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What happens to the advancing blade of a helicopter?


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September 25, 2008 6:41PM

The "advancing blade" of a helicopter refers to the side of the rotor which moves forward in relation to the fuselage. As each rotor blade makes a full circle around the center, on one side of the swing, it moves forward, and on the opposite side it is moving towards the rear of the helicopter.

When the helicopter is moving forward in air, the rotor blades on the advancing side are moving at a higher airspeed than the rotor blades elsewhere. Rotor speed + aircrafts forward airspeed. This results in slightly more lift on that side. Conversely the exact opposite is happening on the other side where you get Rotor speed - aircraft forward airspeed. This creates a tendency for helicopters to want to roll at high airspeed.

This is one of the many odd tendencies of rotor aircraft that pilots are constantly adjusting to balance out.