Special Conditions: Raytheon Model BH.125 Series 400A, DH.125 Series 400A, and HS.125 Series 400B Airplanes; High-Intensity Radiated Fields (HIRF)

These special conditions are issued for Raytheon Model BH.125 series 400A, DH.125 series 400A, and HS.125 series 400B airplanes modified by Envoy Aerospace. These modified airplanes will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification incorporates digital air data computers and displays that perform critical functions. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for the protection of these systems from the effects of high-intensity radiated fields (HIRF). These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.