A/S Limit 2 hydraulic systems INOP VMC value?

A/S Limit 2 hydraulic systems INOP VMC value?

• A. 150 KIAS
• B. 140 KIAS
• C. 170 KIAS
• D. 130 KIAS

Answer: (A)

When two hydraulic systems are inoperative, the boost available to the flight-control surfaces is greatly reduced, so the helicopter requires more airspeed to maintain stable, controllable flight. The UH-60S is designed so that, with only one hydraulic system providing assist, there is still enough control authority at higher speeds, but at lower speeds the reduced hydraulic assist makes it hard to counter rotor and tail rotor forces and to maintain a straight, controlled flight path. The published minimum controllable speed in this condition is 150 KIAS, which gives a safe margin where the remaining hydraulic boost and aerodynamics can keep the helicopter controllable. Speeds lower than that would not provide the necessary control margin, while speeds at or above 150 KIAS are within the allowable limit.

When two hydraulic systems are inoperative, the boost available to the flight-control surfaces is greatly reduced, so the helicopter requires more airspeed to maintain stable, controllable flight. The UH-60S is designed so that, with only one hydraulic system providing assist, there is still enough control authority at higher speeds, but at lower speeds the reduced hydraulic assist makes it hard to counter rotor and tail rotor forces and to maintain a straight, controlled flight path. The published minimum controllable speed in this condition is 150 KIAS, which gives a safe margin where the remaining hydraulic boost and aerodynamics can keep the helicopter controllable. Speeds lower than that would not provide the necessary control margin, while speeds at or above 150 KIAS are within the allowable limit.