Special Conditions; Rickenbacker Avionics, EFS-50 EFIS Installation in Rockwell Twin Commander Model 690B; Protection of Systems From High Intensity Radiated Fields (HIRF)

These special conditions are issued to Rickenbacker Avionics, 2820 Bobmeyer Road, Hangar C-6, Hamilton, OH 45015, for a Supplemental Type Certificate for the Rockwell Twin Commander Model 690B airplane. This airplane will have novel and unusual design features when compared to the state of technology envisaged in the applicable airworthiness standards. This novel and unusual design feature will include the installation of a two-tube Bendix/King EFS-50 Electronic Flight Instrument System (EFIS). The installation also includes components associated with this display system. The applicable regulations do not contain adequate or appropriate airworthiness 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 the airworthiness standards applicable to these airplanes.