TM 1-1520-265-23 INDEX-Continued Subject Paragraph Page Number Number Main Rotor Shaft Nut (MT) ............................................................................................................. 2.5 2-8 Backup Method.................................................................................................................. 2.5.4 2-9 Defects..............................................................................................................................  2.5.2 2-8 Description ........................................................................................................................  2.5.1 2-8 Primary Method ................................................................................................................. 2.5.3 2-8 System Securing ............................................................................................................... 2.5.5 2-9 Main Transmission (ET) ................................................................................................................. 3.2 3-3 Backup Method.................................................................................................................. 3.2.4 3-4 Defects..............................................................................................................................  3.2.2 3-3 Description ........................................................................................................................  3.2.1 3-3 Primary Method ................................................................................................................. 3.2.3 3-3 System Securing ............................................................................................................... 3.2.5 3-4 Marking and/or Recording of Inspection Results............................................................................. 1.3 1-17 N Nondestructive Inspection Methods................................................................................................  1.4 1-17 Acceptance/Rejection Criteria..........................................................................................  1.4.13 1-37 Bond Testing (BT) Method................................................................................................. 1.4.6 1-19 Demagnetization of Inspection Parts.................................................................................. 1.4.9 1-30 Eddy Current (ET) Method...............................................................................................  1.4.11 1-31 Equipment Used for NDI.................................................................................................. 1.4.14 1-37 Fluorescent Penetrant (PT) Method................................................................................... 1,4.7 1-21 Magnetic Particle (MT) Method ..........................................................................................  1.4.8 1-27 Materials Used for NDI .................................................................................................... 1.4.15 1-37 NDI General Safety Precautions........................................................................................  1.4.5 1-19 Post Cleaning and Restoration of Part or Area after NDI..................................................  1.4.16 1-37 Preparation of Helicopter for NDI.......................................................................................  1.4.3 1-18 Preparation of Part or Area for NDI.................................................................................... 1.4.4 1-18 Purpose of Nondestructive Inspection (NDI)...................................................................... 1.4.1 1-17 Radiographic (RT) Method...............................................................................................  1.4.10 1-30 Selecting the NDI Method.................................................................................................. 1.4.2 1-18 Ultrasonic (UT) Method.................................................................................................... 1.4.12 1-35 Nonferrous Bolts and Pins Contained within the Airframe and Landing Gear System (PT).................................................................................................................. 4.37 4-81 Description ......................................................................................................................  4.37.1 4-81 Nonferrous Bolts Contained within the Flight Control System (PT)............................................... 6.24 6-44 Description ......................................................................................................................  6.24.1 6-44 Nonferrous Connecting Links, Rod Ends, Clevises, Levers, and Attaching Parts (ET)............................................................................................................... 6.16 6-31 Backup Method................................................................................................................  6.16.4 6-32 Defects............................................................................................................................  6.16.2 6-31 Description ......................................................................................................................  6.16.1 6-31 Primary Method ...............................................................................................................  6.16.3 6-31 System Securing ............................................................................................................. 6.16.5 6-32 Index 9