This effect is called “translational lift” because the extra lift is generated as the
helicopter translates (moves forward) through the air. Translational lift affects both
model and full-size, man carrying helicopters. Some early, underpowered full-size
helicopters could not climb above about twenty feet without moving forward to gain
translational lift.
Even when a helicopter appears to be hovering in one spot, wind gusts can blow
away the rotor down-wash and generate translational lift. The increased lift will cause
the helicopter to climb. When the wind stops, the helicopter will suddenly fall. Piloting
a helicopter in windy conditions can be difficult, and requires continuous throttle
control inputs as the wind speed changes.
Tail rotors are also affected by translational lift. Forward motion and wind gusts
cause the tail rotor to generate more lift and turn the helicopter. Windy conditions
therefore require both throttle and tail rotor control inputs in order to maintain a
constant altitude and heading.
Translational lift is much easier to control when the main rotor and tail rotor are
turning at high speed because the speed of the down-wash is much greater than the
speed of the oncoming wind. To increase rotor speed, refer to the
Stability, Control
Power and Climb Performance
section of this Operator’s Guide.
Circles
(OSIDHOVR)
Op er a tor's Guide
Learning to Fly
6-8
LITE MA CHINES
Figure 6-7.
