Figure 12-18.  Zero sideslip engine-out flight. Figure 12-17.  Excessive bank engine-out flight. the remaining engine reveals the precise bank angle and  ball deflection required for zero sideslip and best climb  performance. Zero sideslip is again indicated by the yaw  string when it aligns itself vertically on the windshield. There  are very minor changes from this attitude depending upon the  engine failed (with non-counter-rotating propellers), power  available, airspeed and weight; but without more sensitive  testing equipment, these changes are difficult to detect.  The only significant difference would be the pitch attitude  required to maintain V$_{YSE}$ under different density altitude,  power available, and weight conditions. For any multiengine airplane, zero sideslip can be confirmed  through the use of a yaw string. A yaw string is a piece of  string or yarn approximately 18 to 36 inches in length taped to  the base of the windshield or to the nose near the windshield  along the airplane centerline. In two-engine coordinated  flight, the relative wind causes the string to align itself with  the longitudinal axis of the airplane, and it positions itself  straight up the center of the windshield. This is zero sideslip.  Experimentation with slips and skids vividly displays the  location of the relative wind. Adequate altitude and flying speed  must be maintained while accomplishing these maneuvers. With an engine set to zero thrust (or feathered) and the  airplane slowed to V$_{YSE}$, a climb with maximum power on  12-25 XPDR 5537 IDNT LCL  10:12:34 VOR 1 270 ° 2 1 1 2 4 300 4 200 4 100 4 000 3 900 3 800 4300 3600 3500 3400 3300 3200 3100 60 20 000 130 120 110 90 80 70 1 100 9 TAS 106KT OAT 7°C ALERTS NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° Excess bank toward operating engine, no rudder input. Result: large sideslip toward operating engine and greatly reduced climb performance. Yaw  string Relative wind Drag Thrust Yaw  string XPDR 5537 IDNT LCL  10:12:34 VOR 1 270 ° 2 1 1 2 4 300 4 200 4 100 4 000 3 900 3 800 4300 3600 3500 3400 3300 3200 3100 60 20 000 130 120 110 90 80 70 1 100 9 TAS 106KT OAT 7°C ALERTS NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° Bank toward operating engine, no sideslip.  Results: much lower drag and smaller control surface  deflections. Relative wind Drag Rudder force Thrust