Which maneuver helps to recover rotor RPM while in forward flight?

To recover rotor RPM while in forward flight, gently applying aft cyclic is beneficial because it helps to pitch the helicopter up slightly, increasing the angle of attack on the rotor blades, which can enhance lift and allow for rotor RPM recovery. When a helicopter is in forward flight, the rotor blades experience varying airflow, and if RPM drops, adjusting the pitch can help optimize that airflow and increase the efficiency of the rotor system.

Using aft cyclic also helps to reduce the load on the rotor system, allowing it to regain speed without the increased power demand that may come from other adjustments. This can be particularly important in situations where the helicopter is approaching a low rotor RPM condition, enabling the pilot to maintain control of the aircraft effectively while striving for optimal rotor performance.

The other options explore different methods but do not directly contribute to recovering rotor RPM in the same effective manner. For instance, reducing collective would decrease overall lift, which could lead to a further loss of rotor RPM. Increasing throttle may not immediately impact rotor RPM in forward flight, as the relationship between engine power and rotor speed is complex and dependent on various factors. Gently applying forward cyclic tends to push the helicopter's nose down, which might not assist in achieving the desired rotor RPM recovery in the situation described.