A/S Limit 2 hydraulic systems INOP IMC value?

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

Answer: (A)

When one hydraulic system is inoperative in instrument meteorological conditions, the helicopter’s flight controls have less hydraulic boost, so the aircraft must be flown at a lower, safer speed to maintain adequate control authority. The specified airspeed limit with two hydraulic systems inop in IMC is 140 KIAS. This limit ensures you still have enough control responsiveness from the remaining hydraulic system and preserves stability margins during instrument flight and maneuvers.

Choosing a higher speed would reduce control effectiveness under degraded hydraulics, making control harder in IMC, while a significantly lower limit would unnecessarily constrain performance. The value of 140 KIAS strikes the right balance for safe handling when one hydraulic system isn’t available.