Final answer:
The lead stop in helicopters restrains blade movement as the rotor slows, ensuring mechanical safety. Newton's Third Law explains the opposite rotation of the helicopter body, which is counteracted by the tail rotor or dual opposite-spinning main rotors. Pilots must maintain sufficient rotational kinetic energy in the blades to avoid a crash.
Step-by-step explanation:
The lead stop on a helicopter rotor blade system is crucial in controlling the mechanical limits of blade movement and plays a vital role in the aerodynamics and safety of helicopter operation. When the rotor slows down, the lead stop limits the forward movement, or 'lead,' of each blade, ensuring the blades do not exceed their designed angular position relative to the hub. This is essential during flight operations as it prevents excessive flapping, which can lead to mechanical failures or loss of control.
In terms of Newton's Third Law, for every action, there is an equal and opposite reaction, the helicopter's main rotors spinning in one direction will cause the body of the helicopter to rotate in the opposite direction. This is counteracted by the small tail rotor, or in some helicopters, the use of dual main rotors spinning in opposite directions, which eliminates the need for a tail rotor.
Helicopter pilots must be acutely aware of the rotational kinetic energy stored in the blades. They must maintain this energy above a critical level to avoid losing lift, where the helicopter can no longer stay airborne due to insufficient power to quickly spin up the blades. To avoid a potential crash, the helicopter can descend to trade gravitational potential energy for rotational kinetic energy, spinning up the blades before it's too late. Still, there is a critical altitude below which this maneuver becomes ineffective.