What must be ensured when applying RNAV substitution procedures?

When applying RNAV substitution procedures, it is crucial that the procedures are approved by established authorities. This is important because RNAV (Area Navigation) systems rely on specific performance standards and operational guidelines to ensure safety and efficiency in navigation. Approval by regulatory bodies guarantees that pilots are abiding by the necessary regulations and are following the appropriate procedures that have been vetted for safety and effectiveness.

Using unapproved procedures could lead to navigational errors or unsafe flight conditions, as the integrity of the procedures and the systems they rely on have not been validated. Therefore, adherence to authority-approved procedures is a fundamental aspect of safe aviation operations.

In contrast, while manual application, altitude restrictions, and the number of navigational aids are relevant considerations in RNAV operations, they do not encompass the overarching requirement for authority approval that ensures the procedures are recognized as safe and effective by governing aviation bodies.