipped with Avidyne integrated flight displays (IFDs) of an emergency airworthiness directive (AD) issued to address incorrect course deviation indications that occur during some GPS approaches.
The AD, issued May 18, requires owners and operators to incorporate an operational limitation into the Limitations Section of the airplane flight manual or airplane flight manual supplement, containing prohibitions on flying a full procedure (non vector-to-final) GPS approach, with a course change at the final approach fix; and on flying a GPS approach with a direct-to or with an omni-bearing selector leg to the final approach fix.
The emergency AD is effective upon receipt, and was prompted by reports of Avidyne IFDs displaying incorrect course deviation indication information during GPS approaches. The condition—the incorrect display of lateral deviations—"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 FAA said.
The incorrect displays "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)," the FAA noted, discussing the unsafe condition that the AD addresses.
The text of the AD details the IFD models and software releases to which the AD applies, and notes that the products may be installed on, but not limited to, airplanes certificated in any category.
The AD is no longer applicable if software is installed that is different from that referenced in the AD’s applicability section.