Summary
This document proposes to supersede Airworthiness Directive (AD) 99-17-08, which currently requires modifying the generator 2 excitation by removing certain diodes and installing a new 5-amp circuit breaker and suppression filter found on certain Pilatus Aircraft Ltd. (Pilatus) Models PC-12 and PC-12/45 airplanes. The Federal Aviation Administration has determined that the A250 voltage spike suppression filter in the modification kit can cause the circuit breaker 235 to trip because of overload. In extreme circumstances, this can lead to overheating of wiring. The proposed AD would require modifying the generator 2 excitation by removing certain diodes, installing a new 5-amp circuit breaker and new suppression filter requirement in accordance with revised procedures. The proposed AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by the proposed AD are intended to prevent damage to electrical components if generator 2 is not switched off before engine shutdown and it overheats. This could result in loss of electrical power to certain critical airplane components.