Special Conditions; Byerly Aviation; Twin Commander Models 690, 690A, 690B, 690C, 690D, 695, 695A, and 695B; Protection of Systems for High Intensity Radiated Fields (HIRF)

These special conditions are issued to Byerly Aviation, Inc., Greater Peoria Regional Airport, 6100 EM Dirksen Parkway, Peoria, Illinois 61607, for a Supplemental Type Certificate for Twin Commander model series 690/695 airplanes. This airplane will have novel and unusual design features when compared to the state of technology envisaged in the applicable airworthiness standards. These novel and unusual design features include the installation of an electronic flight instrument system (EFIS), manufactured by Meggitt Avionics, for which 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 the airworthiness standards applicable to these airplanes.