What occurs when the collective pitch control lever of a helicopter is raised?

When the collective pitch control lever of a helicopter is raised, it increases the angle of attack of the rotor blades collectively. This adjustment makes each rotor blade pitch higher, allowing them to generate more lift as they rotate through the air. Since all the blades are affected simultaneously, the lift produced by the rotor system increases uniformly across the blades. This is essential for climb or maintaining altitude in flight. The proper functioning of the collective pitch control is crucial to managing the helicopter's ascent and overall flight dynamics.

The other options presented do not accurately reflect the consequences of raising the collective pitch. For instance, increasing lift across the blades does not lead to stalling or descending but rather facilitates additional lift and potential climbing capabilities. Understanding this relationship between the collective pitch and rotor performance is vital for safe and effective helicopter operation.