On August 28, the FAA published an emergency airworthiness directive (AD) 2020-18-51 for certain Sandia attitude indicators with a part number (P/N) 306171-10 or 306171-20 installed, as well as those marketed as BendixKing Model KI-300 or Sandia Model SAI-340A.
This emergency AD was prompted by an initial report of three failed attitude indicators (P/N 306171-10) and, after a thorough investigation, a total of 54 failed attitude indicators with the same part number. The failure of these units can create erroneous attitude data provided to the pilot and autopilot, if equipped. In some instances, the pilot may be unaware the data is erroneous or unreliable. In other instances, where the aircraft is equipped with multiple displays, the pilot may be provided with conflicting information, but will have no way to determine which display contains the correct data.
If not addressed, these failures could result in aeronautical decision-making based on erroneous attitude information, which may result in loss of control. The emergency AD requires, before further flight, revising the existing airplane flight manual for each affected aircraft prohibiting operation under IFR or night VFR, as well as prohibiting these units to couple with the autopilot. As it relates to this AD, attitude indicator P/N 306171-20 is identical to P/N 306171-10 and is also affected by the same unsafe condition.
