What was found
SUBMITTING THIS SDR DUE TO THE LOW ACFT TOTAL TIME & INITIAL INSPECTION REQUIREMENTS CONTAINED IN AD 2014-15-15. DURING AN A CHECK INSPECTION, THE CUSTOMER REQUESTED EARLY COMPLIANCE WITH AD 2014-15-15, INSPECTION OF THE HORIZONTAL STABILIZER RIBS FOR FATIGUE CRACKING. THIS INSPECTION IS ALSO CONTAINED IN THE AIRWORTHINESS & LIMITATIONS MANUAL, TASK CODE 045505. BOTH THE AD & AIRWORTHINESS LIMITATIONS MANUAL REQUIRE INSPECTION OF THE HORIZONTAL RIBS PRIOR TO THE ACCUMULATION OF 7,400 HOURS INITIAL WITH RECURRENT INSPECTIONS EVERY 2,400 HOURS. PERFORMED A BORESCOPE INSPECTION OF THE HORIZONTAL STABILIZER RIBS IAW CHAPTER 55-10-00 IN THE MODEL 400 & 400A MM. FOUND THE LT & RT RIBS PN 45A21112-0005 & 45A21113-0005 WITH FATIGUE CRACKS.