Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Saab AB, Saab Aeronautics Model 340A (SAAB/SF340A) and SAAB 340B airplanes. The NPRM proposed to supersede AD 2012-24-06. AD 2012-24-06 currently requires replacing the stall warning computer (SWC) with a new SWC that provides an artificial stall warning in icing conditions, and modifying the airplane for the replacement of the SWC. The NPRM was prompted by a determination that airplanes with certain modifications were excluded from the applicability in AD 2012-24-06, and are affected by the identified unsafe condition; and the SWC required by AD 2012-24-06 contained erroneous logic. This action revises the NPRM by reducing the compliance time for replacing the SWCs. We are proposing this supplemental NPRM (SNPRM) to prevent natural stall events during operation in icing conditions, which could result in loss of control of the airplane. Since this compliance time reduction imposes an additional burdento operators, we are reopening the comment period to allow the public the chance to comment on these proposed changes.