What does NTS do?

• A. Increase the blade angle when there is a sign of plant negative torque
• B. Increase the blade angle when there is a sign of plant positive torque
• C. Decrease the blade angle when there is a sign of plant negative torque
• D. Maintain blade angle regardless of torque

Answer: (A)

NTS, Negative Torque Sensing, is a protective control that responds to the sign of torque in the drive train by adjusting rotor blade pitch. When the plant torque becomes negative (meaning the drive system is not delivering positive torque or the rotor is driving the engine/gearbox), NTS increases the blade angle. This raises aerodynamic drag and loading on the rotor, helping to prevent instability or a loss of control by keeping the rotor speed and torque within safe limits.

If the system increased blade angle for positive torque, or decreased blade angle when torque is negative, the protective balance wouldn’t be achieved. Maintaining the blade angle no matter what torque is present would defeat the protective purpose of NTS.

So, increasing blade angle in response to negative plant torque is the mechanism by which NTS helps maintain stable, safe operation.