What is a key characteristic of effective translational lift (ETL)?

Translational lift, also known as effective translational lift, is a phenomenon that occurs when a helicopter transitions from a hover to forward flight. The key characteristic of ETL is that it enhances lift during forward flight due to increased airflow over the rotor system. As the helicopter moves forward, the rotor blades encounter undisturbed air, which allows them to generate more lift compared to when the helicopter is stationary in a hover. This increased efficiency occurs generally between about 15 and 25 knots, where the rotor system can fully exploit the increased relative wind and airflow, thereby maximizing lift.

The other options do not accurately reflect the nature of ETL. For example, saying that it occurs during descent or is limited to hovering conditions contradicts the very definition of translational lift, which is most effective during forward flight. Also, mentioning that it is limited to rotorcraft under 10 knots ignores the fundamental mechanics of helicopter flight, as ETL is associated with overcoming hover-induced drag and enhancing lift in forward flight as speed increases. Therefore, the statement that translational lift enhances lift during forward flight aligns seamlessly with the principles of helicopter aerodynamics.