Which of the following best describes the purpose of a mandatory instruction sign?

The purpose of a mandatory instruction sign is to inform pilots of mandatory actions that they must comply with while operating in the vicinity of an airport or airfield. These signs are crucial for safety and regulatory compliance, as they convey information that must be followed to ensure the safe operation of aircraft and the safety of all individuals on the airfield.

For example, signs that indicate "No Entry" or "Runway Hold Position" inform pilots that they must adhere to specific procedures or restrictions to avoid compromising safety. By recognizing these signs, pilots can prevent unauthorized maneuvers and potential collisions.

In contrast, signs that provide general information do not convey the necessity of compliance, nor do they specify locations in a mandatory context. Advertising services similarly does not relate to required actions and is not within the scope of mandatory signs at aerodromes. Thus, understanding the function of mandatory instruction signs is vital in promoting operational safety and regulatory adherence in aviation.