Final answer:
The reference content provided focuses on the importance of maintaining rotational kinetic energy in helicopter blades for flight sustainability, specifically the need to avoid allowing the blades to slow below a crucial velocity and how pilots can use gravitational potential energy for recovery in certain situations.
Step-by-step explanation:
The question appears to be focused on the safety precautions concerning the parts of a rotary wing aircraft, such as a helicopter, that should be avoided for safety reasons. However, the provided reference content predominantly discusses the importance of maintaining rotational kinetic energy in helicopter blades to prevent a crash. It explains that a helicopter's blades must maintain a critical angular velocity to sustain lift and that the helicopter engine has weight limitations, restricting its capacity to recover this kinetic energy during flight should it fall below critical levels. Additionally, it is mentioned that pilots can use the gravitational potential energy of the helicopter to recover the blades' rotational kinetic energy by descending and aligning the blades, which spins them up. This maneuver is contingent on having sufficient altitude to avoid a crash by regaining lift.