What materials are required to secure the aircraft after safely landing on mattresses?

The requirement to use a minimum of four cargo straps after safely landing on mattresses is based on ensuring the aircraft remains securely in place, preventing any movement that could occur due to wind or ground vibrations. Cargo straps are designed to provide strong and reliable securing points that can withstand various forces that an aircraft might experience on the ground.

Using a minimum of four straps is particularly important for stability, as it helps distribute the forces evenly across the aircraft's structure. This practice helps maintain the integrity of the aircraft's position and prevents any potential damage that could occur from shifting or rolling due to environmental conditions.

The other materials mentioned, such as ropes or tie-down chains, may not provide the same level of security and reliability needed for securing an aircraft on mattresses. Utilizing inadequate securing methods could lead to safety hazards. Meanwhile, using elevators and jacks is more associated with lifting or positioning the aircraft rather than securing it after landing. Therefore, cargo straps are the most appropriate and effective choice for this situation.