Special Conditions: Learjet Model 35, 35A, 36, and 36A Airplanes; High-Intensity Radiated Fields (HIRF)

These special conditions are issued for Learjet Model 35, 35A, 36, and 36A airplanes modified by ARINC, Inc. 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 is the installation of a Thommen AD32 Air Data Display Unit (ADDU) which incorporates a digital air data computer and altimeter. This equipment will 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.