Airworthiness Directives; Various Aircraft Equipped With Honeywell Primus II RNZ-850/-851 Integrated Navigation Units

This amendment adopts a new airworthiness directive (AD) that is applicable to various aircraft equipped with a certain Honeywell Primus II RNZ-850/-851 Integrated Navigation Unit. As one alternative for compliance, this action provides for a one-time inspection to determine whether a certain modification has been installed on the Honeywell Primus II NV850 Navigation Receiver Module, which is part of the Integrated Navigation Unit. In lieu of accomplishing this inspection, and for aircraft found to have an affected navigation receiver module, this action provides for revising the aircraft flight manual to include new limitations for instrument landing system (ILS) approaches. This action is necessary to ensure that the flightcrew has an accurate glideslope deviation indication. An erroneous glideslope deviation indication could lead to the aircraft making an approach off the glideslope, which could result in impact with an obstacle or terrain. This action is intended to address the identified unsafe condition.