Final answer:
A helicopter pilot can worsen a helicopter's pendular action by allowing the blades to slow below a critical angular velocity. This can lead to a loss of lift and a potential crash.
Step-by-step explanation:
A helicopter pilot can worsen a helicopter's pendular action by allowing the blades to slow below a critical angular velocity. When the blades lose lift, it is difficult to regain it immediately, leading to a potential crash. To avoid this, pilots must ensure that the rotational kinetic energy of the blades does not drop below a crucial level.