Special Conditions: Learjet 25, 25A, 25B, 25C, 25D, and 25F Airplanes; High-Intensity Radiated Fields (HIRF)

The FAA issues these special conditions for Learjet 25, 25A, 25B, 25C, 25D, and 25F airplanes modified by Envoy Aerospace, LLC. These modified airplanes will have novel or unusual design features when compared with the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification consists of installing Universal Avionics EFI-890 Electronic Flight Displays and Rockwell Collins AHS-1000A Attitude Heading Reference Systems. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for protecting these systems from 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.