Which of the following aircraft components should be avoided at all times?

The main rotor blade, tail rotor blade, and cargo hook are critical components of an aircraft that should be handled with extreme caution and avoided unless specifically trained to manage them. The main and tail rotor blades are essential for the helicopter's lift and stability, and any damage or improper handling can lead to catastrophic failure of the aircraft during flight. The cargo hook is utilized for external loads, and improper interaction with it can result in accidents related to load detachment, accidents during loading operations, or personal injury.

In contrast, while the other options contain components that can also pose risks, they do not encompass the same immediate danger as the rotor blades and cargo hook, particularly in terms of flight operations and safety. Understanding the critical nature of these components emphasizes the need for proper training and adherence to safety guidelines in aviation operations, particularly in air assault missions where precision and safety are paramount.