Effective Translational Lift (ETL) Translational Thrust As speed increases, translational lift becomes more effective,  nose rises or pitches up, and aircraft rolls to the right.  The combined effects of dissymmetry of lift, gyroscopic  precession, and transverse flow effect cause this tendency.  It is important to understand these effects and anticipate  correcting for them. Once the helicopter is transitioning  through ETL, the pilot needs to apply forward and left  lateral cyclic input to maintain a constant rotor-disk attitude.  [Figure 2-41] While transitioning to forward flight at about 16 to 24 knots,  the helicopter goes through effective translational lift (ETL).  As mentioned earlier in the discussion on translational lift,  the rotor blades become more efficient as forward airspeed  increases. Between 16 and 24 knots, the rotor disk completely  outruns the recirculation of old vortices and begins to work  in relatively undisturbed air. The flow of air through the rotor  disk is more horizontal, which reduces induced flow and  drag with a corresponding increase in angle of attach and lift.  The additional lift available at this speed is referred to as the  ETL, which makes the rotor disk operate more efficiently.  This increased efficiency continues with increased airspeed  until the best climb airspeed is reached, and total drag is at  its lowest point.  Translational thrust occurs when the tail rotor becomes more  aerodynamically efficient during the transition from hover  to forward flight. As the tail rotor works in progressively  less turbulent air, this improved efficiency produces more  antitorque thrust, causing the nose of the aircraft to yaw left  D o w n w a r d v e l o c i t y o f a i r m o l e c u l e s u s e d b y a f t s e c t i o n o f  ro to r 1–5 knots 10–15 knots Airflow pattern just prior to effective translational lift Figure 2-39.  The airflow pattern for 1–5 knots of forward airspeed. Note how the downwind vortex is beginning to dissipate and induced  flow down through the rear of the rotor disk is more horizontal.  Figure 2-40.  An airflow pattern at a speed of 10–15 knots. At this increased airspeed, the airflow continues to become more horizontal.  The leading edge of the downwash pattern is being overrun and is well back under the nose of the helicopter. 2-22