Tail Rotor Vortex Ring State  (210-330°) .......................................................11-13 LTE at Altitude...........................................11-13 Reducing the Onset of LTE .......................11-13 Recovery Technique...................................11-14 Main Drive Shaft Failure ................................11-14 Hydraulic Failures...........................................11-14 Governor Failure.............................................11-14 Abnormal Vibrations.......................................11-14 Low Frequency Vibrations.........................11-15 Medium and High Frequency  Vibrations ...................................................11-15 Tracking and Balance ................................11-15 Flight Diversion...................................................11-15 Lost Procedures ...................................................11-16 Emergency Equipment and Survival Gear ..........11-16 Flight Instruments .................................................12-1 Pitot-Static Instruments ....................................12-1 Airspeed Indicator........................................12-1 Instrument Check.........................................12-1 Altimeter ......................................................12-2 Instrument Check.....................................12-2 Vertical Speed Indicator....................................12-2 Instrument Check.........................................12-2 System Errors...............................................12-2 Gyroscopic Instruments ....................................12-3 Attitude Indicator.........................................12-3 Heading Indicator ........................................12-3 Turn Indicators.............................................12-4 Instrument Check.........................................12-4 Magnetic Compass............................................12-4 Compass Errors............................................12-4 Magnetic Variation.......................................12-4 Compass Deviation..................................12-5 Magnetic Dip ...........................................12-5 Instrument Check.....................................12-5 Instrument Flight ...................................................12-5 Instrument Cross-Check ...................................12-5 Instrument Interpretation ..................................12-6 Aircraft Control ................................................12-7 Straight-and-Level Flight..................................12-7 Pitch Control ................................................12-7 Attitude Indicator.....................................12-8 Altimeter ..................................................12-8 Vertical Speed Indicator ..........................12-8 Airspeed Indicator ...................................12-9 Bank Control................................................12-9 Attitude Indicator.....................................12-9 Heading Indicator ..................................12-10 Turn Indicator ........................................12-10 Common Errors During  Straight-and-Level Flight ...........................12-10 Power Control During  Straight-and-Level Flight ...........................12-11 Common Errors During  Airspeed Changes.......................................12-11 Straight Climbs (Constant Airspeed  and Constant Rate)..........................................12-11 Entry...........................................................12-12 Leveloff......................................................12-14 Straight Descents (Constant Airspeed and  Constant Rate) ................................................12-14 Entry...........................................................12-14 Leveloff......................................................12-15 Common Errors During  Straight Climbs and Descents ....................12-15 Turns ...............................................................12-15 Turns to a Predetermined Heading ............12-16 Timed Turns ...............................................12-16 Change of Airspeed in Turns .................12-16 30° Bank Turn............................................12-17 Climbing and Descending Turns ...............12-17 Compass Turns...........................................12-17 Common Errors During Turns...................12-18 Unusual Attitudes............................................12-18 Common Errors During Unusual  Attitude Recoveries ....................................12-18 Emergencies ........................................................12-18 Autorotations ..................................................12-19 Common Errors During  Autorotations ..............................................12-19 Servo Failure...................................................12-19 Instrument Takeoff ..............................................12-19 Common Errors During  Instrument Takeoffs ........................................12-20 Night Flight Physiology ........................................13-1 Vision in Flight .................................................13-1 The Eye .............................................................13-1 Cones ................................................................13-1 Rods ..................................................................13-2 Night Vision ......................................................13-2 Night Scanning .................................................13-2 Aircraft Lighting ...............................................13-3 Visual Illusions .................................................13-3 Autokinesis ..................................................13-3 Night Myopia...............................................13-3 False Horizon...............................................13-3 Landing Illusions .........................................13-4 Night Flight ...........................................................13-4 Preflight ............................................................13-4 Engine Starting and Rotor Engagement ...........13-4 Taxi Technique..................................................13-4 Takeoff ..............................................................13-4 En route Procedures..........................................13-5 Chapter 13—Night Operations Chapter 12—Attitude Instrument Flying viii