You are experiencing retreating blade tip stall, what happens to the aircraft?

When experiencing retreating blade tip stall, the aircraft undergoes a specific aerodynamic phenomenon where the retreating blades (the blades moving away from the direction of the flight) exceed their critical angle of attack and lose lift, leading to a severe change in flight characteristics.

The sensation of a vibration in the cyclic indicates that something is amiss with the rotor system, and the shaking of the airframe reflects an imbalance caused by the stall. When retreating blade stall occurs, the airflow over the retreating blade is disrupted, causing a loss of lift. Most critically, this can lead to a situation where the nose of the helicopter pitches up and may begin to roll to one side.

In this scenario, the helicopter can experience an uneven lift across the rotor system, causing it to roll in the direction of the stall – which is not necessarily predictable and can happen in either direction depending on the state of flight and rotor dynamics. Thus, the characteristics mentioned in the correct answer align well with the expected behavior of the helicopter during retreating blade tip stall, where the loss of lift on the retreating blade causes a pitch-up motion and rolls the aircraft in either direction.

Other answers might incorrectly describe the directional behavior or the associated movements of the aircraft,