When flying at high speed, an increase in the helicopter’s weight affects the balance and control inputs, particularly the cyclic. The cyclic control allows the Pilot to tilt the rotor disc to adjust the helicopter's pitch and roll.

As the helicopter's weight increases, the rotor blades need to generate more lift to maintain flight. This puts additional strain on the rotor system and reduces the available control authority. Both forward and rearward cyclic movement become restricted because:

• Forward Cyclic: When the pilot pushes the cyclic forward, it tilts the rotor disc forward, which causes the helicopter to pitch down and accelerate. However, with increased weight, the rotor system is already working harder to provide lift, leaving less margin to tilt the disc forward.
• Rearward Cyclic: Pulling the cyclic back tilts the rotor disc rearward, causing the helicopter to pitch up. With increased weight, the helicopter’s center of gravity might also shift, making it more difficult to achieve sufficient rearward tilt for desired control.

In essence, when weight increases at high speed, the helicopter's ability to pitch forward or backward becomes limited because the rotor system is already near its performance limits, restricting cyclic movement and making fine control more challenging.