Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Model SAAB-Fairchild SF340A and SAAB 340B airplanes. The existing AD currently requires repetitive inspections for wear of the brushes and leads and for loose rivets of the direct current (DC) starter generator, and related investigative/ corrective actions if necessary. This proposed AD would require installing new improved generator control units (GCUs). Installing the GCUs would end the repetitive inspection requirements of the existing AD. This proposed AD results from reports of premature failures of the DC starter generator prior to scheduled overhaul. We are proposing this AD to prevent failure of the starter generator, which could cause a low voltage situation in flight and result in increased pilot workload and reduced redundancy of the electrical powered systems.