Which statement regarding close-tolerance bolts is correct?

The statement that no substitutions may be made regarding close-tolerance bolts is accurate because the integrity and reliability of structural components depend heavily on the use of specified fasteners. Close-tolerance bolts are manufactured to tighter specifications than standard bolts, allowing for a precise fit and function within critical applications, especially where safety and performance are paramount.

Using the exact type of close-tolerance bolt ensures that the design characteristics, such as strength, stress distribution, and load-bearing capacity, are maintained. Substituting these bolts with alternatives, even if they appear similar, can jeopardize the safety and functionality of the assembly, potentially leading to mechanical failure. Thus, adhering strictly to the specified fasteners is crucial in aviation maintenance and repair practices.