Summary
We propose to adopt a new airworthiness directive (AD) for certain Saab AB, Saab Aerosystems Model 340A (SAAB/SF340A) and SAAB 340B airplanes modified by Supplemental Type Certificate SA7971SW. This proposed AD was prompted by reports of smoke, a burning odor, and possible fire in the flight deck and cabin of the airplane, which was caused by brushes wearing beyond their limits, in the air conditioning motor. This proposed AD would require an inspection to determine if a certain air compressor motor is installed, an inspection to determine the age of a certain compressor hour meter since new or overhauled, and repetitive replacement of the brushes on affected air conditioning compressor motor units. As an option to the replacement, this proposed AD allows pulling the air conditioning circuit breaker and adding a placard. We are proposing this AD to detect and correct worn brushes contacting the commutator, which could result in a fire under the cabin floor with no means to detect or extinguish the fire.