Single-rotor helicopters need a mechanism to neutralize the yawing movement produced by the single large rotor.
Advantages of the tandem rotor system are a larger center of gravity range and good longitudinal stability.
To achieve pitch, opposite collective is applied to each rotor; decreasing the lift produced at one end, while increasing lift at the opposite end, effectively tilting the helicopter forward or back.
[3] Tandem-rotor helicopters have the advantage of being able to hold more weight with shorter blades, since there are two sets.
Both configurations typically require the same power to achieve high-speed flight.