In aviation terminology, the word 'shall' indicates what level of requirement?

• A. Advisory only
• B. Mandatory requirement
• C. Optional guideline
• D. Prohibited action

Answer: (B)

The word shall marks a binding, mandatory requirement. In aviation documents, when you see shall, it means you must perform the action or meet the condition; it is not optional. This is used in regulations, manuals, SOPs, and training materials to enforce safety and consistency. By contrast, should signals a strong recommendation (advisory), may indicates permission or discretion, and need not means the action isn’t required. For example, a pilot shall complete the before-start checklist before engine start, making it a non-negotiable step for safe operation.