Special Conditions: Learjet Models 24 and 25 Airplanes; High Intensity Radiated Fields (HIRF)

These special conditions are issued for Learjet Models 24 B/D/ E/F and 25 B/C/D/F airplanes, modified by Flight Test Associates, Incorporated. These modified airplanes will have novel and unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification incorporates the installation of a dual Innovative Systems and Support Air Data Display Unit system. 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 provided by the existing airworthiness standards.