SECTION I. TROUBLESHOOTING INFORMATION

TM 1-1520-238-T-4 1–2 SECTION I. TROUBLESHOOTING INFORMATION – GENERAL 1–1. SCOPE 1–1 This volume covers equipment description, theory of operation, FIPs, and AVUM and/or AVIM maintenance level instructions for the airframe, landing gear, power plants, rotors and drive system. 1–2. VOLUME CONTENT AND FORMAT 1–2 Equipment description and theory of operation for the helicopter landing gear, power plants, rotors and drive system are presented in Chapters 3, 4, 5, and 6. Before troubleshooting, learn the content and organization of this volume and how it relates to other manuals. For more information on volume content and usage refer to HOW TO USE THIS VOLUME. 1–3. REFERENCE MANUALS 1–3 Refer to APPENDIX A for a complete list of manuals you may need when troubleshooting the helicopter. 1–4. ELECTRICAL DATA 1–4 a. Electrical Units. Unless otherwise specified, the values indicated for electrical units in this volume are as follows: · Phase reference symbol (Æ) for AC voltage (VAC) · Resistance (R) in ohms (W) · Capacitance (C) in picofarads (pf) · Inductance (L) in henrys (H) · Voltage (E) in volts (V) · Current (I) in amperes (A) · Frequency in hertz (Hz) · Power in watts (W) b. Electrical Measurement Tolerances. Unless otherwise specified, tolerances for resistance, capacitance, inductance, voltage and current are ± 10%. c. Grounds. Unless otherwise indicated (such as chassis ground), all grounds shown are common ac, dc and signal grounds. d. DC Voltage Polarities. DC voltages are positive polarity (+28 VDC, etc.) unless otherwise specified. e. AC Voltages. All indicated ac voltages are 400 Hz.