Straight-and-Level Flight Technique Common Errors Technique Turns Straight-and-level flight is flight in which constant altitude  and heading are maintained. The attitude of the rotor disk  relative to the horizon determines the airspeed. The horizontal  stabilizer design determines the helicopter’s attitude when  stabilized at an airspeed and altitude. Altitude is primarily  controlled by use of the collective. Although the cyclic is sensitive, there is a slight delay in  control reaction, and it is necessary to anticipate actual  movement of the helicopter. When making cyclic inputs to  control the altitude or airspeed of a helicopter, take care not  to overcontrol. If the nose of the helicopter rises above the  level-flight attitude, apply forward pressure to the cyclic to  bring the nose down. If this correction is held too long, the  nose drops too low. Since the helicopter continues to change  attitude momentarily after the controls reach neutral, return  the cyclic to neutral slightly before the desired attitude is  reached. This principle holds true for any cyclic input. To maintain forward flight, the rotor tip-path plane must  be tilted forward to obtain the necessary horizontal thrust  component from the main rotor. By doing this, it causes the  nose of the helicopter to lower which in turn will cause the  airspeed to increase. In order to counteract this, the pilot  must find the correct power setting to maintain level flight by  adjusting the collective.  [Figure 9-1]  The horizontal stabilizer  aids in trimming the helicopter about its transverse, horizontal  axis, and reduces the amount of nose tuck that would occur.  On several helicopters, it is designed as a negative lift airfoil,  which produces a lifting force in a downward direction. Since helicopters are not very stable, but are inherently very  controllable, if a gust or turbulence causes the nose to drop,  the nose tends to continue to drop instead of returning to a  straight-and-level attitude as it would on a fixed-wing aircraft.  Therefore, a pilot must remain alert and fly the helicopter  at all times. When in straight-and-level flight, any increase in the  collective, while holding airspeed constant, causes the  helicopter to climb. A decrease in the collective, while holding  airspeed constant, causes the helicopter to descend. A change  in the collective requires a coordinated change of the throttle  to maintain a constant rpm. Additionally, the antitorque pedals  need to keep the helicopter in trim around the vertical axis. To increase airspeed in straight-and-level flight, apply  forward pressure on the cyclic and raise the collective as  necessary to maintain altitude. To decrease airspeed, apply  rearward pressure on the cyclic and lower the collective, as  necessary, to maintain altitude. A turn is a maneuver used to change the heading of the  helicopter. The aerodynamics of a turn were previously  discussed in Chapter 2, Aerodynamics of Flight. Before beginning any turn, the area in the direction of the  turn must be cleared not only at the helicopter’s altitude, but  also above and below. To enter a turn from straight-and-level  flight, apply sideward pressure on the cyclic in the direction  the turn is to be made. This is the only control movement  needed to start the turn. Do not use the pedals to assist the  turn. Use the pedals only to compensate for torque to keep  the helicopter in trim around the vertical axis.  [Figure 9-2] Keeping the fuselage in the correct streamlined position  around the vertical axis facilitates the helicopter flying  forward with the least drag. Trim is indicated by a yaw string  in the center, or a centered ball on a turn and slip indicator. A  yaw string (also referred to as a slip string) is a tool used to  indicate slip or skid during flight. It is simply a string attached  to the nose or canopy of an aircraft so that it is visible to the  pilot during flight. The string measures sideslip and offers  a visual cue to the pilot in order to make yaw corrections. 9-3 1.  Failure to trim the helicopter properly, tending to hold  antitorque pedal pressure and opposite cyclic. This is  commonly called cross-controlling. 2.  Failure to maintain desired airspeed. 3. Failure to hold proper control position to maintain  desired ground track. 4.  Failure to allow helicopter to stabilize at new airspeed. A O M CLUTCH MR TEMP MR CHIP STARTER ON TR CHIP lOW FUEL LOW RPM N E W 3 33 2 4 12 30 6 NAV GS 15 20 I0 0 I0 15 VERTICAL SPEED 100 FEET PER MINUTE UP DOWN 5 5 33 30 24 2I I5 I2 6 3 2 MIN TURN DCELEC L R 30 .0 29.9 2 9. 8 I 0 0 F E T I 4 5 6 7 9 2 0 8 3 CALIBRATED TO  20,000 FEET ALT 20 20 I0 I0 I0 I0 20 20 TEST STBY PWR IN Hg ALg. MANFOLD PRESS 25 5 15 30 20 10 35 20 30 40 50 60 70 80 90 100 0$_{10}$ MPH KNOTS 120 110 100 90 80 70 60 50 40 30 20 110 100 90 80 70 60 50 110 100 90 80 70 60 50 E R %RPM Figure 9-1.  Maintain straight-and-level flight by adjusting the rotor  tip-path plane forward  but adjusting the collective as necessary to  maintain a constant airspeed and altitude. The natural horizon line  can be used as an aid in maintaining straight-and-level flight. If  the horizon line begins to rise, slight power may be required or the  nose of the helicopter may be too low. If the horizon line is slowly  dropping, some power may need to be taken out or the nose of the  helicopter may be too high, requiring a cyclic adjustment.