Special Conditions: Gulfstream Aerospace LP 1125 Westwind Astra; High Intensity Radiated Fields (HIRF)

These special conditions are issued for Gulfstream Aerospace LP 1125 Westwind Astra airplanes modified by Garrett Aviation Services. These modified airplanes will have novel or unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification incorporates the upgrade of one Air Data Computer system and the installation of a second Air Data Computer system, both of which 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 provided by the existing airworthiness standards.