What phenomenon describes the helicopter’s tendency to roll uncontrollably when the critical angle is exceeded and a wheel is on the ground?

What phenomenon describes the helicopter’s tendency to roll uncontrollably when the critical angle is exceeded and a wheel is on the ground?

• A. Dynamic Rollover
• B. Dissymmetry of Lift
• C. Drag
• D. Feedback

Answer: (A)

Dynamic rollover is the unstable rolling behavior a helicopter can exhibit when it pivots on a ground contact point, like a wheel, and the bank angle continues to increase. With a wheel on the ground, that wheel becomes the fulcrum. As the helicopter tilts to the side, the center of gravity shifts toward the outside wheel, and if it moves beyond the pivot, the weight and inertia create a tipping moment that the rotor thrust can’t counter quickly enough. Once the critical angle is reached, restoring forces vanish and the roll accelerates, leading to an uncontrollable rollover. This differs from static rollover, which could occur if the CG is already beyond the pivot without any motion. For context, dissymmetry of lift deals with differences between the blades in forward flight, not this ground-contact rollover scenario, while drag is simply aerodynamic resistance and feedback is not the term used for this instability.

Dynamic rollover is the unstable rolling behavior a helicopter can exhibit when it pivots on a ground contact point, like a wheel, and the bank angle continues to increase. With a wheel on the ground, that wheel becomes the fulcrum. As the helicopter tilts to the side, the center of gravity shifts toward the outside wheel, and if it moves beyond the pivot, the weight and inertia create a tipping moment that the rotor thrust can’t counter quickly enough. Once the critical angle is reached, restoring forces vanish and the roll accelerates, leading to an uncontrollable rollover. This differs from static rollover, which could occur if the CG is already beyond the pivot without any motion. For context, dissymmetry of lift deals with differences between the blades in forward flight, not this ground-contact rollover scenario, while drag is simply aerodynamic resistance and feedback is not the term used for this instability.