Summary
We propose to adopt a new airworthiness directive (AD) for certain Hawker Beechcraft Corporation Model 390 airplanes. This proposed AD would require inspecting for installation of certain serial number (S/N) starter generators and replacing the starter generator if one with an affected serial number is found. This proposed AD results from reports that starter generators with deficient armature insulating materials may have been installed on certain airplanes. We are proposing this AD to detect and replace starter generators with defective armature insulating materials. This condition could result in the loss of operation of one or both starter generators with consequent loss of all non-battery electrical power.