What flight conditions can lead to low rotor RPM with potential blade stall?

A situation leading to low rotor RPM with the potential for blade stall typically arises when the throttle is not managed properly while simultaneously applying excessive collective pitch. When the throttle is rolled incorrectly, it may not provide sufficient power to maintain rotor RPM, particularly when additional collective pitch is added. Increased collective pitch demands more power from the engine to compensate for the increased load on the rotor system. If the throttle adjustment does not match the increase in collective pitch, rotor RPM can decrease to a level where the blades may reach a critical angle of attack, resulting in blade stall.

In contrast, while high weight and lightly loaded rotor blades can affect performance, they do not inherently cause low rotor RPM or blade stall in the same direct manner as improper throttle and collective management. Additionally, rapid cyclic input and gentle winds may not significantly impact rotor RPM unless combined with other factors. Similarly, low density altitude generally improves helicopter performance, making it less likely to cause issues unless other adverse factors are present. Therefore, the relationship between throttle management, collective pitch, and rotor RPM is crucial in understanding the risk of blade stall during flight.