Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Cessna Aircraft Company Model 500, 501, 550, 551, S550, 560, 560XL, and 650 airplanes. That NPRM proposed to require an inspection to determine if certain air conditioning (A/C) compressor motors are installed and to determine the accumulated hours on certain A/C drive motor assemblies; repetitive replacement of the brushes in the drive motor assembly, or as an option to the brush replacement, deactivation of the A/C system and placard installation; and return of replaced brushes to Cessna. That NPRM was prompted by multiple reports of smoke and/or fire in the tailcone caused by sparking due to excessive wear of the brushes in the A/C motor. This action revises that NPRM by revising the optional A/C system deactivation procedure. We are proposing this supplemental NPRM to prevent the brushes in the A/C motor from wearing down beyond their limits, which could result in the rivet in the brush contactingthe commutator causing sparks and consequent fire and/or smoke in the tailcone with no means to detect or extinguish the fire and/or smoke. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.